The RCC was mixed in the trucks for about five minutes. After mixing, drivers drove two ready-mix trucks on a ramp and discharged both 5-yard loads into a Calumet dump truck. The 10-yard dump truck was then covered and went to the jobsite. Scott Noel, Builder's sales manager, commented that their productivity was higher than the company average.
Understanding the potential for RCC in Indiana, Calumet committed to RCC construction and bought a high-density paver. The advantage of this paver over a typical paver is it will consolidate the RCC to about 95% of the maximum density, while a conventional paver will only consolidate to about 80% of the maximum density. This means there is far lesser rolling, resulting in a much smoother finished surface.
The procedures at the jobsite were the same as typical asphalt work. The RCC was deposited from the dump truck into the paver. After the material was placed, its density was verified via ASTM C 1040. Rolling was performed as required to ensure a minimum of 98% of the maximum was achieved. After placement and rolling, workers applied a white pigment curing compound. Finally, the RCC was sawcut in 30-foot increments to control crack locations.St. Joseph County
RCC work has not been limited to central Indiana. St. Joseph County in the northern part of the state also has experience with RCC. The original design for one street was to mill out 4 inches of asphalt and replace it with 5 inches of RCC. However, after looking at the costs of both the asphalt and RCC material, officials chose to place RCC over the milled asphalt areas.
The result was RCC whitetopping. Contractor Walsh & Kelly teamed with Kuert Concrete for the project. Kuert utilized its central mix plant only a few miles away. Unlike other producers, Kuert's mix design consists of a blend of two washed limestones and natural sand. Walsh & Kelly used its conventional (not high-density) paver.
Although more rolling was required than with high-density paver projects, they did achieve adequate compaction. Once cured and sawcut, crews applied an asphalt micro-seal over the RCC to give the appearance of other roadways in the area.
This is only the beginning. Keep your eyes and ears open. Roller-compacted concrete may soon knock on your door.
Christopher Tull is the founder and owner of CRT Concrete Consulting. He consults for contractors, ready-mix producers, owners, and the PCA. He is a member of ACI committees 327: Roller-compacted Concrete; 302: Construction of Concrete Floors; 330: Concrete Parking Lots and Site Paving; and 332: Residential Concrete Work. E-mail firstname.lastname@example.org.