NICOM6

Program Rundown

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DAY 1
2 Dec 2018
(Sunday)

DAY 2
3 Dec 2018
(Monday)

DAY 3
4 Dec 2018
(Tuesday)

DAY 4
5 Dec 2018
(Wednesday)

2 Dec 2018 (Sunday)

TIME

EVENT

5:00 pm - 7:00 pm

Reception

Venue: Atrium Link, Hong Kong Science Park

3 Dec 2018 (Monday)

TIME

EVENT

8:45 am - 9:15 am

Registration

Venue: Charles K. Kao Auditorium, Hong Kong Science Park

9:15 am - 9:25 am

Welcome Remarks

Prof. CHING Pak Chung, B.Eng. (Hons.), Ph.D., D.Sc. (Honoris causa)(Liverpool), FIEE, FHKIE, FHKAES, FIEEE,
Chairman, Nano and Advanced Materials Institute Limited

Prof. Timothy W. TONG, BSc, MSc, PhD, FASME, FHKEng, JP,
President, Hong Kong Polytechnic University

9:25 am - 9:30 am

Opening Remarks

Mr. Nicholas YANG, GBS, JP,
Secretary for Innovation and Technology,
The Govenment of the Hong Kong Special Administrative Region

9:30 am - 9:35 am

Souvenir Presentation

9:35 am - 9:40 am

Group Photo

Keynote Speech

Venue: Charles K. Kao Auditorium, Hong Kong Science Park

9:40 am - 10:15 am

A Chemical Admixture with Carbon Nanotubes

Yuan Gao¹(speaker), David J. Corr², Maria S. Konsta-Gdoutos³, Surendra P. Shah⁴

Carbon nanotubes (CNT) are perhaps the most widely used nano materials in a wide range of applications. CNTs and CNFs (carbon nanofibers) have remarkable properties because of their nanoscale. Many attempts have been made world-wide to incorporate them in concrete. Adding CNT or CNF in concrete poses two challenges: cost and uniform dispersion. Researchers at Northwesten University have successfully tackled those challenges. CNT or CNF are ultrasonicated in an aqueous solution containing superplasticizers. The technique of dispersion will be discussed in this paper. We have observed that the addition of the aqueous solution containing a very small amount of well dispersed CNT or CNF (less than 0.1% by weight of cement) exhibit following remarkable benefits: (1) it reduces the autogenous shrinkage, (2) it delays onset of shrinkage cracking and reduces crack width,(3) it enhances the modulus of elasticity , (4) it makes concrete piezoresistive (so called smart material), (5) it enhances fracture properties and (6) the addition of CNT or CNF delays the corrosion of reinforcing bars due to ingress of chloride. This paper will discuss these multi-functional properties.

Graduate researcher, Civil and Environmental Engineering, Northwesten University
Professor, Civil and Environmental Engineering, Northwesten University
Professor, Civil Engineering, Democritus University of Thrace
Walter P. Murphy Professor (emeritus), Civil and Environmental Engineering, Northwesten University

Prof. Surendra P. SHAH

Walter P. Murphy Emeritus Professor of Civil and Environmental Engineering
Northwestern University, USA

Prof. Surenda P. Shah is a Walter P. Murphy Emeritus Professor of Civil Engineering and was the founding director of the pioneering National Science Foundation Science and Technology Center for Advanced Cement-Based Materials. His current research interests include: fracture, fiber reinforced composites, non-destructive evaluation, transport properties, processing, rheology, nanotechnology, and use of solid waste materials. He has co-authored two books: Fiber Reinforced Cement Based Composites and Fracture Mechanics of Concrete. He has published more than 500 jounal articles and edited more than 20 books. He is past editor of RILEM's jounal, Materials, Structures.

Prof. Shah is a member of the US National Academy of Engineering. He is also a foreign member of the Chinese Academy of Engineering and the Indian Academy of Engineering. He is the only civil engineer who is a member of these three academies. He has received many awards, including the Swedish Concrete Award, American Concrete Institute's Anderson Award, RILEM Gold Medal, ASTM Thompson Award, American Society of Civil Engineer's Charles Pankow Award, and Engineering News Record News Maker Award. He was named one of the ten most influential people in concrete by Concrete Construction Magazine. Recently, he spent time at Indian Institute of Technology, Madras as an Honorary Professor under the auspices of a Fulbright grant. He is an honorary member of American Concrete Institute and RILEM (based in Paris).

Besides teaching at Northwesten, Professor Shah has taught at the University of Illinois, Chicago and served as a visiting professor at MIT, University of Sydney, Denmark Technical University, University of Singapore, Darmstadt University, and Laboratoire Central des Ponts et Chaussees Paris. Currently, he is a member of the Institute of Advanced Studies at Hong Kong University of Science and Technology. He is also honorary professor at Hong Kong Polytechnic University, Dalian Maritime University, Nanjing Technical University and South East University.

Walter P. Murphy Emeritus Professor of Civil and Environmental Engineering,
Northwestern University, USA

10:15 am - 10:50 am

Cement-based Nanocomposites – Chances and Challenges

The use of nanomaterials and nanotechnologies for tailoring the properties of cement-based materials has a huge potential, in particular with respect to achieving entirely new functionalities. The presentation provides an overview of the recent and on-going research on cement-based nanocomposites performed at the TU Dresden and in collaboration with various partners. First, dispersion of carbon nanotubes (CNTs) in water for subsequent application in cement-based systems is discussed, while analyzing the effects of CNT-type (precursor type), ultrasonication regime, molecular architecture of surfactants, temperature and other parameters. Next, the influence of CNTs on mechanical properties is briefly addressed, but the main focus is on sensing and thermoelectric properties of nanocomposites induced by CNTs. The achieved characteristics will enable the use of such nanocomposites as extra durable and multifunctional sensors as well as thermoelectric generators for large-scale thermal energy harvesting. Furthermore, hierarchical all carbon reinforcement with multifunctional properties and enhanced stiffness and interfacial shear strength is presented. Finally, a novel type of textile and bar reinforcements made of continuous carbon fiber (CF) yans impregnated with mineral-based matrix is introduced. Such reinforcement structures exhibit a much higher temperature resistance at elevated temperatures in comparison to conventional CF reinforcements impregnated with polymers.

Prof. Viktor MECHTCHERINE

Professor of Construction Materials
Director of Institute of Construction Materials
Technical University Dresden, Germany

Prof. Dr.-Ing. Viktor Mechtcherine is Professor of Construction Materials and Director of the Institute of Construction Materials at the Technical University Dresden, Germany. Before that, he was Professor at the Technical University Kaiserslauten (2003-2006) and Chief Research Engineer with the Institute of Reinforced Concrete Structures and Building Materials at the Karlsruhe Institute of Technology – KIT (1998-2003). He graduated from the University for Civil Engineering and Architecture of St. Petersburg in 1986 and worked there in Russia as civil engineer before joining KIT in 1990, where he made his Dr.-Ing. (PhD) in 2000.

His current research interests include fibre-reinforced cement-based materials, rheology, concrete technology, additive construction, fracture mechanics, durability and new additives and admixtures. He is chair of RILEM TC 260-RSC "Recommendation for Use of Superabsorbent Polymers in Concrete Construction" and member of RILEM Bureau, RILEM Technical Activities Committee, Steering Committee of the fib Commission "Concrete", Editorial Board of the Jounal "Cement and Concrete Composites", Editorial Advisory Committee of the Jounal "Materials and Structures" and Expert Board "Construction products made of fibre-reinforced cementitious materials" of the German Institute of Structural Engineering (DIBt). Prof. Mechtcherine is a member of Science Academy of Saxony and Russian Academy of Engineering. He is also coordinator of the German Research Society Priority Program DFG SPP 2005 "Opus Fluidum Futurum – Rheology of Reactive, Multiscale, Multiphase Construction Materials" and speaker of German Research Society Research Training Group DFG GRK 2250 "Mineral-bonded Composites for Enhanced Structural Impact Safety".

Professor of Construction Materials, Director of Institute of Construction Materials,
Technical University Dresden, Germany

10:50 am - 11:05 am

Coffee Break

Venue: Charles K. Kao Auditorium Foyer

Parallel Sessions

Venue: Conference Hall 4 - 6, Lakeside 2, Hong Kong Science Park

11:05 am - 11:25 am

Parallel Session 1
Session Chair :
Prof. Viktor MECHTCHERINE
Venue: Conference Hall 4

(Invited Speech)
Investigation on the Interfacial Properties of Nano SiO₂ Modified Cement-based Composite

In this paper, an effective modification method of carbon fiber in cementitious composites is proposed to improve the interfacial properties between carbon fiber and cement matrix. Through the condensation and polymerization of the tetraethyl orthosilicate under alkaline conditions, the SiO₂ thin layer is formed on carbon fiber surface. This surficial formed SiO₂ layer can react with calcium hydroxide (Ca(OH)₂), a cement hydration product, to form calcium silicate hydrate (C-S-H) gel thus improve the interfacial bond strength between the carbon fiber and cement matrix. The morphology and chemical composition of the surficial grown SiO₂ were characterized and analyzed by using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Thus, the presence of SiO₂ on the surface of the modified fiber was confirmed. Finally, a directly single carbon fiber pull-out from cement matrix test was conducted and the experimental results indicated that the interfacial bond strength of surficial SiO₂ coated carbon fiber was greatly enhanced with respected to that of the untreated carbon fiber. Through the single carbon fiber pull-out test, the interfacial enhancement effect of modified carbon fiber were confirmed as well as the effectiveness of this modification method.

Huigang Xiao, Mengyuan Lu, Xiaojiao Li, Hui Li

Parallel Session 2
Session Chair :
Prof. Jae Hong KIM
Venue: Conference Hall 5

(Invited Speech)
Particle Dispersion of Cement Suspensions at The Nano- and Micro-scale

Enhancing the fluidity and workability of concrete is important for ease of construction and success of a construction project. Decreasing the attractive interactions of cement particles to decrease the viscosity of concrete is a key problem to overcome. Although techniques such as cement/concrete rheometry and magnetic resonance imaging help explain the behavior of a cement-based suspension, they have not yet provided a full explanation of the dispersion effect in a comprehensive experiment. Conventional laser-scattering and zeta-potential measurement needs a dilution of samples rather than in situ investigation. For a direct exploration on the cement suspension, here a laser backscattering measurement is adopted. The measurement provides information on the dispersion of agglomerates at microscale. A surfactant providing a high dispersion of cement particles changes the agglomeration state, and a plasticized cement suspension shows their dispersion at nanoscale.

Jae Hong Kim

Parallel Session 3
Session Chair :
Prof. Caijun SHI
Venue: Conference Hall 6

(Invited Speech)
The Impermeability Improvement Effect of Nano-silica on Cement-based Materials with and without Compressive Load

In order to explore the impermeability improvement effect of nano-silica on cement-based materials under different water to cement ratio (W/C) with and without compressive load, such as chloride-ion penetration and water permeability were tested in this research. The results indicate that the impermeability enhancement effect of nano-silica becomes more remarkable at lower W/C. Moreover, after compressive load with the same level, the deterioration degree of cement paste containing nano-silica with lower W/C ratio is much lower than that of cement with higher W/C, thus the reduction of inhibition of chloride ion penetration is much greater in cement paste with lower W/C. Therefore, it can be concluded that nano-silica can play more prominent role to improve the permeability of cement-based materials with low W/C.

Huigang Xiao, Rui Liu, Hui Li

11:25 am - 11:45 am

Influence of Sulfonated Graphene Nano-sheet (SGN) on Mechanical Properties of Cement Based Materials and its Hydration Mechanism

Sulfonate Graphene nano-sheet (SGN) was used to improve the mechanical property of cement-based materials. Meanwhile, hydration kinetics, mineral phase compositions and microstructure characterization of hydration products were also investigated by isothermal calorimetry, in-situ and quantitative X-Ray diffraction and scanning electron microscope. The results showed that the relative low dosage of SGN could promote the toughness of cement based materials. In detail, the addition of SGN would increase the flexural strength, though it exerted a slight decrease in the early compressive strength. However, at later stage, both the flexural and compressive strength of cement based materials with SGN would be promoted. The hydration heat presented that the low dosage of SGN could slightly accelerate the cement hydration, while with the increase of SGN, the duration period will be prolonged and the maximum hydration and total hydration heat will be decreased. According to the results of XRD and SEM, the addition of SGN, characterized with -SO3H-, consumed CH and affected its crystal orientation, leading to a significant microstructure of cement based materials, which probably was the main reason for the promotion of its toughness.

Jinhui Tang, Jiaping Liu, Cheng Yu, Rui Wang

In Situ Examination of Engineered Local Additives in Cement Paste via Neutron-based Scattering Techniques

This work investigates the effect of early-age hydration on microstructural evolution of cement paste with local volcanic ash using neutron-based beamline techniques. Early-age hydration dynamics of Portland cement paste with volcanic ash was examined via Inelastic Neutron Scattering (INS), while the evolution of microstructure was observed with Small Angle Neutron Scattering (SANS). The data obtained from the ratio of Volume Fractal to Surface Fractal clearly showed that greater than 30 % substitution of volcanic ash leads to unreacted volcanic ash and coarser morphology, which could influence the chemo-mechanical properties of the resulting hydration products. INS results showed that the effect of finer-particle-sized volcanic ash contributes to uniform hydration, which accommodates higher conversion of free water to bound water. Such advanced beamline characterization techniques were found useful in providing critical insights into the effect of additives by considering water dyamics along with morphological information during the course of hydration. The multi-scale analysis that combines a time-resolved study of water dynamics along with microstructure is found to provide a basis for optimizing and effectively utilizing engineered additives for the local cement industry.

Kunal Kupwade-Patil, Ali Bumajdad, Terrence Udovic, Kenneth Littrell, Oral Buyukozturk

Nano-zeolite as an Additive for Cement Sheath in HPHT Oil and Gas Wells

Challenges encountered in the cement sheath protecting the oil and gas well steel casing subjected to high-pressure and high-temperature (HPHT) environments have prompted researchers to investigate the nanomaterials as additives. Cement sheath integrity is critical to maintain a healthy well during its service life. The cement in the annular space should have low permeability to prevent the transport of corrosive fluid from the formation to the casing and provide a barrier that inhibits the migration of gases in the micro annulus between the formation and the cement and the cement and pipe casing. Various types of zeolites have been tested previously for cementing high temperature wells in high concentrations as a partial replacement in the cement content. However, nano zeolite, as a cement additive has not been investigated. In this study, the influence of nano zeolite having particle size less than 80 nanometers on the properties of API Class G cement in the presence of other cement additives was investigated. Cement properties, such as thickening time, compressive strength development, porosity, and permeability were studied under HPHT conditions. Nano zeolite (NZ) at 1 to 3% by weight of cement was added to the cement slurry to evaluate the performance nano zeolite mixes. The addition of NZ resulted in accelerating early age compressive strength values, while maintaining higher final strength values as compared to control mix. Required cement compressive strength of 2,000 psi in nanozeolite modified cement slurry was obtained in 33% less time compared to the control slurry, which should reduce the wait-on-cement time. Nano zeolite modified slurry has low permeability and low porosity, which should help prevent the intrusion of aggressive fluids from the adjacent formations. The thickening time of the nano zeolite admixed slurry was higher than the control mix, indicating the retarding effect of nano zeolite.

