Effects of Retarding Admixture, Superplasticizer and Supplementary Cementitious Material on the Rheology and Mechanical Properties of High Strength Calcium Sulfoaluminate Cement Paste

Abstract

In this paper, the effects of retarding admixture, polycarboxylate (PCE) superplasticizer and supplementary cementitious material (SCM) on the rheology of high strength calcium sulfoaluminate (CSA) cement paste are investigated. At the water to binder ratio of 0.3, one PCE, two retarding admixtures, and three SCMs were used in the test. The test results show that much more PCE is needed for paste with citric acid than that with sodium borate to achieve a similar initial flowability. The reference paste and pastes mixed with sodium borate or fly ash exhibit shear thickening; pastes mixed with citric acid or silica fume exhibit shear thinning. The addition of citric acid increases the maximum shear stress of pastes, while the maximum shear stress can be significantly reduced by silica fume. Both the retarding admixtures and SCMs will strongly reduce the early-age compressive strength of the cement paste. At 28 days of age, CSA cement paste incorporating retarding admixtures has comparable strength to the reference paste. Silica fume has less negative effect on the compressive strength of the CSA cement paste due to the significant filling effect.