Cement control with a cement mortar pumping machine
Posted On: 04/03/2021 | Posted by: Haomei Concrete Pumps
The function of a cement mortar pumping machine is to pump cement mortar to a given construction point. The pumping pressure of concrete depends on the liquid phase material to transfer. The function of cement is displayed in two aspects. One is cementation, which makes the concrete keep the state that the solid phase material is surrounded by the liquid phase material in the pumping process. The other is to reduce the friction resistance between the concrete and the mechanical part of the pump, the conveying pipeline and the internal part of the concrete, so that the concrete has good fluidity.
Cement should have good water retention performance, so that the concrete is not easy to bleed in the pumping process. Ordinary portland cement and pozzolanic cement have good water retention, while slag cement has poor water retention. If it is used to mix pumping concrete, it is necessary to increase the amount of cement and properly increase the sand rate or add a part of fly ash, and adopt lower slump. When fly ash cement is used, the fluidity of concrete is better, but the early bleeding is larger. It is better to use lower slump and pump continuously as far as possible.
Amount of Cement
In using a cement mortar pumping machine, the amount of cement should be appropriate. If the amount of cement is insufficient, the pumping volume efficiency will decrease, and the conveying resistance will increase obviously, and the water retention of this kind of concrete is very poor, which is easy to bleed, segregate or block. In contrast, if the amount of cement is too large, the concrete viscosity will be too large, and the conveying resistance will increase, but the pumping volume efficiency will not change much. Compared with crushed stone aggregate, the cement content of crushed stone concrete is larger with the same particle size and gradation. For fine aggregate, artificial crushed sand uses more cement than natural sand. The smaller the pipe diameter and the longer the pipe length, the higher the fluidity, lubricity and water retention of concrete are required, so the amount of cement should be increased. If the aggregate gradation is appropriate, the larger the particle size of large aggregate is, the less the cement consumption is; however, when the particle size of aggregate exceeds 30mm, the continuity of concrete will be destroyed, and it is difficult for cement slurry to fully pack these aggregates. Therefore, the amount of cement can not be reduced.
If you use insufficient fine aggregates less than 0.2 mm, you should increase the ratio of cement while using a cement pumping machine. If the aggregates are too light, the cement amount should be increased, too. Usually the cement amount should be no less than 340kg / m3.
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