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The vacuum dewatering process is a mechanical water absorption method for concrete, and it has been listed as one of the four new technologies for concrete construction in the 1970s. At present, this technology is widely used in domestic concrete construction.

Because the vacuum water absorption process utilizes the pressure and dehydration of the vacuum negative pressure, the compactness of the concrete is improved, the water-cement ratio is lowered, and the physical and mechanical properties of the concrete are improved, which is a solution to the contradiction between the workability and strength of the concrete, and the reduction of cement. Use, save engineering investment, shorten the time of health, and take effective measures to open traffic. At the same time, since the water content of the mixture after vacuum dehydration is reduced, the shrinkage amount during solidification is greatly reduced, and the plastic cracking of the concrete during construction is effectively prevented, and the service life of the road surface can be prolonged.

Vacuum dehydration process requirements:

1. For the construction of small and medium-grade concrete roads with grades 3 and 4, it is preferred to use admixtures in the mixture. If there is no admixture, vacuum dewatering should be used. This process is suitable for concrete panel construction with panel thickness not greater than 240mm. .

2. When using the vacuum dehydration process, the maximum unit water consumption of the concrete mixture can be increased by 3-12kg/m3 compared with the absence of the admixture; the suitable slump of the mixture: 30-50mm on high temperature days; 20-30mm on low temperature days .

3, vacuum dewatering equipment

(1) The vacuum degree is stable, there is an automatic dewatering metering device, and the effective pumping speed is not less than 15L/s.

(2) Vacuum suction pad with uniform vacuum, good sealing performance, high dehydration efficiency, easy operation, easy placement and convenient cleaning. Each vacuum dehydrator should be equipped with no less than 3 suction pads.

Vacuum dehydration should pay attention to the following items:

(1) The working depth of vacuum dewatering should not exceed 30cm, and the water-cement ratio of the mixture should not exceed 0.55;

(2) When purchasing filter cloth and suction pad, select the appropriate size according to the size of the concrete road panel block. Too large or too small will affect the dehydration effect;

(3) The vacuum operator must walk on the self-made "work bridge" and is not allowed to walk on the suction pad at will. Do not wear shoes with hard bottom nails, it is best to wear rubber shoes or sneakers;

(4) Dehydration records should be made during dehydration, and the dehydration time and dehydration uniformity should be well grasped to prevent the occurrence of "spring layer" and cracks in concrete.

(5) When storing or moving the suction pad, avoid contact with hard objects with sharp corners. When rolling up or laying up the suction pad, you should hold the stick. In order to avoid damage to the suction pad.

(6) After the completion of each shift, the suction pad should be cleaned and the sediment of the vacuum pump box should be flushed to drain the water.

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