Study of Reflection Cracking in Asphaltic Concrete Overlay Pavements, Phase I.

This report encompasses the results of a literature search, a survey of state highway departments, and an on-site field inspection of techniques used by state and federal agencies to control reflection cracking in asphaltic concrete overlays principally on portland cement concrete pavements. Procedures were generally for the purpose of isolating the overlay from the effect of movement in the underlying pavement or reinforcing the overlay. These procedures are made more effective by measures designed to prevent or minimize the underlying pavement movement. The methods found helpful in reducing reflection cracking include wire mesh reinforcement in the asphaltic concrete AC overlay use of bond-breakers between the portland cement concrete PCC and the AC overlay addition of an aggregate base course over the PCC followed by an AC overlay pretreatment of the old PCC, such as mudjacking, subsealing, or cracking the old pavement by heavy rolling or with a hydraulic or pneumatic hammer use of additives and other modifications in the AC composition. Many of the test installations inspected are 3 to 13 years old and in good to excellent condition. Normally, when using regular AC overlay procedures, reflection cracking begins to show up within 1 year or season cycle and cracks are larger than when special techniques are used. Results of the study indicate that there is no known 100 effective method for eliminating reflection cracking. Overall, a number of techniques have substantially delayed serious transverse reflection cracking, appear to have reduced longitudinal reflection cracking at pavement widening joints, and have reduced maintenance considerably. Author