As with other asphalt mixtures, problems frequently occur with SMA, too. They may develop at the stage of design, production, or application. Some of the troubles described here also appear in asphaltic concrete or other asphalt mixtures, but a distinctive feature of SMA is that its shortcomings are revealed in a particularly clear, and sometimes painful, way.
This chapter presents an arranged collection of the most common defects observed in SMA. But before we begin, two issues need to be made clear:
• Each group of problems and their probable causes are provided here based on the author’s subjective assessment derived from his experience and consideration. Therefore it is obvious that a reader may have a different view on a given problem or that it may have another cause.
• Always and in each case, while examining a detected problem, one should be open to investigating its various causes, including the less obvious ones. Nobody should limit himself or herself to the pieces of advice contained in this book; an open mind is the recommended approach.
An immediate “blessing” when a problem occurs is having a laboratory or possibly the asphalt plant staff available to help correct the problem; these resources are becoming more widely available. The lab or plant staff can help to evaluate the materials and operations to identify the causes of the problems, such as changes in material properties, plant temperatures, moisture conditions, etc. This chapter will make it apparent that the members of the team preparing road machines and the site team are as important in the final outcome (success or failure) as other elements.[65]
Now it is time to examine with the problems in detail.
