1. Conceptually, gravel is washed by running water passing through a river for a long time, which smoothes the sharp edges and corners of the stone. Gravel is produced in rivers. Gravel is a name in the classification of sediments, which is generally represented by the symbol G. Rock or mineral debris with an average particle size greater than1mm. However, the rubble gives people a very small and messy feeling. Generally, gravel is artificially formed. Gravel is made of natural rocks, pebbles or ores by mechanical crushing and screening, and the particle size of gravel is generally greater than 4.

2. As far as building materials are concerned, gravel is naturally formed. After years of washing and beating, crushed stone has high flatness and no edges and corners, but its hardness is not as good as that of crushed stone, so its building strength in building materials is not high. In addition, the appearance of gravel is smooth, without edges and corners, so it is not easy to mix cement during construction, and the bonding performance between gravel and cement mortar is not as good as that of rough gravel, so the stability of gravel is not very good compared with buildings.