13.4 : 설계 사례: 콘크리트 작업성 관리

Consider concreting work for a raft foundation in the hot sun.

Since the volume of concrete required is large, before preparing such large quantities, the slump test was conducted on the fresh concrete trial mix, which revealed that the workability is low.

The site engineer observed that the reason for low workability was due to the faster loss of water from the concrete mix.

On inspecting, it was observed that the coarse aggregates were hot due to exposure to the sun.

Water is sprayed on the coarse aggregates to reduce the temperature, and a concrete sample is prepared.

The slump test was conducted, and it was found that the slump improved but did not reach the desired slump.

Further, it was analyzed that the workability is reducing because of the rapid evaporation of water from the newly prepared concrete mix due to the hot sun.

Finally, to avoid difficulty in handling the concrete due to loss of water, sugar is added as a retarder, and the slump test is conducted on the trial mix, giving the desired slump.