Compressive Strength and Surface Absorption of High Strength Silica Fume Concrete Under Different Curing Conditions

The effect of curing conditions and silica fume replacement on the compressive strength and the initial surface absorption of high performance concrete is reported. The silica fume contents were 5, 10, 15 and 20%, by weight of cement. Four different curing conditions were used: air curing, control curing and two other curing conditions recommended by BS8110 and ACI308-81. The cementitious material (binder) content was constant (400 kg/m3); the water/cement (w/c) ratio was also maintained at a constant value of 0.35; while the water/binder (w/b) ratio ranged from 0.35 to 0.28. The addition of silica fume enhanced the compressive strength significantly up to 30%. The 28-day compressive strength was found to be 69.9 MPa without silica fume and it was determined to be 89.9 MPa with silica fume under the standard curing condition. The 28-day compressive strength results under the control curing condition were found to be higher than the compressive strength for specimens cured under other curing conditions. The surface absorption (ml/m2.s) was found to decrease as the percentage replacement of silica fume was increased. Control curing also decreases the surface absorption of water compared with air curing. Concrete with silica fume was less sensitive to drying than that without silica fume.