Using Cementitious Materials to Enhance Concrete Properties and Improve the Environment: A Review

Abstract

Cement production significantly contributes to carbon dioxide emissions, which increase global warming. Therefore, reducing cement consumption can support efforts to reduce that risk. On the other hand, the consumption of industrial wastes in concrete production contributes to improving the environment. Industrial waste can be used as supplementary cementitious materials (SCMs) to enhance concrete properties. This paper reviews the effects of SCMs, such as silica fume, fly ash, metakaolin, and ground granulated blast furnace slag (GGBFS), on the properties of fresh and hardened concrete. The findings show that SCMs enhance packing density and reduce permeability. The impact of SCMs on concrete properties appears after a period of curing depending on the availability of calcium hydroxide and activity index. Calcium hydroxide produced from cement hydration reacts with silicates of SCMs to produce additional calcium-silicate hydrates that enhance concrete strength and minimize the relatively large size of calcium hydroxide, which lowers porosity. Silica fume and metakaolin raise water demands and reduce workability, while GGBFS and fly ash improve workability. Silica fume, metakaolin, and (10) μm particle size of GGBFS increase early-age strength, (10-45) μm particle size of GGBFS enhances strength after 28 days, while fly ash raises the strength after 90 days. For low cement content, 10 % or less silica fume, (10-30) % fly ash, (10-20) % GGBFS or metakaolin are considered the perfect percentage to arrive at best strength. For high cement content, (25-30) % silica fume or 40 % fly ash is considered the optimum ratio to reach the highest strength.