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 relationship between the mineralogical and microstructural characteristics of activated fly ash mortars and its mechanical properties has been established, and the results of the investigation show that in all cases (whatever the activator used) the main reaction product formed is an alkaline aluminosilicate gel, with low-ordered crystalline structure.
873 citations
TL;DR: In this paper, the synthesis of alkali-activated binders from blast furnace slag, calcined clay (metakaolin), and fly ash is discussed, including analysis of the chemical reaction mechanisms and binder phase assemblages that control the early-age and hardened properties of these materials.
Abstract: The development of new, sustainable, low-CO2 construction materials is essential if the global construction industry is to reduce the environmental footprint of its activities, which is incurred particularly through the production of Portland cement. One type of non-Portland cement that is attracting particular attention is based on alkali-aluminosilicate chemistry, including the class of binders that have become known as geopolymers. These materials offer technical properties comparable to those of Portland cement, but with a much lower CO2 footprint and with the potential for performance advantages over traditional cements in certain niche applications. This review discusses the synthesis of alkali-activated binders from blast furnace slag, calcined clay (metakaolin), and fly ash, including analysis of the chemical reaction mechanisms and binder phase assemblages that control the early-age and hardened properties of these materials, in particular initial setting and long-term durability. Perspectives fo...
862 citations
TL;DR: In this article, the applicability of the tobermorite-jennite (T/J) and T/CH viewpoints for the nanostructure of C-S-H present in real cement pastes is discussed.
847 citations
TL;DR: In this paper, multi-walled carbon nanotubes after modified by using a H2SO4 and HNO3 mixture solution were added to cement matrix composites to improve the flexural strength, compressive strength, and failure strain.
829 citations
TL;DR: This study measures the composition and solid density of the principal binding reaction product of cement hydration, calcium-silicate-hydrate (C-S-H) gel, one of the most complex of all gels, and quantifies a nanoscale calcium hydroxide phase that coexists with C- S-H gel.
Abstract: Although Portland cement concrete is the world’s most widely used manufactured material, basic questions persist regarding its internal structure and water content, and their effect on concrete behaviour. Here, for the first time without recourse to drying methods, we measure the composition and solid density of the principal binding reaction product of cement hydration, calcium–silicate–hydrate (C–S–H) gel, one of the most complex of all gels. We also quantify a nanoscale calcium hydroxide phase that coexists with C–S–H gel. By combining small-angle neutron and X-ray scattering data, and by exploiting the hydrogen/deuterium neutron isotope effect both in water and methanol, we determine the mean formula and mass density of the nanoscale C–S–H gel particles in hydrating cement. We show that the formula, (CaO)1.7(SiO2)(H2O)1.80, and density, 2.604 Mg m−3, differ from previous values for C–S–H gel, associated with specific drying conditions. Whereas previous studies have classified water within C–S–H gel by how tightly it is bound, in this study we classify water by its location—with implications for defining the chemically active (C–S–H) surface area within cement, and for predicting concrete properties.
827 citations