Fatigue in pavement

What Is Asphalt Fatigue Cracking? Series of interconnected cracks caused by fatigue failure of the HMA surface (or stabilized base) under repeated traffic loading. In thin pavements, cracking initiates at the bottom of the HMA layer where the tensile stress is the highest then propagates to the surface as one or more longitudinal cracks. In thick pavements, the cracks most likely initiate from the top in areas of high localized tensile stresses resulting from tire-pavement interaction and asphalt binder aging (top-down cracking).

After repeated loading, the longitudinal cracks connect forming many-sided sharp-angled pieces that develop into a pattern resembling the back of an alligator or crocodile. See full list on pavementinteractive.

Indicator of structural failure, cracks allow moisture infiltration, roughness, may further deteriorate to a pothole. Inadequate structural support, which can be caused by a myriad of things. A few of the more common ones are listed here: 1. Decrease in pavement load supporting characteristics 1. Loss of base, subbase or subgrade support (e.g., poor drainage or spring thaw resulting in a less stiff base). Strippingon the bottom of the HMA layer (the stripped portion contributes little to pavement strength so the effective HMA thickness decreases) 2. Increase in loading (e.g., more or heavier loads than anticipated in design) 3. A fatigue cracked pavement should be investigated to determine the root cause of failure.

Any investigation should involve digging a pit or coring the pavement to determine the pavement’s structural makeup as well as determining whether or not subsurface moisture is a contributing factor.

Once the characteristic alligator pattern is apparent, repair by crack sealingis generally ineffective. Fatigue crack repair generally falls into one of two categories: 1. Small, localized fatigue cracking indicative of a loss of subgrade support. Remove the cracked pavement area then dig out and replace the area of poor subgrade and improve the drainage of that area if necessary. Patchover the repaired subgrade. Large fatigue cracked areas indicative of general structural failure.

Place an HMA overlay over the entire pavement surface. This overlay must be strong enough structurally to carry the anticipated loading because the underlying fatigue cracked pavement most likely contributes little or. However, it is necessary to determine the reason that the support is inadequate.

Possible Causes: Generally, potholes are the end result of fatigue cracking. As fatigue cracking becomes severe, the interconnected cracks create small chunks of pavement, which can be dislodged as vehicles drive over them. The remaining hole after the pavement chunk is dislodged is called a pothole.

Fatigue or alligator cracking is the most common type of pavement distress, it is infact the major one. Every asphalt surface can handle a certain amount of pressure. A strong foundation is critical to allowing the surface to bear pressure and traffic. Normal traffic loading will result in fatigue unless there is very thick pavement , where the main failure would be either surface-initiated cracking or rutting within bituminous layers.

Crocodile cracking , also called alligator cracking and perhaps misleadingly fatigue cracking, is a common type of distress in asphalt pavement. The following is more closely related to fatigue cracking which is characterized by interconnecting or interlaced cracking in the asphalt layer resembling the hide of a crocodile. Cell sizes can vary in size up to 11.

Step 1: Enter Zip Code. Potholes If alligator cracks and other asphalt stress cracks are not treate water will begin to erode the surface all the way down to the sub base. Most concrete airfield pavement design procedures are based on developing sufficient slab thicknesses to resist fatigue cracking, that is, structural cracking caused by repeated load applications at stress levels less than the ultimate static strength of the concrete. Most semi rigid materials have the ability to flex numerous times before they begin to crack, asphalt is no exception.

This is very common type of asphalt pavement failure. PCA Pavement Design - Fatigue Analysis. The fatigue analysis used in the PCA pavement design method is based on the edge stress condition where the load is situated on the edge of the mid-slab.