Publications
114 results found
Yio MHN, Wong HS, Buenfeld NR, 2016, 3D Pore Structure Characterisation of Blended Cement Pastes using Laser Scanning Confocal Microscopy, Young Researchers’ Forum III, Innovation in Construction Materials
Kia A, Cheeseman C, Wong H, 2016, Development of clog resistant pervious concrete for alleviating localised urban flooding, 3rd Young Researcher’s Forum Conference on Innovation in Construction Materials
Lee HXD, Wong HS, Buenfeld NR, 2016, Self-sealing of cracks in concrete using superabsorbent polymers, Cement and Concrete Research, Vol: 79, Pages: 194-208, ISSN: 1873-3948
Cracks in concrete can self-heal when exposed to prolonged wetting, but this is limited to narrow cracks. In practice, cracks. > 0.2. mm cause leakage and impair performance of structures. The potential of superabsorbent polymers (SAPs) to self-seal such cracks was investigated via transport experiments, microscopy and modelling. Forty samples containing SAP and through-thickness cracks were subjected to 0.12. wt.% NaCl at 4. m/m pressure gradient to simulate groundwater seepage. Results show that SAP can re-swell and seal cracks, for example in the case of 0.3. mm cracks reducing peak flow rate and total flow by 85% and 98% respectively. Increasing SAP dosage accelerates sealing, but imparts a strength penalty and this limits practical applications. Modelling suggests that the effectiveness of SAP can be enhanced by increasing its re-swelling ratio and particle size, and depressing its initial swelling. These variables increase the SAP exposed in a crack and the gel volume available to seal it.
Yio MHN, Mac MJ, Wong HS, et al., 2015, 3D imaging of cement-based materials at submicron resolution by combining laser scanning confocal microscopy with serial sectioning, Journal of Microscopy, Vol: 258, Pages: 151-169, ISSN: 0022-2720
In this paper, we present a new method to reconstruct large volumes of nontransparent porous materials at submicron resolution. The proposed method combines fluorescence laser scanning confocal microscopy with serial sectioning to produce a series of overlapping confocal z-stacks, which are then aligned and stitched based on phase correlation. The method can be extended in the XY plane to further increase the overall image volume. Resolution of the reconstructed image volume does not degrade with increase in sample size. We have used the method to image cementitious materials, hardened cement paste and concrete and the results obtained show that the method is reliable. Possible applications of the method such as three-dimensional characterization of the pores and microcracks in hardened concrete, three-dimensional particle shape characterization of cementitious materials and three-dimensional characterization of other porous materials such as rocks and bioceramics are discussed.
Wu Z, Wong HS, Buenfeld NR, 2015, Influence of drying-induced microcracking and related size effects on mass transport properties of concrete, Cement and Concrete Research, Vol: 68, Pages: 35-48, ISSN: 0008-8846
Microcracking has been suspected of influencing the transport properties and durability of concrete structures, but the nature and extent of this influence is unclear. This paper focuses on the influence of drying-induced microcracking. Samples were prepared with sample thickness/maximum aggregate size (t/MSA) ratios ranging from 2 to 20 and dried to equilibrium at 105 °C or 50 °C/7% RH or 21 °C (stepwise: 93% RH → 55% RH) prior to characterisation of microcracks and transport tests. Results show for the first time that there is a significant size effect on microcracks and transport properties. Samples with smaller t/MSA had more severe microcracking and higher gas permeability. Gas permeability decreased with increasing t/MSA (for a decreasing MSA), and remained constant beyond t/MSA of 10. However, this size effect was not seen on gas diffusivity and sorptivity. The implications of these findings particularly regarding the influence of drying-induced microcracks on the durability of concrete structures are discussed.
