Posted on May 01, 2018
Roller-compacted concrete (RCC) is a durable material increasingly used for parking lots and high-load applications. From intermodal yards to industrial flooring, RCC is already seen as an economical and durable solution. It is now also being used to complete a number of municipal paving projects in Pennsylvania.
The RCC process requires a stiff, zero-slump mix with the consistency of damp gravel. Rolling achieves desired densities and strength without reinforcement. A very low water-to-cement ratio often makes RCC as strong as conventional concrete. Diamond grinding is an option when a surface without roller marks and with precisely defined frictional characteristics is important.
5 Reasons Why Roller Compacted Concrete Is Better Than Asphalt for Local Roads
Stakeholders are becoming increasingly aware of how RCC placed with high-density asphalt pavers compares favorably to the asphalt alternative. Here are five reasons to consider roller-compacted concrete for your next project.
1. Faster Paving
RCC is a simpler form of concrete paving that goes faster, in part because no forms need to be put in place. Also, there are no dowels or steel reinforcement, and little or no finishing is required. RCC is faster than asphalt because it often requires just one lift where two might otherwise have been required.
As a result, RCC can minimize downtime, something of real interest when otherwise busy parking lots and streets are involved. In some cases, roads can be reopened in a matter of hours rather than days.
2. Savings for Taxpayers
Local municipalities with budgetary constraints see RCC as a cost-effective alternative to traditional blacktop. One Cameron County project saved taxpayers an estimated 65 percent. A section of Hercules Road in Shippen Township had deteriorated to the point that patching was no longer a solution. A paving consultant outlined three solutions:
- Total asphalt reconstruction
- Asphalt overlay with geotextile fabric
- RCC overlay
The township opted for the RCC overlay, which ultimately consisted of 200 cubic yards of concrete rolled to a depth of 4 inches. The RCC overlay saved taxpayers money, and it allowed Hercules Road to reopen in only 24 hours.
3. Labor Savings
When two lifts are replaced with one, labor savings can quickly accrue. Compared to traditional blacktop, RCC limits the need for patching and frequent resurfacing, which reduces long-term labor costs. Fewer work zones over the lifespan of the pavement further cut the cost of labor.
Lighter-colored RCC surfaces are easier to see at night than blacktop, and they retain surface integrity. By comparison, heavy vehicles may leave ruts on asphalt roads that become even more of a hazard in icy/snowy conditions. Reduced repairs and resurfacing during the life of RCC pavement increases safety through fewer work zone setups.
Less maintenance translates into energy savings and reduced material use during the pavement's lifecycle. With the right mix of aggregates, sand and fly ash, the amount of cement required is reduced, making the environmental impact of RCC better yet. It is also possible to use recycled crushed concrete rather than local aggregates.
Liquid asphalt is not only derived from crude oil, a fossil fuel, but its price volatility is well known. This may introduce uncertainty into cost calculations from initial project design through project completion.
Two municipal projects in Pennsylvania constitute evidence of RCC's viability for road construction.
Upper Nazareth Township
Upper Nazareth Township used RCC to repave a 425-foot section of Sycamore Street. The section of road had deteriorated to the extent that a consulting engineer said it looked like a "dried creek bed." The township determined that RCC was the most cost-effective alternative available.
After 6 inches of RCC was laid down over a 3-inch base on a Thursday, a 1.5-inch layer of asphalt was added the following Thursday to make it blend with the rest of the road. There was a 20-minute window to get it rolled, and a second 20-minute window to seal it.
A 30-percent cumulative cost saving was attributed to the fact that overall road thickness was reduced from the 16.5 inches asphalt would have required to just 10.5 inches. This reduced the excavation and trucking costs associated with the removal of waste material. Concrete costs were $40/ton at the time, compared to $60/ton for blacktop -- 1,728 yards of concrete cost about $77,000 compared to approximately $99-116,000 for blacktop.
For another road paving project, Conewago Township selected RCC for resurfacing a portion of a municipal street. A 1,500-foot section of Peanut Drive was paved by placing RCC with high-density paving equipment, and it was finished with double-drum rollers. To facilitate comparisons, one phase of the 2013-14 project was completed using traditional hot-melt asphalt (HMA), while the other featured RCC. At the time, the RCC project required PennDOT's prior approval. The state financed the project so it could acquire real-world data about the viability of RCC for future road construction projects.
Additional Pennsylvania Projects
Norfolk Southern Railway used RCC to pave a 170-acre area at the Franklin County Regional Intermodal Facility just south of Greencastle. Just two lifts were required to place 16 inches of concrete. RCC was also used to repave a shoulder of State Route 910 in Allegheny County -- 5.5 inches of existing asphalt was milled and replaced with 5.5 inches of RCC.
Particularly when all lifecycle costs are considered, RCC is a cost-effective alternative to other forms of paving. It is notable that PennDOT now includes RCC standards in Publication 408 (Sections 502, 323 and 658).
For Additional Information
Our mission at the Pennsylvania Aggregates and Concrete Association (PACA) is to educate, promote and market. Please contact us for assistance if you require additional informational resources about roller-compacted concrete.