Pavement Swelling and Heaving at State Highway 6

A stretch of State Highway (SH) 6 in Texas has been experiencing poor ride quality problems caused by continuous pavement swelling and heaving. Because of this, the Texas Department of Transportation (TxDOT) Waco District annually spent hundreds of thousands of dollars to overlay the pavement to keep it smooth. This study is motivated to identify the root causes and solutions to the critical problem. During the forensic study, a systematic approach is employed, which includes nondestructive and destructive tests. On the basis of the overall test results, it is revealed that the problem was initiated within the lower portion of the pavement structure (i.e., subgrade) rather than in the upper pavement structure (i.e., asphalt concrete and flexible base). It was further found that the major factors contributing to the subgrade problem include (1) swelling soils, (2) water penetrating into the expansive clay soils, (3) high organics content in the soil, (4) loss of strength of the lime stabilized layer, and (5) high levels of sulfates in the soils. Performance surveys of various potential treatments for remediating the problem associated with swelling subgrade soil and increased moisture were conducted. These performance histories provide input and guidance for the selection of the pavement rehabilitation strategies. On the basis of the past performance histories, a variety of short-term and long-term strategies were recommended to the Waco District office for solving the problem.