Evolution of mechanical properties of concrete containing ground granulated blast furnace slag and effects on the scaling resistance test at 28 days

Compressive strength, ultrasonic pulse velocity (UPV), non-evaporable water content and the interplay between them were investigated at 1, 3, 7 and 28 days to determine the effects of using ground granulated blast furnace slag (GGBFS) as cement replacement. The variables considered include percentage of GGBFS as cement replacement (0–60%), total binder content (270–450 kg/m3), water-to-binder ratio (0.31, 0.38) and curing period. The dilution effect was observed at day 3, at which point, increasing the amount of GGBFS as cement replacement yielded lower compressive strengths. The results show that the evolution of mechanical properties is affected by the amount of water, percent of GGBFS added and curing regime. By 28 days, the benefit of using GGBFS as cement replacement owing to its effect on the concrete’s packing density and hydration processes was reflected in the compressive strength and UPV measurements when used up to 50% cement replacement. Compressive strength of concrete containing GGBFS is found to increase on average by 10% from 28 days to 120 days. Measurements of non-evaporable water content and mass loss due to scaling revealed that the scaling resistance test for concrete at 28 days is more favorable towards OPC concrete and discriminates against concrete containing high percentages of GGBFS as cement replacement.