VAA Virginia Asphalt Spring/Summer 2021

16 SPRING/SUMMER 2021 THMACO Exceeds Expectations: I-95 Ultra-Thin Bonded AC Overlay David T. Lee., P.E., Vice President, Virginia Asphalt Association For many years, Virginia’s approach to pavement maintenance involved installing traditional asphalt concrete overlays or inlays and the use of Latex Modified Emulsion Treatments (LMET) at a point when the existing surface had nearly reached the end of its service life or beyond. In the late 2000s, Virginia recognized this method alone was not always the best approach and investigated several relatively new preservation treatments. One such method was Ultra-Thin Bonded AC Overlays, otherwise known as Thin Hot Mix Asphalt Concrete Overlays (THMACO). THMACO is a unique process that provides a highly functional wearing course with a thin layer of plant-produced asphalt concrete. At the time, the material was almost exclusively placed with a spray-bar paver. This unique paver-mounted tacking system provided an impervious layer with a substantial bond to the original surface. The surface was then “seated” with relatively few passes of conventional compaction equipment. The thin application, the integrated tacking/paving system, and the light compaction requirements resulted in a very rapid operation. I-95 in Greensville I-95 in Greensville County was completed in December of 2008 as part of a pavement preservation study. The THMACO project I-95 THMACO in Greenville County March 2021