Muhammad Kalimur Rahman, Mirza Talha Baig, Abdulaziz Al-Majed

11:45 am - 12:05 pm

The Critical Role of Carbon Based Nano-fillers in Cementitious Composites

Alva Peled, Oren Regev, Amer Alatawna, Matan Birenboim, Roey Nadiv, Gal Shachar, Matat Buzaglo

A Spectroscopic Study of the Superplasticizer Effect on Early Cement Hydration

Organic/inorganic mixtures were prepared from ordinary Portland cement (OPC), water (w/c 0.22), a fluorescent cyanine dye in aqueous solution (stable at alkaline pH; BAM-I), and two different comb shape polycarboxylates (PCEs), i.e., high charge (PCE-HC) and low charge (PCE-LC), respectively. Rheology and calorimetry measurements were performed prior to optical studies in order to select PCE concentrations. Absorption and fluorescence spectroscopy of the system OPC + BAM-I (CBAM-I) revealed maxima of BAM-I located at 645 nm and 663 nm, respectively. In presence of PCE-HC and PCE-LC, these mixtures displayed a small red shift in reflectance and a faster decrease in intensity compared to studies with CBAM-I; however, only slight differences were observed between the different PCEs. With time, all systems exhibited a decrease in intensity of BAM-I in absorption/reflectance and emission. This could be caused by dye adsorption and possibly decomposition when in contact with cement particles or hydration products.

Alejandra Ramirez Caro, Berta Mota, Claudia Crasselt, Elena Artemeva, Jutta Pauli, Wolfram Schmidt, Ute Resch-Genger

Advanced Dispersion Technology of Nanoparticles and Microparticles for Durable Concrete

Nanoparticles have gained increasing popularity in the concrete industry as they can improve the microstructure and durability of concrete. It has been demonstrated that nanoparticles serve as additives in concrete mixes that act as nucleus to tightly bond with C–S–H gel particles and behave as filler to improve the cement paste microstructure, enhancing the mechanical properties and durability of concrete. The effectiveness of using nanoparticles is largely dependent on the ability to achieve uniform and stable dispersion of nanoparticles in the cement paste. When nanoparticles are added into cement slurry, they would likely form agglomerates and may not achieve its designed reactivity. To tackle this issue, NAMI has developed an innovative dispersion technology, whereby making use of the potential change of the nanoparticles from neutral to alkaline, nano-silica (nSi) serves as carrier to disperse nano-alumina (nAl). The nAl particles are attached on the nSi particles in water because of its opposite surface charge. Afterwards, in highly alkaline cement slurry (pH = 12), the nAl particles become negatively charged and are detached from the nSi particles. As a result, better dispersion can be achieved. In this paper, the attach-release mechanism was demonstrated from SEM images and zeta potential values; particle sizes under various pH levels were evaluated. The optimized proportioning of the aforesaid nanoparticles has been investigated. The improvement in the early strength of concrete by adding nSi and nAl is promising. The 28d strength was significantly improved by 22%, revealing the uniform dispersion and synergy effect of hybrid nSi and nAl. The chloride ion resistance was also largely enhanced by 200%, indicating better dispersion quality of hybrid nanoparticles. Moreover, the attach-release mechanism was also applied to produce concrete admixture to improve watertightness and water absorption resistance of concrete. Water tanks of dimensions 2m x 2m x 1.45m (height) were constructed to demonstrate the applicability of the produced concrete admixture.

Feng Li, Honggang Zhu, Jeffery Lam, Ivan Sham, Chi Sun Poon, Derek K.L. So

12:05 pm - 12:25 pm

Dispersion of Carbon-based Nanofillers in Aqueous Suspension by Polycarboxylate Comb-type Copolymers

In this experimental study, the dispersion behaviour of different carbon-based nanofillers in deionized (DI) water was investigated by using polycarboxylates as surfactants. Carbon nanotubes (CNT), carbon black (CB) and expanded graphite (EG) were firstly characterized with regard to their morphology. Subsequently, they were dispersed in deionised water using two PCE polymers differing in their polymethacrylic backbone lengths. Optical microscopy and light transmission analysis during centrifugation disclosed a clear difference in the dispersibility among the nanofillers under investigation. Small CB particles showed an excellent dispersion in DI water even without any surfactant. CNT showed a significant better dispersibility than EG, whereby in both cases the PCE with the longer backbone obtained a better filler dispersion. Complementary analysis revealed that carbon filler dispersion by PCE in water is govened by the filler morphology, the molecular architecture of PCE as well as by the physical and chemical properties of the aqueous media.

Marco Liebscher, Christof Schroefl, Tin Trong Dinh, Viktor Mechtcherine

Study of Micro-mechanical Properties of Sea-shell and Cement Paste Using Express Nanoindentation Mapping

Over the past two decades nanoindentation technique has been increasingly used to study mechanical properties of micro-structural features in many natural and engineering materials. In the case of nano-composites, such as sea shells and cement paste, mapping of mechanical properties at the micro/nano scale and the associated statistical nanoindentation technique has been developed to visualise and characterise the mechanical properties of the complex microstructural features. Mapping mechanical properties using conventional nanoindentation technique, though a proven valuable method, does have a number of limitations for studying complex, heterogeneous, nano-composite materials. One particular limitation is its relatively slow test speed: typically it takes about 8 minutes to complete one indentation test point, or more than 24 hours continuous testing to cover 200 test points. As a result, insufficient number of test points often leads to poor quality (e.g. low resolution and unrepresentative) of the mechanical properties map generated and unreliable or erroneous results obtained from the statistical analysis.

This paper reports recent studies carried out using the new Express nanoindentation mapping technique developed by Keysight technologies, which offers test speed up to 500 times faster than the conventional method. High resolution mechanical properties mapping (with nearly 10000 test points) of a sea shell specimen reveals that the marine organisms exert exquisite control on mineral formation by tuning structural and material properties to meet functional requirements. Significantly increased number of test points can also benefit characterisation of cement paste specimens using the statistical analysis.

Wenzhong Zhu, Maggie Cusack, Peter Chung, Jesus D. Zea-Garcia, Isabel Santacruz, Angeles G. De la Torre, Diana Londono-Zuluaga

Technology Transfer of Nano-Enhanced Concrete on Active Jobsites

Nanotechnology in concrete has become more popular over the last 25 years as a means to increase strength and durability of concrete. It's because of these enhancements imparted to concrete, that nanotechnology has become more accepted in the concrete and construction industry. The purpose of this presentation is to present case studies that highlight the many forms of nanotechnology in concrete. The case studies focus only on field applications of nanoenhanced concrete. Despite the rise in the popularity of using nanotechnology in concrete, the main obstacle that prohibits the entry of these novel technologies into day-to-day concrete is the lack of adequate case studies. Engineers, superintendents, architects, and concrete producers are uneasy using a concrete product unless there have been repeatable field applications that quantify and qualify the features and benefits. A set of case studies targeted at exemplifying case studies of nanotechnology in concrete, will facilitate the validation of decades of research that has been invested in proving this technology. Most importantly, the publication of a set case studies for nanotechnology in concrete will give concrete producers and engineers another tool to enhance concrete structures and infrastructure throughout the world.

Jon Belkowitz, Whitney Belkowitz, David Harris

12:25 pm - 2:00 pm

Luncheon

Venue: ClubOne, Hong Kong Science Park

Parallel Sessions

Venue: Conference Hall 4 - 6, Lakeside 2, Hong Kong Science Park

2:00 pm - 2:20 pm

Parallel Session 4
Session Chair :
Prof. Maria S. KONSTA-GDOUTOS
Venue: Conference Hall 4

Innovative Capsule Technology for Lightweight Cellular Concrete

The conventional method of making cellular concrete is to introduce pre-formed foam into cement slurry since the pre-formed foam would easily rupture during prolong mixing and transportation. Moreover, coarse aggregate is difficult being added in conventional foamed concrete to minimize the chance of impacting pre-formed foam and therefore aggregate settlement. The application scenarios of foamed concrete are then limited. In this paper, a novel approach to produce lightweight cellular concrete was proposed based on capsule technology. Capsules with alkaline-sensitive polymer as shell and water as core were prepared and used for fabricating the cellular concrete with aggregates. Parametric studies has been carried out to investigate the factors in determining the size, shell thickness, water content and release profile of capsules. By properly controlling the size and shell thickness, the developed capsules in fresh concrete is targeted to survive after 2 hours mixing in mixer and concrete truck without rupture. After setting of concrete, the capsules would slowly rupture under strong alkaline cementitious environment with water inside the capsules being released, resulting the cellular structure in hardened concrete. By further optimizing the formulation, lightweight cellular concrete integrated with produced capsules and aggregates have huge potential to be used in in-situ casting, even for construction of buildings’ structural components.

Ruby Zhu, Krystal Liang, Honggang Zhu, Jeffery Lam, Ivan Sham, Derek So

Parallel Session 5
Session Chair :
Mr. Dietmar STEPHAN

Venue: Conference Hall 5

(Invited Speech)
The Influence of the Chemical and Physical Properties of C-S-H Seeds on Their Potential to Accelerate Cement Hydration

The development of green cements for reducing CO₂ emissions often results in reduced hydration activity, especially in early stages, which conflicts with economic interests and process requirements.

Besides pozzolans like nano-silica, the performance of calcium silicate hydrate (C-S-H) nanoparticles has recently become a focus, due to their outstanding ability to accelerate cement hydration, without compromising the long-term strength of the seeded cement. Many properties of C-S-H have been found to influence their accelerating performance, with controversial results being published regarding the calcium to silicon ratio. While Alizadeh et al. have found that the hydration of C3S is accelerated more when C-S-H seeds richer in silicon are applied, Land et al. have found that seeds richer in calcium are better accelerators. Neither particle size nor respective surface area were kept constant in either work.

Using stoichiometry, this work aims towards a systematic investigation of the influence of the chemical and physical properties of C-S-H. The impact on cement hydration is examined using isothermal heat flow calorimetry as a screening method.

Dietmar Stephan, Elisabeth John

Parallel Session 6
Session Chair :
Prof. Caijun SHI

Venue: Conference Hall 6

Potential Applications of Geopolymerization Technologies in Hong Kong

The cement industry generates more than 5% of greenhouse gas CO₂ emission due to the rapid urbanization and numerous large scale infrastructure projects worldwide. With a target of 18% reduction of greenhouse gas emission by 2050, there is an urgent need for eco-friendly altenatives of ordinary Portland cement. By using recycled industrial by-products such as ground granulated blast funace slag and fly ash, geopolymer cement is widely recognized as a prominent altenative with the unique features of rapid early strength and excellent acid resistance. It is a win-win solution to the recycling of industry by-products and to moderate the environmental issues from cement industry. Strategically located at the heart of Asia and alongside most exciting raw material markets, Hong Kong is not only a renowned worldwide financial center, but also a technology hub for developing advanced construction and building materials, supported by the abundant feedstock supplies from the mainland China. In this paper, the potential applications of geopolymerization technologies in Hong Kong are introduced. The excellent performance of geopolymer based materials in early strength development, sulphuric acid resistance are demonstrated. In light of the applications in rapid repair, precast concrete units, and sewage treatment facilities, adjustment of workability and sufficient one-day strength is crucial and achieved by proper system design characterized by calorimetry. Moreover, by utilizing a proper foaming process, ultra-lightweight geopolymeric materials are also developed for backfilling operations & thermal insulation works.

Garrison C K Chau, Binyu Zhang, Simon Guan, Yong Fan, Chloe Liu, Ivan Sham

2:20 pm - 2:40 pm

The Quantitative Characterization of the Degree of Dispersion of Carbon Nanotubes in Cementitious Nanocomposites: An Impedance Investigation

The homogeneous dispersion of carbon nanotubes (CNTs) in a cementitious matrix is a crucial procedure that affects the properties of the nanocomposites. It is therefore important to quantitatively characterize the factors that affect the degree of dispersion of CNTs. Conventional characterization techniques such as microscopy are cost consuming and provide only qualitative results. Impedance spectra method can be very useful in studying and characterizing the impact of the count of individual CNTs’ reinforcement in nanocomposite materials in a quantitative way. In this study, measurements of the electrical conductivity, bulk and real resistivity and electrochemical capacitance, based on Electrochemical Impedance Spectra (EIS), reveal the nature of circuit elements, that are formed by the nanotube network in the nanocomposites, and provide insight of the nanotubes’ dispersion state. The real part of resistance (resistivity) shows that the amount of 0.1 wt% CNTs denotes the transition of an electron hopping intra-tube or among different CNTs phenomenon to the formation of continuous conductive network which mostly govens the electrical conductivity of the nanocomposites. Values of resistivity, bulk resistance and capacitance are 27%, 28% and 90% lower than that of the plain mortar, respectively. After the conductive network is formed, resistivity values show a little dependence on the CNT content, reaching a plateau. Bulk resistance and capacitance on the other hand were increased, showing an amplified energy storage ability, probably due to the existence of small CNT agglomerates. The observed relationship between capacitance values and flexural strength may provide valuable information on the actual CNT dispersion state in the matrix.

Panagiotis Danoglidis, Maria S. Konsta-Gdoutos

Exploring Energy Harvesting Potentials of Cementitious Materials Through Nanotechnology

The energy crisis is one of the most significant challenges that we face in today's society. More than 80% of the economy relies on fossil fuels coupled with an accelerating growth of global population and greenhouse gas emissions puts our environmental sustainability under threat. Therefore, it is critical to develop advanced technology for renewable energy development or waste energy harvesting. A recent discovery of using nanostructure materials for energy harvesting potentials in cementitious materials will be discussed in this presentation, as a large quantity of waste energy is available in cementitious materials, such as thermal storage and mechanical vibration, which are still untapped. This talk focuses on using polymeric based piezoelectric materials to harvest vibration energy from bendable concrete. β-phase Polyvinylidene fluoride (PVDF) nanofibers were synthesized using high voltage electrospinning methods, and digital integrated circuits (DIC) were fabricated using photolithography process. Engineered cementitious composites (ECC) incorporating flexible PVDF based piezo generators were investigated as an innovative energy harvesting system to scavenge energy from mechanical deflection of ECC. Synchronous flexural test and voltage data recordings were employed to evaluate the voltage capture efficiency at various loading rates. The favorable voltage output has reached up to around 17V. The experimental results lay a solid foundation for potential of using nanostructured materials/devices for energy harvesting applications of the cementitious composite system.

