大粒径再生骨料堆石混凝土抗渗性能研究

Utilizing the large size recycled aggregate formed by the simple crushing of waste concrete replaces the natural rock casting to form rock-filled concrete. This kind of construction waste resource utilization technology can reduce the energy consumption and secondary pollution in the production process of recycled aggregates to a certain extent. However, due to the complex character of the recycled aggregate, the impermeability of the recycled aggregate filled concrete needs to be paid attention to ensure the durability of the material. This study starts with the characteristics of the interface transition zone of large size recycled aggregates, based on the quantitative characteristics of the micro-porosity structure in the transition zone, the influence of aggregate characteristics and other factors on the transitional zone of the recycled aggregate filled concrete interface and the mechanism of action are investigated. Based on visual scanning and CT scanning technology, the external shape and internal structure of large size recycled aggregates are reconstructed in three dimensions. Integrating the law of transition zone and the internal and external characteristics of large size recycled aggregates, the finite element simulation and experimental verification of rock-filled concrete impermeability are carried out, and the internal moisture transport model of concrete under water pressure is developed. It provides theoretical basis and technical guidance for the design of impermeability of large size recycled aggregate filled concrete.

利用废弃混凝土简单破碎后所形成的大粒径再生骨料，替代天然岩石浇筑成型堆石混凝土。该种建筑垃圾资源化利用技术，可以一定程度降低再生骨料生产过程中的能耗和二次污染。但由于再生骨料性态复杂，成型后的再生骨料堆石混凝土抗渗性能需要引起关注以确保材料的耐久性。本研究从大粒径再生骨料的界面过渡区特性入手，基于过渡区的微观孔隙结构量化特征，探究骨料特性等因素对再生骨料堆石混凝土界面过渡区的影响规律和作用机制。基于视觉扫描和CT扫描技术，对大粒径再生骨料的外部形态和内部结构进行三维重建，整合界面过渡区变化规律以及大粒径再生骨料内外部特征，开展堆石混凝土抗渗性能有限元模拟和试验验证，开发考虑水压力条件下的混凝土内部水分传输模型，为今后大粒径再生骨料堆石混凝土的抗渗性设计提供理论依据和技术指导。

利用再生骨料替代天然岩石浇筑成型堆石混凝土，可降低骨料生产过程中的能耗和二次污染，但由于再生骨料性态复杂，成型后的混凝土抗渗性能需要引起关注以确保耐久性。本项目结合试验研究、机理分析与数值仿真等方法，从多尺度分析了再生骨料堆石混凝土的力学与抗渗性能。首先，通过实验室条件与工程实践收集，制备和获取了不同粒径的再生骨料，开展了如下工作。综合考虑压碎指标、吸水率、外部粒型、内部孔隙以及碱活性等特性的再生骨料综合性能全面评价研究；对综合性能较差的再生骨料，通过纳米增强材料对其进行了纳米增强，并复评价了增强后的再生骨料性能；从混凝土流变性、力学性能、抗渗性能以及微观性能等多维度开展分析，明确了再生大骨料的内部孔隙以及过渡区等自身性能是限制混凝土抗渗性等耐久性的关键因素，通过纳米材料增强或者碱活性带来的微膨胀可以适当提升再生大骨料的综合力学与抗渗性能。其次，基于双目视觉三维重建以及CT扫描等技术，建立了再生骨料外观粒型及内部孔隙的数字模型。同时应用相关软件对实验室再生骨料的破碎过程进行了数值模拟，为获取不同形貌的再生大骨料提供了一定的制备方式指导。最后，开展了不同骨料含量及比表面积、ITZ（界面过渡区）孔隙率、净浆孔隙率条件下堆石混凝土渗透特性数值模拟，研究表明，堆石混凝土渗透系数总体和ITZ以及净浆孔隙率呈正相关关系，ITZ的存在增大了净浆的连通性，有助于增大净浆本身的渗透能力；在骨料含量较低时，随着ITZ孔隙率的增大，混凝土渗透系数将逐渐转为受净浆渗透系数主导，当骨料含量较高时，ITZ本身的孔隙率是影响混凝土渗透系数的主要因素。.