United States Department of Transportation
i
Reflective crack mitigation guide for flexible pavements.
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2015-09-01
[PDF-4.80 MB]
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Abstract:Reflective cracks form in pavements when hot-mix asphalt (HMA) overlays are placed over jointed and/or severely cracked rigid
and flexible pavements. In the first part of the research, survival analysis was conducted to identify the most appropriate
rehabilitation method for composite pavements and to evaluate the influence of different factors on reflective crack development.
Four rehabilitation methods, including mill and fill, overlay, heater scarification (SCR), and rubblization, were analyzed using
three performance indicators: reflective cracking, international roughness index (IRI), and pavement condition index (PCI). It was
found that rubblization can significantly retard reflective cracking development compared to the other three methods. No
significant difference for PCI was seen among the four rehabilitation methods. Heater scarification showed the lowest survival
probability for both reflective cracking and IRI, while an overlay resulted in the poorest overall pavement condition based on
PCI. In addition, traffic level was found not to be a significant factor for reflective cracking development. An increase in overlay
thickness can significantly delay the propagation of reflective cracking for all four treatments. Soil types in rubblization pavement
sites were assessed, and no close relationship was found between rubblized pavement performance and subgrade soil condition.
In the second part of the research, the study objective was to evaluate the modulus and performance of four reflective cracking
treatments: full rubblization, modified rubblization, crack and seat, and rock interlayer. A total of 16 pavement sites were tested
by the surface wave method (SWM), and in the first four sites both falling weight deflectometer (FWD) and SWM were
conducted for a preliminary analysis. The SWM gave close concrete layer moduli compared to the FWD moduli on a
conventional composite pavement. However, the SWM provided higher moduli for the rubblized concrete layer. After the
preliminary analysis, another 12 pavement sites were tested by the SWM. The results showed that the crack and seat method
provided the highest moduli, followed by the modified rubblization method. The full rubblization and the rock interlayer methods
gave similar, but lower, moduli. Pavement performance surveys were also conducted during the field study. In general, none of
the pavement sites had rutting problems. The conventional composite pavement site had the largest amount of reflective cracking.
A moderate amount of reflective cracking was observed for the two pavement sites with full rubblization. Pavements with the
rock interlayer and modified rubblization treatments had much less reflective cracking. It is recommended that use of the
modified rubblization and rock interlayer treatments for reflective cracking mitigation are best.
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