Wong HS, Barakat R, Alhilali A, et al., 2015, Hydrophobic concrete using waste paper sludge ash, Cement and Concrete Research, Vol: 70, Pages: 9-20, ISSN: 1873-3948
The feasibility of using a low-cost super hydrophobic powder as water-resisting admixture or water-repellent surface coating for concrete has been investigated. The powder was produced from paper sludge ash (PSA), a by-product from the manufacture of recycled paper. The effect of hydrophobic PSA on workability, strength and transport properties, including sorptivity, water absorption, diffusivity, permeability and electrical conductivity is reported. Samples were prepared at water/cement ratio of 0.38, cured up to 28 days and conditioned at 50 °C to constant mass prior to testing. It was found that replacing Portland cement with 12% hydrophobic PSA reduced water absorption, sorptivity and conductivity by 84%, 86% and 85% respectively, with no major detrimental effects on hydration, strength and density. When used as a surface coating, the hydrophobic PSA reduced both absorption and sorptivity by 85–99% depending on the adhesive used. Samples surface coated with hydrophobic PSA showed excellent water repelling and self-cleaning characteristics.
Abyaneh SD, Wong HS, Buenfeld NR, 2015, Modelling the Effect of Microcracks on the Transport Properties of Concrete in Three Dimensions, 10th International Conference on Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete and Concrete Structures (CONCREEP), Publisher: AMER SOC CIVIL ENGINEERS, Pages: 377-386
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- Citations: 2
Wu Z, Wong HS, Buenfeld NR, 2014, Effect of confining pressure and microcracks on mass transport properties of concrete, ADVANCES IN APPLIED CERAMICS, Vol: 113, Pages: 485-495, ISSN: 1743-6753
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- Citations: 15
Yio MHN, Wong HS, Buenfeld NR, 2014, Fluorescence laser scanning confocal microscopy for real-time imaging of early cement hydration, 15th Euroseminar on Microscopy Applied to Building Materials
Abyaneh SD, Wong HS, Buenfeld NR, 2014, Computational investigation of capillary absorption in concrete using a three-dimensional mesoscale approach, COMPUTATIONAL MATERIALS SCIENCE, Vol: 87, Pages: 54-64, ISSN: 0927-0256
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- Citations: 55
Yio MHN, Phelan JC, Wong HS, et al., 2014, Determining the slag fraction, water/binder ratio and degree of hydration in hardened cement pastes, Cement and Concrete Research, Vol: 56, Pages: 171-181, ISSN: 0008-8846
A method for determining the original mix composition of hardened slag-blended cement-based materials based on analysis of backscattered electron images combined with loss on ignition measurements is presented. The method does not require comparison to reference standards or prior knowledge of the composition of the binders used. Therefore, it is well-suited for application to real structures. The method is also able to calculate the degrees of reaction of slag and cement. Results obtained from an experimental study involving sixty samples with a wide range of water/binder (w/b) ratios (0.30 to 0.50), slag/binder ratios (0 to 0.6) and curing ages (3 days to 1 year) show that the method is very promising. The mean absolute errors for the estimated slag, water and cement contents (kg/m3), w/b and s/b ratios were 9.1%, 1.5%, 2.5%, 4.7% and 8.7%, respectively. 91% of the estimated w/b ratios were within 0.036 of the actual values.
Dehghanpoor Abyaneh S, Wong HS, Buenfeld NR, 2013, Modelling the diffusivity of mortar and concrete using a three-dimensional mesostructure with several aggregate shapes, Computational Materials Science, Vol: 78, Pages: 63-73, ISSN: 0927-0256
Wong HS, Buenfeld NR, Matter K, 2013, Estimating the original cement content and water-cement ratio of Portland cement concrete and mortar using backscattered electron microscopy, MAGAZINE OF CONCRETE RESEARCH, Vol: 65, Pages: 693-706, ISSN: 0024-9831
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- Citations: 22
Dehghanpoor Abyaneh S, Wong HS, Buenfeld NR, 2012, Investigating into the diffusivity of concrete using a three dimensional multi-phase model, 3rd International Conference on the Durability of Concrete Structures
Wong HS, Zimmerman RW, Buenfeld NR, 2012, Estimating the permeability of cement pastes and mortars using image analysis and effective medium theory, Cem. Concr. Res., Vol: 42, Pages: 476-483
Buenfeld NR, Wong HS, 2011, Assessing the durability of new concretes, 31st Cement & Concrete Science Conference
Wong HS, Pappas AM, Zimmerman RW, et al., 2011, Effect of entrained air voids on the microstructure and mass transport properties of concrete, Cem. Concr. Res., Vol: 41, Pages: 1067-1077
Zhao YX, Karimi AR, Wong HS, et al., 2011, Comparison of uniform and non-uniform corrosion induced damage in reinforced concrete based on image analysis, Corrosion Science, Vol: 9, Pages: 2803-2814
Lee HXD, Wong HS, Buenfeld N, 2010, Self-sealing cement-based materials using superabsorbent polymers, RILEM Conference on Use of Superabsorbent Polymers and Other New Additives in Concrete, Publisher: RILEM Publications SARL, Pages: 171-178
Superabsorbent polymers (SAP) have the potential to be used as an admixture to enhance the self-sealing of cracks in cement-based materials such as concrete. In this study, cement paste and mortar specimens containing different types of SAP were cast and mechanically loaded to produce a single through-crack with controllable width between 100µm to 400µm. These specimens were then exposed to 0.02M sodium chloride solution at a pressure gradient of 4 and the flow rates were measured with time to evaluate the efficiency of the SAP for crack sealing. The cumulative flow through specimens containing 5% SAP by weight of cement was up to 85% lower than that of the control specimen.
