LATEX MODIFIED ASPHALT AND EXPERIMENTAL JOINT TREATMENTS ON ASPHALTIC CONCRETE OVERLAYS, EXPERIMENTAL PROJECT NO. 3 - ASPHALT ADDITIVES. FINAL REPORT

This report documents the construction, initial evaluation and final evaluation of several experimental features which were incorporated as part of an overlay of an existing PCC pavement in order to determine the feasibility of extending the asphaltic concrete overlay service life. The experimental features utilized were several type of waterproofing membranes, sawing and sealing of joints in the asphaltic concrete overlay and the use of a latex-modified asphaltic concrete. There were several problems noted during the construction of the overlay. When the roller passed over the transverse joints the hot mix mat appeared to shove, such that a noticeable, transversely oriented six-to-eight-inch-wide hump occurred along the joint. Generally, this condition was found in the membrane sections and only occasionally in the other sections. Reflective cracking immediately occurred at many of the transverse joints during the rolling operation, irrespective of section design. Performance evaluations were conducted over three years and included joint crack mapping, rutting (non detected), ravelling, cracking other than joint cracking, stripping, friction numbers, density and ride quality. The final evaluation revealed: sawing and sealing over the transverse joints in the asphalt concrete overlay appears to be the most effective treatment to control reflective cracking; a slight improvement was noticed in the sawed and sealed sections with latex-modified asphalt concrete versus the sawed and sealed sections with conventional asphalt concrete.