Influence of Superplasticizer and Silica Fume on the Structure Formation and Properties of Cement Stone

Abstract

AbstractThe influence of superplasticizer and silica fume on cement hydration, structure formation, phase composition, and cement stone properties is investigated. It was found that using a polycarboxylate superplasticizer reduces the normal consistency of the cement paste and increases the cement stone strength at 28 days by 22%. Replacing cement with silica fume in the absence of a superplasticizer does not increase the cement stone strength, but it reduces the open capillary porosity of the cement stone by 7%. The combined use of silica fume and superplasticizer increases the cement stone strength by 27% and reduces open capillary pores volume by 17% compared to the control sample without admixtures. According to the X-ray phase analysis results, it was established that the use of polycarboxylate superplasticizer leads to a slowdown in the hydration processes of clinker minerals at 1 day. The use of silica fume accelerates the cement hydration in the early hardening stages and compensates for the plasticizing admixture slowing effect. At 28 days, in the cement stone with silica fume, a decrease in the portlandite content by 39% is observed. The combined use of superplasticizer and silica fume leads to the formation of a cement stone structure with increased content of amorphized low-basic hydrated calcium silicates by 22%, which significantly densifies and strengthens the cement stone structure.KeywordsCement stoneSilica fumeSuperplasticizerNormal consistencyCompressive strengthPorosityPhase compositionPozzolanic reaction