Improvement of shrinkage reducing performance of polycarboxylate superplasticizer by butyl acrylate and its mechanism

Abstract A series of polycarboxylate superplasticizers (PCEs) with different molecular structures and shrinkage reducing performance were synthesized by modifying PCE with butyl acrylate (BA), and their molecular structures were characterized. The influence of BA on the dispersion and shrinkage reducing performance of PCEs and the influence of PCEs grafting different ration of BA on the hydration of cement were investigated in detail. Furthermore, the mechanisms of BA improving PCE shrinkage reducing performance were emphatically analyzed. The results showed that: (1) BA was successfully grafted into the molecular structures of PCEs and the expected molecular structures were obtained by polymerization. (2) BA has little effect on the dispersion of PCEs, but it will affect the hydration process of cement paste mixed with PCEs and significantly improve the shrinkage reducing performance of PCEs. (3) After grafting BA monomer into PCE, the surface tension of PCE solution decreased and the evaporation rate of alkaline solution mixed with PCE also significantly slowed down. Moreover, the retention capacity of pore water of cement paste mixed with PCE was improved. These three reasons were considered to be the main mechanisms of BA improving the shrinkage reducing performance of PCE.