水泥基矽尘泡沫轻质土耐久性能及微观机理研究

Research on the Durability and Microscopic Mechanism of Cement-Based Silica Dust Foam Lightweight Soil

摘要: 为了研究水泥基矽尘泡沫轻质土的耐久学性能和微观机理，以水泥、矽尘作为胶凝材料制作泡沫轻质土，分析湿密度(500 kg/m³、600 kg/m³、700 kg/m³、800 kg/m³)、矽尘掺量(0%、7.5%、12.5%、17.5%、22.5%)及冻融循环次数等因素对泡沫轻质土经历耐久性后的无侧限抗压强度、表观形态、质量损失率、孔泡结构的影响，建立冻融循环性能预测模型。结果表明：随着冻融循环次数的增加，无侧限抗压强度呈现出波动降低趋势；湿密度高于700 kg/m³的试件，冻融30次后的表观形态较完整；并且所有配合比的试件质量损失率均小于5%；矽尘掺量低于12.5%时，能有效提高无侧限抗压强度；相同养护龄期内，设计湿密度与抗压强度成正比；依据实验结果，建立了适用于不同配合比的水泥基矽尘泡沫轻质土的冻融循环性能预测公式；揭示了冻融循环强度微观机理，湿密度越大，泡沫轻质土孔隙率越低；矽尘掺量越多，平均孔径越小。研究成果可以为该材料的工程应用提供依据。

Abstract: In order to study the durability properties and microscopic mechanism of cement-based silica dust foam lightweight soil, cement and silica dust were used as cementitious materials to make foam lightweight soil, and the wet density (500 kg/m³, 600 kg/m³, 700 kg/m³, 800 kg/m³), silica dust content (0%, 7.5%, 12.5%, 17.5%, 22.5%) and the number of freeze-thaw cycles were analyzed to determine the unconfined compressive strength, apparent morphology, mass loss rate and pore structure. The results show that with the increase of the number of freeze-thaw cycles, the unconfined compressive strength shows a fluctuating downward trend. The apparent morphology of specimens with wet density higher than 700 kg/m³ was relatively complete after 30 freeze-thaw times. And the mass loss rate of all specimens is less than 5%; when the dust content of the quarry is less than 12.5%, it can effectively improve the unconfined compressive strength. During the same curing age, the design wet density is directly proportional to the compressive strength. According to the experimental results, a prediction formula for the freeze-thaw cycle performance of cement-based silica dust foam lightweight soil with different mix ratios was established. The microscopic mechanism of freeze-thaw cycle strength was revealed, and the higher the wet density, the lower the porosity of foamed light soil. The more silica dust is added, the smaller the average pore size. The research results can provide a basis for the engineering application of this material.