Pavement life span is often affected by the amount of voids in the base and subgrade soils, and especially by the soil moisture content. Time Domain Reflectometry (TDR) and Ground Penetrating Radar (GPR) are two desirable techniques to indirectly measure the in-situ soil moisture content through electrical properties of soils. The pre-purchased Tektronix 1502B TDR Cable Tester equipped with Campbell Scientific SDM1502 Communications Interface and PS 1502B Power Control Module system was successfully modified, installed, and integrated into the existing weather station in conjunction with the Texas Mobile Load Simulator (TxMLS) research project. The test sections were located on US281 near Jacksboro, Texas. The TDR results from US281 test sites indicated that the TDR sensors responded to the rainfall events favorably. The two-year field test results indicated that the TDR readings interpreted by Topp's (1980) and Ledieu's (1986) equations agreed well with the real measured value for the subgrade; none of the existing models for the base layers was found to be suitable for the soil moisture content conversion used in this research study. An empirical equation was established to determine the weight-based moisture content of the compacted base materials. Although the TDR system provides valuable information, it requires considerable time and effort to process data. In addition, the TDR system consumed too much power and caused malfunctions of the weather station. In that regard, a new Moisture Sensor (MS) system was developed in this study and verified at the Materials and Tests (MAT) section of Texas Department of Transportation. The results from MAT section indicated that the MS system provides a more reliable solution than that of the TDR system. In addition, it is much easier to process the MS data. Furthermore, the MS system consumes almost no battery power and is an ideal solution for a long-term monitoring of pavement moisture content. GPR was also employed at the same test sites. The Inversion Method was applied for converting moisture content of soils. Laboratory tests were satisfactory; yet the field application of this study needs further experiments to improve the results.

The Dynamic Cone Penetrometer (DCP) is a device that is used for the estimation of in situ compaction quality of constructed subgrades and embankments. It is a relatively inexpensive, light-weight and easy to use device that measures the dynamic penetration resistance of the compacted soil, from which an estimate of soil strength and stiffness characteristics can be made. Owing to its ease of use, many DOTs in the U.S. have employed the DCP in their compaction quality control procedures, and over the past few decades, extensive research has been carried out on the development of correlations between the results of the DCP test and the results of strength and stiffness tests performed on compacted soils (e.g., California bearing ratio, and resilient modulus)The objectives of this research are to refine DCP-based quality assurance and quality control correlations for compaction quality control developed by previous research studies carried out at Purdue for the Indiana Department of Transportation, especially focusing on (1) grouping of the soils based on their mechanical response to the DCP loading, and (2) limiting the in situ moisture range of the soils used for development of correlations within -2% of the optimum moisture content of the tested soil. The factors outlined above are studied, and in particular, soil grouping is examined critically. The AASHTO ('A-based') classification employed previously for classification of soils is replaced with a new classification criteria specifically developed for the DCP test. Soils are grouped into one of the two categories of coarse-grained or fine-grained soils on the basis of the size of the dominant particle in the soil. The criteria developed for the classification of soil into one of these two categories is based on index properties of the soil, such as the standard Proctor maximum dry density, optimum moisture content, plasticity index (PI) and fines content.

The objective of this research is to establish the technical engineering and cost analysis concepts that will enable WisDOT management to objectively evaluate the feasibility of switching construction specification philosophies for aggregate base. In order to accomplish this goal, field and laboratory testing programs were conducted on existing HMA pavements and on base layers under construction as well as comprehensive survey was conducted on highway agencies practices pertaining to base layer construction in the U.S. and Canada. This research proposed construction specifications for aggregate base course layers.