Knowledge about cement pumping concrete

Cement pumping concrete is concrete that has a slump of 100 mm or more and is pumped. It has been widely used in Japan and overseas in recent years because it can continuously complete horizontal and vertical transportation at the same time, and is highly efficient and labor-saving. The basic requirements for ensuring good pumping capacity for concrete are:

1. Cement
Use Portland cement, regular Portland cement, slag Portland cement, fly ash Portland cement pumping concrete, and do not use Pozzolan Portland cement.
2. Aggregation
The coarse aggregate used in cement pumping concrete should be continuously tilted so that the needle-like content does not exceed 10%. .. If the height of the pump is less than 50 m, the ratio of large particle size to diameter of the transport pipe should not exceed 1: 3 for gravel and 1: 2.5 for pebbles. The height is 50-100m, the gravel is 1: 4 or less, the pebbles are 1: 3 or less, and the pumping height is 100m or more, 1: 4.5 or less. Using medium sand, the content of particles passing through a 0.315 mm sieve should be at least 15% and the content of particles passing through a 0.160 mm sieve should be at least 5%.

3. Admixtures and admixtures
Cement pumping concrete should be mixed with pumping or reducing agents, fly ash or other active mixtures to improve the pumping capacity of the concrete.
4. Pump concrete mixing ratio design
The proportion of water binder in cement pumping concrete should not exceed 0.60, the total amount of cement and mineral mixture should not exceed 300 kg / m3, no pozzolan cement should be used, the proportion of sand should be 35-45. %must be. .. The air content of pump concrete containing air entraining agent should not exceed 4%. Practice has shown that mixing high quality fly ash and mineral powder with pump concrete can significantly improve workability and save cement without compromising strength. Since concrete pump trucks require a large amount of water and ash, problems such as segregation of concrete and shrinkage cracks are likely to occur.

The concrete used for pumping must meet the requirements for cement pumping concrete. Not all concrete can be pumped. Inappropriate pumped concrete often exacerbates pump wear, causing pipe clogging and pipe rupture.