复合固废矿物掺合料替代粉煤灰抑制混凝土碱硅酸反应的机制OA

To address the challenges associated with the uneven regional distribution of fly ash resources and the limited availability of a stable local supply for dam construction,this study developed a composite solid-waste mineral admixture derived by solid wastes from engineering-side areas as a substitute for fly ash to mitigate alkali-silica reaction(ASR)in concrete while enabling in situ resource utilization of solid wastes.The reaction activity and mitigation effectiveness were evaluated through activity index,hydration heat,and expansion rate,while the underlying suppression mechanisms were elucidated by combining pore-solution ionic analysis with backscattered electron scanning electron microscopy.The influence on material performance was further assessed using compressive strength testing,mercury intrusion porosimetry,and thermogravimetric analysis.The results demonstrate that the composite solid-waste mineral admixture exhibits a lime consumption activity of up to 52.3%,comparable to that of fly ash.A composite solid-waste mineral admixture replacement level of not less than 20%is sufficient to control ASR expansion below the specified limit.Pore-solution ionic analysis result reveals a mitigation mechanism characterized by the reduction of alkali metal ions and the modulation of aluminum species.Thermogravimetric and porosity results indicate that,under the same mix proportion,Ca(OH)2 is continuously consumed and the pore structure gradually densifies with curing age.Overall,this study provides a low-carbon mitigation strategy for ASR control in concrete in regions with constrained fly ash supply.