Sun Zhihua, Xiong Jin, Cao Shubo, Zhu Jianxiong, Jia Xuzhi, Hu Zhigang, Liu Kaiping
School of Materials Science and Engineering, Chang'an University, Xi'an 710061, China.
Shaanxi Hongcheng Mining Technology Corporation Limited, Xi'an 710001, China.
Materials (Basel). 2023 Mar 3;16(5):2080. doi: 10.3390/ma16052080.
The fracture toughness of sand concrete is affected by aggregate characteristics. In order to study the possibility of exploiting tailings sand, available in large quantities in sand concrete, and find an approach to improve the toughness of sand concrete by selecting appropriate fine aggregate. Three distinct fine aggregates have been used. After characterizing the fine aggregate used, the mechanical properties were tested to characterize the toughness of sand concrete, the box-counting fractal dimensions were calculated to analyze the roughness of fracture surfaces, and the microstructure was tested to observe the path and width of microcracks and hydration products in sand concrete. The results show that the mineral composition of fine aggregates is close, but their fineness modulus, fine aggregate angularity (FAA) and gradation vary considerably; FAA has a significant impact on the fracture toughness of sand concrete. The higher the FAA value, the more resistant it is to crack expansion; with the FAA values of from 32 s to 44 s, the microcrack width in sand concrete was reduced from 0.25 um to 0.14 um; The fracture toughness and microstructure of sand concrete are also related to the gradation of fine aggregates, the better gradation can improve the performance of the interfacial transition zone (ITZ). The hydration products in the ITZ are also different because more reasonable gradation of aggregates reduces the voids between the fine aggregates and the cement paste and restrains the full growth of crystals. These results demonstrate that sand concrete has promising applications in the field of construction engineering.
砂混凝土的断裂韧性受集料特性的影响。为了研究利用砂混凝土中大量存在的尾矿砂的可能性，并找到通过选择合适的细集料来提高砂混凝土韧性的方法。使用了三种不同的细集料。在对所用细集料进行表征后，测试了力学性能以表征砂混凝土的韧性，计算了盒维数分形维数以分析断裂面的粗糙度，并测试了微观结构以观察砂混凝土中微裂纹的路径和宽度以及水化产物。结果表明，细集料的矿物组成相近，但其细度模数、细集料棱角性（FAA）和级配差异较大；FAA对砂混凝土的断裂韧性有显著影响。FAA值越高，其抗裂纹扩展能力越强；随着FAA值从32 s增加到44 s，砂混凝土中的微裂纹宽度从0.25μm减小到0.14μm；砂混凝土的断裂韧性和微观结构也与细集料的级配有关，较好的级配可以改善界面过渡区（ITZ）的性能。ITZ中的水化产物也不同，因为更合理的集料级配减少了细集料与水泥浆体之间的空隙，并抑制了晶体的充分生长。这些结果表明，砂混凝土在建筑工程领域具有广阔的应用前景。