Yen Fang Su, Yining Feng, Na (Luna) Lu

The Effect of Activated Fly Ash and Nano-SiO_{2_{on Performance of Self- Consolidating Concrete}}

The Effect of Activated Fly Ash and Nano-SiO₂ on Performance of Self- Consolidating Concrete

Self-Consolidating Concrete (SCC) is a new type of concrete which is characterized by the ability to fill the formwork under its own weight without extenal compaction effort. This research reports on the application of activated fly ash and SiO₂ nanoparticles in SCC. Reference SCC mixtures were produced with up to 50% of class C fly ash. Mixtures with 30% of activated fly ash, nano-SiO₂, and superplasticizer were tested in order to evaluate the potential improvement of early strength. The activated fly ash was mixed with cement and sand and compared to a reference mixtures. Two series of SCC were produced with a total cementitious content of 400 kg/m3 and 500 kg/m3. The fresh properties, and compressive strength were investigated. It was demonstrated that the use of activated fly ash and the addition of small amounts of nano-SiO₂ can greatly improve the performance of concrete.

Konstantin Sobolev, Rani Pradoto, Mohamadreza Moini, Ismael Flores-Vivian, Marina Kozhukhova

2:40 pm - 3:00 pm

Improving Toughness and Stiffness of Nanomodified Mortars Using Hybrid CNT, CNF and PP Reinforcement

Maria Falara, Maria S. Konsta-Gdoutos, Emmanuel Gdoutos

Application of Supercritical Fluids Technology for the Synthesis of Nanoparticles

A fluid is said to be supercritical when both its temperature and pressure are above their critical values: 374°C and 22.1MPa in the case of water. In such conditions, liquid and gas phases merge into a single one and the properties of the fluid change radically. Furthermore, such properties can be varied from gas-like to liquid-like by simply adjusting the temperature and/or pressure; and the control of such variables is particularly fine if continues reactors are used. This has allowed to produce many types of nanoparticles (oxides, metals, sulfides…) with desired sizes and morphologies (preferred growth in particular directions) and/or control of the degree of crystallinity. Lately, the methodology has been applied to significantly increase kinetics in the synthesis of clays and calcium silicate hydrates from many hours to only tenths of seconds. Furthermore, continuous supercritical water methods have proved themselves useful for the synthesis of elusive phases like fibrous tobermorite which not only is metastable at such temperature and pressure but it usually crystalizes in the form of plates or foils. This article contains a review of the hydrothermal synthesis methods of xonotlite and tobermorite including the latest results obtained under supercritical conditions.

Juan Jose Gaitero, Marta Diez-Garcia, Jorge S. Dolado, Edune Erkizia, Cyril Aymonier

Nanoscale Technology Enhancement of Crushed Rocks’ Mechanical Properties for Pavement Applications

The Norwegian Public Roads Administration is currently running the “Ferry-free coastal route E39” project; this highway plan includes the creation of several long tunnels, which will generate a surplus of blasted rocks. They could be used in the road unbound layers close to the place of production providing a sustainable cost-benefit application. A considerable quantity of the excavated rocks does not satisfy the existing code requirements. Two different additive products can enhance the mechanical properties of these “weak” rocks. One additive is polymer-based and the other additive is lignin-based. Los Angeles tests, micro-Deval tests and repeated triaxial load tests thoroughly evaluate the mechanical properties (resilient modulus and permanent deformation) of two investigated “weak” rock types. Scanning electron microscope images display the rock surfaces before and after the treatment. Additive applications show promising positive results.

Diego Maria Barbieri, Sohrab Alex Mofid, Inge Hoff, Bjøn Petter Jelle

3:00 pm - 3:20 pm

Understanding the Role of Nanocellulose on The Strength of Cement Composites: A Macro-to-micro Investigation of Systems with Cellulose Filaments

Nanomaterials are currently attracting a rising research attention in versatile realms including the concrete industry. In this regard, the incredible properties offered by nanocellulose materials (NCMs) – e.g., high elastic modulus, tensile strength, and surface area – are believed to have the potential to unveil new horizons for enhancing concrete performance. This paper discusses the perspectives of using NCMs as a tool for tailoring the properties of cement composites. This was attempted by firstly providing a brief summary of current research progress (with emphasis placed on types of NCMs and their effects on hydration kinetics, fresh properties, and mechanical performance) then later by presenting a case study. In the latter, a macro-to-micro investigation on the properties of cement pastes incorporating cellulose filaments (CF) was conducted. CFs represent a new class of NCMs with highly promising applications in concrete technology. The effect of incorporating CF at rates 0%, 0.05%, 0.1%, and 0.3 wt.% on the macroscale mechanical properties of cement pastes (i.e., elastic modulus and flexural capacity) was examined, along with microstructure investigations (i.e., degree of hydration and micromechanical properties of microstructure phases). The incorporation of CF resulted into 15-25% increments in compressive strength, elastic modulus, and flexural capacity. These improvements were supported by the microstructure investigations showing that CF (even at only 0.05 %) would improve the degree of hydration and enable higher C-S-H micromechanical properties (evaluated with the coupled NI-QEDS method). These results substantiate the viability of CF as a promising material for the development of nanomodified cement composites with enhanced elastic and toughness properties.

Hisseine Ousmane, William Wilson, Luca Sorelli, Arezki Tagnit-Hamoua

Early Hydration in Concrete Using Nano Crystals

Due to the increased use of pre-fabricated structural elements in the construction industry, it has become essential for the pre-fabricated industries to accelerate the production capabilities. The enhancement in the production capabilities depends on the hardening characteristics of the concrete and can be shortened and hence, the overall production process can be made faster by accelerating the hardening process of concrete. Conventionally, this is achieved either by elevated temperature curing or by the use of commercially available hardening accelerators. Elevated temperature curing demands more energy input and can also make some intenal changes in the concrete structure. Commercially available hardening accelerators when used often exhibit durability related problems in concrete. In this study, an attempt has been made to use a sustainable and cost effective hardening accelerator in concrete, synthesized using locally available agricultural waste products. The hardening accelerator in the form of C-S-H nano crystals, when added in concrete provides additional nucleation sites inside the pore spaces between cement particles thereby accelerating the hardening process. Such additional sites are capable of lowering the critical nucleus energy, resulting reduction in the induction period of complex and precipitation reaction. Through experimental study, it has been observed that the C-S-H nano-crystals are capable of reducing the setting time of cement paste and concrete considerably. Further, the faster precipitation of hydration products in cement paste in the presence of nano-crystals has been confirmed through X-ray Diffraction (XRD) study. A higher diffraction peak of Ca(OH)₂ is observed in cement paste with C-S-H nano crystal than without nano crystals, indicating the acceleration capability of nano crystals in the early hydration process.

Saikat Das, Sonalisa Ray, Sudipta Sarkar

Development of Alkali-Activated Dry-Mix Mortars

Alkali-activated materials (AAM) offer high potential for utilization as eco-mortars to replace the Portland cement-based mortars in supporting the green and sustainable materials move within the construction industry. The mortars based on AAM have desirable performance such as good mechanical properties, controllable setting and curing, resistant to chemical attacks and high-temperature, and compatibility with concrete substrates. From practical perspective and quality control point of view, dry-mix (single-part) mortars are better than the conventional on-site wet-mix mortars. However, nowadays, there has been little research and development on alkali-activated materials based dry-mix mortar products. This paper highlights the pioneering research on alkali-activated technology with selected raw materials that enables the development of high performance green dry-mix mortars. The technical challenges need to be overcome by utilizing specific mix ingredients, proper formulations, functional additives and dry-mix blending technology. An experimental programme of developing workable AAM mortar binder encompassing different proportions of GGBS, fly ash and metakaolin, alkali activators with different molar ratios, dosages of additives, sand usage and grading has been studied. A dry-mix AAM mortar formulation is found with excellent mechanical properties of 1-day and 28-day, compressive strength higher than 10 MPa and 50 MPa, respectively. The controllable setting time can be adjusted between 30 and 120 minutes. The accelerated acid resistance test with sulphuric solution of pH 0.5 show that this AAM mortar has no obvious weight loss after 28-day treatment, which indicating its excellent acid resistance comparing to Portland cement.

Simon Guan, Raymond Wan, Martin Kwong, Ivan Sham, Garrison Chau

3:20 pm - 3:40 pm

Carbon Nanotubes Can Improve The Seismic Resistance Of GFRP Bolted Joints

Orthotropic material behaviour and low shear strength of Glass Fibre Reinforced Polymers (GFRP) makes bolted connections goven the design of GFRP framed structure. These, connections become more critical when subjected to seismic activity. In the current study, we show using Multi-Walled Carbon Nanotubes (MWCNTs) dispersed in epoxy prior to fabrication of GFRP can improve the seismic resistance of GFRP bolted connections. Firstly, a numerical analysis on a bracing element within a framed structure when subjected to 1940 El Centro was modelled to determine the displacement time history. Later, double lap bolted joints using GFRP and steel bolts have been fabricated using 0.5wt.% MWCNTs. These GFRP-MWCNTs bolted joints have been subjected seismic displacement time history generated from the numerical analysis. GFRP connection samples were subjected to static tension to failure to determine the post- seismic joint capacity. A 44% increase in seismic capacity and 250% improvement with the post-seismic capacities were observed compared to the Neat GFRP samples.

Rahulreddy Chennareddy, Xiaoyun Guo, Amr Riad, Mahmoud M. Reda Taha

Factors Affecting Microstructure and Phase Evolution of CaO-Al₂O₃-SiO₂-H₂O System

C-A-S-H (calcium aluminosilicate hydrate) gels are perceived to be one of the main products of alkali-activated materials (AAMs). Both the chemical compositions and curing conditions could have effects on the types and proportions of zeolite phases produced, which could affect AAMs' mechanical properties. Thus, it is vital to obtain these threshold values of CaO/SiO₂ ratios at which the amorphous gel tuns to the crystalline phase in this system; and analyse their changes to figure out the factors affecting the crystallizing process, which has a close connection with the microstructure and phase evolution. In this research, nano-SiO₂ and nano-Al₂O₃ are used to synthesize C-A-S-H using the hydrothermal method. XRD analysis is adopted to obtain the threshold values of CaO/SiO₂ ratios at which the amorphous gel tuns to the crystalline phase in the system. Combining XRD quantification (Rietveld method) and SEM, the changes of the relative contents of crystalline and amorphous phases and their microstructure will be obtained, revealing more of the roles of crystalline and amorphous phases in AAMs. The results show that the main products of the C-A-S-H system at room temperature are amorphous. The threshold values of the C-A-S-H system decrease with the increase of the curing temperature, while curing time has little effect. When the curing temperature rises from 60°C to 95°C, the threshold value decreases from 1.6 to 1.3. This research will provide a better understanding of the phase compositions and microstructures of hydration products in AAMs, which is of important significance to the material design.

Kunde Zhuang, Yuan Fang, Hongzhou Wang, Jingbin Yang, Chunyan Zhu, Linli Chi

3:40 pm - 4:00 pm

Nano-amended Cement Waste Forms for Nuclear Waste Storage

This paper reports on research investigating the incorporation of multiwalled carbon nanotubes (MWCNTs) in cement nuclear waste forms. The objective is to understand whether the resulting microstructural changes contribute to offsetting the leaching of a low-level nuclear waste, with an emphasis on technetium (Tc) in its mobile form. Over the last decade, it has been demonstrated that the incorporation of MWCNTs in ordinary Portland cement (OPC) paste and mortar, in concentrations as low as 0.05% in weight of cement, results in enhanced strength and stiffness properties and reduced porosity. It is hypothesized that these ameliorations can curtail Tc re-oxidation and leaching by controlling oxygen diffusion, which may be facilitated in the presence of open pores and cracks (e.g., due to shrinkage).

Leaching tests following the EPA 1315 procedure were performed on nine-day moist-cured OPC paste specimens. The samples were prepared using oxidized MWCNTs and 0.327 mg Tc/kg of cement. Four specimens were tested for each MWCNT concentration ranging from 0% (plain control specimens) to 0.05%. Preliminary results after 28 days of testing show a decrease in the average Tc leachate mass ranging from 30% to 47% for 0.005% and 0.05% MWCNT concentrations, respectively. Additional experimental evidence was obtained through porosity measurements and scanning electron microscopy imaging. This evidence supports the hypothesis that accelerated hydration and porosity reduction in MWCNT-amended specimens are key contributors to leaching reduction.

Fabio Matta, Mabel Cuellar-Azcarate, Enest Wylie, Yohanna Mejia, Shohana Iffat, Mithun Sikder, Brian Powell, Steven Serkiz, Juan Caicedo, Mohammed Baalousha

Application of Cellulose Nanocrystal (CNC) in Cementitious Materials – A Review

Cellulose nanocrystal (CNC) is a lightweight, hydrophilic, nano-sized renewable biomass material, with high tensile strength and high chemical stability. Comparing to "traditional" inorganic nanomaterials used to enhance cement-based material, CNC has many advantages including easy to disperse, low cost, and low health and environmental risks. Meanwhile, nanosized characteristics of CNCs can significantly enhance cement-based materials in terms of workability, microstructures, and mechanical properties. This review summarizes recent advances in development of applications in cementitious materials. A critical review of potential enhancing mechanisms is also presented, followed by a discussion of limitations and current challenges. In addition, a brief introduction of ongoing research on CNC manufacture and applications in Fujian Agriculture and Forestry University is presented.

Tengfei Fu, Demei Yu, Biao Huang, Renhui Qiu

Nanomontmorillonite / Fibre Cementitious Nanocomposites for Pervious Substrates

One of the challenges of cement science is to minimize clinker, responsible for 8% of the manmade CO₂ footprint globally and maximize other constituents emerging from waste, such ash fly ash. Nanotechnology can extend the limits of the permissible reduction in clinker through the wide range of optimization nanoparticles can offer in cementitious nanocomposites, such as the delivering of higher flexural strength, additional pozzolanic activity or seeding effects. In the present study, a reference formulation consisting of 60% Portland cement, 20% limestone and 20% fly ash by total mass of solids and 3% PVA fibres and 2% superplasticizer is optimized with two different types of nano-montmorillonite (nMt) dispersions; an organomodified one and an inorganic one. Flexural strength recorded at day 7, 28, 54 and 90 was improved after day 28 with the addition of inorganic nMt. Thermal gravimetric analyses carried out at day 7, 28, 54 and 90 coupled with XRD (at day 28) showed a distinctively enhanced pozzolanic reaction. Late age relative density measurements of the nMt cementitious nanocomposites showed higher values than these of the reference paste, which can be attributed to better particle packing. Mercury intrusion porosimetry measurements give support to the optimal nMt dosage, being 1% by total mass of binder and water impermeability tests (modified with BS EN 492:2012) suggest that inorganic nMt can be a very useful material for pervious substrates.

