Sustainable concrete using paper ash and stone powder: experimental and microstructural study

Abstract This study evaluates the feasibility of paper ash (PA) as a partial cement replacement (0%, 5%, 10%, and 15% ) with a constant 15% stone powder (SP) as a sand replacement. Fresh and hardened properties were assessed through slump, compressive strength, and split-cylinder tensile tests. Furthermore, the microstructural and mineralogical changes were examined using SEM, EDX, and XRD. The slump decreased from 88 mm for the control mix to 55 mm with increasing PA percentages. It is due to the higher surface area and porous nature of PA particles. The mix made with 5% PA and 15% SP achieved a compressive strength of 25.8 MPa and tensile strength of 2.81 MPa. The achieved compressive and tensile strengths are comparable to the control mix (24.2 MPa and 2.95 MPa, respectively). Microstructural analysis supported mechanical findings. The SEM analysis revealed a denser mix and improved ITZ at 5% PA mix. However, higher PA (more than 5%) produced a more porous structure. The EDX and XRD analyses further support that moderate PA replacement maintained favorable hydration characteristics, and excessive replacement may suggest reduced hydration and a more porous microstructure.