Abstract
The tube suction test (TST) was developed in a cooperative effort between the Finnish National Road Administration and the Texas Transportation Institute for assessing the moisture susceptibility of granular base materials. The moisture-susceptibility ranking is based on the mean surface dielectric value of compacted specimens after a 10-day capillary soak in the laboratory. The factors that influence moisture susceptibility are discussed, and the use of dielectric measurements in the TST is explained. The TST protocol is given. The repeatability of the test is then evaluated at three different dielectric values, and statistical techniques are employed to enable estimation of the number of replicate samples required in the TST to achieve specified levels of tolerance and reliability. On the basis of the promising results of the test, the Texas Department of Transportation will begin implementation of the TST statewide during 2001.