Optimization of polycarboxylate-based admixtures for cementitious compositions

摘要

The present invention provides compositions and methods for modifying hydratable cement compositions, such as concrete or mortar, using at least three different individual carboxylate polymers. Modification can be carried out even if clays that are likely to reduce the quantitative efficiency exhibited by the polycarboxylate polymer used as an agent are present in the concrete or mortar. The three types of polycarboxylate polymers designated as Polymer I, Polymer II and Polymer III are derived from monomer components A, B and C, where component A is an unsaturated carboxylic acid and component B is Polyoxyalkylene and component C is an unsaturated carboxylic acid ester. While the range of component molar ratios of A: B: C is varied as the ratio between polymers I and II, another component molar ratio A: B + C is specified for polymer III. Surprisingly, when the hydratable cementitious composition is treated with the three different polycarboxylate polymers, the initial workability and slump retention are improved, especially in the presence of clay.