Central Concrete, a business unit of U.S. Concrete Inc., and the leader in delivering low-CO2 concrete to the San Francisco Bay Area, along with Jos. J. Albanese, a leading Bay Area concrete contractor, developed several innovative concrete solutions to address the aggressive specifications required by the Zero Waste Energy Development Facility in San Jose, Calif. Not only did Central Concrete and Albanese respond to a significant acceleration in the schedule, but the companies devised mixes and placement solutions that addressed the unique issues faced when working with waste materials. South Bay Construction, a construction firm, headquartered in Campbell, Calif., headed the project.
San Jose’s Zero Waste Energy Development Facility opened Nov. 22, 2013, and is the largest Dry Anaerobic Digestion (AD) facility in the U.S. The Dry AD process converts high solid organic waste into green energy. It is projected that the plant will be capable of processing 90,000 tons of waste and producing up to 1.6 megawatts of renewable power. This is enough to power 2000 homes.
The key to building a plant of this type was making sure that the waste materials, such as methane gas, were properly contained. The team also addressed the corrosive nature of these waste products. In response to these challenges, Central Concrete evaluated several mix design combinations, both in the field and in the lab, to produce the desired performance. The result—dense, durable concrete mixes with tight, low shrinkage specifications. These mixes not only delivered the low required water/cement ratio, but the highly workable mixes allowed Albanese’s crew to place the concrete more efficiently, significantly helping them meet the accelerated schedule.
The team applied the mixes using wet-mix shotcrete. This involved pumping Central’s prepared concrete through a nozzle. Compressed air is then introduced and a gun delivers the concrete. Not only does this wet-mix process allow larger volumes to be placed in less time, but the ability to adjust the water allowed the team to meet the hardening properties required for the job. In addition, the teams poured and placed five extremely large mat floors in the very early hours of the morning to further assist the owner in accelerating the schedule.
“We chose to work with Jos. J Albanese and Central Concrete on this project for their knowledge in shotcrete applications and their ability to get it done,” says Jim Ichley, senior project manager of South Bay Construction.