Mitigating Climate Change Through the Use of Cement Combinations in Concrete Construction

Supplementary cementitious materials are by-products with lower embodied carbon-dioxide (eCO 2 ) contents than Portland cement. But while supplementary cementitious materials could be used to mitigate climate change, their intrinsic hydraulicity and delayed hydration reactions could have negative effect on concrete performance and cost.  Hence, using 17 binary and ternary cement combinations containing fly ash, silica fume and metakaolin at the water/cement ratios of 0.35, 0.50 and 0.65, this paper investigated the effect of supplementary cementitious materials on the strength development, environmental impact and cost of concrete. The results confirmed that cement combination concretes have lower eCO 2 contents than Portland cement concrete. At equal strengths, binary cement concretes with fly ash up to 55% content and silica fume and metakaolin at not more than 5% contents were cheaper than Portland cement concrete. Also, ternary cement concretes with not more than 5% silica fume or metakaolin content at a total replacement level of not more than 35% were cheaper than Portland cement concrete. At equal strengths of 40, 50 and 60 N/mm 2 , results showed that the use of supplementary cementitious materials resulted in a reduction of 5.5-39.0% in eCO 2 content with 50-61.5% of the cement combination concretes being cheaper by 0.1-5.1% than Portland cement concrete. Hence, the use of cement combination in the right proportion would mitigate climate change without having adverse effect on the strength and cost of concrete. Keywords: blended cement, cement additions, compressive strength, embodied carbon-dioxide, supplementary cements