再生混凝土细微观结构和破坏机理研究

On the Micro-and Meso-Structure and Failure Mechanism of Recycled Concrete

再生骨料相当于天然骨料表面附着了一层老砂浆,老砂浆力学性能相对天然骨料较差,造成了再生混凝土内界面过渡区的数量、分布和性能的不同,从而影响了再生混凝土的力学性能.首先通过试验方法研究了再生混凝土中老砂浆的含量和分布;利用扫描电镜考察了新老界面过渡区形貌的异同,分析了老砂浆对界面过渡区的影响;采用有限元软件ANSYS对再生混凝土细观结构的受力特征和破坏机理进行了初步分析.最后利用不同强度等级的废旧混凝土加工成再生粗骨料,制备成再生混凝土,测试其抗压强度和劈裂抗拉强度,验证了再生混凝土受力的破坏机理.

The recycled aggregate is the natural aggregate attached with old hardened mortar. The old hardened mortar has a relatively weak mechanical property than that of natural aggregate. The old hardened mortar influences the quantity and quality of interfacial transition zone（ITZ） of concrete. Therefore the recycled concrete has different mechanical properties incompared with the normal concrete. In this paper,the quantity percentage of the old hardened mortar as well as the distribution in the recycled concrete are tested and evaluated. The difference between old ITZ and new ITZ is analyzed with the scanning electronic microscope（SEM） . And the influence of the old hardened mortar on the ITZ is also discussed. Based on the stress and strain characteristic in the meso-and micro structure of recycled concrete,the failure mechanism of recycled concrete is preliminarily simulated and analyzed by finite element software ANSYS. At last,the compressive strength and tensile splitting strength of the recycled concrete made of recycled aggregate from different strength grade waste concrete are experimentally investigated. The test results can be applied to explain the mechanical mechanism and the failure essence of the recycled concrete.