Better Roads Digital Magazine
Issue link: http://read.dmtmag.com/i/221550
Photo courtesy of Cement Council of Texas RoadScience Detail of New Braunfels roller-compacted concrete pavement was grooved to provide a smooth riding surface. say. "A first-cost savings of 15 to 25 percent can be expected if RCC is specified as a pavement alternative for projects requiring wheel loadings of 50,000 to 120,000 pounds." These cost benefits are driving use – and research – of RCC in Arkansas, where RCC is proving to be a cost-effective alternate for building energy sector haul roads that will stand up to trucks serving new natural gas wells and infrastructure. This haul traffic is tearing up existing roads: More than 1,000 miles of roadways in Arkansas have been adversely affected by the increased traffic loadings, leading to a sharp acceleration of pavement distress. In response, the Arkansas State Highway & Transportation Department is seeing how new RCC pavements are performing in the Fayetteville Shale "play" area. "The accelerated pavement distress that has become prevalent in the area illustrates the need to examine cost-efficient rehabilitation strategies that can provide a long service life," the agency says. "Roller-compacted concrete pavement is one such potential alternative ... [t]he reduced cement content and ease of construction result in substantial cost savings. RCC is strong and well-suited for heavy traffic loadings, but the success of any pavement depends on the quality of its foundation." In this area, two test sections were constructed, each 1-mile long. Section I had 6 inches of full-depth cement-treated base reclamation, topped by 7 inches of RCC. Section II had an 8-inch RCC overlay of the existing pavement including levelup. Safety edge was used on both sections. Both sections were diamond-ground to improve smoothness, a major criticism of RCC surfaces. The project took less time and money than reconstructing 8 December 2013 Better Roads the existing two-lane rural road. Construction of both miles took nearly one month, where reconstruction would have taken most of a construction season. The cost for the project was $1.9 million for the two miles, compared to the average $3 million per mile the Natural State spends for reconstructing a two-lane rural roadway. Ultimately, this project saved Arkansas nearly $2 million per mile compared to conventional asphalt reconstruction, and the RCC pavement should be able to withstand the increased weight loads from the heavy vehicle traffic. This month, a subcommittee exploring standard specs for roller-compacted concrete was to meet to further develop specs for testing RCC in the lab. ASTM International's Subcommittee C09.45 on RollerCompacted Concrete is working on three proposed standards for roller-compacted concrete. They are the following: WK33682, Test Method for Preparation, Compaction and Density Determination of Roller-Compacted Concrete Specimens by Means of the Gyratory Compactor. According to subcommittee member Dr. Stacy G. Williams, Ph.D., of the University of Arkansas, because the Superpave gyratory compactor was developed during the 1980s as a means to provide a laboratory simulation of the compactive effort imparted by rollers on a Superpave asphalt mat, it may be applicable to RCC, as it's compacted using the same type of roller. Therefore, preparing RCC specimens in a laboratory can be expected to provide similar results to those experienced in the field. WK41101, Practice for Molding Roller-Compacted Concrete in Beam Molds Using a Vibrating Hammer. Once approved, WK41101 will be used to consolidate RCC into beam molds with established flexural strengths. This is important because RCC is gaining use as a pavement for roads, shoulders and streets, and all pavements need flexural strength data for design purposes. WK42461, Test Method for Density (Unit Weight) and Air Content (Pressure Method) of Freshly Mixed Roller-Compacted Concrete. WK42461 covers the determination of density and air content of freshly mixed concrete. WK42461 will be used in the design of roller-compacted concrete mixtures and to aid in controlling the quality of those mixtures during RCC construction. Web Extra: Read "Roller-Compacted Concrete Field Demos" at betterroads.com/rcc-demos.