硫酸盐侵蚀下再生骨料混凝土界面过渡区损伤机制及性能劣化模型研究

It is of vital importance to recycle the large amount of waste concrete, to ensure sustainable development of the construction industry. Till now, there are not enough studies on performance deterioration or the corresponding mechanism of recycled aggregate concrete (RAC) against sulphate ingress, which has limited the application of RAC in marine environments and in inland China with abundant sulphate. Interfacial transition zones (ITZs) can provide paths and space for penetration of external sulphate, concentration of expansive errosion products and cracking. There are more types and a larger amount of ITZs contained in RAC; damages of these ITZs should be key to revealing the mechanism of RAC’s performance degradation under sulphate ingress. Therefore, this study focuses on how the damages of ITZs in RAC on the micro scale can influence the deterioration of RAC performance on the material and member scales, respectively, under the attack of sulphate ingress. By using quantitative testing techniques combined with statistical analysis, this study aims to explore property degradation of the diverse types of ITZs contained in RAC under sulphate ingress, and thereby to select out the proper integrated ITZ parameters which can comprehensively reflect the multiple ITZ properties and their damage development over age, based on which the damage mechanism of ITZs of RAC under sulphate ingress can be described quantitatively. On a basis of the ITZ damages, this study also aims to establish the deterioration models of mechanical properties and durability of RAC materials and performance of reinforced RAC beams under sulphate ingress by using correlation analysis, and moreover, to reveal the corresponding mechnaism of such deterioration, in a quantitative way. The output of this study will not only contribute to the supplement of the theory system of RAC durability, but also lay a beneficial foundation for wider application of RAC in environments with abundant sulphate.

废混凝土循环再生是建筑行业可持续发展的重要方面。现阶段对硫酸盐侵蚀下再生骨料混凝土性能劣化规律及机理研究不够深入，制约了其在海洋及富硫酸盐内陆环境的应用。混凝土中界面过渡区是硫酸盐侵蚀、腐蚀产物富集及膨胀开裂的主要场所和路径；再生混凝土含多类界面过渡区，界面损伤是探索其在硫酸盐侵蚀下宏观性能劣化机理的关键。本项目拟从不同空间尺度出发，揭示再生混凝土在硫酸盐侵蚀下“界面过渡区损伤－宏观材料性能劣化－结构构件性能退化”的损伤传递模式。采用量化测试结合统计分析，探索再生混凝土多类界面性能随腐蚀龄期的劣化规律，确立能反映界面综合性能及其损伤程度时变发展的界面参数，定量揭示界面过渡区损伤机制；基于相关性分析，从界面损伤出发，构建硫酸盐侵蚀下再生混凝土力学、耐久性能及梁构件服役性能时变劣化模型，定量揭示其劣化机理。研究成果可丰富再生混凝土耐久性研究理论体系，为其在富硫酸盐环境的推广应用夯实理论基础。

将废弃混凝土循环再生应用于土建工程，是实现建筑业绿色、可持续发展的重要途径。与普通骨料混凝土(NAC)相比，再生骨料混凝土(RAC)抗硫酸盐侵蚀性能更差，其本质原因在于后者含有更多种类、数量的界面过渡区。探索界面过渡区性能的时变损伤机制，是从细微观尺度上揭示硫酸盐侵蚀下混凝土宏观性能劣化机理的切入点。项目设置了不同硫酸盐侵蚀环境，研究硫酸盐侵蚀下再生骨料混凝土宏观材料性能时变劣化规律，证实硫酸钠溶液浸泡和干湿循环两种条件下，再生骨料混凝土宏观性能劣化相较于普通骨料混凝土更快、更严重，其长期抗硫酸盐侵蚀能力更差，且干湿循环加剧了再生骨料混凝土在硫酸盐侵蚀下的宏观性能劣化程度。基于界面过渡区微观性能定量测试，探索界面过渡区损伤机制，发现再生骨料混凝土中老界面过渡区抗硫酸盐侵蚀性能优于新形成的界面过渡区，在硫酸盐侵蚀前期，新、老砂浆性能时变差异性不显著，但侵蚀后期，老砂浆性能劣化较新砂浆更为严重，因此新界面过渡区和老砂浆是再生骨料混凝土在硫酸盐侵蚀下的薄弱材料相。综合分析微观尺度上再生骨料混凝土各材料相在硫酸盐侵蚀下的性能时变特征，提出能综合表征硫酸盐侵蚀下各类界面过渡区及新、老砂浆性能时变损伤的细微观综合参数，通过对该细微观综合参数与再生骨料混凝土硫酸盐侵蚀下宏观性能的相关性分析，对参数有效性进行评价，基于此定量阐释硫酸盐侵蚀条件下再生骨料混凝土宏观性能劣化的内在机理。在上述研究成果的基础上，从改善界面过渡区性能出发，采用快硬性硫铝酸盐水泥复合浆液对再生粗骨料表面进行处理，从而对再生骨料混凝土抗硫酸盐侵蚀性能进行改善，实验结果表明，骨料表面处理后，所配制的再生骨料混凝土工作性、宏观力学性能（抗压强度、密实度、动弹模量）均有所提高，在硫酸盐侵蚀下侵蚀速度减缓，再生骨料混凝土的整体抗硫酸盐侵蚀性能有所改善。