Improvement of silica fume blended cements by using superplasticizer

In silica fume blended cements, the water of consistency increases with the silica fume content due to its high surface area. Therefore, the porosity is increased and the compressive strength decreased. To get full benefits o f the partial substitution by silica fume, it was decided to demonstrate th e effect of superplasticizer which reduces the water demand and/or improves the workability of cement paste. The effect of different dosages of superp lasticizer BVF addicrete obtained from the Chemicals for the Modern Buildin g Company, namely 0., 0.5, 1.0, 2.0 and 4.0 wt. % of cement, on the blended cement pastes was studied. By adding different dosages of BVF to the blend ed cement with 20 wt. % silica fume, the water of consistency decreases and the time of set is shortened. It was concluded that a high strength concre te is obtained by adding the superplasticizer to the silica fume blended ce ment. The free lime content increases up to 7 days then decreases up to 360 days. As the dosage increases the content of combined water decreases.