再生骨料残余砂浆覆盖率测试及其对混凝土渗透性的影响

为了实现盐侵蚀环境下再生骨料的评价与优选，提升再生混凝土渗透性研究水平，提出基于图像分析原理的再生骨料残余砂浆测试方法，该方法通过图像识别技术手段定位并识别再生骨料表面的残余砂浆，定量分析残余砂浆在再生骨料表面的二维覆盖率，结合二维图像三维重构方法获取再生骨料表面残余砂浆的真实覆盖率。采用不同残余砂浆覆盖率的再生骨料制备再生混凝土，通过电通量法研究残余砂浆覆盖率对再生混凝土抗渗性的影响。试验结果表明：采用图像分析方法测试的3种粒径再生骨料残余砂浆覆盖率符合正态分布，证明图像分析覆盖率数据可靠；当再生骨料粒径为5~10，10~20 mm和20~30 mm时，残余砂浆覆盖率的最小样本数量为46，31和50，变异系数比的波动范围为1±5%。多实验室重复试验结果表明，该方法具有较好的重复性和再现性。再生混凝土电通量试验结果表明，再生骨料残余砂浆覆盖率越大，其制备的再生混凝土电通量值越高；再生骨料附着的残余砂浆增加了再生混凝土新砂浆-残余砂浆界面过渡区的数量；残余砂浆覆盖率越高，新砂浆-旧砂浆界面过渡区在再生混凝土中所占比例越大，氯离子更易传输到再生混凝土内部；与残余砂浆附着率相比，残余砂浆覆盖率与再生混凝土抗氯离子渗透性具有更高的关联度。

Test of Coverage Rate of Residual Mortar on Recycled Aggregate and Its Influence on Permeability of Concrete

To evaluate and optimize recycled aggregates under a salt erosion environment, improving the research level of the permeability of recycled concrete, a method for measuring the residual mortar of recycled aggregate based on the principle of image analysis is presented in this paper. Image recognition technology was used to locate and identify the residual mortar on the surface of the recycled aggregate, quantitatively analyzing the 2D coverage of the residual mortar on the surface of the recycled aggregate. The real coverage of the residual mortar on the surface of the recycled aggregate was obtained by transforming the 2D image into a 3D reconstruction method. The influence of the residual mortar coverage on the anti-permeability of recycled concrete was studied using electric flux. The results show that the residual mortar coverage of the three types of particle sizes tested using the image analysis method conform to a normal distribution, which proves that the image analysis coverage method is feasible. When the particle size of the aggregate are 5-10 mm,10-20 mm, and 20-30 mm, the minimum sample numbers of residual mortar coverage are 46, 31, and 50, respectively. The fluctuation range of the coefficient of variation is within 1±5%. The results of the electric flux test show that the recycled concrete electric flux increases with an increase in the residual mortar coverage. The amount of interfacial transition zone (ITZ) between the new and the residual mortar is increased by the residual mortar attached to the aggregate. The higher the residual mortar coverage, the greater is the proportion of ITZ in the recycled concrete, and the more easily can harmful ions such as chloride ions be transmitted to the recycled concrete. Compared to the adhesive rate of the residual mortar, the coverage rate of the residual mortar has a higher correlation with the chloride ion permeability of the recycled concrete.