基于再生骨料方位的模型再生混凝土损伤演化分析

Damage Evolution Study of Modeled Recycled Concrete Based on Orientation of Recycled Aggregate

摘要:

制作了正方形模型骨料以及不同放置方位情况下模型再生混凝土，试验研究其受压破坏过程中裂缝发生、发展规律，并利用数字图像相关技术和有限元模拟相结合的方法分析应变分布与发展情况，总结归纳再生骨料方位对再生混凝土损伤演化规律的影响。研究结果显示，骨料水平方向放置时应变集中现象首先出现在骨料两侧的界面区；当骨料放置为22.5°时，试件强度和割线模量均高于其他两种情况，应变集中首先在骨料上下两顶点处孕育并向骨料两侧界面区发展成裂缝；当骨料放置为45°时，骨料上下两顶点处应变集中程度最高。在荷载达到80%峰值荷载之前，模型再生混凝土的应变集中程度相对模型普通混凝土要小，对于3种骨料放置方位，分别小15%、32%和39%，这是因为老砂浆的弹性模量介于天然骨料和新砂浆之间，所以削弱了应变集中程度。根据再生骨料放置方位对其损伤演化规律影响的研究，证明可采用去除骨料尖端和减少针片状骨料含量的方法对再生骨料进行优化改性。

Abstract:

The modeled recycled concrete containing modeled square aggregates in different directions were applied to study the propagation of cracks at compression loading. The strain distribution and development were analyzed using digital image correlation and the finite element method， and the influence of the direction of aggregates on its damage evolution was investigated. The results show that when the modeled aggregate is placed horizontally， the strain concentration first appears in the interface on both sides of the aggregate. When the aggregate is placed in the direction of 22.5°， the strength and secant modulus are higher than the other two cases， and the strain concentration first propagates at the upper and lower vertices of the aggregate and develops into cracks along the interface on both sides of the aggregate. When the aggregate is placed in the direction of 45°， the upper and lower vertices of the aggregate have the highest strain concentration. Before the load reaches 80% of the peak force， the strain concentration of modeled recycled concrete is lighter than that of modeled normal concrete. For three directions of the aggregate， the strain concentration of modeled recycled concrete is 15%， 32%， and 39% smaller than that of modeled normal concrete. Because the elastic modulus of old mortar is in between the natural aggregate and new mortar， the strain concentration of the modeled recycled concrete is reduced. Based on the research on the influence of the direction of recycled aggregate on its damage evolution， it is proven that the methods of removing tips of aggregates and reducing needle flake aggregates can optimize and modify the recycled aggregates.