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PASER -- Evaluation <br />Asphalt <br />pavement <br />distress <br />The key to a useful evaluation is identifying different types of pave- <br />ment distress and linking them to a cause. Understanding the cause <br />for current conditions is extremely important in selecting an appropri- <br />ate maintenance or rehabilitation technique. <br />There are four major categories of common asphalt pavement sur- <br />face distress: <br />1. surface defects: ravelling, flushing, polishing <br />2. surface deformation: rutting, rippling and shoving, settling, <br />frost heave <br />3. cracking: including transverse, reflective, longitudinal, block and <br />alligator cracks <br />4. patches and potholes <br />Deterioration has two general causes: <br />• environmental, due to weathering and aging <br />• structural, caused by repeated traffic loadings <br />Obviously, most pavement deterioration results from both environ- <br />mental and structural causes, However, it is important to try to distin- <br />guish between the two in order to select the most effective rehabilita- <br />tion techniques. <br />The rate at which pavement deteriorates depends on its environment, <br />traffic loading conditions, original construction quality, and interim <br />maintenance procedures. Poor quality materials or poor construction <br />procedures can significantly reduce the life of a pavement. There- <br />fore, two pavements constructed at the same time may have signifi- <br />cantly different lives, or certain portions of a pavement may deterio- <br />rate more rapidly than others, due to material or construction prob- <br />lems. On the other hand, timely and effective maintenance can <br />extend the life of a pavement. Crack sealing and seal coating can <br />reduce the effect of moisture in aging of asphalt pavement. <br />With all of these variables, it is easy to see why pavements deterio- <br />rate at various rates and why we find pavements in various stages of <br />disrepair. Recognizing defects and understanding their causes helps <br />us rate pavement condition and select cost - effective repairs. The <br />pavement defects shown on the following pages provide a back- <br />ground for this process. <br />Page 37 <br />