废混凝土骨料和废砖骨料再生混凝土的模型化研究

为了更加清晰方便地观察并研究再生混凝土裂缝开展规律,利用模型混凝土的概念,将普通混凝土、废混凝土骨料混凝土和废砖骨料混凝土平面化,制得模型再生混凝土试件。在试件受压破坏的过程中,利用数字图像相关技术在模型混凝土前后两个表面制作不同尺度的散斑,分别用一般工业相机和显微镜相机采集图像,并分析得到全局应变场和界面过渡区附近的局部应变场,用以揭示再生混凝土裂缝开展过程和损伤演化机制。研究结果显示,废砖骨料模型再生混凝土的弹性模量最小,但是抗压强度反而比废混凝土骨料模型再生混凝土的高。废混凝土骨料模型再生混凝土全局应变场能表征应变集中位于旧砂浆区域,但不能区分新、旧界面过渡区,而局部应变场更加细致地显示裂缝首先在旧界面过渡区开展,然后新界面过渡区才有裂缝开展。对废砖骨料模型再生混凝土的分析发现,砖骨料和新砂浆之间的界面过渡区首先出现了应变集中,但是裂缝并未沿界面过渡区开展,而是贯穿了砖骨料,然后位于界面过渡区的应变集中由于应力重分布而削弱。

Investigation on modeled recycled concrete prepared with recycled concrete aggregate and recycled brick aggregate

In order to observe and study the crack development of recycled concrete more clearly and conveniently, modeled concrete specimens were prepared from normal aggregate concrete and recycled aggregate concrete which used recycled waste concrete aggregate and recycled waste brick aggregate as the aggregate respectively, according to the concept of two-dimensionalized concrete. The specimens were subjected to a compressive loading, and during the loading process, images of the front and back surfaces and the speckle pattern of different scales were captured with a normal digital camera and a high resolution camera, respectively to obtain the global and local strain fields. By analyzing the global strain field and the local strain field near the interfacial transition zones (ITZ), the crack development process and damage evolution mechanism of the modeled recycled concrete were revealed. The results show that the elastic modulus of the modeled concrete with the waste brick aggregate is the smallest, but its compressive strength is higher than that prepared with the recycled waste concrete aggregate. The global strain field of the recycled concrete shows that the strain concentrates around the old mortar area, while the local strain field shows that cracks develop in the old ITZ first, and then in the new ITZ. For the modeled concrete prepared with the waste brick aggregate, it is found that strain concentration first appears in the ITZ between the brick aggregate and the new mortar. The cracks do not develop along this ITZ, but run through the waste brick aggregate. The strain concentration in the ITZ is weakened due to the redistribution of stress.