Production of eco-friendly alkali-activated concrete for sustainable highway infrastructure by effective utilization of recycled construction and foundry wastes

Abstract

A sustainable substitute for conventional pavement concrete composite is provided by alkali-activated concrete (AAC), which is made from industrial byproducts and which has less of an impact on the environment than conventional cement-based materials. The purpose of this research is to combine waste foundry sand (WFS) with recycled concrete aggregates (RCAs) to manufacture alkali-activated slag concrete (AASC) and to create a circular economy model that maximizes the use of recovered materials, minimizes waste disposal issues, and uses less energy during the extraction and manufacturing of raw resources. The desirable grade of the AASC mix was carefully formulated to comply with Indian Standards for high-quality pavement applications. The optimal mix proportions were determined through a series of experiments based on the hardened and fresh properties of concrete. The resulting AASC composite consisted of 20% WFS and 50% RCA based on volume. The ideal compressive strength of the mix of 64 MPa was attained after 28 days, which exceeded the required strength for the desired paving concrete. The combination that was used showed a rise of 9.67% in split tensile strength and an increase of 20.3% in flexural strength between the period of 7 and 28 days. Models of simple linear regression (SLR) and multiple linear regression (MLR) were used to predict compressive strength. SLR analysis revealed that RCA and WFS had considerable negative impacts on compressive strength, with coefficients of −0.026315 and −0.13476, respectively. With an R-squared value of 0.8044, the MLR model demonstrated strong predictive ability. The study focuses on how AASC supports resource efficiency, promotes sustainable building practices, and reduces reliance on natural aggregates. The findings contribute significantly to our understanding of how AAC might be widely applied in the building industry to promote a circular economy and to enhance environmental sustainability.