Sand is one of the key component of concrete and sand pulp, and it is also the fundamental raw material of civil construction and engineering.
Sand can be divided into natural sand and artificial sand. Natural sand is formed in nature condition(mainly from rock weathering). Generally, we call it natural sand for those rock grainsize is below 5mm. Artficial sand is machanism sand, which refers to the rock grainsize less than 4.75mm which has been processed and screened by crusher machine.
The standard sand is divided into three kinds of coarse, medium and fine according the modulus of fineness.

Coarse: the modulus of fineness is 3.7-3.1, the average grainsize is above 0.5mm

Medium: the modulus of fineness is 3.0-2.3, the average grainsize is 0.5-0.35mm
Fine : the modulus of fineness is 2.2-1.6, the average grainsize is below 0.25 mm.
The modulus of fineness is more fine, the sand is more coarse. The range of modulus of fineness for regular concrete sand is 3.7-1.6. The medium size sand is better. Or you can mix few fine sand to coarse sand, and the mixing proportion is 4:1.

The sand's grain composition refers to proportion of the sand grainsize. The space cavity of two same size sand is large, and it will be small under the condition of the proportion of two different grainsize; it will be smaller if there are three kinds of grainsize. So, the rate of space cavity depends on the proportion of different grainsize. It can save cement comsumption, and increase the density and strength of concrete and sand pulp if the proportion is well.

Kefid Machinery Co., Ltd produces a wide range sand making machine(vertical shaft impact crusher), with the advantage of low consumption, cost effective, the final product size is shaped well and low iron and dust pollution. Its fineness size can be adjusted, so the sand and gravel proportion is well, which is suitable for providing aggregate to highway, railway, civil engineering, dam construction and concrete batching plant.