Many state, county, and municipal highway agencies have experienced the formation of bumps when placing single-lift overlays or the first lift of amultiple lift overlay. These bumps are produced at the location of a previously-existing crack, and even then almost exclusively when the crack has been sealed prior to the overlay. When such bumps are not covered with a subsequent lift, what remains is often a rough ride on a newly-overlaid roadway. This paper describes the effects of crack sealant material type and the geometry (shape) of the routed cracks in the existing surface on the formation of bumps in bituminous overlays. A factorial of four sealant type treatments and six geometries was designed, and implemented in a testsection in Jackson County, Minnesota. The overlay on the test section was constructed in September 2007. The results of this investigation indicate that cooler temperatures, no crack sealant overband, hot-poured crumb rubber and hot-poured elastic provided the best resistance to the formation of bumps in overlays.
Abstract