Does a carport slab need expansion joints at interior piers or the perimeter?
I assume the pier is above the finished floor. You are correct in thinking to provide the full depth expansion joint around the pier, as well as around the perimeter of the slab that will be poured against existing concrete.
If the garage area is large, in addition to the expansion joint, it is recommended to have a control joint at an approximate 10'-15' interval in each direction to minimize the potential for random crack. The control joint (1/8&quot;-1/4&quot; wide x 1&quot; depth) shall be made by saw-cut within 24 hours of concrete placement. Around the pier, the diamond-shaped control joint is recommended to avoid diagonal cracks at the reentrant corners of the slab.
The last recommendation is the fresh concrete shall have at least 5% of entrained air to improve its durability against weathering, especially in the cold regions.