Common distresses in asphalt pavement
In asphalt pavement various types of distresses are found because of different factors like poor mix design, construction, or ecological conditions or a combination of both as well as mostly due to traffic. Given below, the lists of several types of distresses :-
BLEEDING: Bleeding refers to the presence of asphalt binder on the surface of the pavement. This type of surface defect occurs due to extreme asphalt binder in the surface asphalt mix layer. It is calculated in square meters. The various conditions of bleeding comprise of discoloration, wrapping of aggregate with a thin re?ective surface, and loss of texture.
BLOCK CRACKING: Block cracking stands for a pattern of crack that segregates the surface into rectangular pieces (>0.1 m2). Such cracks happen because of shrinkage of asphalt mix since volume is modified in the base or subgrade.
It is calculated in square meters, and its intensity can be defined as low (crack width =6 mm or sealed cracks whose width is immeasurable, with sealant in good condition, moderate (crack width >6 mm but =19 mm or any crack with mean width =19 mm and adjacent low-severity random cracking), and high (crack width >19 mm or any crack with mean width =19 mm and adjacent moderate- to high-severity random cracking)
CORRUGATIONS: Corrugations stand for ripples which are developed laterally across an asphalt pavement surface. These happen due to deficit of strength of the hot mix asphalt (HMA) at a location where traffic starts and stops or on hills where vehicles stop downgrade.
The reasons for the deficit of strength are too much or too soft asphalt, a high sand content, and the existence of smooth and rounded aggregate in the mix in a large amount.
DELAMINATION: Delamination means the disjointing of the top wearing layer from the layer below. It happens because of weak bond or by failure of the bond among the two layers. The weak bond is caused by an imperfect surface development or tack coat prior to the use of the wearing layer and/or a comparatively thin wearing layer. The loss of bond happens due to several ecological factors like penetration of water and frequent freeze-thaw cycles.
EDGE CRACKS: Edge cracks are detected in pavements with unpaved shoulders. They come with crescent-shaped or moderately continuous cracks that bisect the pavement edge. The cracks are found within 0.6 m of the pavement edge close to the shoulder. Longitudinal cracks outside of the wheelpath and within 0.6 m of the pavement edge are also categorized as edge cracks.
The cracking is caused by the lack of lateral (shoulder) support, base or subgrade weakness due to frost action, and insufficient drainage. It is computed in meters, and severity is indicated as low (cracks devoid of breakup or loss if material), moderate (loss of material and breakup in up to 10% of the cracked area), or high (loss of material or breakup in more than 10% of the cracked area).
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