Patent ID: 6277191
Filing Date: 2001-08-21
Classification: C04B,C08L

Abstract:
A method for improving air entrainment in a cementitious composition having an oxyalkylene shrinkage reduction admixture, comprising introducing to the shrinkage reduction admixture a polyoxyalkylene copolymer having a di-block structureR.sup.1 --[OA.sup.1 ].sub.m --[OA.sup.2 ].sub.n --OR.sup.2 ;orR.sup.1 --[OA.sup.2 ].sub.n --[OA.sup.1 ].sub.m --OR.sup.2wherein R.sup.1 and R.sup.2 represent hydrogen, an alkyl group, a cyclo alkyl group, or an aryl group; OA.sup.1 represents an oxyalkylene group wherein O represents oxygen and A.sup.1 represents ethylene groups; and OA.sup.2 represents an oxyalkylene group wherein O represents oxygen and A.sup.2 represents propylene groups, butylene groups, or mixture thereof; m is an integer of 5-200; and n is an integer of 5-200; said method further comprising adding an alkali or alkaline earth metal salt into the cementitious composition; said shrinkage reduction admixture and said salt being present in the cementitious composition in the amount of 0.1-10% s/s based on the weight of cement in the composition, and said polyoxyalkylene copolymer being present in the cementitious composition in the amount of 0.005-5.0% s/s based on the weight of cement in the composition.