Role of water–binder ratio on the strength development in mortars incorporated with silica fume

An experimental investigation on the variation of compressive strength, with water–binder (w/b) ratios in mortars incorporated with silica fume, has been reported. The w/b ratios varied between 0.35 and 0.50 at a constant increment of 0.05. The silica fume content varied from 0% to 30%. The strength development with w/b ratio has been studied at different ages of 3, 7, 28 and 90 days. Abrams' generalized water–cement (w/c) ratio law has been verified for mortars with silica fume at all the ages. From the test results, it has been observed that, in plain cement mortars, the strength of mortar decreases as the w/b ratio increases at any age of mortar. However, the mortar mixes containing silica fume did not follow the same variation as has been observed in plain cement mortars. At early ages of 3 and 7 days, the strength of mortars with silica fume decreases with w/b ratio up to 0.45. Between w/b ratio 0.45 and 0.50, the strength has been observed to increase with w/b ratio. However, at the ages of 28 and 90 days, the strengths of mortars at w/b ratios of 0.35, 0.40 and 0.50 were observed to be more or less the same. But, at w/b ratio of 0.45, the strength has been observed to be the lowest at any silica fume content. At w/b ratio of 0.50, the influence of silica fume (>27.5%) was pronounced significantly at later ages. Moreover, it has been observed that the variation of strength with w/b ratio could not comply with the Abrams' generalized w/c ratio law in mortars containing silica fume