Achieving concrete sustainability using crumb rubber and GGBS

Abstract

Concrete is one of the most widely used construction materials globally. As a result, the production of concrete contributes significantly to the carbon footprint due to cement manufacturing and aggregates mining and production. Therefore, producing more sustainable concrete is vital for the reduction of the global carbon footprint. Consequently, there is an urgent need to focus on the use of waste materials in the design and production of concrete to become more sustainable and more environmentally friendly while maintaining most of its desirable properties. This paper explored the use of Crumb Rubber (CR), which is a by-product of shredding disposed automobile tires, as a partial replacement of aggregates and the use of Ground-Granulated Blast furnace Slag (GGBS), a by-product of the iron and steel industry, as a partial replacement of cement as a binder. Different percentages of crumb rubber and GGBS combinations are used to produce different mix designs. The fresh concrete properties (slump) and hardened properties (compressive strength, flexural strength, split tensile strength) of the optimal design mix were compared with that of the control design mix with zero CR and zero GGBS (CR0G0), i.e.,100% cement, normal weight aggregate, to examine their effect on the properties of concrete. It is determined that the optimum design mix obtained was the one with 5% CR and 50% GGBS (CR5G50). It has been observed that the 28 days compressive strength of the CR5G50 was 30.2 MPa while that of the CR0G0 was 60 MPa, i.e., a decrease of 50%. The 28 days flexural strength of the CR5G50 was 5.12 MPa while that of the CR0G0 was 7.8 MPa, i.e., a decrease of 34.4%. The 28 days split tensile strength of the CR5G50 was 6.92 MPa while that of the CR0G0 was 4.92 MPa, i.e., an increase of 40.7%. The slump (workability property) for the CR5G50 was 220 mm and that of the CR0G0 was 230 mm, i.e., a decrease of 4.4%. Therefore, this study shows that the use of CR in conjunction with GGBS is a potentially viable solution to produce sustainable concrete with relatively comparable mechanical properties compared to that of normal-weight concrete.