How to Transport Concrete?

The following requirements are required to be followed on how to transport concrete.

(1) The concrete transportation process should maintain the uniformity of the concrete and avoid the phenomenon of stratification and segregation. The concrete shall be transported to the pouring place in accordance with the slump specified during pouring (see Table 1).

Items	Structure type	Slump (mm)
1	Bedding layers such as foundations or floors, thick structures without reinforcement (retaining walls, foundations or thick blocks, etc.) or structures with sparse reinforcement	10-30
2	Structure of slabs, beams, and large or medium-sized poke surfaces	30-50
3	Structures with dense columns of reinforcement (thin-walled, bucket silos, silos, thin columns, etc.)	50-70
4	Structure with extra dense reinforcement	70-90

(2) Concrete should be transported from the mixing place to the casting place with the least number of transit times and the shortest time. The continuation time of concrete from the discharge of the mixer to the completion of the pouring shall not exceed the provisions of Table 2.

Concrete strength grade	Temperature(℃)	Temperature(℃)
	No higher than 25℃	Above 25°C
30 and below	2h	1.5h
Above C30	1.5h	1h

Note: 

1. When mixing concrete with admixtures or using fast hardening cement, it should be determined according to the test.

2. When transporting light-aggregate concrete, the pouring continuation time should be shortened appropriately.

(3) The transportation work should be carried out to ensure that the concrete is poured continuously.

(4) The container for transporting concrete should be tight. Its inner wall should be flat and smooth, not absorbing water and not leaking slurry. The adhering concrete residue should be removed frequently. It should be protected from exposure, rain, and freezing.

Concrete transportation methods

Concrete transportation methods are divided into three cases: ground transportation, vertical transportation, and floor transportation.

Ground transportation of concrete 

If the transport distance is far, it can be used self-unloading car or concrete mixing truck; if the transport distance is close, it can be used two-wheeled trolley.

Vertical transportation of concrete 

Concrete vertical transportation currently mainly used tower cranes, derricks, or concrete pumps. Tower crane transportation has the advantage of ground transportation, vertical transportation, and floor transportation can be used. Concrete on the ground by the horizontal transport tools or mixer is directly unloaded into the bucket, lifted and transported to the pouring part for pouring.

Concrete transportation tools

Concrete Mixer Truck

A concrete mixer truck (Figure 1) is a pear-shaped reversing discharge mixer installed on the chassis of a lorry or special car, which has the dual function of carrying concrete and mixing concrete. It can transport concrete while mixing it slowly to prevent the concrete from segregation or initial setting, so as to ensure the quality of concrete. It can also be loaded with a certain ratio of dry mix before driving, and mixed with water 15-20 min before reaching the pouring place, and can be used upon arrival. This truck is suitable for long-distance concrete transportation and is a necessary transportation machine for commercial concrete.

Concrete Pump Transportation

Concrete pump transportation, also known as pumping concrete, is to use the pressure of concrete pump to transport concrete through pipes to the pouring place, completing horizontal transportation and vertical transportation at one time. Concrete pumping has the advantages of large conveying capacity (maximum horizontal conveying distance up to 800 m, maximum vertical conveying height up to 300 m), high efficiency, continuous operation, and labor-saving.

The pumped concrete equipment has a delivery pipe, concrete pump (see Figure 2), and distributing device (see Figure 3).

1 Concrete Pump

2 Concrete piston

3 Hydraulic cylinder

4 Hydraulic piston

5 Piston rod

6 Hopper

7 Horizontal valve

8 Vertical valve

9 Conveying tube

10 Water tank

11 Diverter valve

12 High-pressure hose

13 Flange for water washing

14 Sponge ball

15 Cleaning piston

Notes on how to transport concrete

The concrete transportation process needs to focus on the following matters.

(1) Make the transportation route as short and straight as possible, with flat roads and smooth vehicles to reduce oscillations during transportation; avoid long transportation time and distance and too many times of transit.

(2) The concrete container should be smooth and clean, not absorbing water and not leaking slurry. Before loading, moisten them with water. It is advisable to cover them in hot weather or stormy weather to prevent water evaporation or water ingress. Take insulation measures into consideration in winter.

(3) Concrete transported to the pouring site shall be mixed twice before it is put into the mold if it is found to have segregation or initial condensation. Concrete that has already set shall be scrapped and shall not be used in the project.

(4) When pumping concrete construction, in addition to the prior preparation of the construction plan, the selection of pumping equipment, and the preparation of construction work, the following provisions should be observed during construction.

①The supply of concrete must ensure that the concrete pump can work continuously.

②The arrangement of the conveying pipeline should be as straight as possible, with few and slow turns and tight pipe-to-pipe joints.

③The inner wall of the conveying pipe should be lubricated with an appropriate amount of cement slurry or cement mortar of the same composition as that in the concrete before pumping.

④If the pumping interval is expected to exceed 45 min or if the concrete appears to be segregated, the residual concrete in the pipe should be flushed immediately with pressure water or other methods.

⑤When pumping concrete, there should always be enough concrete in the receiving hopper of the pump to prevent the formation of blockage by inhaling air.

After reading this article, I believe you have a better understanding of how to transport concrete. If you have any suggestions or ideas, please leave a comment to discuss.

Also to read:

Slow-setting Problems of Ready-mixed Concrete & the Preventive Measures