In-place engineering properties of recycled and stabilized pavement layers

Abstract

1.0INTRODUCTION Now that most of the new road construction in the United States is complete, the major emphasis has switched to maintaining those roads. The focus of many of Texas districts in the Texas Department of Transportation (TXDOT) is the maintenance and rehabilitation of the existing highway network. The rural districts now have large portions of their networks which need major rehabilitation and reconstruction. Many districts are experimenting with innovative rehabilitation strategies for repairing the wide range of pavement types found around the state. One area of major interest is in rehabilitating thin flexible pavements which are near the end of their service lives. I PROBLEM STATEMENT To address this problem in a cost-effective manner, some of the districts have been actively recycling thin surfaced pavements and stabilizing bases in an attempt to correct deterioration and increase the structural capacity. In a one pass operation the existing surface and base are mixed and stabilized with small quantities of either lime or cement. Frequently the reshaped and compacted base is simply sealed with a one course surface treatment. For higher volume roads sometimes a new grade I flexible base is added with a thin asphalt surfacing. The goal of this research is to investigate the performance of existing projects and evaluate the impact of the different variables (like stabilizer type, percentage, thickness of layer, etc.) used during their construction. 1.2RESEARCH CONCLUSIONS Monitoring of the sections included visual condition assessment, structural strength testing with falling weight deflectometer (FWD) and Dynaflect, Dyna@c Cone Penetrometer (DCP) testing and Ground Penetrating Radar (GPR). In general, describe the following: ) Comparison of DCP tests results with the back calculated subgrade modulus as estimated from MODULUS 5. 1. Thus, a correlation between DCP values & the subgrade modulus was developed. ii)A correlation between the stabilizer content and the layer moduli values was established. iii) Development of a preliminary approach to select percent stabilizer.