The quality requirements of aggregate
1．The sizes of coarse aggregate are divided as follows: the first gradation, 5～20 mm; the second gradation, 5～20，20～40 mm; the third gradation, 5～20，20～40，40～80 mm; the forth gradation, 5～20，20～40，40～80， 80～120（150）mm.
2．The control of fine aggregate and its fineness modulus is general 2.4~2.8. The basic types of the aggregate (source)
1）Natural aggregate: low cost, but the gradation is different with the designed gradation of concrete.
2）Artificial aggregate: good quality, the aggregate can be used at the stone that is dug out, but the cost is high
3）Mixed aggregate: natural aggregate is given priority and artificial aggregate is used as supplement.
Aggregate processing and processing equipment
Processing the collected raw materials, usually need to do crushing, screening and washing to get rubbles and artificial sands that comply with gradation and have no impurities. According to the aggregate processing process flow, the aggregate processing plant will be built.
1. The aggregate crushing uses crusher to do stone crushing and the commonly used equipments are Jaw Crusher, Cone Crusher and Impact Crusher.
2. In order to be graded, the aggregate, the gathered natural raw materials or the crushed mixture should be screened. There are two kinds of grading methods, hydraulic screening and mechanical screening. The large scale screening usually uses mechanical screening. There are two kinds of mechanical screening, eccentric vibration and inertia vibration.
4. Sand making: sand box is used to place the distributaried sewage mortar. Then after first washing, the sewage mortar is sent to sand washing machine for next washing. Artificial sands are processed by rod mill.
5、Aggregate processing plant Large scale aggregate processing plant usually puts the processing machinery equipments according to process flow, which is crushing, screening, washing ,transportation and stacking. Among this, screening floor is the aggregate processing plant that mainly does screening work.