Investigating the mechanical and microstructural effects of partially replacing cement with common bean straw ash in non-structural concrete

This study focuses on using common bean straw ash to partially replace cement in producing non-structural concrete. The study investigated the effect of cement replacement with common bean straw ash, specifically 0%, 5%, 10%, and 15%. Firstly, the common bean straw ash was created from the straw of the common bean plant, and its chemical composition was analyzed, confirming it as a class-C pozzolanic material. As the percentage of common bean straw ash replacement increased, the workability of the concrete decreased, and the concrete’s water absorption capacity also increased. However, at 5% replacement, the workability and water absorption of the concrete remained within acceptable limits. The highest improvement in compressive strength, 3.65%, was observed in the concrete with 5% common bean straw ash replacement. This enhancement was attributed to the formation of additional calcium silicate hydrate gel within the concrete. Microstructural examination using X-ray diffraction revealed that at 5% replacement, there were more calcium silicate hydrate gels than in the control mix. The scanning electron microscope image also depicts fewer pores and micro-cracks at 5% replacement than control concrete. Overall, a 5% replacement level resulted in improved compressive strength, acceptable workability, water absorption capacity, and enhanced microstructural properties. These findings offer insights into the sustainable utilization of agricultural by-products in the construction industry.