Sand and gravel aggregate refers to the granular loose material that plays the role of skeleton or filling in concrete, and has important applications in the production of cement concrete, asphalt concrete, road foundation, railway slag, mortar, etc. Sand and gravel aggregates can be divided according to the source, aggregate particle size, and aggregate density. According to the source of aggregates, it can be divided into natural rock aggregates, artificial aggregates and recycled aggregates. According to the particle size of aggregate, it can be divided into two types: coarse aggregate and fine aggregate. According to the density of aggregates, it can be divided into three types: ordinary aggregates, light aggregates and heavy aggregates. Sand and gravel aggregate is widely used in building construction, road and bridge engineering, hydropower facilities and other projects, and is one of the indispensable and important raw materials in infrastructure construction.