engleski

Influence of amorphous silica (silica dust) on the properties of Portland cement mortars

The effect of silica dust emerged as a by-product of the production of ferro-silicon, on the physical and mechanical properties of concrete mortar have been studied. Silica dust in concentration of 2, 5, 8, 11 and 15 wt% on expense of cement was added. It has been established that the cement mortar containing 8 wt% of silica dust shows the highest compressive strength. Porosity measurements and pore size distribution show that porosity decreases by addition of silica dust up to 8 wt% and if more silica is added, porosity increases. Pore size distribution curves show a discontinuous pore structure. The quantity of free calcium hydroxide in mortars with and without addition of silica dust during the hydration period and sulphate attack in aggressive solutions of Na2SO4 and MgSO4 has been estimated by differential thermal analysis. X-ray powder diffraction (XRD) was used to study the hydration products at different ages. The corrosion process has been studied by measurements of the elastic modulus, by determination of mortars expansion exposed to attack of sulphate, and by scanning (SEM) and transmission (TEM) electron microscopy.

Portland cement; silica fume; pozzloanic reaction; sulphate attack; XRD; SEM; TEM.

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