Concrete is a composite material that consists of a binding medium and aggregate particles and can be formed in several types. It may be considered to consist of three phases: a cement paste, the aggregate, and the interfacial transition zone (ITZ) between them. In addition to ordinary Portland cement, the essential components of the base of concrete are aggregates and water. For practical requirements, additives and admixtures can be added to these raw materials to improve some desirable characteristics. The following requirements should be considered in producing high performance concrete (HPC): (i) low water/cement (w/c) ratio; (ii) fine aggregate; (iii) large quantity of mineral additives, silica fume, and fly ash; (iv) high dosage of superplasticizer; and (v) high-pressure steam curing. The microstructure of high performance concrete (HPC) is more homogenous than that of normal concrete (NC) due to the physical and chemical contribution of the additives (silica fume and fly ash) as well as it is less porous due to reduced w/c ratio with the addition of a superplasticizer. Inclusion of additives (individually or in combination) helped in improving the strength and durability of concrete mixes due to the additional reduction in porosity of cement paste and an improved interface between it and the aggregate.
Part of the book: High Performance Concrete Technology and Applications