Laboratory and field moisture conditions for flexible pavement

The primary source of water in pavements is from surface infiltration. Water from surface infiltration and other sources increases pavement maintenance costs and shortens pavement life. These effects can be mitigated by including a subdrainage system in the pavement design. A study of pavement subdrainage systems has been conducted that included a phase for laboratory tests for the hydraulic characteristics of materials used in three test sections built on I-469 at Fort Wayne, Indiana. The purpose of building these test sections was to evaluate the subdrainage performance and materials used in the sections. The sections differ in the permeable drainage layer as well as the filter (separation) layer. The sections were instrumented with different types of sensors. Instrumentation installed in the sections included time domain reflectometry (TDR) probes, moisture suction blocks, temperature probes, resistivity tree, and rainfall and outflow tipping buckets. Other features of the instrumentation site included an air temperature probe and access tube for a nuclear moisture content probe. The laboratory hydraulic characteristic test results on the materials are presented. Field moisture condition in the layers is also presented. Calibration equations for the TDR are developed for the field materials. A summary of three rainfall events and pavement outflow volumes recorded for the tests is presented. Recommendations are made for materials to be used in subdrainage systems.