Styliani Papatzani, Sotirios Grammatikos, Kevin Paine

4:00 pm - 4:15 pm

Coffee Break

Venue: Conference Hall Lobby

Parallel Sessions

Venue: Conference Hall 4 - 6, Lakeside 2, Hong Kong Science Park

4:15 pm - 4:35 pm

Parallel Session 7
Session Chair :
Prof. Johann PLANK
Venue: Conference Hall 4

Mechanical Properties and Microstructure of Multiwalled Carbon Nanotube-reinforced Cementitious Composites at Sub-zero Temperature

This research investigated mechanical properties and microstructure of cementitious composites prepared with functionalized multiwalled carbon nanotubes (MWCNTs) and cured in low temperatures. MWCNTs was added to cement paste at the amount of 0, 0.05%, 0.1% and 0.2% by weight of cement, respectively. The flexural and compressive strengths of the hardened samples were determined after curing 35 days (7 days in deepfreeze + 28 days in standard curing condition). Mercury intrusion porosimetry (MIP) was used to analyze the microstructure of cement-MWCNTs systems. Research results showed that the addition of MWCNTs led to a pronounced increase, up to 16.9% and 11.6%, in flexural and compressive strength, respectively. Further, the additional MWCNTs were able to compensate for intensity loss caused by freezing to some extent. MIP analysis of the results indicates that total porosity of the mixes with CNTs was found to fine pore size distribution and reduce the porosity of cementitious composites. Moreover, an important effect of additional MWCNTs was a reduction in the number of meso pores.

Xinchun Guan, Shuai Bai

Parallel Session 8
Session Chair :
Prof. Viktor MECHTCHERINE
Venue: Conference Hall 5

(Invited Speech)
Influence of Rheology Modifying Admixtures on Hydration of Cementitious Suspensions

The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has an enormous influence on the early hydration of cement. The hydration is retarded and the timing of formation and the morphology of hydrates is affected. This short paper presents experimental results about the influence of delayed addition time of PCE SPs on hydration of cement and alite pastes, investigated by isothermal heat flow calorimetry. For cement as well as for alite pastes the hydration is retarded with SP, whereby the high charge PCE has a stronger retarding effect than the low charge PCE. The retardation caused by PCE is much more pronounced for alite than for cement mixes. If PCE is added later to the mix, the induction period is shortened and the hydration is accelerated compared to simultaneous addition. This applies for cement and alite pastes. With delayed PCE addition the alite shows a clearly less retarded setting and main hydration than after simultaneous addition. It is obvious that for alite pastes there is less retardation the later the addition of SP.

Claudia Crasselt, Wolfram Schmidt, Heinz Sturm

Parallel Session 9
Session Chair :
Dr. Wengui LI
Venue: Conference Hall 6

Characterization on Cement Paste Using Nanoindentation, Modulus Mapping and Peak-force QNM

Three types of nanomechanical methods including static nanoindentation, modulus mapping and peak-force quantitative nanomechanical mapping (QNM) were applied to investigate the quantitative nanomechanical properties of the same indent location in hardened cement paste. Compared to the nanoindentation, modulus mapping and peak-force QNM allow for evaluating local mechanical properties of a smaller area with higher resolution. Besides, the ranges of elastic modulus distribution measured by modulus mapping and peak-force QNM are relatively greater than that obtained from nanoindentation, which may be due to a result of the shaper probe and local confinement effect between multiple phases. Moreover, the average value of elastic modulus obtained using peak-force QNM were consistent with those obtained by modulus mapping, while the different in modulus probability distribution could be related to the different nanomechancial theories and contact forces. The probability distributions of elastic modulus measured using nanomechanical methods to provide a basis for the different types of phases existing in cement paste. Based on the observation with high spatial resolution, cement paste can be likely found as nanocalse granular material, in which different submicron scale or basic nanoscale grain units pack together. It indicates that the peak-force QNM can effectively provide an effective insight in to the nanostructure characteristic and corresponding nanomechanical properties of cement paste.

Wengui Li

4:35 pm - 4:55 pm

An Overview of the Application of Graphene Nanoplatelet in Cement Composites

Graphene has been attracting increasing interests from researchers and practitioners in construction industry, attributed to its excellent mechanical, electrical and thermal performances. Previous studies have demonstrated the viability of using graphene or graphene oxide in reinforcing cement pastes in terms of compressive and tensile strength. However, the high cost of such materials restrains the wide application to concrete, the most widely used construction material globally. Such factors have driven the study into using graphene nanoplatelet (GNP), a low cost material, as reinforcement in cement composites. This paper will review the research activities in dispersing GNP and the advantages of GNP-cement composites. The effectiveness of using ultra-sonication and superplasticizer in dispersing GNP in water is characterized by UV-spectrophotometer, aiming to determine the optimum sonication time and superplasticizer dosage. The influence of GNP as barrier to harmful ions is discussed and the reducing effectiveness will be compared to a modified analytical theory. Another benefit brought to concrete by GNP is the piezo-resistivity, which can enable the traditional building material to sense its own mechanical deformation and damage. This paper will also present the influence of GNP addition on the sensitivity of this nanocomposites, under compressive or tensile stress. Overall, our studies have identified and characterized the advantages led to concrete by a small addition of GNP. Future research direction and approaches to investigate the application of GNP to concrete will also be presented in this paper.

Hongjian Du, Sze Dai Pang

High Performance Cement-based Composites with Aluminum Oxide Nano-fibers

Aluminum oxide nano particles can be used in small quantities to create high performance or ultra-high performance cementitious composites. High volumes, up to 20% of supplementary cementitious materials such as silica fume or metakaolin, are often used to achieve the high strength in high performance and ultra-high performance cementitious composites. This research demonstrates that when aluminum oxide nano-fibers are used in cement based composites, the required high strength, up to 175 MPa, can be achieved at very low dosages of silica fume and metakaolin. This effect is achieved at low water to cementitious materials ratio, selection of cement, along with the seeding effect and reinforcing of calcium silicate hydrates by the nano-fibers. Furthermore, the ultra-high performance cement-based composite (UHPC) can include polyethylene fibers which provide enhanced strain hardening and multi-cracking behavior. These composites were tested to determine if the improved durability due to superhydrophobic modification. However, results demonstrate that superhydrophobic admixtures may reduce the performance of developed composites with Al2O3 nano-fibers. High performance cementitious materials are critical for the next generation of infrastructure. The incorporation of small quantities of aluminum oxide nano-fibers in UHPC may prove to be a viable option.

Scott Muzenski, Ismael Flores-Vivian, Konstantin Sobolev

Cement Composites with Bismuth Oxide Nanoparticles for X-ray Shielding

In this research work, the X-ray shielding properties of new cement-composites produced with Bismuth oxide nanoparticles have been investigated.

Bismuth - a cheap, non-toxic and biocompatible element, characterized by having a high atomic number Z (Z=83) - has been used as additive and the study has been carried out on samples with different percentages of bismuth oxide nanoparticles (1%, 5% and 10% with respect the weight of cement for each composition), by using a CT-Scanner for medical tomography. Samples have been exposed to the ionising radiations afterwards the 28 days curing time for the complete cement hydration.

Through the processing of the data acquired by the CT scanner it has been possible to appreciate the good reactivity of the new cement composites. The radio-opacity of the samples is directly related to the content of bismuth oxide nanoparticles: the higher the percentage, the opaquer they are. Furthermore, by analysing the averages of measurable ROI data for single slice (distance per slice: 4/10 mm), it has been possible evaluate the good homogeneous distribution of bismuth oxide nanoparticles added for each batch.

The shielding properties shown by the experimental samples during the tests allow to state that bismuth can be used as a "smart" nanomaterial in cement-based composites, thanks to its chemical-physical properties and above all its non-hazardousness and its low cost.

Luciana Restuccia, Alberto Favero, Giuseppe Andrea Ferro, Pravin Jagdale, G. Cavalot

4:55 pm - 5:15 pm

Influence of PCE Kind and Dosage on Ettringite crystallization Performed Under Terrestrial and Microgravity Conditions

Early ettringite crystallization in the presence of 2 chemically different polycarboxylate superplasticizers was studied by hydrating a commercial portland cement (CEM I 52.5 N) for 10 seconds. It was found that the presence of polycarboxylate superplasticizers leads to ettringite crystals which are longer, yet slimmer (higher aspect ratio), compared with the crystals obtained from neat cement paste. This finding suggests that the polycarboxylate (PCE) polymers predominantly adsorb on the lateral faces of the hexagonal-prismatic crystals of ettringite. For the methacrylate-based PCE, this effect increases with increasing superplasticizer dosage, whereas for the IPEG-PCE, the effect achieved at a very low dosage (0.05%) is not altered when dosage increases. The behaviors of both PCE polymers can be explained by their different adsorption behavior, whereby the IPEG-PCE reached the saturated adsorbed amount at much lower dosage than the MPEG-PCE. Microgravity only has a minor effect on the growth of ettringite. There, generally smaller crystals are observed.

Lei Lei, Markus Schonlein, Johann Plank

Super Elastic Oleogel Enhanced by Tricalcium Silicate Released Nanoparticles with High Recoverability and Thermal Stability

Guoxing Sun, Lefan Li, Rui Liang

Cementitious Sensors with Acoustic Stopbands Using Carbon Nanotubes

Shreya Vemuganti, John Stormont, Sang M. Han, Thomas Dewers, Laura J. Pyrak-Nolte, Mahmoud Reda Taha

5:15 pm - 5:35 pm

Pore Structure and Physical Properties of Concrete Prepared with Nano-silica Improved Recycled Aggregate

Herein, authors investigated the pore structure and physical properties of nano-silica improved recycled aggregates (SI-RAs) and the concrete prepared by SI-RAs. Firstly, recycled aggregates (RAs) were soaked into nano-SiO2 solutions with five concentrations (0%,1.0%,1.5%,2%,2.5%) to obtain SI-RAs. Afterwards, the crushing index and water absorption of SI-RAs were determined to identify the optimal soaking concentration. Results showed SI-RAs soaked by the optimal concentration (2%) achieved 28% reduction in crushing index and 20% decrease in water absorption in comparison with RAs. Furthermore, the compressive strength of concrete incorporating 100% SI-RAs achieved a 20% increase in the compressive strength. As the consequence, the nano-silica soaking method was verified to effectively strengthen RAs and compensate compressive strength loss of concrete incorporating with RAs.

Xuefei Chen, Zhiyuan Yang, Shicong Kou

Nano-modified Recycled Aggregate Concrete: Current Status and Research Progress

As one of the most interesting topics in the materials field, nanotechnology has attracted increasingly more attention in the area of concrete research due to many superior properties of nanomaterials, such as volume effect, surface effect and size effect. The application of nanomaterials in recycled aggregate concrete (RAC) has also been studied to improve its quality, which is generally poorer relative to that of the natural concrete with the same mix proportion. The main aim is to broad the use of recycled aggregate (RA) in concrete production. In this paper, nanomaterials and nanotechnology were firstly introduced, and then existing problems of RAC were discussed. In the third part, a review of the research progress of nano-modified RAC was conducted. In the fourth part, the modification mechanisms of nanomaterials in cement-based materials and the interfacial transition zone (ITZ) were analysed. The review show that nanomaterials like nano-SiO₂, nano-CaCO₃ can improve mechanical and durability properties of RAC significantly. The properties of RAC can be comparable with those of conventional concrete, since the use of nanomaterials can promote the hydration reaction, react with cement based materials, fill pores and control the process of crystallization, the improvement is more obvious to RAC of low strength at an early age. The compressive strength increases with the substitution rate of nanomaterials. The 7-day compressive strength could increase by 20% and the 28-day compressive strength equalizes with natural concrete with incorporation of 3% nano-silica in RAC. However, nanomaterials are prone to agglomerate that difficult to be stirred evenly, the workability of RAC is affected largely. Some suggestions are provided at last for future researches about nanotechnology for RAC.

Jianzhuang Xiao, Xianglei Chen, Zhenhua Duan, Tan Li

4 Dec 2018 (Tuesday)

TIME

EVENT

Keynote Speech
Session Chair: Prof. Surendra P. SHAH

Venue: Charles K. Kao Auditorium, Hong Kong Science Park

9:15 am - 9:50 am

Cement Hydration Studied Under Zero Gravity Condition

Under zero gravity, chemical reactions in solution are considerably slowed down as they are controlled by diffusion only and no convection occurs. Furthermore, larger crystals will not precipitate from the solution. Cement hydration in principle involves a dissolution – precipitation process which should be significantly affected by the absence of gravity. To find out more, a series of experiments was performed on parabolic flights which offer short periods (~ 25 seconds) of zero gravity.

At first, pure C₃S was hydrated during the zero gravity period. Most surprisingly, globular nano particles (~ 20 - 60 nm) were detected as the very first hydration product of C₃S. This observation led to a series of experiments which demonstrated that also under terrestrial conditions, such droplets constitute the metastable precursor from which later nanofoils of C-S-H and finally the well-known C-S-H needles present in hardened cement develop.

In a second experiment, ettringite was crystallized from Ca(OH)₂ and Al₂(SO₄)₃ solutions. Here it was found that smaller, yet more abundant crystals develop compared to terrestrial conditions. The reason is that under zero gravity, the oversaturation period is prolonged, therefore more nuclei can develop while their growth then is more restricted as the ions available will be consumed by more nuclei.

Furthermore, monosulfo aluminate and C₄AH₁₃ were synthesized under short-term zero gravity. For AFm it was found that it crystallizes as nano platelets which again are considerably smaller than under normal gravity. Similarly, C₄AH₁₃ crystallizes in a dense network of nanothin foils (d ~ 5 nm).

Overall, the experiments under zero gravity gave unprecedented insight into the very early nucleation and crystal growth occurring in cement hydration. They allow us to better understand how cement hydrates actually are formed which under earthen conditions analytically is hard to follow, considering the extremely fast kinetics of early cement hydration. As such, these experiments also provide inspiration on how to optimize concrete through intelligent crystal engineering.

Prof. Johann PLANK

Chair for Construction Chemistry, Department of Chemistry
Technology University Munich, Germany

Professor Dr. Dipl. – Chem. Johann Plank is full professor for Construction Chemistry and head of the Institute for Inorganic Chemistry at Technical University Munich. He studied chemistry in Regensburg, Germany and in 1980 eaned a Ph.D. degree there. He then joined SKW Trostberg as a research group leader in construction polymers. He founded SKW's oilfield chemicals business and in 1997 became General Manager of SKW Construction Polymers GmbH. In 2001, he joined Technical University Munich, Germany, as a full professor for Construction Chemistry. His current research interests include cement and admixture chemistry for concrete, gypsum, mortar and oil well cementing. Prof. Plank has published about 400 scientific papers, holds 40 patents in the field of construction admixtures and has received many awards and honor professorships from universities in Japan, China, Singapore and Thailand.

