An additive to hydraulic cement or an admixture for concrete or mortar that causes air to be incorporated in the form of minute bubbles on the concrete or mortar during mixing, usually to increase its workability and frost resistance. Air-entrained Ordinary Portland Cement contained agents, such as calcium lignosulphate, which entrain 4%-5% minute, discontinuous uniformly distributed air bubbles, The density reduction may mean a decrease in strength of up to 15%. Ashurst (1983); RS Means Building Glossary (undated). [J. Cassar, R. de Angelis].