Pavement Management

Flexible Pavement Distress

An introduction to common forms of distress in flexible pavements.

Microcracking

Description Short transverse cracks usually 25 – 75 mm (1 – 3 inches) long and 25 – 75 mm (1 – 3 inches) apart that appear on the mat surface during compaction. Problem By itself, microcracking is only a small detriment to pavement performance; the cracks are usually quite shallow and small. However, microcracking can … Read more »

De-Bonding of HMA Pavements

De-Bonding Study Recent evidence in Washington State indicates that de-bonding of HMA surface layers may become a significant problem. “De-bonding” describes a condition where adjacent layers of HMA lose adhesion to one another and can become separated. Typically, design and construction practice is to build in a certain amount of bonding, however the appropriate amount, … Read more »

De-Bonding of HMA Pavements/Case Studies

Case Studies Case studies on three different projects were conducted in association with this research. The goal of these case studies were to look for signs of pavement de-bonding and attempt to correlate them to pavement core condition, milling operations, existing pavement structure and construction quality of the previous overlay. Details on each case study … Read more »

De-Bonding of HMA Pavements/Core Logs

Core Logs A set of core logs was obtained from the WSDOT Materials Laboratory and analyzed for evidence of de-bonding. These logs were opportunistically gathered by the Materials Office and do not represent complete information or a statistical sample. In all, 3,042 core records were analyzed. These cores were grouped by identifying number or general … Read more »

De-Bonding of HMA Pavements/Construction Observations

Construction Observations of Some Washington State Projects The following section presents tack coat application photos and noted overlay construction issues from various WSDOT contracts. These photos and notes are intended to serve as a preliminary collection of data to be used in identifying construction practices and conditions that lead to de-bonding and bottom-up cracking. Information … Read more »

Top-Down Cracking

Top down cracking appears to be a common mode of HMA pavement distress in at least several states and countries. Traditionally, pavement cracking is thought to initiate at the bottom of the HMA layer where the tensile bending stresses are the greatest and then progress up to the surface (a bottom-up crack). Most traditional transfer … Read more »

Surface Waves

Description Surface waves can appear in several different forms: Washboarding. Small waves generally about 75 – 100 mm (3 – 4 inches) apart. Short waves (also called ripples or auger shadows). Generally about 0.3 – 0.9 m (1 – 3 ft) apart with 0.45 – 0.60 m (1.5 – 2 ft) being the most common … Read more »

Longitudinal Cracking

Description Cracks parallel to the pavement’s centerline or laydown direction. Can be a type of fatigue cracking or top-down cracking. Problem Allows moisture infiltration, roughness, and it may indicate the possible onset of alligator cracking and structural failure. Possible Causes Poor joint construction or location. Joints are generally the least dense areas of a pavement. … Read more »

Rutting

Description Surface depression in the wheelpath. Pavement uplift (shearing) may occur along the sides of the rut. Ruts are particularly evident after a rain when they are filled with water. There are two basic types of rutting: mix rutting and subgrade rutting. Mix rutting occurs when the subgrade does not rut yet the pavement surface … Read more »

Stripping

Description The loss of bond between aggregates and asphalt binder that typically begins at the bottom of the HMA layer and progresses upward. When stripping begins at the surface and progresses downward it is usually called raveling. Although the displacement of asphalt on the aggregate particle surface by water (stripping) is a complex phenomena and … Read more »

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