![]() Gaboriaud, F., Nonat, A., Chaumont, D., Craievich, A. The nature of C–S–H in hardened cement pastes. Temperature effect on concrete creep modeled by microprestress-solidification theory. on Creep, Shrinkage, and Durability of Concrete and Concrete Structures (Hermes Science, London, 2005).īazant, Z., Cusatis, G. in Creep, Shrinkage, and Durability Mechanics of Concrete and Other Quasi-Brittle Materials (eds Ulm, F. Cement Chemistry 2nd edn (Thomas Telford, London, 1997).Īcker, P. Experimental Researches on the Constitution of Hydraulic Mortars (McGraw, New York, 1905). 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. We show that the formula, (CaO) 1.7(SiO 2)(H 2O) 1.80, and density, 2.604 Mg m −3, differ from previous values for C–S–H gel, associated with specific drying conditions. 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 also quantify a nanoscale calcium hydroxide phase that coexists with C–S–H gel. 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. Sometimes, quartz flour and fiber are the components as well for HPC having ultra-strength and ultra ductility, respectively.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. However, for very high strengths, more than 98Mpa, it is necessary to use the slag in conjunction with silica fumes. Slags are suitable for use in high-strength concrete at dosage rates between 15-30 %. 6.3 Ground Granulated Blast Furnace Slag (GGBFS) For high strength concrete, fly ash is used at dosage rates of about 15 % of cement content. Therefore, for higher strengths, silica fume must be used in conjunction with fly ash. Most fly ashes will result in strengths of not more than 70 MPa. Fly ash is, unfortunately, much more variable than silica fumes in both their physical and chemical characteristics. 6.2 Fly Ashįly ash has been used extensively in concrete for many years. With silica fume, it is easier to make HPC for strengths between 63-98 MPa. Beyond that strength level, however, silica fume becomes essential. It is possible to make high strength concrete without silica fume, at compressive strength of up to 98 MPa. In developed countries, it is already available readily blended with cement. Silica fume is available in different forms, of which the most commonly used now is in a densified form. Silica fume is a waste by-product of the production of silicon and silicon alloys. The cementitious component of high or any combination of cementitious material such as slag, fly ash, silica fume. It is an essential component of high-performance concrete that is added into the concrete mix to reduce water to cement ratio. The selection of coarse aggregate is crucial since it may control the strength of high-performance concrete. Fine AggregateĬoarse fine aggregate is desired compared to finer sand to produce high-performance concrete since finer sand increases the water demand of concrete. Water is a crucial component in high-performance concrete which should be compatible with cement and mineral/chemical admixtures. Nonetheless, a certain quantity of C3A is important for cement from a strength point of view. For instance, cement with low C3A is the most desired type of cement to produce high-performance concrete because the C3A creates incompatibility of cement with a superplasticizer.Īdditionally, the rheology of cement containing low C3A can be controlled easily. CementĬhemical and physical properties of cement can help in selecting desired cement to produce high-performance concrete. The composition of high-performance concrete usually consists of the following materials: 1. Composition of High-Performance Concrete.
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