I am a general contractor who hired a company to shotcrete a new swimming pool.

Question:
I am a general contractor who hired a company to shotcrete a new swimming pool.
They began on Friday, a very hot day, and they were placing concrete very slowly (27 yards in 4 hours). Their pump broke down and they were unable to complete the job that day so they returned on Monday. My Question is about the "cold joint" between the work on Friday and the work on Monday. What is your opinion of this situation?


Answer:
On large swimming pools, it is not unusual to have joints that are left over a weekend or longer. The key is the means by which the joint is dealt with. As with any concrete joint, the surface needs to be clean and free of laitance or other contamination. This can be accomplished by cleaning the joint while it is green on the first day or by cleaning with waterblasting, sandblasting, or wire brushing after the surface has gotten hard. As long as the joint is clean, all gloss has been removed, and the joint is dampened the structure should not be impacted by the joint. Also, 27 cubic yards in 4 hours is not necessarily slow production. Depending upon the circumstances, I would think that 27 cy in 4 hours was quite productive.