Classification and Utilization Strategy of Biomass Solid Waste: Synergistic Effect of Fly Ash Assisted Gelling and Ash Aggregate Replacement

本研究系统探究了生物质飞灰与灰渣在水泥基材料中的资源化利用潜力，通过活性指数测试及抗压/抗折强度分析，揭示了其胶凝活性演变规律与改性机制。结果表明：生物质飞灰的火山灰活性显著低于传统掺合料，其28 d强度活性指数随掺量增加呈线性下降，主要归因于有效硅铝相不足及未燃尽碳颗粒的孔隙劣化效应。而生物质灰渣作为细骨料替代河砂时，预湿处理触发的内养护效应显著优化了长期性能，28d抗折强度反超未掺组。抗压强度则呈现掺量阈值效应：小于10%替代时，28 d强度保持基准组的95%以上，但15%掺量因胶凝稀释与孔隙劣化导致强度骤降13%。研究提出分级应用策略：飞灰宜作为辅助胶凝材料(掺量 ≤ 20%)，灰渣可安全替代10%河砂用于承重结构，高掺量场景需结合机械活化或化学激发。该成果为生物质固废的低碳建材化提供了理论与技术支撑。This study systematically investigated the potential for resource utilization of biomass fly ash and bottom ash in cement-based materials. Through tests of pozzolanic activity indices and analysis of compressive and flexural strengths, the study revealed the evolution of pozzolanic reactivity and the modification mechanisms of these ashes. The results indicated that the pozzolanic activity of biomass fly ash is significantly lower than that of conventional admixtures. The 28-day strength activity index of fly ash decreases linearly with increasing dosage, primarily due to insufficient reactive silica and alumina phases and the pore-deteriorating effect of unburned carbon particles. In contrast, when biomass bottom ash is used as a fine aggregate to replace river sand, pre-wetting treatment triggers an internal curing effect that significantly optimizes long-term performance, with the 28-day flexural strength exceeding that of the control group. Compressive strength exhibits a threshold effect: when the substitution level is below 10%, the 28-day strength remains above 95% of the reference group; however, at a 15% substitution level, strength drops by 13% due to pozzolanic dilution and pore deterioration. Based on these findings, a tiered application strategy is proposed: fly ash is suitable as a supplementary cementitious material (dosage ≤ 20%), while bottom ash can safely replace up to 10% of river sand in load-bearing structures. For higher substitution levels, mechanical activation or chemical activation is recommended. This study provides theoretical and technical support for the low-carbon utilization of biomass solid waste in building materials.