concretebaby
Civil/Environmental
- May 8, 2009
- 13
Hello All,
A large raft (7,000 m3)is to be cast in two lifts with each layer thickness of 1.5 to 2.0 meters. The mix contains Flyash and Microsilica with strength of 40 Mpa (ASTM). We would like to know what shall be the minimum time gap between casting next layer (second and final layer). The contractor wants to cast after 24 hours of casting the first layer which will be disaster because the preceding layer hasn't achieved the required strength to receive the second layer plus the heat of hydration differences between first and second layer may create a thermal shock and cracks may occur.
Another problem is cold joint which will occur if two layers are cast at different periods.
Please send us your valuable suggestions.
Thanks in advance.
A large raft (7,000 m3)is to be cast in two lifts with each layer thickness of 1.5 to 2.0 meters. The mix contains Flyash and Microsilica with strength of 40 Mpa (ASTM). We would like to know what shall be the minimum time gap between casting next layer (second and final layer). The contractor wants to cast after 24 hours of casting the first layer which will be disaster because the preceding layer hasn't achieved the required strength to receive the second layer plus the heat of hydration differences between first and second layer may create a thermal shock and cracks may occur.
Another problem is cold joint which will occur if two layers are cast at different periods.
Please send us your valuable suggestions.
Thanks in advance.