Evaluation of sustainable metakaolin-geopolymer concrete with crushed waste clay brick

In the last decades, with the speed up of urban construction and infrastructure, the large amounts of new concrete and, at the same time a huge quantity of construction and demolition waste are generated every year. Therefore, the sustainability of concrete technology and building industry has taken priority with respect to, CO2 emission during cement manufacturing, natural resources depletion, environmental pollution and ecology unbalance. This study aims to assess the possibility of produce a more eco-friendly geopolymer concrete using Iraqi metakaolin (MK) and crushed waste clay brick (CWCB) as coarse aggregate, regarding the highest compressive strength and more sustainable curing method. The variations in the mechanical properties of MK-based geopolymer concrete with different contents (0%, 10%, 20%, and 30%) of waste clay brick as a replacement by volume of natural coarse aggregate were investigated. The fresh density and mechanical properties (compressive, splitting and flexural strengths), also the dry density was evaluated at age of 7 and 28 days. The results showed that all mixes with CWCB had lower fresh and dry densities. Geopolymer concrete mix with 30% CWCB showed a reduction in fresh and dry densities of 3.22%and 6.30 % respectively relative to the concrete mix without CWCB. Also, the compressive and splitting tensile strength reduce with the increase of CWCB content, the percentage reduction is 53.37% and 45.09% for 30% CWCB replacement level respectively relative to reference specimens (0% CWCB aggregate). On the other hand, specimens with 10% of CWCB showed a slight improvement in flexural strength, while with 20 and 30% CWCB there is a reduction in flexural strength. Generally, production of moderate strength MK-geopolymer concrete incorporates waste clay brick as coarse aggregate will improve the sustainability and lead to open wide areas for civil engineering applications.