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Use of waste glass as sand in mortar: Part II - Alkali-silica reaction and mitigation methods

Waste glass may be used in concrete provided that the potential deleterious expansion caused by alkali-silica reaction (ASR) could be mitigated. In this study, the influence of glass content, color and particle size on ASR expansion of mortar was determined by the accelerated mortar bar method. Two approaches to control ASR expansion were investigated for green, brown and clear glass sand mortar. They were: (1) by replacing cement with pozzolans, that is, 30% fly ash, 60% GGBS, 10% silica fume, or 20% glass powder; (2) by adding a suppressor, that is, plain steel fibers, and lithium chloride and lithium carbonate compounds. Test results showed that the ASR expansion increased with higher glass content in the case of clear glass sand mortar, but would decrease with increasing content for green and brown glass sand mortar. The ASR expansion also decreased with smaller glass particle size, regardless of glass color. Fly ash and GGBS were the most effective in mitigating ASR expansion, followed by silica fume, st…

Author: Du, Hongjian, Tan, Kiang Hwee
Publication year: 2013
Publication type: Journal article
Status: Live|Last updated:22 November 2017 6:32 PM
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All roads lead to Rome: the universality of the Roman ideal in Achille Funi’s incomplete fresco cycle for the Palazzo dei Congressi in EUR, 1940-43

Abstract not available.

Author: Marcello, Flavia
Publication year: 2017
Publication type: Journal article
Status: Live|Last updated:22 November 2017 6:32 PM
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Use of 2-D Graphene Nanoplatelets (GNP) in cement composites for structural health evaluation

This study investigates the use of Graphene Nanoplatelets (GNP) in cement composite to quantify the material damage extent. The damage sensing capability of this new cement composite is demonstrated by experimentally measuring the electric potential across prisms with known notch depth and comparing it with finite element simulations. Meanwhile, the damage extent is directly related to the change in electric potential based on a mathematical analogy between the electrostatic field and the elastostatic field under anti-plane shear loading. It is shown that the fractional change in electric potential arising from damage is equivalent to the fractional change in elastic compliance, which can be exploited for structural health evaluation.

Author: Le, Jia-Liang, Du, Hongjian, Pang, Sze Dai
Publication year: 2014
Publication type: Journal article
Status: Live|Last updated:22 November 2017 6:32 PM
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Effect of particle size on alkali-silica reaction in recycled glass mortars

The effect of particle size on alkali-silica reaction (ASR) was investigated to clarify the difference in long-term ASR expansions in mortars using recycled green and brown glass as fine aggregates. Test results revealed that green particles of 1.18 and 2.36 mm showed the highest reactivity while the other sizes resulted in relatively low ASR expansions. Brown glass less than 2.36 mm did not result in large ASR expansion. Furthermore, different ASR suppressors were explored to suppress ASR expansion in mortar using 1.18 mm green glass particles. These included supplementary cementitious materials, steel fiber reinforcement and lithium compounds.

Author: Du, Hongjian, Tan, Kiang Hwee
Publication year: 2014
Publication type: Journal article
Status: Live|Last updated:22 November 2017 6:32 PM
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Waste glass powder as cement replacement in concrete

The pozzolanic reactivity of waste glass powder was experimentally studied at cement replacement levels of 0, 15, 30, 45 and 60% by weight. Results revealed that the concrete compressive strength was not decreased by the cement substitution after 28 days because of the pozzolanic reaction between glass powders and cement hydration products, if the replacement is below 30%. Also, the resistance to chloride ion and water penetration continuously increases with increasing glass powder content up to 60% cement replacement. At 60% replacement level, the electrical resistivity and water penetration depth were reduced by 95% and 80%, respectively, while the compressive strength was maintained as 85%. These improvements in durability properties are due to the refined microstructures, particularly at the interfacial transition zone. Pore size distribution was measured to confirm the refinement in the capillary pores, which partially block the pathways for water and chloride ions. This study also demonstrates that high…

Author: Du, Hongjian, Tan, Kiang Hwee
Publication year: 2014
Publication type: Journal article
Status: Live|Last updated:22 November 2017 6:32 PM
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Durability performances of concrete with nano-silica

This study investigated the durability properties of concrete containing nano-silica at dosages of 0.3% and 0.9%, respectively. Due to the nano-filler effect and the pozzolanic reaction, the microstructure became more homogeneous and less porous, especially at the interfacial transition zone (ITZ), which led to reduced permeability. Tests on the durability properties verified the beneficial effects of nano-silica. The channels for harmful agents through the cement composites were partially filled and blocked. The pore size distribution also indicated that the large capillary pores were refined by the nano-silica, due to the combined contribution of the nano-filler effect and the pozzolanic reaction.

