再生骨料的内腐蚀机理与混凝土行为响应

Abstract: Recycled aggregate inevitably carry corrosive medium such as chlorides, sulfates or carbonates, due to the complicated service environment of the parent concrete. When it was used to mix concrete, the recycled aggregate with corrosive medium just like diffuse lesions in the concrete. After it meets reaction condition, the corrosive medium will react directly in the concrete, which will influence the microstructure, long-term mechanical properties, durability and damping capacity of concrete. However, there is lack of research on the related field currently. Based on this, in this project, the recycled aggregate with different dosage of corrosive media was chosen firstly to study the distribution forms, existing forms and dissolution characteristics and transmission mechanism of different corrosive media in recycled aggregates under the condition of cement hydration. Then the mechanism of internal corrosion from recycled aggregate(ICRC) will be revealed. Next，the reaction condition and product of internal corrosion under the condition of cement hydration, and the change of the interface transition zone between recycled aggregate and cement paste will be investigated with time. After this, the effect of ICRC on the long-term mechanical properties, durability and damping capacity of concrete will be studied. Sequentially, the superposition effect of recycled aggregate and external conditions on properties of concrete will be researched, the relation between interface characteristics of recycled aggregate and macro-performance of concrete will be explored. Finally, the mechanism of internal corrosion from recycled aggregate on behavior response of concrete will be studied.

受母体混凝土长期复杂服役环境影响，再生骨料不可避免的携带氯盐、硫酸盐或碳酸盐等腐蚀介质，用之制备混凝土，携带腐蚀介质再生骨料犹如混凝土内分散病灶，时机成熟便直接在混凝土内发生腐蚀作用，影响混凝土微观结构及其长期力学性和耐久性等宏观性能，而目前这方面缺乏深入系统研究。基于此，本项目拟选择受氯盐、硫酸盐和碳酸盐腐蚀程度不同的再生骨料为对象，研究再生骨料携带不同腐蚀介质的分布形式、存在形态及其在水泥水化环境下的溶出特性与传输机制；探究再生骨料携带不同腐蚀介质在混凝土中与水泥水化产物发生反应的条件及产物种类与结构，以及对再生骨料界面过渡区特征的依时性影响规律，揭示再生骨料的内腐蚀机理；研究再生骨料内腐蚀性对混凝土长期力学性能、耐久性和减振性影响，探明混凝土再生骨料内腐蚀性与外部环境作用的叠加效应，建立内腐蚀再生骨料界面特征与混凝土宏观性能间量化关联，揭示混凝土宏观性能对再生骨料内腐蚀性响应机制。

再生骨料受母体混凝土复杂服役环境影响，不可避免携带一定量的腐蚀介质，这些腐蚀介质可在再生骨料制备的混凝土中发生内腐蚀，进而影响其结构和性能，而目前这方面缺乏深入系统研究。基于此，本项目选择受氯盐、硫酸盐腐蚀程度不同的再生骨料为对象，研究了携带腐蚀介质再生骨料对混凝土力学性、收缩性等的影响；深入分析了内腐蚀作用下再生混凝土多重界面结构变化规律及腐蚀产物分布情况；揭示了再生骨料携带腐蚀介质在水泥水化环境中的扩散机制；结合灰色关联理论和层次分析法，建立了内腐蚀作用下再生混凝土宏观性能预测模型并成功模拟其力学损伤过程。研究结果表明，随再生骨料取代率和腐蚀程度增加，混凝土早期强度略微提高，其长期力学性和收缩性降低，矿物掺合料则可有效提高再生混凝土的力学性与耐久性；再生骨料携带硫酸根离子、氯离子与水泥水化产物反应生成的腐蚀产物主要为AFt、石膏和Friedel盐等，并大多分布于界面过渡区附近；随再生骨料腐蚀程度和替代率增大，结构内孔隙增多，多重界面过渡区性能降低；随龄期增加，硫酸根离子从再生骨料中溶出并扩散到浆体中，可用Nernst-Einstein方程模拟其动态变化过程，再生骨料界面处的扩散速度远远高于浆体内部；基于细微观性能建立的再生混凝土三类内腐蚀性因子与宏观力学性能关联性颇高，通过选择对应的内腐蚀性参数可进行宏观性能预测；采用优化算法编写的随机骨料再生混凝土模型程序，基于ABAQUS有限元法模拟再生骨料内腐蚀作用下的混凝土力学损伤过程。该研究成果可为再生混凝土高性能化设计提供理论指导，并为相关技术标准修订提供依据。