In the late 1980s and early 1990s, the Alabama Department of Transportation (ALDOT) noticed a decline in skid trailer numbers on concrete pavements shortly after grinding operations. The engineers at the time suspected that the coarse aggregate led to decline of skid trailer numbers and the resulting conclusion led to a ban of carbonate aggregates in mainline concrete pavement that is still in place. Recently, ALDOT has decided to reexamine the ban on carbonate aggregates in mainline concrete pavement and perform a comprehensive and detailed study of the issue.
It appears that there is sufficient data to begin using carbonate aggregates in mainline concrete pavements in Alabama provided each source is properly and fully tested. Both the researchers and ALDOT have provided sets of recommended specification language to this end.