Concrete pumping

Adding water to an already made concrete mixture may increase its workability but at the same time it lowers its strength. However, concrete must be workable enough to efficiently pass be-tween the narrow spaced steel reinforcement. This is achieved by use of a super-plasticizer added (1.0 to 2.0 kg/m³) inside the drum containing the wet concrete mixture before its dis-charge and mixed for 3 to 5 minutes in high rotating speed (8-12 R.P.M.). The addition of water or sealing ingredients on site, is forbidden.

Generally, the concrete used for the casting of foundation footings does not require a high level of workability and therefore adding a super-plasticizer is not necessary. On the other hand, in strip foundation, usage of super-plasticizer may be required when casting the pedestal, some-thing always done after the completion of the footing’s concreting. Finally when casting stair-cases (or sloped slabs) super-plasticizers should be avoided because the workable concrete flows towards only one side of the formwork.