huangyhg

low heat cement in machine foundation
it is quite common to have thick slab [800mm to 1200mm or more] foundation for heavy machines in minining sites. in such cases we should use low heat cement. theoretically, special form work with heat insulators are required for such type of massive pours.
i have not seen any low heat cement and special formwork for foundation design so far in the projects that i was involved with. my question is, if it is really mandatory to use low heat cement and special formwork for machine foundation? and if we do not use that, there is a possibility that cracking will appear on the slab and time to time those cracks are to be attended to. probably the structural strength of the foundation will not be in jeopardy, because, in majoirity of cases, the thickness is governed by the dynamics of the equipment.
ideally we should use low heat cement and special formwork; but in reality it is difficult and very expensive to follow it up in remote mining sites. using standard concrete with heavy reinforcement [for crack control] and standard formwork is the easy option. please share your experience in this subject.
your experience and frustration is common. rare to be able to control concrete temperature well on remote sites. casting very early in the day should help some. for large projects, can sometimes get ice plants to cool mixing water.
in your 800 to 1200 thick footings or slabs, lack of compaction is probably the most likely cause of cracking. consolidation continues after initial vibration, thus creating plastic settlement cracks directly over the top bars. this can be largely avoided by revibration, and the time to do this depends a lot on the temperature of the concrete when placed.

hokie66, thank you for your response - this is what i am experiencing. sorry, i could not respond earlier - my computer crashed! it is working now.
regards
am

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