ULTRATHIN PAVEMENTS MAKING THE GRADE

Abstract

In 1994, the Iowa Department of Transportation (Iowa DOT), Federal Highway Administration and Iowa State University joined forces to construct an 11.6 km ultrathin portland cement concrete overlay research project. This marked the beginning of the use of thin whitetopping for rehabilitation of existing asphalt roadways on primary highways in Iowa. The research was designed to evaluate long term performance of ultrathin whitetopping. Four major variables were chosen for evaluation and 41 test sections, each 213 min length, were constructed. Some 24 additional sections were used to transition from one set of parameters to the next. Research efforts over the last two years have consisted of visual distress surveys conducted on a quarterly basis and measurement of overlay interface strains measured three times per year at some 35 sites on the project. This paper provides insight into the changes in condition of the test sections which have occurred since construction over two years ago. The overall performance to date has been very good. Isolated areas of distress have been noted and are beginning to provide some trends in the data.