Specially engineered concrete supplied by Central Concrete -a business unit of U.S. Concrete (NASDAQ-USCR) - is being used in the construction of Zero Waste Energy’s 90,000 ton (81,600 tonne) per year dry anaerobic digestion facility in San Jose, California.
According to the concrete supplier, also based in San Jose, it had to develop several innovative concrete solutions to address the demanding specifications required by the biogas facility.
The company said that along with concreting contractor Jos. J. Albanese, it not only responded to a significant acceleration in the schedule, but also devised mixes and placement solutions that addressed the unique issues faced when working with waste materials.
The project is being constructed by Campbell, California based South Bay Construction.
The dry AD process used at the facility will convert high solid organic waste into biogas for energy generation and fertiliser. It is expected to process around 90,000 tons of waste and produce up to 1.6 MW of electricity
According to Central Concrete the key to building a plant of this type is making sure that the waste materials and the methane gas are properly contained.
In addition, the company said that its team needed to address 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 was said to be dense, durable concrete mixes with tight, low shrinkage specifications.
The company claimed that the mixes not only delivered the required low water/cement ratio, but the highly workable mixes allowed Jos. J. Albanese's crew to place the concrete more efficiently, significantly helping them to meet the accelerated build schedule.
The Jos. J. Albanese team applied the mixes using a process called wet-mix shotcrete.
This process involved pumping Central Concrete's prepared mix through a nozzle. Compressed air was then introduced and a ‘gun’ delivered the concrete.
According to the company, 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, teams from Central and Jos. J. Albanese poured and placed five extremely large mat floors in the very early hours of the morning to assist Zero Waste Energy accelerate the schedule.
The facility is targeted for completion in December 2013 and is expected to be the largest Dry Anaerobic Digestion facility in the U.S.
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