What happens to strand tensioned during cool morning temperatures when higher temperature concrete is poured on it?

When cooler morning temperatures cause strand tension, and then higher temperature concrete is poured on it, the tension in the strands can reduce. This happens because the heat from the concrete can cause thermal expansion, which results in a reduction of the effective tension. As the concrete cures and heats, it can create a differential temperature between the strands and the concrete, which may cause the strands to relax or lose some of their tension.

This thermal effect can create stresses that impact the bond between the strands and the concrete, potentially leading to a loss in the strength that was originally imparted to the strands during the tensioning process. In summary, the interaction of temperature differences can indeed result in the strands losing their strength as the higher temperature concrete is poured onto the pre-tensioned strands.