Advancing sustainable construction through waste valorization using plastic aggregate and industrial slag

To lower overall carbon emissions, this study investigates the viability of replacing cement and river sand with steel slag from electric arc furnaces and replacing coarse aggregate in concrete with plastic aggregate (PA). According to optimisation, it was best to replace 30% of the cement with slag (SAC), 30% of the coarse aggregate with PA, and 50% of the coarse aggregate with fine slag aggregate (SAFA), as this combination showed compressive strength values of 30, 29.14, and 41.16 MPa. The mixed mix that included 30% PA, 50% fine aggregate replacement, and 30% cement replacement was examined. The compressive strength of the mix, including cementitious slag and PA, was noticeably low (i.e., 36%). Other combined mixes showed a reduction in compressive strength value of up to 15.6%. These results underscore the importance of selecting suitable combinations in concrete mixes to ensure adequate tensile and compressive strengths. It is to note that the tensile strength of these mixed mixes was determined to be insignificant. This can be the result of inadequate cementitious slag-plastic bonding. Overall, the flexural strength of the mix with SAC and PA showed only marginal contributions, while SAFA showed upto 98% increase in strength value in comparison to the normal mix. While the mix with slag as cement and fine aggregate was showing an increase in flexural strength of up to 58%. Additionally, microstructural analysis identified a significant presence of CSH, ettringite, and portlandite. The CSH component enhances strength and rheological properties, ettringite aids in early setting time and strength development, and portlandite acts as a bonding agent.