粉煤灰-盾构渣土基混凝土性能优化与机理分析

Performance optimization of fly ash-shield soil dreg concrete and mechanism analysis of shield soil dreg

摘要:

为解决盾构渣土（SSD）堆存量日益增加和河砂短缺问题，采用未经筛分处理SSD替代河砂、粉煤灰（FA）替代水泥，以SSD替代率、FA替代率、水胶比和用水量为因素，坍落度、抗压强度、生命周期评价（LCA）为评价体系，采用响应面法（RSM）对优化配合比进行评价分析，并通过微观形貌特征分析SSD在混凝土中的作用机理。结果表明：在满足基本工作性能和力学性能前提下，掺入FA并利用RSM优化混凝土配方能将SSD成功用作混凝土用砂，优化配方后SSD混凝土生态影响相较同等性能普通混凝土最多下降11%；微观结果表明：SSD主要驱动机制为粘附效应、离子吸附交换作用、内养护效应及改变界面过渡区（ITZ）宽度和有效水胶比，进而影响混凝土抗压强度。

Abstract:

To address the increasing challenges posed by shield soil dreg (SSD) accumulation and the shortage of river sand, unscreened SSD is used as a replacement for river sand, and fly ash (FA) is used as supplementary cementitious material. The response surface methodology (RSM) is employed to optimize the mix proportions, with SSD replacement rates, FA replacement rates, water-to-binder ratio, and water content as factors. The evaluation metrics include slump, compressive strength, and life cycle assessment (LCA), complemented by microstructural analysis to elucidate the mechanisms of SSD in concrete. The results indicate that: (1) Under the conditions of meeting basic workability ?and mechanical properties, incorporating FA and utilizing RSM to optimize the concrete proportions can enable the successful utilization of SSD as sand in the production of concrete. Compared with ordinary concrete of similar performance, the ecological impact of SSD concrete with optimized mix proportions can be reduced by up to 11%. (2) The microscopic results indicate that the influence of SSD on compressive strength is primarily attributed to adhesion effects, ion adsorption and exchange mechanisms, internal curing effects, and its ability to alter the interfacial transition zone (ITZ) width and the effective water-to-binder ratio.