The DIA Concourse C RON Project included 20,862 Square Yards of 8" Roller Compacted Concrete for the pavement areas adjacent to the concourse apron areas, where snow removal efforts stockpile excess snow from around the DIA concourses during heavy snow events. The City and County of Denver, the Owner for this project, required the heavy duty serviceability of concrete pavement, but had budget constraints requiring another pavement alternative. IHC recommended the use of Roller Compacted Concrete (RCC) to meet the Owner's needs and financial goals. The Owner chose the RCC alternative because it brought all of the characteristics of a concrete pavement at a price cheaper than a Portland Cement Concrete (PCC) alternative and also cheaper on a first cost basis with an asphalt alternative as well. Denver International Airport had never specified an RCC alternative pavement in any of its previous pavement applications, so IHC, with support from the Portland Cement Association, and the Rocky Mountain Cement Shippers Council, drafted and presented appropriate RCC specifications for the project. The engineering firm of DMJM Harris reviewed and collaborated in the development of the specifications ultimately used for the project.
The RCC material was produced with an Excel Pugmill set up within airport property, with double end dump tractor/trailers feeding an Ingersoll Rand Titan 8820 ABG paver. Moisture Density readings taken immediately behind the paver prior to compaction by the rollers yielded densities between 90 and 92 percent consistently. The compactive effort behind the paver consisted of a 10 ton dual drum vibratory roller, followed by a combination pneumatic roller and a 2 ton dual drum roller for surface sealing. The 8" RCC pavement was placed on top of 6" of recycled concrete pavement base, utilizing on-site waste concrete as an environmentally friendly alternative to virgin base materials. The project was placed in late fall in conditions whereby the daytime highs were in the 50's and 60's, with overnight temperatures reaching into the low 30's. All pavement placed when overnight temperatures were expected to be below 35 degrees were covered with paving blankets to protect it from freezing. In-pavement Hi-Low Temperature Sensors recorded the actual overnight pavement temperatures to assure compliance with specifications. Four inch (4") pavement cores were taken within 24 hours of RCC placement to test for concrete pavement strength. Once pavement compressive strength testing showing compressive strengths greater than 2000 PSI, blanket protection was able to be removed. Consistently throughout the project, 24 hour compressive strengths on pavement cores yielded average strengths of 3,325 PSI. While RCC pavements generally do not require sawed joints like PCC pavements for long term performance and serviceability, the Owner required pavement joints to be cut and sealed on a 30' x 30' joint pattern. The relief sawing was accomplished with a Sofcut saw, allowing the relief cutting to be performed immediately upon final surface roll, with widening and sealing performed with silicone sealant.
Moisture content and density tests were taken at specified intervals behind the finished pavement section, utilizing a Nuclear Moisture/Density Gauge in accordance with ASTM C1040. The Modified Proctor for density testing was in accordance with ASTM D1557. Optimum moisture was established at 5.9%. All tests performed indicated moisture content within specified parameters, with all density tests exceeding 96% of Modified Proctor. Aggregates were selected and blended in accordance with the Portland Cement Association's (PCA) gradation specification for RCC pavements. Although the project specifications required 4000 PSI Compressive Strength at 28 days, average 28 day Compressive Strengths on cylinders cast in the field according to ASTM 1435, yielded average 28 day breaks of 6069 PSI.
RCC in this application provided a very serviceable concrete pavement at a significant cost savings to the customer. While the surface characteristics vary slightly in appearance and aesthetics from that of a concrete pavement, RCC can prove a very cost effective alternative to either concrete or asphalt pavements for industrial applications. The RCC pavement application provided the Owner with a pavement that can stand up to heavy snow plowing and heavy truck traffic during snow events, resistance to turning and rutting common with asphalt pavements, with the added advantage of not deteriorating under melting conditions where large stockpiles of snow are present.