What Is Transportation of Concrete?
Transportation of concrete is a method of moving fresh concrete from mixing plant to to place probably where it needs to be deposed in the structural element. Since the time taken in the method transportation of concrete mainly depends on the initial setting time and the need for workability at the site, it should be a design parameter.
For deciding appropriate admixtures in concrete to improve specific properties, the transportation of concrete method is pre-decided in advance.
Precaution: The homogeneity obtained at the mixing time should be maintained while being transported to the deposition’s final place.
Methods for Transportation of Concrete
Following are the different adopted transportation of concrete,
1. Mortar Pan
Mortar pan is a commonly used method in our country, especially for small-scale works, where the concrete is carried in small quantities. This method is more labor-intensive.
There are significantly fewer possibilities of concrete segregation, but this method exposes larger surface areas of concrete for dry conditions in thick members.
This results in a substantial water loss due to more concrete exposure to an environment in hot weather.
This method is mostly adopted for ground level, below ground level, and above ground level construction work without more difficulties.
The mortar pan must be wetted to start with, and it must be clean during the entire operation of concreting.
2. Crane, Bucket, And Ropeway
Crane and Bucket are mostly correct transportation of concrete equipment, especially for above-ground level. Cranes give more preference to high-rise construction projects.
Cranes are quick and versatile to move concrete horizontally and vertically along the boom and enable concrete placement at the exact point. Those cranes carry buckets or skips containing concrete. Skips have a discharge door at the bottom, whereas buckets are tilted for emptying.
Excessive free fall of concrete should be avoided to minimize the segregation defect in concrete.
Note: For a medium-scale job, the bucket capacity may be 0.5m3.
Ropeway and Bucket for various sizes are used for transporting concrete to a place, where a simple method of transporting concrete is found not feasible.
The Bucket size is considerably large, and concrete is not exposed to sun and wind. There would not be much change in the state of concrete workability.
Ropeway and bucket method is more suitable for works in valley, over high piers and long dam sites, bridgework.
The freefall of concrete should not be at a high level, and that concrete should be discharged from the smallest height.
3. Wheel Barrow or Hand Cart
It is generally used on the ground level (i.e., road construction and other similar structures. Segregation can occur if transportation of concrete is done on rough roads over a long distance. However, this vibration problem can be minimized if pneumatic tires are used.
4. Belt Conveyor
It has limited application in the concrete construction sector due to chances of segregation on steep slopes, roller points, and changes in the direction of the belt. Segregation also takes place due to the vibration of a rubber belt.
Modern belt conveyors can have adjustable reach, traveling diverter, and variable speed both forward and reverse. Conveyors can quickly place a large volume of concrete where access is limited, and portable belt conveyors are used for short distances or lifts. The end discharge arrangements must prevent segregation and remove all the mortar on the belt’s return. In adverse, It also involves over-exposure of concrete to the environment.
Precaution: Concrete should be remixed at the end of delivery before placing the final position.
5. Truck Mixer And Dumper
For large-scale concrete works, mostly concrete to be placed at ground level, trucks and dumpers or ordinary open steel-body tipping lorries can be used.
It is a most improved and better method for long lead concreting. The concrete is covered with a tarpaulin if transported in open trucks. If long-distance is involved, agitators should be used, which prevents segregation and stiffening, and it also helps the mixing process at a slow speed.
For road construction using slip form paver, a large quantity of concrete must be supplied continuously.
Another name of small dumper is tough riders, and it is used for factory floor construction.
Note: The dumper’s capacity is 2 to 3 cubic meters, and the truck is four cubic meters.
Before loading with concrete, the body’s inside should be just wetted with water.
6. Skip and Hoist
High-rise structures for transporting concrete vertically up are a widely used method.
Then concrete is fed into the skip, which travels vertically on rails like a lift. After discharge, it is better to turn over the concrete before avoiding segregation. Transportation of concrete is practically impossible with the mortar pan and ladder for more than 3 to 4 number floors; in that case, the skip and hoist method is adopted.
The mixer feeds the skip, and the skip travels up over the rail up to the level where concrete is needed, and at that point, the skip discharges the concrete automatically or manually.
The quality of concrete, i.e., freedom from segregation, will depend upon the extent of travel and rolling over the rails. If the concrete has traveled a considerable height, concrete on discharge must be required to be turned over before being placed finally.
It is usually used for concreting in deep locations.
The workability should not be changed to suit the delivery by a chute.
This method is extensively used in the field, though it is technically not a very good method.
The slope should not be lower than 1V:2.5H; otherwise, concrete will not slide down smoothly.
8. Transit Mixer
In the ready-mix concrete plant, the transit mixer is one of the most popular concrete transporting equipment types.
They are truck-mounted transit mixers with 4 to 7 cubic meters.
There are two variations; they are as follows;
1) Mixed concrete is transported to the site by keeping it agitated at a speed varying between 2 to 6 revolutions per minute.
2) At the central batching plant, the concrete is batched, and in the truck mixer, mixing is done either in transit or immediately before discharging concrete at the site.
9. Pump and Pipe-Line Method
It is the most complicated method uniquely proper for limited space or when a large quantity of concrete can be poured except cold joints.
The pumping of concrete can be done @ the rate of 8 to 70 cubic meters per hour. (The horizontal distance is approximately 300 meters, and a vertical distance is about 90 meters)
Generally, the pipe diameter is 8 to 20 cm, and it is made of steel, plastic, or aluminum.
The slump value should be a minimum of 40 to 100 mm or 0.90 to 0.95 compacting factor for pumped concrete.
The workability may be reduced by 25% because of compaction at the delivery point, and while designing the mix, this factor should be kept in mind.
What are the different modes of transportation of concrete?
The following are different methods of transportation of concrete,
Crane, Bucket, And Ropeway
Wheel Barrow or Hand Cart
Truck Mixer And Dumper
Skip and Hoist
Pump and Pipe-Line Method
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