Concrete Incorporating Supplementary Cementing Materials: Effect of Curing on Compressive Strength and Resistance to Chloride-Ion Penetration

Abstract

This paper presents the results of an investigation dealing with the effects of curing method on the compressive strength and the resistance to chloride-ion penetration of concrete incorporating supplementary cementing materials. The concrete was cured under wet burlap for 7 days, followed by exposure to the laboratory air or cured using three different curing compounds. The effect of the water-cement ratio (w/c) and the type of supplementary cementing materials, including fly ash, silica fume, and ground granulated blast furnace slag, were evaluated. The compressive strength of the concrete was determined at 7 days, 28 days, and 91 days, and the resistance of the concrete to the chloride-ion penetration was determined at 28 days and 91 days. For the portland cement concrete (PCC) with a w/c of 0.32, the compressive strength and the resistance of the concrete to the penetration of chloride ions were not affected significantly by the curing conditions. The PCC with w/c of 0.55 and 0.76 and cured under wet burlap had significantly higher resistance to the penetration of chloride ions and higher compressive strength than that cured using Curing Compound I. For the PCC with a water-to-cementitious materials ratio (w/cm) of 0.32 and incorporating silica fume and slag, the compressive strength of the cores taken at 7 days and 28 days and the resistance of the concrete to the penetration of chloride ions were not affected significantly by the curing conditions. However, at 91 days, the cores taken from the concrete cured under wet burlap had higher compressive strengths than those cured using Curing Compound I. For the concrete with a w/cm of 0.32 and incorporating ASTM Class F or Class C fly ash, the compressive strength of the cores taken at 7 days was not affected by the curing conditions. However, at 28 days and 91 days, the concrete cured under wet burlap showed higher compressive strengths than that cured using Curing Compound I. For the concrete incorporating ASTM Class F fly ash, the resistance to the penetration of chloride ions was affected by the method of curing, with the concrete cured under wet burlap showing superior resistance to that cured using Curing Compound I. For the concrete incorporating ASTM Class C fly ash, the resistance to the penetration of chloride ions was not affected significantly by the method of curing. In general, the type of curing compounds used did not affect either the compressive strength or the resistance of the concrete to chloride ion penetration significantly.