1. The classification of machine-made sand shows the characteristics of "more at two ends and less in the middle", in which the residue of particle sieve with particle size greater than 2.360mm is as high as 40%, and that of particle sieve with particle size less than 0.075mm is as high as 15%. Poor gradation leads to large void ratio between aggregates and poor strength and workability of concrete.
Second, the content of stone powder is too high, which leads to quality problems such as the decrease of concrete strength and the increase of shrinkage deformation.
Third, there are many edges and corners. The workability, fluidity and compactness of machine-made sand concrete are worse than those of river sand concrete with circular particles under the same amount of slurry.
According to many years' production experience of machine-made sand, it is found that the production quality of machine-made sand can be improved by improving the production technology. The 5S high-quality sand aggregate processing technology of "double desliming, double impact, double circulation and double powder separation" ensures the qualified product quality and stable performance. The problems of dust, water pollution and waste treatment in traditional technology have been solved through measures such as air separation and dust removal, sealing of semi-finished and finished product silos and waste recovery.
1)5-stage crushing and secondary shaping.
Firstly, the mother rock is pre-crushed (roughly crushed) by the 65438th extrusion with the jaw crusher, so as to reduce the diameter of the mother rock and reduce the production pressure of the impact crusher.
Then, the master batch is crushed for the second time (medium crushing) by an impact crusher in the form of riprap impact, so that the aggregate microcracks generated by crushing further develop, and finally the aggregate is crushed again from the microcracks, thus completing the second crushing and 1 shaping of the aggregate;
Finally, the aggregate is crushed (finely) for the third time with a vertical shaft impact crusher, and the aggregate is reshaped for the second time in the way of "stone to stone" or "stone to iron".
2) secondary desliming
Before coarse crushing, the mother rock and soil with particle size less than 30mm shall be desliming for the first time 1 time, and before medium crushing, the aggregate with particle size less than 10mm shall be desliming for the second time to remove the soil and stone chips in the aggregate to ensure that the MB value of the aggregate is less than 0.5.
3) Grading adjustment
There are circulating screening systems in the middle crushing and fine crushing stages, and the bunker can be adjusted by GSP, so that some aggregates can be returned through the circulating system and re-crushed into smaller particles, and the production ratio of aggregates with different particle sizes can be adjusted as needed, and then the content of small particles can be adjusted by air separation and powder control, thus solving the problem of "more at two ends and less in the middle" in classification.
4) air separation and powder control
Fine aggregate is first subjected to 65,438+0 gravity winnowing to control the powder content, and the stone powder content is controlled at about 65,438+00%. Before the finished sand enters the silo, the air pressure extracted by the air separator should be adjusted as needed, and the stone powder content should be adjusted again to meet the requirements of different strength concrete for the powder content of machine-made sand and machine-made stones.
5) automatic humidification
After the air separation process is completed, the finished machine-made sand is automatically humidified, and the moisture content of the machine-made sand is controlled at 2.5% ~ 3.5%. Stable moisture content is convenient for concrete production and quality control, which can effectively avoid dust during production and transportation and prevent aggregate segregation during loading, unloading and transportation.
Technology of machine-made sand production line