By: Matthew W. Singel, PE
Who said roller-compacted concrete (RCC) pavement was only for lower-speed roads or industrial applications? Not TxDOT. In November, the Texas Department of Transportation completed its first mainline, high-speed RCC Federal Highway in Leakey, 100 miles West of San Antonio. Read more...
LEAKEY'S U.S. 83 SERVES LEISURE TRAVELERS AND HEAVY HAULERS
Leakey, in the heart of the Texas Hill Country, is a hub for tourists seeking summer water activities, fall leaf-watching, motorcycle rides and year-round camping. However, this portion of U.S. 83 is also a heavy truck route servicing nearby aggregate quarries and oil/gas activities. TxDOT needed a heavy-duty, low-maintenance pavement that could improve safety and accommodate this busy mix of leisure and heavy hauling activity, without major traffic disruption.
RCC + FDR PROVIDE FAST, HEAVY-DUTY SOLUTION
Looking for solutions to road damage in energy sector corridors, TxDOT designed U.S. 83 as an 8-inch RCC section on 8-inches of full-depth reclaimed (FDR), cement stabilized subbase (recycled in place; TxDOT item 275). This also included a short stretch of RM 337 and its intersection with US-83 in downtown Leakey. RM 337 was designed with 7 ½ inches of RCC pavement on the same 8-inch subbase.
Recycling the old pavement in place with 4% cement created a quickly constructed, durable platform that served as a temporary surface for traffic and a stiff, non-erodible subbase layer on which the RCC was placed within days. The prime contractor, Allen Keller Company, stabilized the recycled subbase using GPS-guided motor graders, establishing an accurate final grade on which the RCC pavement would then be placed and compacted. The FDR subbase also saved time and money by eliminating the need for new base material, excavation of the old, and associated trucking for over 30,000 tons of material.
The 50,500 square yards of roller-compacted concrete pavement (TxDOT ss3253) was placed in a 3-week period averaging nearly ½ lane mile per day. This impressive production rate was achieved while keeping the adjacent lanes open to traffic. The fast construction and uninterrupted traffic flow, in an off-peak time of year, minimized losses for the many small business in Leakey.
FULL TRAFFIC ON RCC IN DAYS--OR EVEN 24 HOURS
US-83 in Leakey serves as a key truck route for aggregate quarries to the south, and for energy sector traffic known for its devastating impact on rural highways. This fact prioritized the need to remain open day and night. The resilience of the cement-stabilized FDR subbase provided a high-performance temporary surface for traffic. The RCC, placed with high-density asphalt-style pavers in a single lift, was normally opened to traffic within days of paving, once it achieved an unconfined compressive strength of 2,500 psi. RCC’s density and low water content contribute to its high early strength, which allowed several critical RCC sections to resume full traffic within 24 hours of placement.
HIGH-QUALITY RIDE WITH NO DIAMOND GRINDING
The contract also specified diamond grinding, if necessary, to meet TxDOT’s tight surface tolerance specification. However, the RCC subcontractor, Peltz Companies, Inc., achieved specified ride quality, even in the 55 mph sections, without grinding. Key to accomplishing this were quality materials, an optimized 3-part aggregate blend, and an ideal mix design. Additionally, use of a high-volume pug mill and high-density asphalt-style pavers, operated by an experienced contractor were essential. Peltz Companies, Inc., has been building RCC pavements for over 30 years.
SPECIFYING RCC FOR MORE TXDOT PROJECTS
Roller-compacted concrete is currently built under a TxDOT “special specification,” allowing it to evolve from one project to the next in any TxDOT District. The specification used for this contract was TxDOT ss3253.
TxDOT continues to roll out more RCC pavement; Peltz Companies, Inc. immediately moved from Leakey to I-20 near Fort Stockton to pave a safety rest area now under construction.
For more information about this project, RCC paving, or full-depth reclamation with cement, contact Matthew Singel directly at 817-709-4313 or firstname.lastname@example.org.