Admixtures make inconveniently located projects possible by extending placement times beyond 45 minutes. A 12-foot-wide East Wetlands hike and bike trail was built by Cemex in 2013 in the City of Yuma, Ariz., which required the delivery truck to back up a quarter-mile. The arid climate and hauling time would have compromised traditional RCC mixes, but the mile-long installation of 5-inch RCC shows no random cracking a year later thanks to the addition of GRACE V-MAR VSC500, which was dosed at a rate of 3 to 5 cwt depending on the ambient conditions and the expected haul time. The mix design included 520 pounds of cement; 805 pounds of coarse aggregate; 1,675 pounds of intermediate aggregate; 805 pounds of sand; and 6.5% water. The maximum aggregate size was ½ inch, which provided the tight surface texture required for this application.
The first diamond-ground RCC road is performing well five years after placement. Built in August 2009 by Morgan Corp. for the South Carolina DOT, the project entailed milling 10 inches of asphalt, recompacting the subgrade, and placing 10 inches of RCC in one lift. The mile-long, four-lane project was completed in 15 days. Material was mixed in a Rapid International USA Inc. Rapidmix 600C pugmill near the jobsite in the city of Aiken, transported in dump trucks, and delivered to a Gomaco Corp. Inc. RTP-500 rubber-track placer that conveyed it to an ABG Titan 7820 paver. The pavement was cured and sawcut for control joints every 20 feet. Traffic was allowed 24 hours later. With a speed limit of 45 mph, the desired International Roughness Index (IRI) was 85 inches/mile. Pre-grind IRI was 100 to 120 inches/mile in areas with stiffer subgrades and up to 200 inches/mile in areas of softer subgrades. The average post-grind IRI for each lane was 58.1, 73.6, 65.2, and 72.1 inches/mile with an overall average of 67.2.
Despite carrying 400 tractor-trailers a day, a 69-acre RCC parking lot in Rome, Ga., displays only minimally visible random and mid-panel cracks after three years. Lowe’s Home Improvement bid RCC instead of asphalt with conventional concrete dolly pads after touring facilities with RCC and weighing upfront costs. Seven inches of RCC were placed on top of 6 inches of aggregate base in 30-foot sections using an ABG Titan 7820 paver and Aran ASR 500 continuous pugmill mixing 280 to 300 cubic yards/hour. Transverse and longitudinal control joints were sawcut on a 15-by-15-foot pattern and sealed with Sika Corp.’s Sikaflex. The project was built in two months and 11 days by AG Peltz Group LLC and Peltz Companies Inc. in fall 2011.
In summer 2013, the Southern Tier Catholic School in Olean, N.Y., needed a new pavement surface for the parking lot. The local contractor proposed to the school board a conventional concrete overlay as well as an RCC overlay. Due to the speed of installation, as well as the ability to open the pavement to traffic the following day, the board chose RCC. This became the first documented RCC-bonded concrete overlay. RCC was placed 5 inches thick over 5,600 square yards of asphalt pavement using a standard VT LeeBoy asphalt paving machine. The RCC was sawcut at 10-foot joint spacing. While New York has experienced a severe winter, the parking lot is reportedly performing well so far.