Abstract: 1. A cement .Iadd.mortar .Iaddend.composition comprising a mixture of Portland cement, mineral aggregate, about 5%-25% based on the weight of said Portland cement of styrene-butadiene-1,3 copolymer having a styrene to butadiene weight ratio of about 30:70 to 70:30, water in amount not in excess of about 40% based on the weight of said Portland cement, and, based on the weight of said copolymer, (a) 2-10% of non-ionic surfactant, (b) 1-7.5% of anionic surfactant, at least 15% of which is a sodium alkyl sulfate in which the alkyl group contains 9-17 carbon atoms, and (c) .[.1-5% of.]. polyorganosiloxane fluid surfactant, .Iadd.in an amount equal to about 2.5% of a polyorganosiloxane emulsion containing 29% of the polyorganosiloxane .Iaddend.the sum of (a) and (b) not exceeding about 14% by weight of said copolymer and the weight ratio of (a) to (b) being within the range of about 0.7:1 to 10:1.