Transportation of concrete

Transportation methods of concrete

1. TRANSPORTATION OF CONCRETE 1 Richu George Varghese Assistant Professor Mangalam College of Engineering and Technology

2. Introduction Transferring of concrete from mixing plant to construction site Important activity in the production of concrete. Time taken in transit should be a design parameter as it depends on Initial setting time Requirement of workability at the destination. Method of transportation adopted at site should be decided in advance so that suitable admixtures can be decided 2

3. Precautions and Objective Precautions: Transportation of concrete tends to produce segregation and loss of slump, if the distance is long Movement of hand trolley or truck on rough road surface makes vibration Results in deposition of heavy aggregates at bottom of truck Water and cement slurry comes on top Main objective – ensure that water cement ratio, slump or consistency, air content and homogeneity are not modified from their intended states. 3

4. 4 Goals : to prevent segregation to not reduce the workability of the mix. General rule of thumb, Thirty to sixty minutes - small jobs At ready-mix plant, concrete should be discharged from a truck mixer or agitator truck within two hours. If non-agitating transporting equipment is used, this time is reduced to one hour.

5. 5 Types of transportation Vertical Horizontal

6. Methods of transportation of concrete Mortar pan Wheel barrow, hand cart Crane, bucket and rope way Truck mixer and dumpers Belt conveyors Chute Skip and hoist Transit mixer Pump and pipe line Helicopter 6

7. Mortar pan Labour intensive method Generally used for small works No chances of segregation of concrete Greater surface area of concrete exposed to sun, drying conditions great loss of water particularly in hot weather Mortar pan must be wetted to start with and must be kept clean 7

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9. Cran e , bucket an d rop e way Crane bucket and ropeway are used for transporting concrete above ground level Crane : Main consideration in selecting the crane is height and radius of operation Fast and versatile and allows movement in all directions Depending upon the site, cranes may be - derrik crane, tower crane, crawler mounted, wheel mounted, or hydraulic crane 9

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11. Bucket 11 Square or circular Needs the aid of a crane, cableway, or hoist so that it can be moved horizontally or vertically. Types: Opening at bottom: door opened and released Opening at top: discharged by tilting or using forced action □ Size – 0.5 m^3

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13. Ropeway 13 Suitable for works in valley, over high piers and long dam sites. Excessive free fall of concrete should be avoided to minimize segregation Concrete is transported in a container with help of rope and pulleys

14. Belt conveyors It has limited application due to Chances of segregation on steep slopes, roller points and changes in direction of belt Over-exposure of concrete to environment. Used for continuous operations Low slump concrete - for slower moving belts and higher slump concrete - faster moving belts 100 - 350 cubic yards per hour Concrete mix is spread very thinly on the conveyor and is susceptible to loss of moisture during hot weather conditions . 14

15. 15 used in horizontal directions, but can be moved in the vertical direction (i.e. up to 35 o ) with some adjustments to the conveyors.

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17. Chute Used for concreting in deep locations. Care should be taken that slope should not be flatter than 1V:2.5H, otherwise concrete will not slide down. Workability should not be changed to suit the delivery by chute. Technically it is not a very good method but it is extensively used in the field. Should only be used in short lengths since concrete becomes more susceptible to segregation and drying out. 17

18. 18 When they are used, it is very important that the concrete mix is workable and cohesive, hence should be re-mixed at the lower end by passing down through a funnel-shaped pipe or drop chute.

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20. Helicopter more economical in the hilly regions like high mountains. Very fastly one can transport concrete to the construction site within mins. 20

21. P NEUMATIC GUNS ( SHOTCRETE ) 21 □ Used where concrete is to be placed in difficult locations and where thin sections and large areas are needed

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23. T REMIE 23 In the Tremie Concrete method, concrete is placed below water level through a pipe, the lower end of which is kept immersed in fresh concrete so that the rising concrete from the bottom displaces the water without washing out the cement content. The tremie concrete method is often used in bridges that span bodies of water. In this case, the pier footing is supported by a tremie. Tremie pipes are also used to pour the concrete in slurry walls.

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25. Us e of technology 21 Using live monitoring and remote database one can transport concrete with ease. GPS is installed in the truck mixer and along with the live monitoring system and remote database the truck GPS are interconnected. Thus making the transport more feasible.