Utilization of Egyptian by-products in the preparation of blended cements

Condensed silica fume is a by-product in the production of silicon or its alloys. Ferrosilicon is produced from quartz, coke and iron ore. Reduction of quartz in the presence of carbon at 2000 degrees C, in the arcs between electrodes submerged in the charges, results in the formation of silicon. About 10 to 15\% quartz in the charge is lost in the form Si and SiO vapours which react with air to form SiO2. Upon cooling, the SiO2 fumes condense into tiny spherical particles, composed essentially of amorphous silica. Blastfurnace slag is a by-product formed during the manufacture of iron from the fusion of limestone with ash from coke and the siliceous and aluminous residue remaining from the iron ore after the reduction of iron. The by-products such as condensed silica fume and granulated slag were used for the preparation of blended cements. They help to reduce the cost and conserve energy sources and the environment. The results revealed that the addition of 5 to 10\% silica fume improves the physico-mechanical properties of ordinary Portland cement as well as of slag cement pastes.