Improvement of Shrinkage Reduction and Superplasticity of Polycarboxylate Admixture by Ester and Silane Groups

Abstract

Polycarboxylate ether (PCE) superplasticizers are widely used in concrete, but in some cases, PCE aggravates the occurrence of cracks. This study evaluates the shrinkage reduction and plasticizing properties of a newly synthesized shrink-reducing polycarboxylate polymer (KH-SRPC) modified with ester and silane groups. When the KH-SRPC was implemented at a dosage of 0.3% by weight of cement, the adsorption capacity on the surface of the cement particles and the spreading diameter of the cement improved with respect to traditional PCE. Furthermore, the autogenous shrinkage and drying shrinkage of the mortar containing KH-SRPC were also investigated. When the KH-SRPC content was 0.2% of the weight of the cementitious material, the autogenous shrinkage of the KH-SRPC mortars at 3 and 7 days was reduced by 72.6% and 43.5%, respectively. The drying shrinkage of KH-SRPC mortars decreased by 38.3% at 3 days, 39.0% at 7 days, 39.1% at 14 days, and 35.7% at 28 days. It was found that KH-SRPC changed the pore structure of the solidified mortar, reduced the surface tension of the pore solution, and slowed down the rate of hydration, thereby reducing the total shrinkage of the mortar system.