Alternative Methods of Flexible Base Compaction Acceptance (0-6587-1)

In the Texas Department of Transportation, flexible base construction is governed by a series of stockpile and field tests. A series of concerns with these existing methods, along with some premature failures in the field, led to this project investigating the current system of flexible base acceptance. Specifically, concerns over the lack of moisture control during compaction, and the lack of stiffness or modulus parameters in the field testing stage, led to this project that investigated new mechanistic based methods for flexible base acceptance. This report summarizes the concerns expressed with the current TxDOT methods, presents approaches some TxDOT districts have taken to overcome problems, and summarizes the current status of other agencies' efforts at mechanistic-based acceptance for flexible base. Next, this report presents results and findings from a full-scale compaction experiment, where a Grade 1 and Grade 2 flexible base were placed and tested with new non-density based devices. The results to date indicate acceptance with nondensity based devices should be feasible. Additionally, the results indicate that flexible bases should not be worked significantly wet of optimum, because when the base is worked in that manner inferior mechanical properties result even though high density is achieved. To guide the second year's work, possible approaches for non-density based acceptance, and a field test plan, are outlined.