Morley Construction Company is providing concrete services for this 23-story criminal, family, and civil courts building in downtown San Diego. Replacing the current courthouse, the project will encompass a full city block and will include a new 182-foot-long pedestrian bridge and tunnel connecting the new courthouse with the existing Hall of Justice. Crews broke ground for the construction of the San Diego Central Courthouse, Superior Court of California in May 2014, and Morley began concrete work on September 25, 2014.
Morley was selected through the general bidding process, but was the only contractor to address the thermal control of the mat footing during the bid process. This is the first mechanically cooled mass concrete mat in San Diego.
Morley placed the foundation, which includes the massive pour of 6,650 cubic yards, but also five smaller placements, one of which was 4,500 cubic yards, bringing the total for the project to 16,000 cubic yards.
About 12 miles of chilled water piping was used to cool the concrete slab, preventing the hydrating concrete from gaining too much heat and potentially affecting its structural integrity.
A total of 4,000,000 pounds of reinforcing steel was used, and 92 trucks provided 682 loads of concrete, with an average of one concrete truck every 54 seconds.
Morley also formed and poured slightly more than a mile of curbs and walls for the precast curtain wall to set upon, and placed all the concrete on metal composite decks throughout the building.
Morley coordinated more than 600 ready-mixed concrete deliveries to supply five concrete pumps during mat slab placing operations.
The project budget for structural concrete was approximately $13 million. Morley used its cost control system to track man-hour productivity and unit-price trends throughout the project. Cost codes are analyzed weekly and work that is trending in unexpected directions is scrutinized or modified for better production rates. Constant coordination with the general contractor on the construction sequence helped minimized schedule impacts.
For the mass concrete in the mat foundation, Morley hired a heat consultant who did a complete thermal model of the foundation before any concrete was placed. The heat consultant specified wireless monitoring of the footing temperature with thermal loggers in order to control the temperature by the minute. When the pour was completed, the actual temperature in the mat was never more than two degrees off of the thermal model. This system was over 90% accurate.
The sequencing of when and where to place concrete so that rebar placement could also progress, thermal control could be maintained, and the constant rerouting and dismantling of the cooling system required intricate innovative planning.
Mitigation of heat gain required nearly 12 miles of chilled water piping. This was the first time mechanical cooling has been used in San Diego and a first for Morley Concrete.
The greatest challenge was allowing other work to continue during concrete placement, ultimately preparing for the erection of structural steel. Morley met this challenge by preparing a sequence to simultaneously place rebar and pour the foundation while allowing sections of the mat to be covered with blankets to maintain thermal control.
Morley built the cast in place 30-foot-high basement walls, miscellaneous blast walls, and planter walls at the street level.
Encompassing a full city block, the courthouse includes a new 182-foot-long pedestrian bridge and includes 30,000 square feet of finished slab.