Experimental and simulation analysis of RCA and para-wood ash as partial substitutes for NCA and cement in recycled aggregate concrete

Recycled concrete aggregate (RCA) is widely used as an alternative recycled material in engineering, while para-wood ash (PWA) is a natural agricultural waste product. To advance sustainable construction, it is crucial to thoroughly examine their impact on concrete’s mechanical properties to ensure safety in engineering applications. This paper presents a series of experiments on recycled aggregate concrete (RAC) incorporating PWA to investigate these effects. RCA replaces natural coarse aggregate (NCA) at 0%, 50%, and 100%, while PWA substitutes cement at 0%, 10%, and 20%. The experiments include compression tests on mortar, as well as compressive, tensile, and flexural tests on RAC, accompanied by microstructure investigations. The results indicate a decrease in strength with higher proportions of RCA and PWA. Microstructure investigations were conducted using scanning electron microscopy with energy-dispersive X-ray analysis (SEM/EDX). The EDX results reveal a direct correlation between the Ca/Si ratio and the strengths of mortar and RAC. Correlation studies between compressive strength-replacement parameters, tensile-compressive strength, and flexural-compressive strength demonstrate that the proposed equations accurately predict the experimental data, with R² values of 0.60 for mortar and 0.94, 0.95, and 0.71 for RAC, respectively. Two numerical simulations validate the proposed model and demonstrate potential engineering applications. Finally, a 10% replacement of PWA for cement can reduce the embodied energy value (EEV) by approximately 9.46% for mortar mixed with PWA and around 10% for RAC mixed with RCA and PWA. Although using recycled materials such as RCA and PWA in concrete mixtures leads to a decrease in strength, their appropriate use can reduce environmental impact and is sufficient for engineering applications that require low or medium strength. This approach also promotes the recycling of materials, contributing to the use of sustainable materials in construction.