Research on the effectiveness of polycarboxylate superplasticisers with different side-chain lengths

Abstract

Polycarboxylate superplasticiser (PCSs) are commonly used and studies to enhance their compatibility with other concrete raw materials have been undertaken. However, the effect of the side-chain length (SCL) in PCSs on the properties of cement-based materials (CBMs) has not gained enough attention. To fill this research gap, five types of PCSs with different SCLs were synthesised through a redox initiator system. The workability, hydration behaviour, microstructure formation and cracking sensitivity of CBMs containing PCSs with different SCLs were thoroughly examined. The results showed that, with an increase in the SCL of the PCS, the initial fluidity of the cement paste increased first and then decreased but fluidity losses decreased gradually. Compared with PCSs with short side-chains, PCSs with long side-chains improved the hydration heat peak value and shortened the dissolution period, thus accelerating the hydration and microstructure formation of cement. The 28 d strength and anti-cracking behaviour of the CBMs increased first and then decreased with an increase in SCL. The results of this study suggest that there is an optimum SCL for PCSs that produces good workability and the lowest crack sensitivity in CBMs.