As construction sand, washed sand needs to meet certain standards. It is necessary to ensure that the sand washing machine has a good washing effect, the ratio of fine sand to coarse sand is reasonable, and the sand making raw materials should be selected from rocks with higher hardness. The basic requirements of concrete for sand are as follows: 1. The total surface area of the sand particles should be small, that is, the sand should be as coarse as possible. In concrete, cement paste is effectively bonded through the surface of aggregate particles. The smaller the total surface area of the aggregate, the more economical the cement is. 2. The sand has a good particle size distribution. Particle gradation refers to the situation where sands of different particle sizes are matched with each other. The size of the sand particles is reasonably matched to achieve step-by-step filling and reduce the porosity to achieve the highest possible density. It can be seen that the use of wel