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Concrete FAQ


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Commonly asked questions about concrete and its placement.

Why is the concrete specified to be "continuously placed" on a post-tensioned slab project?

Because the design of a post-tensioned slab foundation is based on the entire member acting as a unit utilizing the full allowable strength of the concrete and the steel tendons.

Are "cold joints" detrimental to the design?

Cold joints are to be avoided for the reason outlined above.  Joints can be allowed for purposes of controlling the placement by the engineer but must be depicted on the plan.

What about cold weather curing additives such as calcium carbonate?

Calcium carbonate (CC) must be limited to a max of 1% of the design mix to prevent corrosion of the steel reinforcement.

Is continuous inspection of the concrete placement necessary?

Fortunately, yes.  Not just because it is prescribed for structural members by the UBC but also to help assure the builder that placement is continuous and the mix strength is as specified on the engineered plans.



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