Evaluation of Concrete Slab Fracturing Techniques in Mitigating Reflective Cracking Through Asphalt Overlays

About the report:

This report presents the results of an evaluation of concrete slab fracturing techniques as a means of arresting or retarding reflective cracking through asphalt overlays placed on severely distressed portland cement concrete pavement. The study involved monitoring the performance of five pavement rehabilitation projects over a period of up to 8 years. Two of the projects were originally constructed of jointed plain (unreinforced) concrete, and the other three consisted of jointed reinforced concrete pavement. The test sections were fractured with a guillotine drop hammer and then seated with a 50-ton pneumatic tire roller. For comparative purposes, control sections, which were not fractured prior to placement of the asphalt overlay, were constructed just beyond the bounds of three of the fractured test sections. Detailed visual condition surveys were conducted annually at all sites. For each survey, the number of occurrences of reflective cracks that formed in fractured sections was directly compared to the number of cracks observed in the control sections to quantify the tendency of fracturing to retard or arrest the formation of reflective cracks. The results of this study show that fracturing and seating distressed concrete pavements appear to be an effective means of retarding the formation of reflective cracking through asphalt overlays on jointed, unreinforced pavements. In the case of reinforced pavements, however, the fracturing technique was somewhat less successful in that the formation of reflective cracks appeared to be delayed for only about 3 years. Beyond that point in time, the fractured reinforced sections exhibited approximately the same amount of reflective cracking as the control section. The researcher concludes that any observed benefit in terms of extended pavement service life or enhanced ride quality resulting from even a slight delay in reflective crack propagation would likely offset the rather nominal cost of the fracturing and seating operation itself.

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