12. Mat Problems

Mat problems can be defined as defects that occur in the asphalt mixture during or soon after the laydown and compaction operations have been completed. These problems fall into two primary categories: 1) equipment-related problems and 2) mixture-related problems. Within each of these two categories, poor workmanship and failure to adhere to best practices lead to many of the mat problems described below. In this section, major mat problems are reviewed, and a description of each problem is presented, including its causes, solutions, and effects on long-term pavement performance. Since segregation can be a serious mat problem, Chapter 10 of this manual is dedicated to this issue.

Table 13 summarizes the mat problems reviewed. The first column lists the various problems, while the remaining columns enumerate possible causes for each. The checks indicate equipment-related causes, while the x’s indicate mix-related causes, which should generally be corrected by changes in the mix design. Provided throughout the discussion of causes are cross-references to earlier sections where greater detail can be found. Note that because of the interaction of various equipment-related and mix-related causes, no attempt has been made to rank the various causes.

Table 13. Mat Problems and Their Causes

Find problem above: ✓ indicates causes related to the paver and X indicates other problems to be investigated
NOTE: Many times a problem can be caused by more than one item; therefore, it is important that each cause listed be eliminated to ensure that the problem will be solved.