Effect of some superplasticizers on the properties of silica fume blended cement pastes

Blended cements were made with Portland cement and 10, 20 and 30 wt\% condensed silica fume. Three different types of admixtures (mater soluble condensates) were used: superplasticizers BVF (sulphonate naphthalene formaldehyde condensate), BVD (sodium gluconate) and BVS (sulphonate naphthalene formaldehyde condensate and sodium gluconate). The cement pastes were mixed with adequate water of consistency and cured up to 360 days. Compressive strength and hydration kinetics were studied. The water demand and the setting time decrease with the dose of admixtures. On the other side, the compressive strength and bulk density increase, whereas the total porosity decreases. The combined water content increases with silica fume content. On the other hand, the free lime decreases up to one year. It was concluded that a very high strength concrete with low porosity can be produced by combination of condensed silica fume and superplasticizer.