State Highway 66 runs through the foothills of the Colorado Rockies between Lyons and Longmont. CDOT repaired 27 lane-miles (244,000 square yards) of the roadway with 6-in. thin whitetopping in 2009. After two years in service, the pavement shows no signs of distress.
CDOT cuts longitudinal joints in thin whitetopping with several band saws ìganged together.î The technique keeps joints straight and consistent.
Thin whitetopping requires closely-spaced construction joints—a deterrent to some municipalities that favor quicker repair techniques. The 6-in. thin whitetopping project pictured here has longitudinal and transverse joints every 9 ft.
In 1999, Centennial, Colo.-based Castle Rock Construction Co. placed a 5-in. thin whitetopping overlay on Parker Road, a high-volume urban corridor on the southeast side of Denver. The $2.9 million project covers 12.5 lane miles.
After 12 years, repairs to the thin whitetopping on Denver’s Parker Road have been limited to minor transverse cracks. “I am confident it has another 10 years in it,” says Ralph Bell, chief operation officer for Castle Rock Construction Co.
CDOT tested the limits of thin whitetopping on four lane-miles of State Highway 287 in 1997. The “ports to plains” trucking route from Mexico to Canada withstands a million 18,000-lb. equivalent single axle loads a year. In 2008, test sections were removed to gauge the 6-inch overlay’s performance. Some sections were severely cracked; others showed no cracking at all.
In 1998, Bruns Concrete & Construction and Golden Concrete teamed up to resurface the LifeBridge Christian Church (formerly First Christian Church) parking lot in Longmont, Colo. with thin whitetopping. The contractor placed 11,160 sq. yds. of 3-in. concrete at $10/sq. yd.
As with any thin whitetopping, the overlay required close joint spacing. For good measure, the design included expansion joints with 1/2-in. fiber board in several places.
In 15 years, no repairs have been made to the parking lot; only minor cracking and spalling is evident. Dale Bruns, co-owner of Bruns Concrete & Construction, says a good subgrade is the key to its success. To prepare the surface, the contractor removed only the badly cracked patches of asphalt and filled them with crusher fines. After the concrete was placed and compacted, it filled the patched areas without a visible difference on the finished surface.
As shown in this joint detail, a 4-inch thin whitetopping requires closely-spaced construction joints and transverse dowels—a deterrent to some owners that favor quicker repair techniques.
In urban areas, curbs and gutters pose a challenge to thin whitetopping design. CDOT has two approaches: covering the curb face with an angled, mountable profile, which can be safer for vehicles that stray from the road.