06-09-2022, 09:39 AM
CHECKLIST FOR CONCRETE TRANSPORTATION
The Site Engineer has to keep a watch on several points during transportation so that the concrete workability and its uniformity remains unaffected. The checks are
follows:
If the concrete is transported by transit mixers it is necessary to maintain revolutions within the prescribed limits (70 to 100 revolutions) at mixing speed. Any additional revolutions should be at agitating speed only. This is necessary to avoid segregation due to overmixing.
The water tank on the transit mixer is at times misused by the mixer operator who often add water in the mixer without consulting the Engineer at site. It is therefore advisable to keep these water tanks empty and addition of water and other ingredients preferably be done at the batching mixing plant only.
Some specifications limit the time within which concrete must be placed. It is felt that time limit is unnecessary as long as concrete can be properly placed , fully compacted and adequately finished without any need for adding more water. Addition of water to cater to drop in workability due to delay in transportation is prohibited. Any addition in the concrete should be done after consulting the Engineer in charge and keeping the water to cement ratio of the mix unchanged.
During hot weather and / or strong winds concrete must be covered if transported in open containers such as trucks, dumpers, wheel barrows or gamelas. This is necessary if the duration of the transportation is considerably long.
Similarly the concrete during the monsoon period should be protected from water contamination if transported in the modes described above.
The concrete containers get coated with mortar during loading, transporting and unloading process. The coating must be removed and hosed off with water jet at the earliest possible break, to prevent further mortar caking up above the dried mortar on the container surfaces. This is special ly observed at the sharp corners.
Contamination of concrete by oil , dirt or wind blown dust must be prevented.
Container should be leakproof to prevent loss of mortar or cement slurry during transportation . Baskets to carry concrete by head loads should not be permitted.
Concrete transported through long distances may segregate due to vibrations, incorrect use of chutes, placers, pipelines or bumps due to rough road surfaces etc. The mix if found segregated should be remixed before placing.
If the concrete mix is not transported quick enough or due to any other problem the mix placement is delayed, there is a drop in workability and mix stiffens. If such delays are anticipated then the mix should be designed with a higher workability or using workability retention admixtures. In a massive pour if the gap between the subsequent layers is planned at 30 to 45 minutes, the concrete mix should be designed having higher workability and using proper concrete additives, in such a manner that even upto 1 hour 30 mts. the concrete in the earlier (lower) layer can be easily compacted.
for more details visit or download
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concrete transportation and placement fd.pdf
The Site Engineer has to keep a watch on several points during transportation so that the concrete workability and its uniformity remains unaffected. The checks are
follows:
If the concrete is transported by transit mixers it is necessary to maintain revolutions within the prescribed limits (70 to 100 revolutions) at mixing speed. Any additional revolutions should be at agitating speed only. This is necessary to avoid segregation due to overmixing.
The water tank on the transit mixer is at times misused by the mixer operator who often add water in the mixer without consulting the Engineer at site. It is therefore advisable to keep these water tanks empty and addition of water and other ingredients preferably be done at the batching mixing plant only.
Some specifications limit the time within which concrete must be placed. It is felt that time limit is unnecessary as long as concrete can be properly placed , fully compacted and adequately finished without any need for adding more water. Addition of water to cater to drop in workability due to delay in transportation is prohibited. Any addition in the concrete should be done after consulting the Engineer in charge and keeping the water to cement ratio of the mix unchanged.
During hot weather and / or strong winds concrete must be covered if transported in open containers such as trucks, dumpers, wheel barrows or gamelas. This is necessary if the duration of the transportation is considerably long.
Similarly the concrete during the monsoon period should be protected from water contamination if transported in the modes described above.
The concrete containers get coated with mortar during loading, transporting and unloading process. The coating must be removed and hosed off with water jet at the earliest possible break, to prevent further mortar caking up above the dried mortar on the container surfaces. This is special ly observed at the sharp corners.
Contamination of concrete by oil , dirt or wind blown dust must be prevented.
Container should be leakproof to prevent loss of mortar or cement slurry during transportation . Baskets to carry concrete by head loads should not be permitted.
Concrete transported through long distances may segregate due to vibrations, incorrect use of chutes, placers, pipelines or bumps due to rough road surfaces etc. The mix if found segregated should be remixed before placing.
If the concrete mix is not transported quick enough or due to any other problem the mix placement is delayed, there is a drop in workability and mix stiffens. If such delays are anticipated then the mix should be designed with a higher workability or using workability retention admixtures. In a massive pour if the gap between the subsequent layers is planned at 30 to 45 minutes, the concrete mix should be designed having higher workability and using proper concrete additives, in such a manner that even upto 1 hour 30 mts. the concrete in the earlier (lower) layer can be easily compacted.
for more details visit or download
concrete transportation and placement fd.pdf