Chair for Construction Chemistry, Department of Chemistry
Technology University Munich, Germany

9:50 am - 10:25 pm

Advanced Cement-based Materials through Nanotechnology

In this presentation, advanced cement-based materials through application of nanotechnology will be introduced. One example is to use cement to generate 5 nm nanoparticles to strengthen the hydrogel. By adding 5-nm inorganic particles in organic matrix, hydrogels with the best all-round performance in the world has been successfully developed in aspects of strength, elastic recovery and ultimate stretch ratio. Also, by adding organic or inorganic nano particles into cement based materials, the flexural strength of the cement-based materials increased significantly. For cement paste, bending strength is increased by three times without lowering the compressive strength. Moreover, with newly developed inorganic-organic combined nano particles, the hydration heat of cement-based materials can be reduced and their toughness will be improved without degrade their compressive properties. Finally, the high modulus concrete developed through the addition of nano particles will be introduced.

Prof. Zongjin LI

Chair Professor, Institute of Applied Physics and Materials Engineering
University of Macau, Macau

Prof. Zongjin Li is Chair Professor at Institute of Applied Physics and Materials Engineering at University of Macau (UM). He joined UM after his service at The Hong Kong University of Science and Technology from 1994 to 2016. He received his B.E. from Zhejiang University, Hongzhou, China in 1982 and obtained both his M.S. and PhD from Northwesten University, Chicago, U.S.A, in 1990 in 1993, respectively. He is a fellow of American Concrete Institute and a registered professional engineer in Hong Kong, China. He is a member of committees of ISO/TC71, First Vice Chair of China Group of RILEM and Founding President of ACI China Chapter.

He has done extensive researches in the area of cement-based materials and non-destructive evaluations. As the chief scientist, he has led a China Key National Basic Research Project (973), 'Basic study on environmentally friendly contemporary concrete', which has made a great contributions to advance concrete technology in China. As the founding chair of Gordon Research Conference, 'Advanced Materials for Sustainable Infrastructure Development' in 2014, he has brought the research conference of building materials into a higher scientific level.

He has published 5 technical books, in which 'Advanced Concrete Technology' published by John Wiley has been collected by many national libraries and most major university libraries and used by many universities as text or reference books for civil engineering. He has also published more than 400 technical papers with a SCI H-index of 38 and Scopus H-index of 41. In 2016, he has been selected as the one of the 150 most cited authors in Civil engineering field. He has also been awarded five US and seven Chinese patents. Three of his patents have been developed into commercial products.

He received the Arthur R. Anderson Medal from American Concrete Institute in 2017 and Distinguished Visiting Fellowship Award from British Royal Academy of Engineering in 2014.

Chair Professor, Institute of Applied Physics and Materials Engineering
University of Macau, Macau

10:25 am - 11:00 am

Quest for the Finest Concrete: How Nanotechnology Can Change the Concrete World

This presentation reviews recent developments in the field of nanotechnology applied to concrete. Various pathways for effective production of nano-SiO₂ and CSH seeds are discussed. Specifically, the aspects of development and fine tuning of nano-seed products for nano-engineered concrete are discussed. It is demonstrated that the mechano-chemical activation of portland cement or fly ash systems with superplasticizer and nano-SiO₂ in aqueous solution enables the formation of CSH seed product capable of considerable enhancement of strength performance of portland cement and blended binders. Experimental results demonstrate an increase in the compressive and flexural strength of mortars with developed nano-seed particles. Furthermore, it was demonstrated that the boost of performance of cementitious systems including self-consolidating concrete with activated components is due to the presence of super-reactive ultrafine and nano-seed particles.

Prof. Konstantin SOBOLEV

Professor, Department of Civil and Environmental Engineering, CEAS
University of Wisconsin-Milwaukee, USA

Dr. Konstantin Sobolev is a Professor and Chairman, Department of Civil and Environmental Engineering, College of Engineering & Applied Science, University of Wisconsin-Milwaukee, WI (USA). After receiving his B.S./M.S. degree from the Moscow State Civil Engineering University (Russia), he eaned a Ph.D. in 1993 from the Research Institute of Concrete and Reinforced Concrete (Russia). Since then Dr. Sobolev has been developing innovative and effective technologies for advanced materials including high-performance cement and concrete. Dr. Sobolev has published more than 180 articles in research jounals and proceedings of scientific conferences, in English, Russian, Spanish and Turkish. He has presented scientific papers in the Americas, Middle East, Europe and Asia. Dr. Sobolev is a member of Mexican Academy of Sciences (AMC), a fellow of the American Concrete Institute (ACI), a founding chair of ACI committee 241(236D) "Nanotechnology of Concrete," and a chair of "Nanotechnology-Based Concrete Materials" subcommittee AFN10(1) of TRB - Transportation Research Board of National Academies (USA).

Dr. Sobolev's current research interests are in application of nano-admixtures and nanotechnology in cement and concrete; application of evolutionary algorithms; modeling of dense packings of particulate materials; design, modeling and application of high-strength and high-performance materials, materials with photocatalytic properties, super-hydrophobic materials, smart stress-sensing materials.

Professor, Department of Civil and Environmental Engineering, CEAS
University of Wisconsin-Milwaukee, USA

11:00 am - 11:15 am

Coffee Break

Venue: Charles K. Kao Auditorium Foyer

Parallel Sessions

Venue: Conference Hall 4 - 6, Lakeside 2, Hong Kong Science Park

11:15 am - 11:35 am

Parallel Session 1
Session Chair :
Dr. Congcong JIANG
Venue: Conference Hall 4

(Invited Speech)
Rhodamine B Removal of TiO₂@SiO₂ Core-shell Nanocomposites Coated to Buildings: Influence of SiO₂ Coating Thickness

Surface application of photocatalyst in cement-based materials could endow with photocatalytic properties, however, weak adhesion between photocatalyst coatings and the substrates may result in poor durability in outdoor environment. In the study, TiO₂@SiO₂ core-shell nanocomposites with different coating thicknesses were synthesized by varying experiment parameters. The photocatalytic activities (rhodamine B removal efficiency) of theses samples were measured. The results indicate that SiO₂ coating accelerated the RhB removal to a certain extent owing to the its high surface area, however, more SiO₂ coating decreased the photocatalytic efficiencies. After the two samples were coated on white cement paste, RhB degradation rates were tested, and the values were higher than that of P25-coated paste. After curing, their degradation rates significantly increased. After an accelerated weather process, the RhB removals of all specimens were decreased, among them, and the reduction of WC P25 was obvious. Meanwhile, pastes coated samples with more SiO₂ coating have the minimum reduction value. TiO₂@SiO₂ core-shell nanocomposites endowed the cement matrix with photocatalytic property and improved durability of photocatalytic property in particular for a harsh weathering process.

Dan Wang, Pengkun Hou, Lina Zhang, Ning Xie, Xin Cheng

Parallel Session 2
Session Chair :
Prof. Zongjin LI
Venue: Conference Hall 5

(Invited Speech)
The Pore Structure of Hydrating Cementitious Materials Visualized and Studied by NMR and MIP

During cement hydration the pore structure is continuously changing and becoming denser. It is difficult to study this porosity in time without destroying the samples and stopping hydration. Nuclear Magnetic Resonance (NMR) can be applied to non-destructively study not only the total water content but also the pore size distribution. In this research, the T2 relaxation times were studied, which are proportional to the pore size distribution. The obtained pore sizes are compared to different models found in literature: the Powers and Brownyard, Feldman and Sereda and the Jennings Colloidal Model (CM-II) model. Furthermore, the obtained results are compared with Mercury Intrusion Porosimetry (MIP) data on the same samples. A good correlation was obtained when using planar pores for the T2 experiments. The main pore sizes found are in the range of 1.5-2 nm and of 8-12 nm reflecting the gel pores. In addition some bigger capillary pores (10 to 1000 nm) are found. These correspond to values used in the models and results obtained with MIP on hardened samples with and without superabsorbent polymers. NMR is an effective technique to study the water signals in different pores as a function of time and to relate it to the pore structure development.

Didier Snoeck, Leo Pel, Nele De Belie

Parallel Session 3
Session Chair :
Prof. C. S. Poon
Venue: Conference Hall 6

Understanding of the Photocatalytic Products of NOx Degradation in TiO₂-based Cementitious Materials

Cementitious materials, by incorporating photocatalytic anatase titanium dioxide (TiO₂) nanoparticles, can effectively remove smog-producing nitrogen oxide species (NOx) from the atmosphere. In the presence of UV light, TiO₂ catalyzes reactions that break down and oxidize NOx to nitrogen (N) species, where it is believed that the photocatalytic products nitrite (NO₂-) and nitrate (NO₃-) ions remain on and within the near-surface substrate. However, few studies have investigated the exact destination of the nitrite and nitrate ions in this region. To understand their interactions with cementitious phases, various characterization methods are employed in this paper. The X-ray diffraction (XRD) results show new peaks in the samples after NOx exposure, which are attributed to calcium nitrite or calcium nitrate. The Fourier Transform Infrared Spectroscopy (FTIR) results show the calcium nitrate is formed after NOx exposure. However, the FTIR peaks may be influenced by their coincidence with those for calcium hydroxide.

Qingxu Jin, Michael VanderZwaag, Sarah Horden, Yuanzhi Tang, Kimberly Kurtis

11:35 am - 11:55 am

Novel Anti-bacterial and Anti-dust Coating with Nanoparticles for Air Ducting

Indoor air quality (IAQ) is a popular issue inside the buildings and occupants are recognizing a growing need for controlling the growth and the spread of bacteria in air ducting in buildings. Cleaning alone may not be useful for removal of the microbes, and especially for air ducting, not to mention the inconvenience cleaning steps resulting in expensive cleaning fee due to dust and dirt aggregation in air pipe. This study is to develop a novel anti-bacterial and anti-dust coating with nanoparticles applied in the inner surface of air ducting to reduce dust aggregation. This can also prevent the growth of bacteria, mold and midew that can cause stains and odors on the inner surface of air ducting. The coating exhibits good antibacterial performance with at least 99% reduction of Staphylococcus aureus and Escherichia coli. The coating also displays superior dust-free function with eliminating static charge and reducing dust aggregation in the inner surface of air ducting. Moreover, the developed coating has excellent acid and alkali resistance with the incorporation of nanotechnology. No abnormal appearance or loss of adhesion was noticed after 5% H2SO4 solution/5% NaOH solution on the surface of coating for 24 hrs. The coating can be applied on metal surface directly and was not picked off after 180 degree bend (1T bend) of the coated metal. The hardness of the coating can achieve at least 2H or above. These superior performances, easy application and cost effective features of the coating can enable the buildings with air pipe clean for long period and the cleaning frequency of air ducting will be decreased with the saving of cleaning fee.

Su Ping Bao, Wen Jun Luo, Man Lung Sham

Upscaling Creep Property of Hardened Cement Pastes Considering Imperfect Interface Effect

Interfaces always exist in composite materials between the inclusions and the matrix. These interfaces might not be well bonded leading to imperfect interface, which would no doubt affect the mechanical properties of the composites such as cementitious materials. In this study, the effective creep properties of cement pastes with w/c ratios of 0.3, 0.4, and 0.5 are homogenized from the calcium silicate hydrate (CSH) scale. The Mori-Tanaka (M-T) scheme with the assumptions of perfect and imperfect interfaces between the inclusions and the matrix is employed for the prediction. The imperfect interface is characterized by spring-layers of vanishing thickness in the tangential directions, and an interface sliding parameter (π/d) is used to reflect the imperfection of the interfaces. The predicted results are then compared to the measured one by instrumented indentation. It is found that the perfect interface condition would underestimate the effective creep property by 44.3 %~84.6 %, and the underestimation increases with increasing w/c ratio. Whereas, the imperfect interface condition can predict the creep property of cement pastes very well. This indicates that the imperfect interfaces might exist in cement pastes between the matrix and the inclusions at different scales.

Ya Wei, Siming Liang, Zehong Wu

Indoor Photocatalytic Paints: Air Decontamination and Mold Growth Control Assessment

Photocatalytic building materials containing TiO₂ were extensively studied for outdoor applications using solar radiation. Nowadays, the market offers a wide variety of these materials with self-cleaning and air purification functionalities. However, visible light heterogeneous photocatalysis applied in indoor construction materials was less developed. The objective of this work is to investigate the photocatalytic performance of modified TiO₂ with UV-visible light absorption replacing the pigments in indoor wall paint formulations. To achieve this goal, two model indoor air pollutants were selected: a VOC and an environmental mold. On the one hand, the photocatalytic oxidation of acetaldehyde in gas phase was carried out using different photocatalytic paint formulations varying the type of modified TiO₂ (carbon doped, nitrogen doped and undoped one) and its amounts (12-18% w/w). The air decontamination process was conducted using regular indoor light, first in a flat plate laboratory scale photoreactor, and later in a chamber bench scale photoreactor simulating a room. In the lab scale system the optimal photocatalytic paint formulation for the acetaldehyde oxidation was determined, being the paint containing 18% w/w carbon doped TiO₂ the best one. Then, this paint formulation was tested in the reaction chamber varying the main environmental conditions that affect the photocatalytic process: air change rate, irradiance, relative humidity and initial acetaldehyde concentration. On the other hand, the fungicide effect of the optimal paint formulation was evaluated. The conidia of Aspergillus niger was selected as the model microorganism and the inactivation tests were performed under UV and visible light. It was found a progressive conidia damage on the photocatalytic paint surfaces under both illumination types, which can continue even after the irradiation tests. The results reveal the air purifying and fungi growth control power of photocatalytic paints under indoor conditions.

Maria de los Milagros Ballari, Federico Salvadores, Silvia Mercedes Zacarias, Orlando Mario Alfano

11:55 am - 12:15 pm

Modifications on the Microstructural Properties of a Graphene Oxide-cement Composite

The modifications on the microsturctural properties of cement paste samples by the incorporation of 0.05 wt% of ultra highly concentrated single-layer graphene oxide solution in aqueous medium after 3, 28, 56 and 91 days of curing were studied by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), N2 adsorption and scanning electron microscopy (SEM). Thermogravimetric and XRD analysis demonstrated that the presence GO accelerates the degree of hydration and increases the amount of cement hydration products at the early ages. The N2 adsorption studies reveals how the high aspect ratio of GO found to be detrimental in increasing the surface area and the cumulative pore volume of the GO-Cement composite. SEM analysis showed that the nucleation effects of GO caused the formation of more cement hydration products and hence a denser morphology. Based on the results, the very high surface area and nucleation affects of effects of GO nanoreinforcement can modify the microstructural properties by forming more cement hydration products in the early stages.

