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There are several types of equipment which are used to transfer and pour concrete after it has been discharged from a mixer. For instance, steel buckets, rail cars and trucks, chutes, tremie, belt conveyor, sprayed concrete, barrows, pumping, and concrete carts.
These tools are selected based on their suitability for the construction conditions. Concrete transfer and placement equipment need to be utilized appropriately in order to prevent concrete segregation and loss of slump.
1. Steel Bucket
It handles and pours concrete satisfactorily provided it is operated properly. Discharge quantity of concrete and its direction shall be controlled when steel bucket is used.
Steel bucket is not suitable in the case where concrete is required to be transported over a long distance because concrete segregation, bleeding, and slump loss (greater than 2.54cm) are highly possible.
Fig. 1: Steel Bucket
Sometimes, trucks and railcars are used to transport concrete after mixing. In this method, concrete may suffer stratification; coarse aggregate layer at the bottom and layer of water above it.
If stratification occurs, concrete needs to be remixed at discharge gate or by sending air through stratified concrete. Added to that, stratification is prevented by adding water at the construction site(transfer concrete as dry mixer).
Fig. 2: Railcars
Chutes are often used to pour concrete, but its utilization needs to be controlled, especially at the discharge end, to prevent segregation and slump loss. Discharge needs to be vertical and the use of short length downward pipe is highly beneficial. Long chutes are required to be covered to prevent mixing water evaporation due to sun and wind.
Fig. 3: Chutes Used to Pour Concrete
It is another type of equipment used for transportation and placement of concrete. There is a risk of segregation and slump loss when belt conveyor is used. These issues can be prevented by shielding belt conveyor to prevent evaporation of mixing water due to sun and wind, and concrete discharge should be vertical.
Fig. 4: Belt Conveyor for Concrete Transfer and Placement
It is used for concrete placement over fairly long distances and at great heights. The maximum pumping distance is decreased by harsh concrete, curves, and lifts. It is required to install agitator in the pump feed hopper to avoid segregation.
Fig. 5: Pumping Concrete
It is used to transport concrete over short distances, for instance, from hopper to the forms.
Concrete is directly applied onto the forms. Basically, mechanical feeder (gun), mixer, and compressor are needed in this method of concrete placement. This method is suitable for building up shapes without the need for side forms.
Tremie is a tube used to place concrete under water. The diameter of the tube is around 1ft at the top and flared at the bottom, the length should be enough to reach the bottom where concrete is deposited.