Lee HXD, Wong HS, Buenfeld NR, 2010, Self-sealing concrete using superabsorbent polymers, International RILEM Conference on Use of Superabsorbent Polymers and Other New Additives in Concrete, Publisher: RILEM Publications SARL, Pages: 171-178
Abstract: Superabsorbent polymers (SAP) have the potential to be used as an admixture to enhance the self-sealing of cracks in cement-based materials such as concrete. In this study, cement paste and mortar specimens containing different types of SAP were cast and mechanically loaded to produce a single through-crack with controllable width between 100µm to 400µm. These specimens were then exposed to 0.02M sodium chloride solution at a pressure gradient of 4 and the flow rates were measured with time to evaluate the efficiency of the SAP for crack sealing. The cumulative flow through specimens containing 5% SAP by weight of cement was up to 85% lower than that of the control specimen.
Lee HXD, Wong HS, Buenfeld NR, 2010, Estimating the swelling ratio of superabsorbent polymers in cement-based materials, Use of superabsorbent polymers and other new additives in concrete, Publisher: RILEM
Grassl P, Wong HS, Buenfeld NR, 2010, Influence of entrained air on shrinkage induced micro-cracking of concrete and mortar, Symposium on Concrete Modelling CONMOD 2010, Pages: 207-210
Wong HS, Zimmerman RW, Buenfeld NR, 2010, Estimating the permeability of cement-based materials using image analysis and effective medium theory, Symposium on Concrete Modelling CONMOD 2010, Pages: 37-40
Grassl P, Wong HS, Buenfeld NR, 2010, Influence of aggregate size and volume fraction on shrinkage induced micro-cracking of concrete and mortar, Cem. Concr. Res., Vol: 40, Pages: 1139-1148
Lee HXD, Wong HS, Buenfeld NR, 2010, The potential of superabsorbent polymer for self-sealing cracks in concrete, Advances in Applied Ceramics, Vol: 109, Pages: 296-302
Wong HS, Zhao YX, Karimi AR, et al., 2010, On the penetration of rust from reinforcing steel into concrete due to chloride-induced corrosion, Corrosion Science, Vol: 52, Pages: 2469-2480
Wong HS, Matter K, Buenfeld NR, 2009, Estimating the water/cement (w/c) ratio of hardened concrete using backscattered electron microscopy, 12th Euroseminar on Microscopy Applied to Building Materials, Publisher: TU Dortmund, Pages: 96-97
Grassl P, Wong HS, Buenfeld NR, 2009, Influence of aggregate size on shrinkage induced micro-cracking of mortar and concrete, 12th International Conference on Fracture
Zheng JJ, Wong HS, Buenfeld NR, 2009, Assessing the influence of ITZ on the steady-state chloride diffusivity of cement-based materials using a numerical model, Cem Concr Res, Vol: 39, Pages: 805-813
Wong HS, Buenfeld NR, 2009, Determining the water-cement ratio, cement content, water content and degree of hydration of hardened cement paste: Method development and validation on paste samples, Cem. Concr. Res., Vol: 39, Pages: 957-965
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