Abstract

A fundamental issue with the active ingredient of concrete, Portland cement, is its energy-intensive manufacturing process, which has led to the cement industry emitting up to 10% of global CO2 levels. To facilitate the reduction in the embodied CO2 of concrete, the Portland Cement (PC) content has been entirely replaced volumetrically with Hydrated Lime (HL) and ground granulated blast furnace slag (GGBS or SL). GGBS was used to replace hydrated lime content in 10% increments up to 100% GGBS. Analysis of compressive and flexural strength and density testing was performed on samples to investigate the mechanical and physical properties at 7, 28 and 91-day curing ages, whilst flexural testing was conducted at 91 days curing age. Four standard mix ratios, 1:1:3, 1:2:3, 1:1:2 and 2:1 was made for comparison. Two curing conditions were tested at 91-day curing age, these being air-cured and water curing. Results have shown the optimum mix ratio to be 1:1:2 for all mixes. The optimum mix being HL 1:1:2 SL80%, water cured exceeding 25MPa. Throughout the different ratios, it can be concluded that the optimum replacement of GGBS lies between 80-90%; it can also be noted that 100% GGBS content sees a significant drop in compressive and flexural strength, indicating the presence of hydrated lime to be a catalyst for strength gain.