Antony Joseph, Suad Al-Bahar, Amer Al-Arbeed, Fatemah Al-Abkal

Nanoscale Structural Investigation of Activated Ground Granulated Blast-funace Slag: An Extended X-ray Absorption Fine Structure (EXAFS) Study

Yeonung Jeong, Sung-Hoon Kang, Juhyuk Moon

TiO₂ Containing Coatings - Photocatalytic and Optical-radiative Properties

A manifold positive contribution to climate change mitigation and in the improvement of air quality of built environments can be provided by the use of titanium dioxide (TiO2), also - but not exclusively - as coating for building envelope materials, to spread its beneficial effect on the largest surface area possible. The benefits in applying TiO2 coatings - containing in particular the anatase phase - rely, first of all, on the UV-activated photocatalytic degradation of pollutants mediated by it, which can mitigate pollution arising from industrial sources, heating, and transportation. Moreover, changes in wettability upon UV irradiation lead to a superhydrophilic state which, coupled with photocatalysis, results in the so-called self-cleaning effect, allowing materials to retain a cleaner and more reflective surface over time. Reducing the impact of aging on the optical-radiative performance of built environment surfaces has a strong influence on the thermal comfort and energy consumption of buildings. In this contribution we describe an unexpected increase in anatase near infrared (NIR) reflectance observed during environmental exposure. We unveil its complex mechanisms, based on the contact with nitric acid generated by NOx photocatalytic degradation, which causes partial reduction and decrease in crystallinity to TiO2. This finding may open the way for introducing multiple environmentally beneficial effects on TiO2 pollutants degradation, self-cleaning, and energy performance.

MariaPia Pedeferri, Maria Vittoria Diamanti, Dario Borroni, Riccardo Paolini

12:15 pm - 12:35 pm

Nano-SiO₂ Modified Chemical Conversion Coating on building Steels for Improving the Concrete Durability

Congcong Jiang, Shifeng Huang, Guozhong Li, Xiuzhi Zhang, Xin Cheng

Characterization of Self-healing Reaction Products in Cementitious Mortars via Nano-Indentation: A Cross-collaboration in the Framework of COST Action SARCOS

This paper aims at paving the way to a comprehensive investigation of self-healing in cement based materials trying to correlate not only amount of crack sealing with recovery of mechanical properties but also with the signature properties of healing products. This will allow the healing to be designed as a function of the properties to be recovered, as for the intended application, and healing concepts to be incorporated into durability based design approaches. Prismatic mortar specimens (40 x 40 x 160 mm3) have been prepared with two different paste mixes, with and without a healing agent (crystalline admixture), formulated from concrete mixes employed in previous investigations by the authors. Specimens have been cracked in bending at 28 days age, up to complete breakage into two halves. From the broken specimen halves “tile” samples were cut and cured in open air and under water. At selected exposure durations nanoindentation on the crack surfaces has been performed to identify the intrinsic signature properties of self-healing products. Companion specimens, with discrete fibre reinforcement to control the crack, have been pre-damaged in 3-point bending up to prescribed crack width and subjected to same exposure conditions of the specimen halves to be nanoindented. After same durations, crack sealed has been visually assessed and quantified through image analysis in order to define a crack sealing index. Correlation among recovery of mechanical properties, crack sealing, chemical nature of healing products and nano-scale properties of the same products will allow to have a thorough and deep insight into the healing mechanisms.

Liberato Ferrara, Spyridon Kassavetis, Francesco Lo Monte, Maria Stefanidou

Durability of TiO₂ Cement-based Materials

MariaPia Pedeferri, Maria Vittoria Diamanti, Nicoletta Luongo, Silvia Massari, Bruno Daniotti, Sonia Lupica Spagnolo

12:35 pm - 2:00 pm

Luncheon

Venue: ClubOne, Hong Kong Science Park

Parallel Sessions

Venue: Conference Hall 4 - 6, Lakeside 2, Hong Kong Science Park

2:00 pm - 2:20 pm

Parallel Session 4
Session Chair :
Prof. Yuxi ZHAO
Venue: Conference Hall 4

(Invited Speech)
Effect of Nano Materials on Cement Mechanical Properties and Hydration Process: A Review

Pengkun Hou, Xinming Wang, Xin Cheng

Parallel Session 5
Session Chair :
Prof. Jiri NEMECEK
Venue: Conference Hall 5

(Invited Speech)
Fracture Properties of Hydrated Cement Paste Constitutents Assessed with Microbending Tests and Nanoindentation

Nanoindentation and Focused Ion Beam (FIB) milling are used to study fracture properties of distinct microscopic phases of hydrated cement paste at the level of a few micrometers. Micro-beams are milled by FIB with high precision using small ion currents and long milling times in individual phases of cement paste. Then, the micro-beams are loaded by the nanoindenter at the free end, bent and finally broken. The fracture of the phases is more or less brittle but in some cases also descending branch of the load-deflection diagram can be captured with the displacement control. The load-deflection diagram captured during the tests allows to assess both elastic and inelastic properties including fracture energy and tensile strength of the microlevel phases that were, so far, investigated very rarely. Compared to macroscopic characteristics where the tensile strength of cement paste exhibits values in the order of a few MPa, the microscopic strength of individual phases is much higher, in the order of hundreds of MPa. The results are consistent with atomistic simulations and multiscale modeling. The difference is caused by the hierarchical character of the composite that is characterized with multiple defects in the form of pores, cracks and crystalline inclusions at higher composite levels that are not present at the micrometer scale within a single phase.

Jiri Nemecek, Vit Smilauer, Jan Manak

Parallel Session 6
Session Chair :
Dr. Florence SANCHEZ
Venue: Conference Hall 6

(Invited Speech)
Nano-engineering of the Mechanical Properties of Tobermorite-14Å with Graphene via Molecular Dynamics Simulations

Nanotechnology has opened the door for enhancing the strength of cement-based materials by tuning the molecular-level mechanical properties of calcium-silicate-hydrate (C-S-H), the main binding phase in Portland cement pastes. One strategy to enhance the mechanical properties of C-S-H is to use nano-reinforcements such as graphene-based nanomaterials. In this study, molecular dynamics simulations were used to investigate the tensile properties of tobermorite-14Å (T14) reinforced with a single graphene nanosheet (GNS). The fracture strength of the T14/GNS composite was increased, and the in-plane normal and shear stiffness of the composite were also enhanced. Graphene had, however, no effect on the out-of-plane stiffness of the composite. The fracture strength results from MD simulations and micromechanics-based volume fraction method showed similar values.

Florence Sanchez, Baig Al Muhit

2:20 pm - 2:40 pm

Elastic and Viscoelastic Properties of Nanoclay Modified Oil Well Cement

Type-G cement is the most used cement in oil-well cementing (OWC) applications. Nanoclay has been widely promoted as silica and alumina particles that can improve cement hydration and potentially limit creep. In this investigation, type-G cement mixed with 1.0 wt.%, 3.0 wt.% and 5.0 wt.% nanoclay and with water/cement ratio of 0.45 was prepared and cured for 7 days under high temperature and high pressure of 80 oC and 1500 psi respectively. Dynamic mechanical analysis (DMA), scanning electron microscope (SEM) and X-Ray Diffraction (XRD) measurements were performed to realize stiffness and creep compliance evolution of OWC incorporating nanoclay. SEM and XRD observations are used to explain the microstructural changes that take place in OWC with the increase of nanoclay content. It is suggested that relatively high nanoclay content can increase and maintain stiffness growth while limiting creep of OWC cured under high temperature and pressure.

Muhammad Rahman, Shreya Vemuganti, Mahmoud Reda Taha

Effect of Nano-SiO₂ on Mechanical and Fracture Properties of PVA Fibre Reinforced High-volume Fly Ash Cement Mortar

Using a high dosage of fly ash in concrete is an effective approach to control the heat release rate, reduce the material cost and enhance the sustainability. However, high-volume fly ash (HVFA) concrete often exhibits inadequate mechanical and fractural properties at the early stage up to 28 days, which limits the material to non-structural or semi-structural applications. In this paper, to further improve the performance of Polyvinyl alcohol (PVA) fibre reinforced cement-based mortar containing high-volume fly ash (PVA/HVFAM), a series of mortars was tested to investigate the effect of nano-SiO2 (NS) on the mechanical strength and fracture toughness of PVA/HVFAM. Four NS/binder weight ratios of 0% 0.5%, 1.0% and 1.5% were adopted, with the fly ash/binder ratio fixed at 50% by weight and the PVA fibre volume fractions fixed at 0.5%. Experimental results showed that the addition of NS significantly improved the 28-day mechanical strength, fracture properties and modulus of elasticity of PVA/HVFAM. By characterizing the microstructure using scanning electron microscopy, it was found that the NS contributes to forming a dense layer of hydration product on the fibre/matrix interface, which is responsible for the considerable enhancement of mechanical properties.

Jing Yu, Gengying Li

Experimental Investigations of Nano Insulation Materials for Application in Building Constructions

Building constructions and their corresponding building materials need to fulfil several requirements with respect to their miscellaneous properties and intended functions. As the world’s attention during the last decades is drawn stronger toward energy efficiency and lowered negative environmental impact within several sectors, these aspects are also becoming more important to address for the building and construction sector. In this context, the thermal resistance of the building envelope is playing a crucial role. Thus, new high-performance thermal insulation materials are being developed. These are often termed as super insulation materials (SIM) with thermal conductivity values at least below the value for stagnant air, i.e. about 26 mW/(mK), and with other borderline values (e.g. 20, 15, 10, 5 and 4 mW/(mK)) also used depending on if the SIM is achieving its low thermal conductivity with air at atmospheric pressure, low-conducting gases (e.g. Ar, Kr or Xe) or vacuum. In this work we present the attempts to make SIMs by fabricating materials with nanopores filled with air at atmospheric pressure, i.e. nano insulation materials (NIM). A possible NIM candidate may be hollow silica nanospheres (HSNS) synthesized by a sacrificial template method, where the sphere diameter and shell thickness are being attempted optimized to reach as low thermal conductivity as possible. In addition, as concrete is one of the world’s most widely used construction materials, we will have a look into our ongoing efforts of increasing the thermal resistance of concrete while still maintaining as much mechanical strength as possible by manufacturing concrete samples with a high volume loading of aerogel granules, i.e. aerogel-incorporated concrete (AIC).

Bjøn Petter Jelle, Sohrab Alex Mofid, Tao Gao, Serina Ng

2:40 pm - 3:00 pm

Using Rheology to Design the Mix Proportions of Semi-flow Architectural Glass Mortar

With the incorporation of nanoclay, it is feasible to produce semi-flow architectural glass products with 100% recycled glass cullet as aggregate by using an extrusion approach. By adopting this approach, the viscosity of the freshly prepared glass mortar is largely improved that it can be not only flowable like the self-compacting mortar, but also able to be extruded to the desired form without the use of molds. In this way, the industrial production of the architectural glass products becomes feasible.

Current studies generally correlate the mix proportioning of glass mortar with the mechanical properties. Much more interests should be taken into the rheological properties when designing a mix of semi-flow architectural glass mortar to provide the freshly prepared mortar with desired flowability and shape-holding ability at the same time.

This study examines the effects of some main factors like nanoclay dosage, superplasticizer dosage, and standing time on the rheology of fresh glass mortar. Also, the corresponding mechanical properties including flexural and compressive strength were evaluated.

Zhenhua Duan, Chi-Sun Poon, Amardeep Singh, Shaodan Hou

Characterization of CNF-strengthened Interface Transition Zone (ITZ) Between Polyethylene Fiber and Cement Paste

In this study, the interface transition zone (ITZ) between CNF-coated polyethylene (PE) fiber and cement paste matrix was characterized. The microstructure and mechanical properties of CNF-strengthened ITZ were investigated and compared with the control ITZ between pristine PE fiber and cement paste. Specimens embedded with one singe fiber were prepared and cleaved at the fiber section to expose the longitudinal section of the ITZ. The distinct microstructure of the CNF strengthened ITZ was revealed by SEM analysis. Nanoindentation tests were also carried out to evaluate the mechanical properties of ITZ with different microstructure. The results show that the CNF-strengthened ITZ has denser microstructure and improved mechanical properties as compared with ITZ without CNFs. It demonstrates that the use of CNF coating realized an attempt to strategically strengthen the critical ITZ, which dominates the macroscale properties of the overall composites.

En-Hua Yang, Shan He

Thermal Insulating Cementitious Composite Containing Aerogel and Portland Cement

Thermal conductivity is an important material property in the energy design process of the buildings. While cement-based materials are the most consumed materials in construction industry, thermal properties of these materials can play a significant role in energy efficiency of the buildings. Cementitious materials with low thermal conductivity can be desirable for using as a part of heat insulation or for thermal bridge calculations. In this study, aerogel granules were used as aggregate and combination of Portland cement and fly ash was considered as the binder in order to achieve a material with low thermal conductivity. Replacement of 50 vol% hardened cement paste (hcp) by aerogel granules led to about 70% reduction in thermal conductivity of air dried samples (from 0.67 W/mK to 0.20 W/mK). However, this reduction was nearly 50% in moist samples submerged in water for three days (from 0.97 W/mK to 0.50 W/mK) due to replacement of air by water in hcp pores, which can be avoided by using hydrophobic agents. The thermal conductivity can be reduced by increasing water-cement ratio as well as aerogel content. This type of composite can be used as cast concrete or on-site 3D printing of wall elements.

Mohammad Baghban Hajmohammadian, Mohaddeseh Tahanpour Javadabadi

3:00 pm - 3:20 pm

Novel Ultra-flexible Nano-modified Polymer Cementitious Waterproofing Materials

In Hong Kong, over 55% of the buildings encounter water seepage problem, especially those built for over 10 years. The polymer cementitious waterproof coating can be used to form an elastomeric coating to prevent water penetration and avoid water seepage. However, traditional polymer cementitious waterproofing coating has low flexibility and inferior bonding strength on concrete. This study is to develop a novel polymer cementitious coating material that can integrate high flexibility, excellent adhesion and superior waterproof performances and act as an effective binder on the concrete surfaces and even on the wet surfaces. The environmental-friendly nano-modified polymer cementitious coating consists of two components of liquid emulsion and cement powder. The nanoparticles dispersing in liquid emulsion acted as self-lubricating agents in the developed coating product to withstand and transfer the tensile force and imparted a positive impact on the orientation of polymer molecular chains in the coating for waterproof function. Therefore, the developed coating can exhibit 2 times better flexibility than that of market-available products and 1.5 times better adhesion than that of market-available products. Moreover, this coating can withstand 5 bar water pressure over 72 hour under DIN 1048-5 and BS EN 12390-8 standards with no water leakage. The developed coating can be easily applied in various construction waterproofing fields and even on wet substrates, e.g. basements, toilet, terraces, swimming pools, water tanks, decks, etc.