Author: Du, Hongjian, Du, Suhuan, Liu, Xuemei
Publication year: 2014
Publication type: Journal article
Status: Live|Last updated:22 November 2017 6:32 PM
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Habits and the social phenomenon of leadership

Leadership research has grown into two opposing approaches, the scientific approach and the critical approach. The first is focused on leadership, the second on the leaders. For reasons of practicality, they will be described as the leadership-centric and the leader-centric approach, respectively. Each of the two approaches is characterised by two different perspectives: leadership-centric research highlights science and process; leader-centric research deals with the leader using cognitive faculties and drawing on cultural practices. This opposition has created an unproductive gap in leadership scholarship. The present article focuses on how to reduce that gap by bridging some of the differences that currently undermine scholarship. The concept of habits is used to support an argument in favour of leadership as a social phenomenon. The main idea is that a social phenomenon involves both social interactions happening in everyday shared knowledge and intentionality that influences agents’ experiences. By borro…

Author: Betta, Michela
Publication year: 2017
Publication type: Journal article (In press)
Status: Live|Last updated:22 November 2017 5:32 PM
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Convergence properties of halo merger trees; halo and substructure merger rates across cosmic history

We introduce GBPTREES: an algorithm for constructing merger trees from cosmological simulations, designed to identify and correct for pathological cases introduced by errors or ambiguities in the halo finding process. GBPTREES is built upon a halo matching method utilizing pseudo-radial moments constructed from radially sorted particle ID lists (no other information is required) and a scheme for classifying merger tree pathologies from networks of matches made to-and-from haloes across snapshots ranging forward-and-backward in time. Focusing on SUBFIND catalogues for this work, a sweep of parameters influencing our merger tree construction yields the optimal snapshot cadence and scanning range required for converged results. Pathologies proliferate when snapshots are spaced by less than or similar to 0.128 dynamical times; conveniently similar to that needed for convergence of semi-analytical modelling, as established by Benson et al. Total merger counts are converged at the level of similar to 5 per cent for…

Author: Poole, Gregory B., Mutch, Simon J., Croton, Darren J., Wyithe, Stuart
Publication year: 2017
Publication type: Journal article
Status: Live|Last updated:22 November 2017 4:32 PM
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Precision calculations of the cosmic shear power spectrum projection

We compute the spherical-sky weak-lensing power spectrum of the shear and convergence. We discuss various approximations, such as flat-sky, and first-and second-order Limber equations for the projection. We find that the impact of adopting these approximations is negligible when constraining cosmological parameters from current weak-lensing surveys. This is demonstrated using data from the Canada-France-Hawaii Telescope Lensing Survey. We find that the reported tension with Planck cosmic microwave background temperature anisotropy results cannot be alleviated. For future large-scale surveys with unprecedented precision, we show that the spherical second-order Limber approximation will provide sufficient accuracy. In this case, the cosmic-shear power spectrum is shown to be in agreement with the full projection at the sub-percent level for l > 3, with the corresponding errors an order of magnitude below cosmic variance for all l. When computing the two-point shear correlation function, we show that the flat-sk…

Author: Kilbinger, Martin, Heymans, Catherine, Asgari, Marika, Joudaki, Shahab...
Publication year: 2017
Publication type: Journal article
Status: Live|Last updated:22 November 2017 4:32 PM
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The nature of massive transition galaxies in CANDELS, GAMA and cosmological simulations

We explore observational and theoretical constraints on how galaxies might transition between the 'star-forming main sequence' (SFMS) and varying 'degrees of quiescence' out to z = 3. Our analysis is focused on galaxies with stellar mass M-* > 10(10) M-circle dot, and is enabled by GAMA and CANDELS observations, a semi-analytic model (SAM) of galaxy formation, and a cosmological hydrodynamical 'zoom in' simulation with momentum-driven AGN feedback. In both the observations and the SAM, transition galaxies tend to have intermediate Sersic indices, half-light radii, and surface stellar mass densities compared to star-forming and quiescent galaxies out to z = 3. We place an observational upper limit on the average population transition time-scale as a function of redshift, finding that the average high-redshift galaxy is on a 'fast track' for quenching whereas the average low-redshift galaxy is on a 'slow track' for quenching. We qualitatively identify four physical origin scenarios for transition galaxies in th…

Author: Pandya, Viraj, Brennan, Ryan, Somerville, Rachel S., Choi, Ena, Barro,...
Publication year: 2017
Publication type: Journal article
Status: Live|Last updated:22 November 2017 4:32 PM
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