Expansion post-pouring belt: mainly aimed at the wet expansion and dry shrinkage characteristics of concrete, in the super-long structure, concrete will crack under the action of dry shrinkage, so the post-pouring belt is reserved.
In order to avoid affecting the free settlement and tension, it is required to disconnect the steel bars thrown out of the post-cast strip.
The second pouring is the first pouring for the structure construction by closing the post-pouring belt after the two sides are stable.
Strictly speaking, the secondary casting is not only for the post-cast strip. Common appellation: If the wall is high, it is not allowed to pour to the top at one time, with a height of 500 each time, so as to ensure the vibrating quality of pouring and the stability of formwork. This is called layered pouring, not secondary pouring. In mass concrete, if the thickness of the raft is more than 2m, in order to avoid excessive hydration heat, it is not possible to reach the top at one time and pour it twice to speed up heat dissipation. According to the calculation of calorific value, the second pouring time is often after 7 days, which is also called second pouring.
Usually, the second pouring is in the post-pouring zone, which is determined by the final setting.
In addition, there is an expansion strengthening belt, which is separated by a quick-closing net, and the mechanism is the same as that of the expansion post-pouring belt. It is only poured together with the concrete on both sides, but the difference is that the shrinkage can be compensated by pouring expansive concrete.