Investigation on Permeability of SCC Incorporating Silica Fume and GGBFS

Self-Compacting Concrete (SCC) is one of the innovative products in concrete technology which has been developed in recent years. SCC has gained great popularity due to its benefits such as reduction in labor and equipment costs, acceleration of construction, providing flexibility in filling highly reinforced sections and complex formworks, lowering the noise on job site and having superior surface quality.\r\nHowever, many researchers are still trying to optimize the mixture proportions and investigate the incorporation of new materials in SCC. The typical high content of Portland cement in SCC is one of the main challenges in optimization of its mixture proportions. This high cement consumption increases the production cost of SCC and is also undesirable from an environmental point of view, considering the large amount of CO2 emitted during Portland cement production. \r\nNowadays cement replacement materials are being widely used in concrete mixtures and blended cements allocate noticeable amount of cement consumption in the world. Still, use of these materials is negligible in Iran and needs more attention by construction industry. Use of cement replacement materials, depending on their properties, can bring about improvements such as reduction in production costs, rheological improvements, reduction of heat of hydration and concrete durability enhancement.\r\nIn this paper the results of an experimental study on effects of silica fume and Ground Granulated Blast Furnace Slug (GGBFS) on resistance of high-strength SCC against chloride ion penetration are presented. Five concrete mixtures were prepared and tests were conducted to investigate the effects on high-strength self-compacting concrete. Filling ability, passing ability and segregation resistance of fresh mixtures were evaluated using slump flow, T50 and V funnel tests; while compressive strength, electrical resistivity and water adsorption tests were carried out on hardened concrete at different ages. The results show that GGBFS replacement decreases the viscosity of concrete and consequently the needed superplasticizer dosage. Also, results imply that use of silica fume and GGBFS decreases permeability of concrete. Finally the mixture containing 10% silica fume and 10% GGBFS cement replacement are introduced as the optimum SCC mixture.