When concrete deteriorates, the blame usually falls on the curing, the aggregate, the mixture, or the quality control. Cement composition is seldom considered. Perhaps this is because all cements of the same type are believed to be equal if they have passed the same standard tests. However, cements of the same type, but from different plants, can vary widely in the property of extensibility (the resistance to cracking). Causes of self-stress are discussed in relation to cement content, water-cement ratio, cement fineness, alkalies, admixtures, and other factors.