Effect of sonication on the reactivity of silica fume in Portland cement mortars

Currently, the use of silica fume for the production of mortars and high-performance concrete is of great importance to the construction materials sector. Different applications of silica fume have generated extensive studies about its high reactivity as a pozzolanic material, in addition to its effect on the properties of some materials within which it is incorporated. In this study a sonication process was applied by means of which the deagglomeration of the larger particles of densified silica fume (CSF) was achieved. The result is a CSF treated with the ultrasound probe, which is obtained for different tests where the parameters of sonication such as sonication power level and sonication time are varied. This treatment makes it possible to increase the quantity of submicrometric particles in the sample. The effect of sonication process on CSF produces a greater quantity of very fine particles, which improve the pozzolanic reactivity of silica fume and increase the fixation of hydrated lime. This behaviour also produces higher mechanical strength in mortars manufactured with sonicated silica fume (SSF). The mechanical strengths of SSF mortars were greater than those for control and CSF mortar. Different percentages of cement were substituted (between 0 and 15% by weight), and in all cases the SSF mortars showed important differences from the CSF mortar. It was observed that for the longest sonication times and highest sonication power levels, mechanical strengths were increased.