基于势能显式基面力元法的再生混凝土细观裂缝研究

为研究再生混凝土内部微裂纹演变过程与再生骨料取代率、骨料分布及骨料形状的关系,建立再生骨料取代率为0%,30%,50%,70%及100%的二维圆形及任意凸多边形随机骨料模型,通过势能显式基面力元法模拟位移控制模式的单轴压缩试验。结果表明:基面力元法可以用于研究再生混凝土等非均质材料的细观断裂损伤;单轴受压时内部微裂纹首先出现在粘结带位置,随后绕骨料形成离散裂纹,最终在骨料密集区域形成1~2条斜向45°连续破坏裂缝;试件内部微裂纹沿圆形骨料切向方向发展为与骨料直径呈垂直状态的斜向连续破坏裂缝,沿凸型骨料外轮廓线向骨料尖端方向发展为与骨料外轮廓线呈平行状态的斜向连续破坏裂缝;随着骨料取代率的增加,再生混凝土抗压强度逐渐递减,最终趋于稳定,凸型骨料再生混凝土抗压强度略高于圆形骨料再生混凝土。

RESEARCH OF THE MESO-CRACK OF RECYCLED AGGREGATE CONCRETE BASED ON EXPLICIT BASE FORCE ELEMENT METHOD ON POTENTIAL ENERGY PRINCIPLE

In order to investigate the effects of the recycled aggregate replacement ratio, the aggregate shape and distribution on the meso-cracks of the recycled aggregate concrete under the uniaxial compression loading,several 2-D random models of the circular and convex polygon aggregates by varying the replacement ratios of 0%, 30%, 50%, 70%, and 100% are established. The uniaxial compression test with a displacement load is simulated based on the potential base force element method(BFEM). The results show that the BFEM is a good method to study the meso-fracture damage of the recycled aggregate concrete. Generally, the cracks are always first formed in interfacial transition zones(ITZs), then the cracks are developed into isolated cracks around the aggregate. Finally, up to 2 cracks grow along the 45°direction through the aggregate-concentrated areas. For the circular aggregate, the continuous cracks are developed along the tangential direction of the aggregate and perpendicular to the aggregate diameter. For the convex aggregate, the continuous cracks are developed along the outer contour toward the tip direction of the aggregate parallel to the outer contour of the aggregates. With the increases of the replacement ratios, the compression strength decreases and stabilizes eventually. The compression strength of the convex polygon aggregate of the RAC is slightly higher than that of the circular aggregate.