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 of the partial substitution by silica fume, it was decided to demonstrate the effect of superplasticizer which reduces the water demand and/or improves the workability of cement paste. The effect of different dosages of superplasticizer BVF addicrete obtained from the Chemicals for the Modern Building 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 blended 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 concrete is obtained by adding the superplasticizer to the silica fume blended cement. 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.