DU’s Taxiway F, originally constructed between 1986 and 1988, has deteriorated due to age, as well as Alkali-Silica Reaction (ASR) in the concrete, and is scheduled for rehabilitation. Currently, the project is in its first year of a two-year construction effort to replace a portion of the taxiway. This $26 million project involves removal of 34” of existing material (a combination of concrete/asphalt base/subgrade) and replacement with 16” of concrete, 6” of lean concrete base course, and 12” of recycled concrete aggregate subbase.
Early in the planning process, the decision was made to recycle the concrete material from the demolished taxiway. A site for a temporary crushing operation was designated on RDU property for use by the contractor, which includes the stockpiles for the uncrushed concrete, crushing equipment, and resulting recycled concrete aggregate.
The recycled concrete aggregate base course is being utilized for subgrade remediation which requires removal and disposal of the top 12-inches of the subgrade soils and replacement with 12-inches of recycled concrete as a subbase layer. The recycled concrete will provide a stable base upon which the pavement structure is built. It will also provide a more permeable layer that will improve migration of water to the new underdrain system.
By using the recycled concrete material, several goals are accomplished: 1) there is a cost savings related to using the recycled material both in material cost and cost of transporting both the demolished materials and raw materials to the site, 2) use of the recycled material means less raw material is needed, and 3) the original, demolished concrete is not being dumped or buried in a landfill. An additional benefit is the recycled material is stockpiled on RDU property and can be used as needed for repairing haul routes or potholes.
Construction of the project is currently underway and expected to be complete in the fall of 2018. Once complete, the taxiway will be good go for a several decades.
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