再生混凝土构件复合受力性能和冻融环境下结构力学性能试验研究与设计方法

The objective of the project is to conduct the experimental study and design method for the combined force performance of the recycled concrete structural member and the basic mechanical properties of the recycled concrete structure in the freeze-thaw condition. The main contents include: (1) To study the refined classification for recycled aggregate and the scientific preparation method of the recycled concrete, to establish a design method for the mixture ratio of the recycled concrete, and for different strength grade of the recycled concrete, to found the key qualification for the recycled aggregate. (2) To carry out the experiments and the theoretical study of the combined force performance of the recycled concrete structural member, and to conduct the contrast tests and the theoretical study of the basic mechanical properties of the recycled concrete structural member, to reveal the failure characteristics, interface morphology and microstructure mechanism of the failure structure under the combined force action. (3) To perform the experiments and the theoretical study of the basic mechanical properties of the recycled concrete structure under the freeze-thaw cycle action, to lay a foundation for the limit state design and durability design of the recycled concrete in the cold region, to improve the frost-resistant safety of the structure. (4) To establish the design method and the safety evaluation for the recycled concrete structure under the combined force action and under the freeze-thaw cycle action, to guide the engineering design of the recycled concrete structure. Through the study of this project, the design theory of the recycled concrete structure will be improved, and the more systemic analysis and the design theory of the recycled concrete under the freeze-thaw cycle action will be proposed, which will advance our research level of the recycled concrete, and promote the popularization and application of the recycled concrete.

针对再生混凝土构件复合受力性能和冻融循环作用下结构基本力学性能及相应的设计方法展开研究。主要内容包括：(1)研究再生骨料精细化分级与再生混凝土科学化制备方法，建立再生混凝土配合比设计方法及用于不同强度等级混凝土的再生骨料关键技术指标。(2)进行再生混凝土构件压弯剪扭复合受力性能试验及基本力学性能对比试验与理论研究，揭示复合受力作用下结构失效的破坏特征、界面形态以及微观机制。(3)进行冻融循环作用下再生混凝土结构基本力学性能试验与理论研究，为寒冷地区再生混凝土结构极限状态设计及耐久性设计奠定基础，提高结构的抗冻安全性。(4)建立复合受力再生混凝土结构设计方法及冻融循环作用下再生混凝土结构设计方法及安全性评价，指导再生混凝土结构工程设计。通过本项目的研究，完善再生混凝土结构的设计理论，同时形成冻融循环下再生混凝土结构较系统的分析与设计理论，提升我国再生混凝土研究水平，促进再生混凝土的推广应用。

本研究项目针对再生混凝土配合比设计、再生混凝土构件复合受力性能和冻融循环作用下结构基本力学性能及相应的设计方法展开了研究。具体工作如下：.1. 建立了再生粗骨料各项技术指标与基体混凝土的关系，对比了不同制备工艺和配合比设计方法对再生混凝土力学性能的影响；探讨了强化前后再生粗骨料性能参数的变化规律，分析了不同强化工艺对再生混凝土力学性能的影响。.2. 通过自制试验加载装置完成了75根再生粗骨料取代率分别为0%、30%、50%、70%和100%的再生混凝土空心圆柱体试件的纯剪和压剪复合受力的试验研究。基于试验结果，在综合分析多种强度准则的基础上利用八面体应力理论建立了再生混凝土压剪复合受力的破坏准则。.3. 通过自主设计的加载装置完成了18根近足尺再生混凝土构件在纯扭、弯剪、剪扭和压弯复合受力下的工作性能试验研究，探讨了复合受力下的承载能力和破坏模式，建立了适用于再生混凝土构件的复合受力设计方法。.4. 系统考察了基体混凝土类型和制备工艺对引气再生混凝土抗冻性的影响，通过切片分析并采用浆体开裂率和界面开裂率来表征再生混凝土各部分的开裂破坏程度，从细观层面揭示了再生抗冻性混凝土的冻融破坏机制。.5. 完成了72个棱柱体试件冻融损伤后的单调受压和反复受压性能试验，建立了再生混凝土冻融损伤后的反复受压本构模型；通过28组84个试件的单向及重复拉拔试验系统考察了冻融循环作用下再生混凝土与钢筋间的粘结性能，给出了冻融环境再生混凝土结构钢筋的临界锚固长度；.6. 完成了冻融循环后9根再生混凝土梁的抗弯性能试验和18根再生混凝土柱的偏心受压性能试验，提出了适用于寒冷地区再生混凝土结构的设计公式和建议。