Topic
Cement
About: Cement is a research topic. Over the lifetime, 68440 publications have been published within this topic receiving 829356 citations.
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TL;DR: In this paper, the potential benefits of the synergistic effect of an ASTM C 618 Class F fly ash (FA) and a high-range polycarboxylate superplasticizer (SP) in the production of conventional concrete are discussed.
Abstract: This article presents experimental research work oriented toward developing practical design tools for industrial application, and illustrates the potential benefits of the synergistic effect of an ASTM C 618 Class F fly ash (FA) and a high-range polycarboxylate superplasticizer (SP) in the production of conventional concrete. The different concretes considered in this study were produced with mass substitutions of cement by FA between 15% and 75%, and a target slump of 200 mm ± 20 mm. The total water content was minimized through the use of an optimum SP dosage that resulted in water reductions of 18%, 15% and 11% respectively for the reference mixtures of w/b = 0.5, w/b = 0.55, and w/b = 0.6, which leads to the same percentage reductions of cement. Heat release and heat flow were analyzed through isothermal and semi-adiabatic calorimetry, illustrating that heat release per unit mass of cement is independent of w/b, contrasting with the time of setting results that vary by several hours between the three different w/b ratios. The paper highlights the beneficial effect of the SP in terms of cement reduction and slump retention. Correlations between the FA substitution and slump loss, setting times, compressive strength and static modulus of elasticity (E) were established and they represent very useful tools for the practical applications of the results. Compressive strength developments up to an age of 56 d are also reported, as well as correlations between the modulus of rupture and compressive strength or splitting tensile strength at an age of 28 d.
169 citations
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TL;DR: Rajghat fly ash from Delhi, India, and Baumineral fly ash near Bochum, Germany, were mixed with the locally available soils in different proportions to stabilize the fly ash-soil mixtures.
169 citations
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TL;DR: In this paper, the authors compared the effects of adding silica fume and nanosilica to concrete and provided a better understanding of the changes in the concrete nanostructure.
Abstract: It is well recognized that the use of mineral admixtures such as silica fume enhances the strength and durability of concrete. This research compares the effects of adding silica fume and nanosilica to concrete and provides a better understanding of the changes in the concrete nanostructure. Nanoindentation with scanning probe microscopy imaging was used to measure the local mechanical properties of cement pastes with 0% and 15% replacement of cement with silica fume. A reduction in the volume fraction of calcium hydroxide in a sample with silica fume provides evidence of pozzolanic reaction. Furthermore, replacing 15% cement by silica fume increased the volume fraction of the high-stiffness calcium silicate hydrate (C-S-H) by a small percentage that was comparable with the decrease in the volume fraction of calcium hydroxide. A parallel study of cement pastes with nanosilica showed that nanosilica significantly improves durability of concrete. This research provides insight into the effects of nanosilica on cement paste nanostructure and explains its effect on durability of concrete. The nanoindentation study showed that the volume fraction of the high-stiffness C-S-H gel increased significantly with addition of nanosilica. Nanoindentation results of cement paste samples with similar percentages of silica fume and nanosilica were compared. Samples with nanosilica had almost twice the amount of high-stiffness C-S-H as the samples with silica fume.
169 citations
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TL;DR: In this paper, the authors investigated the contact between foam cement concrete and polystyrene granule contact zone and showed that the contact of these two materials is very close, without any fractures or micro-cracks.
Abstract: Crumbled recycled foam polystyrene waste as well as spherical large and fine blown polystyrene waste is used to produce the filler for a light thermo-insulating composite, the matrix of which is light foam cement. For better cohesion, fillers are hydrophilizated with foam cement surfactant solution. Polystyrene granules and foam cement concrete interaction schemes are discussed. The investigation of foam cement concrete and polystyrene granule contact zone showed that the contact of these two materials is very close, without any fractures or microcracks. Adherence of the two components depends on the size and shape of granules used. When a polystyrene granule is ripped out of foam cement concrete, the emerged “hole” closely repeats the structure of the granule and there is some polystyrene residue left in it. This proves the fact that foam cement concrete contact zone is stronger than the polystyrene granule material. When fine polystyrene granules are used, it disintegrates along the contact zone. Such composite has the lowest adhesion strength, however, it is stronger in comparison with a composite, made with different foam polystyrene granules, provided by better macrostructure. Strength and thermal conductivity of the composite depend on its density, the filler, its sort and amount used, and is defined by regression equations.
169 citations
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TL;DR: In this paper, the freezing and thawing resistance of air-entrained and non-air-rained concrete concretes with a water/cement (w/c) ratio of 0.45 was investigated.
169 citations