EFFECT OF DELAYING ADDITION TIME OF SMF SUPERPLASTICIZER ON HYDRATION CHARACTERISTICS OF BLENDED CEMENT PASTES

摘要

This paper aims to study the effect of delaying addition time of sulphonate melamine formaldehyde superplasticizer (SMF) onthe rheology and hydration characteristic of blended cement pastes up to 90 days. The optimum dosage of superplasticizerwas chosen as 1.0 mass %, this dosage gives the higher compressive strength and bulk density as well as lower total porosity.The optimum delaying time of superplasticizer was 7.5 min which gives the highest fluidity, bulk density, compressivestrength and chemically combined water contents of cement pastes, whereas, the delaying addition time of 15.0 min showsthe lower values of bulk density, compressive strength and combined water contents. This is attributed to the reduction ofhydration rate of cement, due to the formation of a polymer film around the cement particles and/or hydrated products. Thesuperplasticizing effect improved with a delayed sulphonate melamine formaldehyde superplasticizer addition time.