Under ASTM C150 specifications, the eight recognized standard classifications of Portland cement comprise Type I (general purpose), Type IA (air-entraining general purpose), Type II (moderate sulfate resistance and moderate heat of hydration), Type IIA (air-entraining moderate sulfate resistance), Type III (high early strength), Type IIIA (air-entraining high early strength), Type IV (low heat of hydration), and Type V (high sulfate resistance).