Kennedy Space Center Finds Value in Concrete Recycling
Employees and management at Kennedy Space Center (KSC) have committed to maximizing reuse and recycling. KSC mission and support facilities contain vast quantities of concrete. During refurbishment or replacement, concrete that meets reuse standards can be processed and made available for a variety of applications.
Causeway and shoreline applications
In 2009, a vital transportation route across the Indian River and into NASA was due for repairs. Wave action had damaged the causeway seawall. KSC applied 30,000 tons of reclaimed concrete in solving that problem.
Last fall’s Hurricane Matthew caused extensive erosion along the Banana River shoreline. Restoration of that shoreline will include crushed concrete from KSC.
Further reuse in paving and construction
Another KSC project, the Propellants North Administrative and Maintenance Facility, earned a LEED Platinum rating in 2010. The project used 1.2 million pounds of reclaimed concrete as part of the facility foundation and paving subbase materials.
The KSC team recycled 5,671,100 pounds of concrete in 2016. One of KSC’s commercial launch providers used a portion of that in building a landing zone for their rocket. Additionally, almost one million pounds were reused in the construction at the KSC Visitor Complex.
In 2017, roughly 8 million pounds of crushed concrete have been brought to a 1.5-megawatt solar farm expansion construction site. Crushed concrete serves as a ground cover beneath solar panels. Additional finely crushed concrete is used in a road that runs between arrays of solar panels.
How concrete is recycled
In general, clean concrete from KSC demolition projects is brought to the Diverted Aggregate Reclamation and Collection Yard (DARCY) for processing. There, a series of operations, including crushing, screening, conveying, and stockpiling is involved in processing concrete pavement or structural debris. Crushing process equipment includes a vibrating feeder, jaw crusher, impact crusher, vibrating screen, and belt conveyor. To protect personnel as well as the equipment, all protruding reinforcement or rebar is removed or cut to a minimum before crushing.
Typically, a vibrating feeder evenly and gradually feeds material to crushing equipment through a hopper. After primary crushing, the material is transferred to the impact crusher by belt conveyor for secondary crushing. Crushed materials are then transferred to a vibrating screen for separating. After separating, aggregate that meets the size requirements is transferred for storage as the final product. Any remaining larger aggregate is returned to the impact crusher, thus forming a closed circuit. The size of final products can be combined and graded according to project needs and specific requirements.
Requirements for recycling
Reclaimed waste concrete must be free of contaminants. No oil-stained concrete will be accepted. Painted or coated waste concrete will only be allowed at the DARCY as long as the hauler can provide evidence that the concrete has not been contaminated by PolyChlorinated Biphenyls (PCB) or RCRA 8 heavy metals having Toxic Characteristic Leaching Potential (TCLP). Acceptable evidence includes paint or coating analysis results from a certified laboratory and written verification from the project manager. Historical data and/or generator knowledge will be considered by NASA environmental assurance personnel on a case-by-case basis.
Concrete suspected of having PCBs in applied coatings cannot be brought to DARCY. Instead, PCB-contaminated waste must be disposed of in accordance with KSC environmental requirements. Restrictions also exclude concrete previously utilized as a transformer pad.