基于骨料表面改性的再生混凝土多重界面调控及多尺度力学行为

再生骨料由于表面附着砂浆的存在，其性能与天然骨料存在显著差异。并且，由再生骨料制备的再生混凝土内部存在多重薄弱界面(ITZ)结构，宏观力学性能和耐久性能都弱于普通混凝土，限制了再生骨料的大规模应用。针对这一难题，本项目拟通过浆体预包裹法对再生骨料进行表面改性，在包裹浆体中引入粉煤灰、硅灰及纳米SiO2等多尺度火山灰活性组分，优化浆体组分配比，填充和修补附着砂浆及老ITZ中多尺度孔隙及裂纹等初始损伤，强化新ITZ微结构，实现多重ITZ协同调控，阐明包裹浆体法对多重ITZ微结构的调控机理；通过对比改性前后再生骨料的基本性能，验证浆体预包裹法的可行性；结合强度测试、X-CT和SEM等技术，获得考虑多重ITZ改性的再生混凝土多尺度力学行为，阐明微裂纹在多重ITZ间的扩展模式；重构再生混凝土三维结构，建立再生混凝土力学本构模型，为再生骨料的大规模、高效化推广应用提供理论基础和技术支撑。

The root cause of the inferior properties of recycled concrete aggregates (RCA) compared to the natural aggregates lies in the presence of attached mortar on the aggregate surface. Also, the attached mortar results in the formation of multiple interfacial transition zones (ITZ) in recycled aggregate concrete, which leads to the weaker mechanical and durability properties of recycled aggregate concrete. Given that, the project intends to coat the RCA with the pozzolana slurry. In which, the fly ash, silica fume and nano SiO2 will also be introduced and the mix proportion is carefully designed to make sure that the multiscale pores and cracks in the attached mortar and old ITZ could be filled and repaired. The efficiency will be evaluated by the comparison of basic physical and mechanical properties of RCA before and after surface modification. Further, the active agents in the slurry could also play a role in the formation of new ITZs and the microstructure of ITZs before and after modification will also be quantitatively determined and compared to reveal the mechanisms. Then, the multiscale mechanical behavior of the recycled aggregate concrete will be quantitatively characterized by macro mechanical performance test, X-CT and SEM. And the 3D microstructure of recycled aggregate will be reconstructed based on the real particle shape and ITZ microstructure obtained from previous examinations. Overall considering the modification of the microstructure and the improvement of mechanical properties of recycled aggregate concrete, the feasibility of the adopted method will be evaluated. The achievements of this project will lay a solid foundation for the wide application of the RCA.