基于三维扫描的水射流冲击下再生混凝土断面形貌特征分析

Fracture surface morphology analysis of recycled concrete under water jet impact based on three-dimensional scanning

国内每年因旧建筑物拆除产生的建筑垃圾超过17亿t,造成建筑垃圾快速增长的主要原因是现有拆除方式侧重于高效拆除和定向倒塌,而忽略了对于混凝土原材料和构件再利用性能的保留。将混凝土旧建筑物中仍具备再利用价值的主要承重构件无损拆除,作为再生混凝土构件再利用成为目前研究的重点问题。再生混凝土断面粗糙度直接影响新旧混凝土构件的界面连接性能,基于此考虑,开展了高压磨料水射流拆除混凝土旧建筑物的试验研究,提出了一种基于三维扫描数据在宏观层面定量分析混凝土断面粗糙度的简单计算方法,对比分析了水射流冲击下普通混凝土和加速老化混凝土的断面形貌特征,使用扫描电子显微镜观察了混凝土骨料与水泥浆体结合状态的微观特征。结果表明:在水射流冲击下,普通混凝土断面纹理深度为0~4.0 mm,加速老化影响了混凝土的破碎效率,面对水射流冲击时纹理深度提升了0.5~1.0 mm。基于点云重构封闭曲面数据计算的普通混凝土断面粗糙度在1.11~1.19,加速老化混凝土的断面粗糙度普遍提升了4.0%~14.9%。水射流冲击下的混凝土破坏模式主要以压缩剪切和拉伸剪切破坏为主,断面区域大致可分为光滑区、过渡区和撕裂区。研究结果可为水射流拆除混凝土旧建筑物的工艺优化和工程应用提供指导。

In China,more than 1.7 billion tons of construction wastes are generated each year due to the demolition of old buildings.The main reason for the rapid growth of construction wastes is that the existing demolition methods focus on efficient demolition or directional collapse,without considering the retention of the mechanical performances of concrete materials or components.Therefore,the reuse of the main load-bearing components as recyclable concrete materials in old buildings has become a key issue.Fracture surface morphology of the recycled concrete brings significant effects on the connection performances of the recycled concrete components.Towards improving the reusability of the recycled concrete,a high-pressure abrasive water jet method was presented to demolish old buildings.A simple method to quantitatively calculate the fracture surface roughness in macro-level based on three-dimensional(3D)scanning was proposed,the fracture surface morphology of the recycled concrete under water jet impact was analyzed.Furthermore,a scanning electron microscope was employed to observe the microscopic characteristics of the adhesion of cement onto aggregates in micro-level.The results show the fracture surface texture depth of the non-treated concrete ranges from 0 to 4.0 mm based on 3D scanning.Accelerated aging could promote the removal efficiency of concrete,by increasing the texture depth by 0.5 to 1.0 mm under water jet impact.Based on the reconstructed 3D scanning data,the calculated fracture surface roughness of the non-treated concrete is between 1.11 and 1.19,and the roughness of the accelerated aged concrete generally increases by 4.0%to 14.9%.Failure mechanisms of concrete under water jet impact mainly involve compressive shearing failure and tensile shearing failure.Fracture surfaces of concrete under water jet impact can be roughly divided into the smooth region,the transition region and the tearing region.The research results provide guidelines for process optimization of old building demolition by water jet.