WMI Waste Transfer Station - Commerce City, CO

Project Focus
The project consisted of 1,316 Square Yards of 12 inch thick Roller Compacted Concrete (RCC) placed in the truck load out area, and another 2,985 Sy of 9“ thick RCC for the dolly pads constructed in the truck and trailer parking area. The Owner of the project, Waste Management of Colorado, was concerned about the ability of an asphalt alternative to stand up to the rigorous demands of the pavement in its intended application. The transfer truck load out area needed a pavement capable of supporting 40,000 lb fully loaded semi-trailer trucks turning on a short radius while backing up to and departing from the load out area.

Rutting and shoving of asphalt under these conditions, as well as semi-trailer dolly wheels penetrating an asphalt surface, required a concrete alternative. An additional consideration was the necessity of providing a pavement type that would allow only a 60 hour shutdown (Friday night to Monday morning) of load-out activities for construction and for subsequent curing of the subject pavement.

Concrete pavement was the pavement of choice for its ability to withstand the demands of the application, however, placing High Early Strength Concrete in this application was prohibitive because of the cost. Roller Compacted Concrete was selected for this application because of its concrete like characteristics after placement, its ability to put traffic back on after much shorter periods of time than that of concrete, and most importantly because of it’s in place cost in relation to either the concrete or asphalt alternative.

Project Details
Construction & Innovation
Because of the schedule demands of the project, the placement operations were performed on Friday night to allow for maximum cure time Saturday and Sunday prior to traffic being put back on the pavement Monday morning. The RCC material was batched out of a central mix batch plant at an offsite location and trucked approximately 45 minutes to the project site. The loads were covered to prevent excessive drying of the material during transport. The material was placed with D-7 Dozer running off a Topcon GPS system to place the RCC material to initial rough grade, followed by initial compaction with a 10 ton vibratory roller. A 14G Motor Grader operating with the same GPS system cut the surface to final tolerance, and a 5 ton steel drum roller was used to provide the final seal.

Quality
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 D2922. The Standard Proctor for density testing was in accordance with ASTM D698. Optimum moisture was established at 5.6% +- 2%. All tests performed indicated moisture content within specified parameters, with all density tests exceeding 95% compaction. Aggregates were selected and blended in accordance with the Portland Cement Association’s (PCA) gradation specification for RCC pavements. Compressive strength results at 3, 14, and 28 days were 2,846; 4,262; and 4,704 PSI respectively.

Summary
RCC pavement was selected for this pavement application because of its concrete like characteristics, its short cure time, and its low cost. The customer was able to put traffic back on the pavement within the 60 hour timeframe without the added expense of high early strength concrete, making it an ideal solution for this heavy duty industrial pavement application.