PROPERTIES AND DURABILITY OF ALKALI-ACTIVATED SLAG CONCRETE

The purpose of this study was to formulate the proportioning of concrete mixes made with ground granulated blast furnace slag activated with sodium silicate, and to determine their properties and durability. Six mixes were made with a solution having silicate modulus M(s) = 1.47 and one mix with sodium silicate of M(s) = 1.22. All the mixes were air-entrained. Compressive and flexural strengths, Young's modulus of elasticity, shrinkage, and chloride ion penetration were determined. Measurements of length and mass changes, as well as resonant frequency and pulse velocity, were performed to evaluate the resistance of the concretes to repeated cycles of freezing and thawing. Sulfate resistance was evaluated by the same technique. The study shows that air content, volume of air-entraining admixture, slump, and early-age compressive strength are affected by the sodium silicate-slag ratio. Compressive and flexural strengths of the concretes at 7 days and beyond are comparable to or better than those of a portland cement concrete with equivalent water-cement ratio and workability. Drying shrinkage and expansion shrinkage strains were higher than those of a comparable portland cement concrete. Low sodium silicate-slag ratios adversely affected the resistance to repeated freezing and thawing cycles but improved the resistance to chloride ion penetration. Longer term test measurements are necessary to evaluate the resistance of the concretes to sulfate attack.