Su Ping Bao, Xinkun Lu, Man Lung Sham

Elastic Moduli and Microhardness of Cement Compounds

The nanoindentation technique has been widely used to explore the nano-properties of many materials, such as thin films and metals. In this technique, a small stress is applied at the surface of the material and a nano-scaled indentation is formed. The mechanical properties of the materials, such as the Young's modulus, hardness, toughness and so on, are determined. On the other hand, the predictions of the mechanical properties of the cement-based materials through the microscopic observations have long been issues and remain a challenge. In view of the potential applications of nanoindentation on cement-based materials, this study tries to measure the microhardness, reduced moduli, and toughness of the cement compounds and ettringite, including the C3S, C3A, C4AF, and ettringite. Results show that the reduced modulus is not positively correlated with the hardness. There is no clear relationship between the toughness and the reduced modulus or the microhardness.

Yu Ting Chou, Chun Tao Chen

Subsurface Concrete Rebar Corrosion Damage Localization using Nanocomposite Coatings and Noncontact Tomography

Reinforced concrete (RC) is one of the most widely used materials for building infrastructure systems worldwide. Despite its advantages, exposure to harsh and aggressive environments can induce corrosion in embedded steel reinforcement bars in RC structures. Corrosion could initiate subsurface and remain undetected during regular inspection. Thus, the objective of this study is to develop a noncontact, subsurface, imaging technique that can be used as a rapid corrosion detection tool. The technique proposed here is centered around the theory of electrical capacitance tomography (ECT). The ECT hardware uses a set of electrodes arranged to form a circular ring. By propagating a time-varying electric field within the sensing area defined by the array of electrodes and then measuring the induced capacitance responses, the ECT inverse problem is solved to reconstruct the permittivity distribution of the sensing area. In addition, a corrosion-sensitive thin film was designed such that its permittivity would change in response to pH (as a precursor to corrosion) and can be pre-deposited onto steel rebars prior to concrete casting. When corrosion occurs, localized areas of the film would sense corrosion and induce electrical permittivity changes, which can be detected by ECT. To validate this, accelerated corrosion tests were conducted on reinforced mortar specimens with both nanocomposite-coated and pristine steel rebars. The specimens were interrogated using the ECT hardware at different time intervals for quantifying rebar corrosion nondestructively. The results showed that ECT, in conjunction with the embedded nanocomposite, could detect the location and severity of corrosion in steel reinforcement bars.

Kenneth Loh, Sashank Shivakumar, Sumit Gupta, Xi Qiu

3:20 pm - 3:40 pm

Modification of Recycled Aggregate Concrete (RAC) by Surface Treatment with a Sulphoaluminate Cement Slurry and a Nano-silica Composite Slurry

The modification effects of recycled aggregate concrete (RAC) by surface treatment of recycled aggregates (RA) with two strengthening slurries were experimentally studied. The first slurry was prepared by nano-silica and ordinary portland cement, while the second one was a sulphoaluminate cement slurry with an optimized water cement ratio. RA properties before and after the surface treatment were tested, and the RAC performance including workability, mechanical properties and durability were also investigated. Test results show that both the two slurries can significantly improve the properties of RA and RAC, on the macro scale. Microhardness and nanoindentation test results demonstrated that after RA’s surface treatment, ITZ1s and ITZ3s which formed between the old coarse aggregate and the new mortar, and between the old and new cement mortars, were enhanced. ITZ2s which originally existed inside RA particles between the old coarse aggregate and the old adhering cement mortar were not enhanced. The old cement mortar was surface strengthened by the surface treatment. In general, the modification effects of the two strengthening slurries on performance of RAC were comparable, however, given the higher cost-efficiency as well as the easier preparation of the strengthening slurry by using sulphoaluminate cement, surface treatment of RA by the sulphoaluminate cement slurry has a better prospect on the wide application in real projects.

Hongru Zhang, Yuxi Zhao, Hui Liu, Shangliang Su

Effect of Mixing on the Generation of Nanoparticles in Cementitious Materials

Hela Bessaies-Bey, Aileen Vandenberg, Kay Wille, Nicolas Roussel

"Smart Cement" with Sensing Properties from Inorganic Nanoparticles: Tracking Cement Hydration via Piezo - Resistivity

Addition of ~0.1 % by weight of cement of inorganic basalt nanofibers makes cement a powerful sensor. For example, by recording resistivity the setting and hydration of cement can be tracked in a similar way from heat flow calorimetry, i.e. in real-time and non-destructive. Further information like the w/c ratio, salt influxes or other contaminations can be detected from specific changes of the resistivity: R = ρ * K

Firstly, the principle method is explained and then the behavior of different cements during early hydration (0 - 24 h). Furthermore, the resistivity index will be shown to be a reliable indicator to predict the 28 day compressive strength of any cement sample. Importantly, incorporation of the inorganic nanofibers tuns cement into a piezo - resistive material. As such, any compressive stresses on e.g. a concrete structure can be detected early, and the maximum stress tolerated by a cement or concrete sample before crack formation occurs can be determined in a non-destructive way.

In concrete, chemical admixtures are frequently used. Because they present polyelectrolytes which definitely alter the electrical properties of cement paste, a series of experiments was performed on cement pastes admixed with a superplasticizer and a retarder. It was found that the presence of such chemical admixtures does not change the principle electrical properties of cement, and thus allows to capture the same information as from neat cement. For example, the superplasticizer increased 28 day compressive strength and produced a denser microstructure whereas the retarder clearly delayed cement hydration over first 2 days.

This method can be used to monitor cement hydration and diagnose potential failures in the field, e.g. on cementitious floor screeds, on oil well cements etc., and this accurately, in real-time, non-destructive and even at wireless transfer of data.

Johann PLANK, Cumaraswamy Vipulanandan

3:40 pm - 4:00 pm

Exploring the Potential of NS@PCE Used as A Kind of Surface Treatment Agent for Cementitious Materials

Yue Gu, Wei She, Qianping Ran

Experimental Study on Hydrothermal Synthesis System of Tobermorite from Fly Ash

The fly ash-based tobermorite has been synthesized by hydrothermal reaction using fly ash as precursor. The effects of molar ratio of CaO to SiO₂, alkali, reaction temperature, reaction time and various filling degrees on the synthesis of hydrothermal product were explored. And the micro-performance characterization of FA-T was carried out. The results show that the alkaline environment is a prerequisite for hydrothermal reaction of Al-substituted tobermorite from fly ash, and the preferably concentration of NaOH is 0.2 mol/L. The best molar ratio of CaO to SiO₂ is 1.1. The optimum reaction temperature and time are 220°C and 10h, respectively. The various filling degree can reach up to 70%. There are lots of dimers in the intenal structure of the FA-T, and the chain length is short, the mean chain length (MCL) is 6.12. Al mainly exists in the form of Al [4] which Si is substituted by Al in SiO₄ tetrahedra, and part of the Al [6] exists in the interlayer. Scanning electron micrographs indicated that FA-T has a network structure which entangled by the 2.0 μm fibrous and foil pieces. FA-T has a hardness of 0.234 GPa and an elastic modulus of 6.917 GPa.

Xiaolu Guo, Tangjun Zhang

The Tailoring of Calcium-silicate-hydrates in Portland Cement Systems: A Sol-gel Approach to Nucleation Seeding

This work focuses on the innovative use of sol-gel silicates as seeding agents, to tailor the nanostructural properties of calcium-silicate-hydrates (C-S-H) and to promote the nucleation and self-assembly of hybrid C-S-H nano-building units, to deliver superior performance and resilience in cement based materials. The formation of the basic silicate species in cement hydration and the sol-gel processes follow similar routes. In this pioneering work, sol-gel technology is used as a tool to develop low-carbon multifunctional concrete. Sol-gel material was synthesised at predetermined molar ratios of H₂O, NaOH, tetraethoxysilane and 3-glycidoxypropyltrimethoxysilane. These were used at dosages of 1, 3, 5 and 10% by mass of cement to prepare pastes at w/c 0.5 and analysed by isothermal calorimetry. Specimens prepared at w/c 0.35 aged for 1 and 28 days were examined by a suite of analytical tools. Due to the brief nature of this report, only results from TGA, solid-state 29Si MAS NMR and FESEM, are reported. The findings show that the parameters for the sol-gel synthesis can be used as a pathway to tune the early age hydration kinetics and to facilitate the formation of C-S-H with denser microstructures. TGA data reveals the formation of additional hydrates and reduced portlandite formation compared to controls. NMR spectra display an increase in the mean chain length of C-S-H. The linking of glycidoxypropyl group to the middle and end group of the silicate chains of C-S-H network in Portland cement is reported for the first time.

Muzzamil Shakil, Juliana Calabria-Holley, Kevin Paine, Martin Ansell

4:00 pm - 4:15 pm

Coffee Break

Venue: Conference Hall Lobby

Parallel Sessions

Venue: Conference Hall 4 - 6, Lakeside 2, Hong Kong Science Park

4:15 pm - 4:35 pm

Parallel Session 7
Session Chair :
Prof. Yuxi ZHAO
Venue: Conference Hall 4

Early-age Hydration and Rheological Development of Cement Paste with In-situ Nanomodified FA

There have still been a lot of effort needed to be taken to achieve well dispersion and appropriate rheology for state-of-the-art application of nanomaterials in cement-based materials. Accordingly, we proposed here on a promising strategy to produce modified fly ash (FA) with in-situ precipitated nanoparticles (nano-CaCO₃, nano-SiO₂ and their hybrids) on its surface. The preparation of nanomodified FA was carried out through a microbubble mineral carbonation of cost-effective industrial raw materials. The morphology and mineral composition of nanomodified FA were revealed and characterized by TG, TEM, SEM, and XRD. The effect of various in-situ coated nanoparticles as well as different replacement levels of nanomodified FA on the early-age hydration and rheological behavior of cement paste were investigated by isothermal heat conduction calorimetry and rheometer. Results showed that accelerated hydration and superior dispersion were obtained by cement pastes incorporated with nanomodified FAs in comparison with control paste. It also provides a potential route for developing low-carbon, eco-friendly cementitious materials with integrated nanoengineering and carbon dioxide capture and sequestration (CCS) technology.

Yaping Wang, Ganghua Pan

Parallel Session 8
Session Chair :
Prof. Jiri NEMECEK
Venue: Conference Hall 5

Elastic, Viscous and Creep Response of Gamma Irradiated C-S-H

The proposed extended life cycle of the US fleet of light water reactors to 80 years of operation has opened questions regarding the effects of irradiation on the concrete biological shield. The estimated neutron/gamma doses on the biological shield after 80 years are < 7·1019 n/cm2 (E > 0.1 MeV) (Field et al., 2015, Remec, 2014) and 50-200 MGy (Esselman et al., 2013, Kontani et al., 2013, Remec, 2013). Siliceous aggregates are affected by neutron radiation which causes radiation induced volumetric expansion (Field et al., 2015), while cement paste suffers dehydration due to radiolysis induced by gamma rays (Kontani et al., 2013). A predictive numerical model of irradiation damage with neutron fluence for concrete has shown that creep delays the onset of damage (Giorla et al., 2017). Creep was considered independent of neutron fluence. However, in a case scenario with gamma and neutron exposure, it is possible that creep/viscous properties of cement paste change due to dehydration induced by gamma rays. C-S-H is responsible for creep properties in cement, and it is more viscous with high water content (Alizadeh et al., 2010). Previous studies suggest an increase in silicate mean chain-length and/or degree of cross-linking decreases the viscous response of C-S-H (Hunnicutt et al., 2016). Drying C-S-H could remove water from its interlayer and promote higher degree of cross-linking and an increase in the mean silicate chain-length. This could impact its mechanical properties. The viscous/elastic response of compressed pellets of C-S-H with Ca/Si ratios of 0.75, 1 and 1.33, conditioned to 11%RH, was tested with nanoindentation stress relaxation/traditional indentation tests, after adsorbed gamma doses of 2.24 MGy. Creep tests were also performed in selected samples. The morphology, composition, basal spacing, and silicate anion structure were studied with TEM, TEM-EDX, XRD and 29SI NMR. Non-irradiated samples were used as control.

Elena Tajuelo Rodriguez, William Albert Hunnicutt, Paramita Mondal, Yann Le Pape

Parallel Session 9
Session Chair :
Dr. Florence SANCHEZ
Venue: Conference Hall 6

The Strength of Cement-graphene Composite in The Complex Stress State

Nanotechnology of cementitious materials is attracting continuous interest of scientists all over the world. One of the main trends in nanotechnology of cement-based composites is based on nanoengineering, which involves modification of concrete structure by incorporating nanoparticles into cement matrix to obtain high performance composites with unprecedented and controllable properties. Numerous recent studies have indicated that the application of nanomaterials, such as nano-silica, nano-titania, nanoiron oxide, nano-alumina, carbon nanotubes, graphene oxide or graphene nanoplatelets, can lead to an improvement of cement paste microstructure and thus to a significant enhancement of the mechanical properties of cement composites. In particular, in the last decade graphene has emerged as an exciting material possessing unprecedented properties thereby holding potential to impact many areas of science and technology. The extraordinary electronic, thermal and mechanical properties of graphene make it a promising candidate for technological applications in electronics, sensing, energy storage and conversion, as well as in catalysis and biological labeling. Although several approaches have been proposed for enhancing the properties of cementitious materials, it is important to note that the development of guidelines for designing structural elements made of new material is a highly complex task, the first step of which should be providing a material model that could be used in numerical analyses. Therefore, it is necessary to examine a new composite in a complex stress state to obtain a boundary surface. Here we investigate the strength of cement mortar reinforced with graphene in the complex stress state. Cement mortar with the 0,05 wt% additive of graphene was fabricated and tested in the triaxial apparatus. The cylindrical specimens were examined under constant side pressure and increasing pressure in the longitudinal direction of the sample. On the basis of this research the first meridian of the boundary surface of cement-graphene composite was determined.

Malgorzata Krystek, Marcin Gorski, Leszek Szojda, Artur Ciesielski

4:35 pm - 4:55 pm

Influence of Core/ Shell TiO₂@SiO₂ Nanoparticles on Cement Hydration

TiO₂@SiO₂ nanoparticles with a core/shell structure widely used in photocatalytic fields were used in this paper to improve the hydration properties of the Portland cement. To this end, the core/shell TiO₂@SiO₂ nanoparticles were synthesized first and then characterized by a series of techniques including transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR) and X-ray photoelectron spectra (XPS). Second, the influence of the core/shell TiO₂@SiO₂ nanoparticles on cement hydration was investigated and compared with nano-TiO₂ through isothermal calorimetry. The results showed that an amorphous SiO₂ layer can be deposited uniformly on nano-TiO₂ particles by forming new Si-O-Ti chemical bonds at the interface between the SiO₂ coating layer and nano-TiO₂ particle surface. This uniform layer was conducive to decrease the aggregation of nano-TiO₂ effectively. Compared with nano-TiO₂, the core/shell TiO₂@SiO₂ nanoparticles exhibited better hydration properties in terms of accelerated early cement hydration and resulted in a higher cumulative heat release, even though both particles modified cement hydration.

