The Effects of Different Cementing Materials and Curing on Concrete Scaling

As part of a project to determine the long-term durability of concrete made with an alkali-silica reactive coarse aggregate, six concrete mixtures were made with a variety of cementing materials: high-alkali portland cement (HAPC), low-alkali portland cement (LAPC), 25% ground granulated blast-furnace slag (GGBFS), and 50% GGBFS with high-alkali portland cement, 18% Type F fly ash with high-alkali portland cement, and 3.8% silica fume with high-alkali portland cement and 25% GGBFS. Concrete slabs were cast and cured under three conditions: 14 days in the moist room at 23°C, 14 days outdoors covered under wet burlap and plastic sheet, and 28 days in the laboratory air after application of a curing compound. The slabs were tested at an age of 28 days for 50 freeze-thaw cycles in the scaling test using a 3% sodium-chloride (NaCl) solution. The slabs cured outside under wet burlap generally had a high resistance to scaling, with the exception of the mixture with 50% GGBFS. This concrete also exhibited scaling of a full-scale outdoor slab on grade during the first winter. The slabs cured, according to the test method, in the moist curing room generally showed a low resistance to salt scaling. Erratum to this paper appears in 17(1).