Improving Lab Compaction Methods for Roadway Base Materials

The Texas Department of Transportation (TxDOT) employs the impact hammer method of sample compaction for laboratory preparation of road base and subgrade materials for testing. Experience has shown that this method may not adequately represent the true field performance of the materials. This report describes results investigating how different lab compaction methods influence the laboratory characterization of the materials. As compared to Tex-113-E, Modified compaction improved the performance of a Grade 2 Texas base, but not the Grade 1 material tested. Vibratory compaction resulted in improved performance for both bases tested. Unfortunately, efforts to study the soil fabric to investigate what lab technique best mimics the field structure were unsuccessful. However, future work in this project will utilize four additional Texas base materials, including field sections, in efforts to validate the preliminary findings described in this report.