A Concrete Solution: Admixtures Change PCC Performance

This article discusses the chemistry of admixtures used in Portland cement concrete (PCC) to explain how the admixtures can improve PCC. PCC admixtures can be classified as either chemical or mineral and can be added before or during mixing. Mineral admixtures such as fly ash chemically react with cement to reduce bleeding of mix water, hydration heat, permeability and susceptibility. Fly ash can also benefit concrete in terms of concrete strength and approved workability. Silica fume, another mineral admixture, operates at the nanoscale to improve the durability of concrete exposed to deicing salts. Chemical admixtures, including surfactants, are used mainly for air entrainment, reduction of water or cement content, control of setting time, or plasticization of fresh concrete mixtures.