Mitigating autogenous shrinkage of cement paste with novel shrinkage-reducing polycarboxylate superplasticizer

This study aims to disclose the working mechanisms of a novel shrinkage-reducing polycarboxylate superplasticizer (SR-PCA) in mitigating autogenous shrinkage of cement paste. The properties of pore solutions (-including the surface tension and contact angle), ions concentration in pore solutions, internal relative humidity (RH), dynamic elastic modulus, pore structure characteristic and autogenous shrinkage are thoroughly investigated. The results indicate that SR-PCA substantially reduces the autogenous shrinkage of cement paste. From the perspective of pore solution properties, SR-PCA increases the hydrophobicity of the pore solution and reduces the surface tension, thus lowering the internal RH depression, capillary stress development and autogenous shrinkage of the cement paste. Also, SR-PCA reduces the volume fraction of mesopore (pore size less than 50 nm) where the capillary stress is exerted, thereby lowering autogenous shrinkage. Moreover, the presence of SR-PCA increases the expansion stress mainly induced by portlandite, reduces the capillary stress and enhances the dynamic elastic modulus of cement pastes, contributing to controlling autogenous shrinkage.