微波辅助混凝土骨料资源化回收中的多场效应研究

Recycled concrete aggregate is one kind of important way for the resource recycling of construction wastes, and the solution of contradiction between requirement of construction materials and environment disruption. The quality of recycled aggregate is the key point restrict the resource utilization. Microwave assisted aggregate extraction could efficiently improve the quality of recycled aggregate. It is a new green technology with low energy consumption and less pollution. The objective of this proposal is to research the multi-field effect for microwave assisted aggregate resource recycling. Laboratory test, theoretical analysis and numerical simulation would be employed to study the project. Effects of mineral composition, mortar strength grade and other factors on concrete dielectric property and microwave penetrating depth would be investigated to improve the understanding of microwave heating concrete. The quantitative relation between microwave parameters and concrete temperature would be established. Evolution of temperature and thermal stress of concrete under microwave irradiation would be theoretically analyzed. The temperature gradient and mismatch thermal stress at aggregate-mortar interface of would be further discussed. Based on the fracture toughness and crack energy release rate, the debonding process and critical irradiation for break separation between aggregate and cement mortar would be systematically studied to reveal the working mechanism of electro-magneto-thermo-mechanical fields for microwave assisted aggregate resource recycling. The results of this project could provide important theoretical support for the development and application of this new green technology.

混凝土骨料回收再利用是建筑垃圾资源化处置以及解决建筑材料需求与环境破坏矛盾的重要途径之一，再生骨料品质是制约其资源化利用的关键因素。微波辅助混凝土骨料的分离提取，能有效提高再生骨料的品质，是新型能耗低、污染少的高效绿色技术。本项目以微波辅助混凝土骨料资源化回收中的多场效应为研究对象，采用试验研究、理论分析和数值模拟相结合的方法，研究骨料矿物组成、砂浆强度等级等因素对混凝土介电性能和微波穿透深度的影响规律，探索微波加热混凝土的物理机制，明确微波参数与混凝土加热升温之间的量化关系；研究微波照射下混凝土内部温度场与热应力场的演化规律，明确微波参数和混凝土材料参数对骨料-砂浆界面温度梯度、热失配应力的影响规律；结合骨料-砂浆界面裂纹能量释放率与断裂韧性，探讨微波照射下骨料与砂浆分离的力学机理与临界照射条件，揭示骨料分离中的电-磁-热-力多场作用机制，为该新型技术的发展和推广应用提供重要的理论支撑。

本项目以微波辅助混凝土骨料资源化回收中的多场效应为研究对象，采用了试验研究、理论分析和数值模拟相结合的方法，对微波加热过程中混凝土电磁-热-力多场耦合力学机理进行研究。首先通过理论研究的方法，结合材料电物理和热力学参数，对微波在骨料和砂浆传播过程中的损耗特征进行了研究；其次，通过试验研究和数值模拟的方法，对微波照射下混凝土内部电磁场、温度场与热应力场的演化规律进行研究，分析了加热参数例如加热时间、功率、频率等对混凝土内部温度、应力、混凝土破碎及骨料分离率的影响，研究加热过程中骨料、砂浆及两者界面力学性能的变化，探讨了微波照射下骨料与砂浆分离的临界照射条件范围；同时，通过理论和试验研究相结合的方法，对不同条件微波照射后的骨料力学性能进行了分析，研究不同微波能量输入下骨料内部裂纹萌生和扩展表征方法，并将微观变化与宏观力学性能变化相结合，建立微波照射工况参数与粗骨料宏观力学性能之间的定量联系，全方位评价回收骨料的力学性能。