Slump retention in cementitious compositions

摘要

Disclosed is method for achieving slump retention in cement comprising adding into a cement binder three different components which comprise: (a) a first polycarboxylate comb polymer superplasticizer having pendant ionized cement anchoring groups and having pendant non-ionizable dispersing groups, wherein the ratio in said first polycarboxylate comb polymer superplasticizer of said ionized cement anchoring groups is 1:1 to 20:1 with respect to said non-ionizable dispersing groups; (b) a biopolymer polysaccharide; and (c) a second polycarboxylate comb polymer superplasticzer having pendant initially-non-ionized cement anchoring groups, which become ionized over time after being mixed into the wet cementitious mixture, and pendant non-ionizable dispersing groups, wherein the ratio in said second polycarboxylate comb polymer superplasticizer of said initially non-ionized cement anchoring groups is 1:1 to 20:1 with respect to said non-ionizable dispersing groups.