Threshold moisture content and matric suction potentials in expansive clays prior to initiation of cracking in pavements

Abstract

Numerous low- to medium-volume roads constructed on expansive clay subgrades have experienced severe pavement cracking and premature loss of serviceability. These roads often become distressed due to volume change associated with seasonal moisture content fluctuation in the underlying soils. An attempt is made in this paper to study field moisture content and soil suction potentials of expansive subsoils, and investigate the potentials at which soil and pavement cracking occur. Two types of sensors were utilized to measure volumetric moisture content and matric suctions in the soils. These sensors were installed at three pavement subgrade sites in Fort Worth, San Antonio, and Paris Districts in Texas, USA. Test results show that site environmental conditions, such as climate and large trees near the test sections, have a strong influence on expansive soil movements and related pavement cracking. Three possible scenarios where pavement cracking could occur in the field, determined from analysis of the data, are outlined. Theoretical correlation developed between the laboratory-based shrinkage strain tests and changes in soil compaction moisture content was successfully used to estimate surficial crack widths in the field. Finally, methods to control desiccation cracking in the field are outlined.