Palm oil boiler ash as a viable substitute for cement

• Palm cement was produced using palm oil boiler ash at replacement levels of 10-30%. • The chemical composition of palm oil boiler ash was dominated by SiO₂ (58.13%). • Particle size metrics: polydispersity index = 1, fit error = 0.08, 81.9% in range. • The optimal palm cement paste formulation achieved compressive strengths over 28 MPa. The production of ordinary Portland cement (OPC) is a major contributor to global CO₂ emissions, while the palm oil industry generates substantial solid waste, such as palm oil boiler ash (POBA). The research focuses on identifying optimal POBA replacement levels that maximize mechanical and durability performance in palm cement (PC) formulations. The aim is to develop high-performance, eco-efficient formulations that effectively reduce the reliance on conventional cement and minimize landfilling of agricultural waste. The physicochemical properties of POBA were characterized using X-ray fluorescence, scanning electron microscopy, X-ray diffraction, and particle size analyzer. The impact of nSO₂ content (0 - 3%) on PC mechanical performance was assessed through compressive strength and deformation characteristics, informing optimal formulation. With a high SiO₂ content (58.13%) and significant P₂O₅ (7.34%), K₂O (7.88%), and CaO (7.25%), POBA’s chemical composition indicates strong pozzolanic potential, suitability for OPC replacement. POBA particles exhibit a broad and heterogeneous size distribution (polydispersity index = 1), with acceptable measurement quality (fit error = 0.08308) and 81.91% within the measurement range. All PC concretes with 60% and 70% POBA substitution (PC1-PC9) exhibited compressive strengths exceeding 21 MPa after 56 days of curing. Optimal compressive strength for PC concrete with POBA substitution below 20% was achieved with 9% and 19% POBA and 1% nSiO₂ (PC9S1 and PC19S1), closely matching OPC performance. POBA substitution in PC product not only mitigates environmental impacts but also unlocks economic value from palm oil waste. Future studies should explore circular economy frameworks to further validate its sustainability.