Concrete incorporating supplementary cementing materials: Effect on compressive strength and resistance to chloride-ion penetration

This paper presents the results of an investigation dealing with the effect s of curing method on the compressive strength and the resistance to chlori de-ion penetration of concrete incorporating supplementary cementing materi als. The concrete was Mired under wet burlap for 7 days,followed by exposur e to the laboratory air of cured using three different curing compounds. Th e effect of the water-cement ratio (w/c) and the type of supplementary ceme nting materials, including fly ash, silica fume, and ground granulated blas t furnace slag, were evaluated. The compressive strength of the concrete wa s determined at 7, 28 and 91 days, and the resistance of the concrete to th e chloride-ion penetration was determined at 28 and 91 days. For the portland cement concrete with a w/c of 0.32, the compressive streng th and the resistance of the concrete to the penetration of chloride ions w ere not affected significantly by the curing conditions. The portland cemen t concrete with w/c of 0.55 and 0.76 and cured under wet burlap had signifi cantly higher resistance to the penetration of chloride ions and higher com pressive strength than that cured using Curing Compound I. For the portland cement concrete with a water-to-cementitious materials ratio (w/cm) of 0.3 2 and incorporating silica fume and slag, the compressive strength of the c ores taken at 7 and 28 days and the resistance of the concrete to the penet ration of chloride ions were not affected significantly by the curing condi tions. However, at 91 days, the cores taken from the concrete cured under w et burlap had higher compressive strengths than those cured using Curing Co mpound I. For the concrete with a w/cm of 0.32 and incorporating ASTM Class F or Class fly ash, the compressive strength of the cores taken at 7 days was not affected by the curing conditions. However, at 28 and 91 days, the concrete cured under wet burlap showed higher compressive strengths than th at 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 fly ash, the resistance to the penetration of chl oride ions was not affected significantly by the method of curing. In gener al, the type of curing compounds used did not affect either the compressive strength or the resistance of the concrete to chloride ion penetration sig nificantly.