Beginning at midnight on Friday, June 8, Sundt Construction executed the first of two massive concrete pours that will form the foundation of the new 290,000 SF courthouse shared by Pima County and the City of Tucson.
Construction at the site, located at Toole and Stone avenues in Downtown Tucson, began Feb. 1 and is scheduled for completion in August 2013. The first seven to nine months of the job are being spent on the foundation, just getting to grade level.
Some facts about the project:
- The concrete mat slab is divided into two parts: A and B. Section A was poured June 8. The second pour happens on June 29.
- The pours must be performed at night because of the lower temperatures and the traffic impacts. The ideal temperature for pouring concrete is about 70 degrees. Sundt uses chilled water and spray bars to keep the concrete cool.
- Pour A took approximately eight hours to complete:
- 440 cubic yards of concrete placed per hour
- 3,553 cubic yards total
- 20,000 SF, approximately
- 70 trucks per hour for a total of 380 truckloads
- Pour B is expected to encompass:
- 700 cubic yards of concrete placed per hour
- 4,000 cubic yards total
- 24,000 SF, approximately
- The two sections of the foundation (A and B) will be joined with a construction joint. The weeks between pours gives the project team a jump on the construction schedule in order to begin the concrete foundation walls.
- The foundation is 25 feet below grade and will measure approximately one acre.
- The steel-frame building will have seven floors above grade. Its exterior skin is unitized curtain wall and precast concrete.
- The concrete has to be placed within 90 minutes of leaving the batch plant. Beyond that, it can’t be used because it will set up too quickly and may not cure to the specified design strength of 5,000 psi.
- Two redi-mix companies are supplying the concrete. One is located at I-10 and Tangerine; the other is in Vail.
- Continuous on-site testing during and after the pour ensures the mix is accurate and cures to the required strength.
- Sundt’s contract for the core and shell: $48.2M.