Setting of concrete mixing time for each batch

It is forbidden to shorten the mixing time without bottom line. A single method of setting the mixing time is suggested.

 

The national standard GB / t14902-2012 ready mixed concrete stipulates that the mixing time of concrete in the mixer shall not be less than 30s. The national standard gb50164-2011 concrete quality control standard stipulates that the minimum time for concrete mixing is 60s, and it also stipulates that the double horizontal shaft forced mixer can appropriately shorten the mixing time under the condition of ensuring uniformity. According to the above two standards, the concrete mixing time shall not be less than 30s.

 

The current situation is that many mixing plants reduce the production cost by continuously reducing the mixing time. Some mixing times are only 15s and 20s, and the operators are mostly young people. One reason for the continuous deterioration of concrete quality is to reduce the mixing time, reduce the operation time, reduce the work intensity and increase the rest time. Some operators infer the concrete state according to the mixing current, completely ignoring that the mixing time required for different concrete is different. All concrete is considered according to the same mixing time. When the mixing current is high, water adding measures will be taken. Some concrete needs a long mixing time. When the mixing time is set to be short and the mixing current is high, once the water is added and the current is appropriate, the concrete strength loss will be large, which will cause engineering accidents.

 

In actual production, there are many factors affecting the mixing time. Concrete with different strength grades needs different mixing time; The concrete is different in thickness and mixing time; For concrete of the same strength grade, the construction position is different and the mixing time is different; For concrete with the same strength grade, the admixtures are different, especially after adding powder, the mixing time is different; The mixing time of normal temperature concrete is different from that in winter; The size of stones is different, and the mixing time is different; How many stones are different, and the mixing time is different.

 

Therefore, the mixing time shall be set in the mix proportion sheet, and the mixing time specified in the mix proportion sheet shall be given priority. At present, most mixing plants can not do this. They can only set the mixing time in the mixer. All concrete shall implement this mixing time. In case of concrete with different mixing time, it is a very cumbersome thing to adjust the mixing time back and forth. Therefore, the new station pays special attention to this point. When purchasing the operation procedure, two requirements should be put forward: first, in the operation procedure, it is stipulated that the mixing time can be set separately in the mix proportion and implemented preferentially, which can greatly improve the mixing speed; Second, it is forbidden to shorten the mixing time at will, and it is not allowed to provide convenient conditions for operators to shorten the mixing time at will.

 

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