[C M Dordi]

MECHANISATION OF CONCRETING 
CONCRETE PLACING BY PUMPING
Taken from : Ambuja Technical  Literature Series -13

PLACING OF CONCRETE
Concrete is often transported to its final position by a number of methods. Even though it is desirable to place the concrete directly into position, it is not always possible to achieve the same. However, placing can be done to the desired quality if following recommendations are carefully observed .

• Deposit the concrete at or as near as possible to its fin al position. Use of shovel or poker vibrator to push the concrete to its desired position may lead to segregation.
  
• Place the concrete in uniform layers so that no segregation takes place. In walls and columns, in order to prevent air entrapment, the layer thickness should be restricted to 450 mm while placing.
  
• There is no need to restrict the height from which concrete is dropped so long as the mix is cohesive and the drop is unobstructed and through a
  tremie or a pipe chute.
  
• Segregated mixes due to bad placing cannot be fully compacted. 
  
• Place concrete as quickly as possible. However, the placed concrete must also be compacted at the same time.
  
• Before placing each layer the lower layer must be fully compacted.
  
• Avoid cold joint formation by placing the layer of concrete over the previous layer which can still be compacted.
  
• In columns and walls the placing must be done in such a manner that concrete does not strike formwork, reinforcement or inserts. Any obstruction along the path of placing will cause segregation and the mortar (finer portion) of the concrete mix will stick to the reinforcement and formwork while coarse particles will drop below.   
  
• Always make sure, the location at which the concrete is being placed is visible to the naked eye. 
  
• For good and uniform finish in wall and columns it is necessary to fill the forms at a rate greater than 2.0 to 3.0 m height per hour.
  

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[Manish Jain]

Concrete Pumping

Amongst the various equipment's now available, concrete pumps are most versatile as compared to other placing equipment. This publication deals at length with the concrete pumping method for placing concrete.

CONCRETE PUMPS
Generally concrete pumps are either mounted on a truck or on a trailer . The pumps are either diesel or electrically operated. The concrete is
pumped through the pipeline of diameter between 100 mm to 180 mm. The most popular and suitable diameter for normal pumping is 125 mm.
Modern portable concrete pumps now manufactured in the overseas countries are in their fifth generation having enormous power, high capacity and absolutely reliability hydraulic system. They can pump concrete to a height of nearly 500 M or cover horizontal distance upto 2000 M. The p-umps have hydraulic system which ·an take concrete pressures upto 200 bars. The pumps' outputs range from 19 to 150 CuM per hour. Different manufacturers have developed different types of valves or systems. The rock valve , 'C' valve system , flat gate valve and 'S' trunk system  are generally adopted depending on the customer's choice, and use or the manufacturer's patented system. However it may be noted that the a rock valve system got its name in Germany. In German language rock mens a woman's skirt and since the valve has a similar shape and movement it is called so.

Pumps are generally designed with adequate protection against adverse usage, they are insensitive to rough treatment and operation on construction sites, have sturdy construction and are easy to maintain. The gate valves cut through concrete and are fully lined with highly wear resistant metal and can be quickly replaced if it is worn out. Rams are of special vulcanized rubber, lined with steel core, and are easy to replace as they have quick detachable connectors. The metal core is fully encased to avoid concrete adhesion.

for more details download ..... 
 MECHANISATION OF CONCRETING PART 2 FD.pdf