Evaluation of microsilica admixture for production of high strength concrete.

PDFTech ReportFHWA/LA-90/227LTRC #88-1C(B)Silica fumePortland cement concreteHigh strength concreteEvaluationLouisianaLouisiana Transportation Research CenterRasoulian, MasoodLouisiana Transportation Research CenterLouisiana. Dept. of Transportation and DevelopmentUnited States. Federal Highway AdministrationUS Transportation CollectionThis study consisted of a laboratory evaluation of the effect of microsilica on the physical properties of both plastic and hardened portland cement concrete. Microsilica (silica fume) is a by-product of the industrial manufacture of ferro silicon and other metallic silicones in high-temperature electric arc furnaces. Microsilica is a very fine material, pozzolanic in nature. Due to its physical and chemical characteristics, microsilica when used as an admixture has the potential of enhancing the properties of portland cement concrete. In this study the variable selected for evaluation is the dosage rate of microsilica. Other variables included the microsilica source; the cement factor and the dosage rate of the other admixtures. All experimental and control mixes contained cement and aggregate of the same type and from the same respective source. When utilized, air entraining and high-range water reducer admixtures were also of the same type and from the same respective source. The results of this evaluation indicate that the inclusion of microsilica in a portland cement concrete mix can improve compressive and flexural strengths, increase the modulus of elasticity, improve resistance to scaling and decrease permeability. Physical properties that may be adversely affected by this admixture include freeze/thaw durability and workability. No conclusions could be drawn on the effect of microsilica on set times and length change and abrasion resistance. A reommendation is made to further evaluate microsilica admixtures by and through the utilization of the product on selected project(s)