Xiaodong Shen, Jinfeng Sun, Weifeng Li

Influence of Intensive Mixing During Preparation of High Performance Concrete/Ultra-high Performance Concrete (HPC/UHPC)

Nanomaterials are already contained in many products today, such as paints, car paints, sun creams and building materials. Nanotechnology is also regarded as the key to innovative products in the development of building materials. Research is carried out on materials that clean themselves and on paints that break down pollutants and odours.

Furthermore, there are now already self-cleaning roof tiles or dry mortars. With the help of sunlight, a bunt or applied surface layer destroys organic dirt particles. The addition of nanoparticles is also intended to improve classic building materials such as concrete. Concrete has always been a nanomaterial. During curing, the finest needles cross-link inside and grow together. This is how the building material forms its strength. A disadvantage of concrete is that pores remain after curing. Damaged areas can form in it. This is to be prevented by adding nanoparticles to the cement. A forerunner of nanoblock concrete is already on the market today, high performance concrete/ultra-high performance concrete (HPC/UHPC).

In order to fully utilize the capabilities of HPC/UHPC, it is essential not only to optimize the mix design and to apply the specific processing and curing techniques required, but also to observe the specifications place on production itself. The mixing process plays a crucial role here. At the present time, however, mixing is typically regarded to only limited extent as one of the factors that significantly influences the properties of UHPC. Since qualitative factors have been determined in most cases, discussion is mostly limited – compare to normal concretes – only to the fact of “longer mixing” for HPC/UHPC. High and Ultra-high performance concretes, other than normal concrete require more intensive mixing for the distribution of the high specific surface materials like micro- and nano-silica.

The mixing process effects the properties of the fresh and hardened concrete independent on “normal” concrete as well as high and ultra-high performance concrete.

MASCHINENFABRIK GUSTAV EIRICH GmbH & Co KG, a well-known mixer manufacturer from Germany, has extended its range of process technologies. It has incorporated several technological innovations from different industry applications in saving production costs/raw materials and they offering complete preparation technologies such as in the building material industry.

Ralf Loebe

Molecular Dynamics Study on Water and Ions Transport in the C-S-H Gel Coated with Graphene-based Material

The excellent impermeable nature of graphene-based nanomaterial makes it potential membrane to repel detrimental ions invasion. In this study, molecular dynamics is utilized to investigate the solution transport in 3.5 nm channel of the calcium silicate hydrate (C-S-H) substrate with graphene sheet and graphene oxide sheet with different functional groups. The early stage of water and ions imbibition depth as the function time follows constant-velocity and visco-inertia regimes for NaCl solution transport in the nanometer channel of C-S-H. The incorporation of graphene and GO sheets in the C-S-H interior surface can resist the water and ions transport in the gel pore by blocking the gel pore and immobilizing the ions with the functional groups. On the one hand, the graphene sheet, dissociating from the C-S-H gel, contributes little to resisting water and ions penetration. On the other hand, the hydroxyl and carboxyl groups in the GO sheets provide plenty of oxygen sites to accept the H-bonds and to associate with the neighboring sodium ions, which resists the ingress of the water molecules and ions. The GO-COOH sheets, deeply rooted on the C-S-H, further block the transport channel connectivity and “cage” the water and ions in the entrance region of gel pore. This study provides useful guideline for design of the high-performance graphene-based material.

Dongshuai Hou, Xiaoqian Xu, Pan Wang

4:55 pm - 5:15 pm

Scalable Processing of Cementitious Composites Reinforced with Carbon Nanotubes (CNT) and Carbon Nanofibers (CNF)

Utilizing the unique properties of CNTs and CNFs to enhance the mechanical and fracture properties of cement based materials and develop smart cementitious nanocomposites can be a challenge in terms of developing scalable manufacturing methods. Scaling up the manufacturing size of CNT and CNF reinforced cement based materials and produce multifunctional concrete that exhibits exceptional strength, stiffness and toughness and multifunctionality requires optimization of dispersion procedure. The effectiveness of successfully using CNTs and CNFs in concrete depends on the fiber count, the volume fraction of sand and coarse aggregates. In this work, we present the flexural strength and stiffness, fracture toughness and brittleness of nanomodified pastes and mortars reinforced at amount of 0.08 and 0.1 wt% and an investigation on the optimization of the fiber count proportioning of concrete. The addition of a very low amount, 0.1 wt%, of both CNTs and CNFs, increases approximately 1.5 times the flexural strength and the Young`s modulus of concrete nanocomposites. The nanomodified concrete also exhibits 60% higher energy absorption capability.

Panagiotis A. Danoglidis, Maria G. Falara, Myrsini E. Maglogianni, Maria S. Konsta-Gdoutos, Surendra P. Shah

On Nano/Micro-mechanical Characterisation of Early Aged Cement Paste

The present paper summarises recent achievements and challenges discovered in the field of sample preparation and micromechanical characterisation of early aged Portland cement paste hydrated for 24 hours. Specimen preparation to preserve the weak and fragile microstructure (result of the low degree of hydration), and measures to identify and prevent restart of hydration on specimen surface during nano/micro-mechanical characterisation are discussed. It is shown that growth of hydration phases on well-polished specimen surface could occur during the nanoindentation testing period (usually from several hours to a few days), leading to erroneous/faulty test results. We also present test results of such specimens obtained using PeakForce QNM™ technique and discuss issues related to results interpretation. Peak-force tapping atomic force microscopy enables high-speed and high-resolution DMT modulus mapping of the investigated sample.

Wenzhong Zhu, Torsten Howind, Svetlana Guriyanova, Bend Kummerling, Sebastian Seufert

6:00 pm - 9:00 pm

Symposium Dinner
Guest Speaker Ir. Derek K. L. SO
Executive Director, Hip Hing Construction Co Ltd.
Technology Transfer in Action: Researchers Applying Nanotechnology in Construction with Industry Practitioners

ClubOne, Hong Kong Science Park

5 Dec 2018 (Wednesday)

TIME

EVENT

Keynote Speech
Session Chair: Prof. Konstantin SOBOLEV

Venue: Charles K. Kao Auditorium, Hong Kong Science Park

9:15 am - 9:50 am

Use of Nano-materials in UHPC

Nanomaterials have attracted much interest in cement-based materials during the past decade. The effects of different nano-CaCO₃ or nano-SiO₂ contents on performance of ultra-high performance concrete (UHPC) matrix and UHPC made with 2% steel fibers were investigated. The investigated performance involves mechanical properties, calcium hydroxide content, and pore structure. The dosages of nano-CaCO₃ were 0, 1.6%, 3.2%, 4.8%, and 6.4%, while the dosages of nano-SiO₂ were 0, 0.5%, 1.0%, 1.5%, and 2%, by the mass of cementitious materials. Test results indicated that the optimal dosages to enhance compressive and flexural strengths of UHPC matrix were 1.6% to 4.8% for the nano-CaCO₃ and 0.5% to 1.5% for the nano-SiO₂. Thermal gravimetry (TG) analysis demonstrated that the calcium hydroxide (CH) content in UHPC matrix decreased significantly with the increase of nano-SiO₂ content, but remained almost constant for those with nano-CaCO₃. UHPC specimens with 3.2% nano-CaCO₃ or 1.0% nano-SiO₂ exhibited the highest compressive and flexural strengths. Beyond these critical values, the mechanical properties of UHPC decreased due to increased porosity associated with agglomeration of the nano-particles.

Prof. Caijun SHI

Chair Professor, College of Civil Engineering,
Hunan University, China

Professor Caijun Shi received his B. Eng and M. Eng from Southeast University, Nanjing, China and Ph.D from the University of Calgary, Canada. He is currently vice president of Asia Concrete Federation, Chair Professor in the College of Civil Engineering, Hunan University, Editor-in-Chief of “Jounal of Sustainable Cement-based Materials”, Co-editor of “Jounal of Ceramics in Moden Technologies”, Associate editor of “Jounal of Chinese Ceramic Society”, editorial board member of “Cement and Concrete Research”, “Cement and Concrete Composites”, “Construction and Building Materials”, “Jounal of Structural Integrity and Maintenance”, “Materiales de Construccion”, “Jounal of Building Materials”, “Materials Review”, “Jounal of Chongqing Jiaotong University”, and former associate editor of “Jounal of Materials in Civil Engineering”. Dr. Shi serves on many ACI and RILEM technical committees.

His research interests include characterization and utilization of industrial by-products and waste materials, design and testing of cement and concrete materials, development and evaluation of cement additives and concrete admixtures, and solid and hazardous waste management. He has developed several novel technologies and products, and has been granted four US patents and more than 15 Chinese patents. One of his inventions, Self-sealing/ Self-healing Barrier, has been used as a municipal landfill liner in the world's largest landfill site in South Korea. He has authored/coauthored more than 310 technical papers, seven English books, three Chinese books and edited/co-edited eight intenational conference proceedings. Dr. Shi has been invited to give presentations on a variety of topics all over the world. In recognizing his contributions to researches in waste management and concrete technology, he was elected as a fellow of Intenational Energy Foundation in 2001, a fellow of American Concrete Institute in 2007, and a Fellow of RILEM in 2016.

Chair Professor, College of Civil Engineering
Hunan University, China

9:50 am - 10:25 am

Passivation Process of Galvanized Steel Bars in Cement Mortars Prepared with Nano-silica

In recent years, nano-silica, as a kind of ultra-fine pozzolanic material, has been explored for use in concrete. Large amount of studies have demonstrated that it is an innovative admixture to improve the durability of concrete. But the effect of the nano silica on the corrosion of steel bars in concrete was rarely reported. The present work studied the effect of the nano silica on the passivation of galvanized steel bars (a kind of corrosion-resistant steel bar) in cement mortars. To achieve this, the intenal environmental factors of the mortar were firstly monitored and then the passivation process of the galvanized steel bars was monitored using traditional electrochemical tests and the surface characterization methods. The results showed that the presence of nano-silica influenced the passivation process of the galvanized steel bars and improved the stability and protective properties of the passive film formed. The morphology of the interface between the galvanized steel bars and the mortar was changed when the nano-silica was added. The galvanized steel bars showed good compatibility with the nano-silica in terms of the corrosion resistance of concrete structures.

Prof C. S. POON

Associate Head, Department of Civil and Environmental Engineering
The Hong Kong Polytechnic University, Hong Kong

Prof. C.S. Poon obtained his PhD from Imperial College, London. He spent two years as a Post-doctoral Fellow at Oxford University, specialising in cement and concrete research. Currently, he is the Chair Professor of Sustainable Construction Materials and Associate Head (Research) at the Civil and Environmental Engineering Department of The Hong Kong Polytechnic University. He has been awarded the title of Changjiang Chair Professor by the Ministry of Education. He specialises in teaching and research of concrete technology, eco-friendly construction materials and waste management. He has published over 400 papers in intenational jounals and conferences (including over 300 intenational jounal papers, and 8 patents). Prof. Poon is a Fellow of the Hong Kong Institution of Engineers and the Hong Kong Concrete Institute (HKCI). He is currently the President of the HKCI, and was a past President of the American Concrete Institute (China) Chapter.

Associate Head, Department of Civil and Environmental Engineering
The Hong Kong Polytechnic University, Hong Kong

10:25 am - 11:00 am

Tailoring the Piezoresistive Strain Sensing of Carbon Nanotube Reinforced Mortar Sensors

Carbon nanotubes (CNTs) and nanofibers (CNFs) can supply the cementitious matrix with enhanced stiffness and durability properties, as well as with excellent electromechanical and piezoresistive characteristics. This presentation highlights current research on the smartness and self-sensing characteristics of nanomodified concrete using Impedance Spectroscopy. To accurately evaluate the smartness of the nanoengineered cementitious materials it is necessary to take into consideration both resistive and capacitive phases: the resistivity values can provide the nanofibers’ percolation threshold; while the capacitive characteristics of a nano-reinforced mortar or concrete can evaluate the actual CNT/CNF distribution in the cementitious matrix, and correlate dispersion with mechanical properties and piezoresistive behavior. Furthermore, piezorestivity experiments of CNT mortar sensors, embedded into concrete elements, show the ability of the sensor to detect strain, crack propagation and damage accumulation of the concrete element at all stages of deformation, up to failure.

Prof. Maria S. KONSTA-GDOUTOS

Professor, Director of the Laboratory of Applied Mechanics
Department of Civil Engineering
Democritus University of Thrace, Greece

Dr. Konsta-Gdoutos, Professor of Civil Engineering and the Director of the Division of Mechanics in the Department of Civil Engineering of Democritus University of Thrace in Greece, is the director of the Center for Multifunctional Nanocomposite Construction Materials, and Adjunct Professor in Civil Engineering at Northwesten University. She develops high performance smart cementitious nanocomposites, reinforced with carbon nanotubes and nanofibers to achieve tailored properties for civil infrastructure and investigates the relationship between the microstructure and structural performance of these advanced cement based nanocomposites.

Maria is a Fulbright scholar, a member of the Intenational Academy of Engineering, and the recipient of the A.S. Kobayashi Young Investigator Award in Experimental Science in 2012. She holds 3 US patents for her work on the dispersion of carbon nanofibers and carbon nanotubes and their introduction in reinforcing cementitious nanocomposites. She has published over 85 papers in refereed jounals and conference proceedings and has been the invited speaker for more than ten symposia intenationally in the last five years. She is also the editor of the book "Measuring, Monitoring and Modeling Concrete Properties" published by Springer and the guest editor of several special issues in refereed jounals published by Springer and Elsevier.

She is a member of the ACI committees 236 Material Science of Concrete, 241 Nanotechnology of Concrete and currently serves as the chair of the ACI 241 Task Group committee "Nanofibers." She is also a member of the Society for Experimental Mechanics (SEM). She serves as the Executive Editor in Chief of the Springer Intenational Jounal "Frontiers in Structural and Civil Engineering" and is a member of the Editorial Boards of "Cement and Concrete Composites," by Elsevier and the "Jounal of Structural Integrity and Maintenance" by Taylor and Francis.

Professor, Director of the Laboratory of Applied Mechanics
Department of Civil Engineering
Democritus University of Thrace, Greece

11:00 am - 11:30 am

Closing

Venue: Charles K. Kao Auditorium, Hong Kong Science Park

11:30 am - 12:45 pm

Luncheon

Venue: ClubOne, Hong Kong Science Park

1:00 pm - 5:00 pm

Cultural Visit (Optional)