UC Davis Institute of Transportation Studies

This report presents the results of construction, Heavy Vehicle Simulator (HVS) tests, deflection tests, post-HVS forensic testing, and analysis on dowel bar retrofitted (DBR) concrete pavement test sections at Palmdale, California. This project was originally proposed in 2000 by the Caltrans Headquarters Division of Design. Benefits expected from this research are to provide Caltrans with information about design and construction of DBR to help determine where DBR may be a cost-effective strategy for rehabilitating rigid pavement and to help obtain best performance where DBR is selected as the preferred rehabilitation strategy.

HVS Tests: Pavement sections include retrofitted joints and transverse cracks with three and four epoxy-coated steel dowels, four hollow stainless steel dowels, and four fiber-reinforced polymer dowels per wheelpath. HVS and FWD results at Palmdale also are compared with the results from previous HVS testing. HVS testing showed that joint performance with four epoxy-coated steel dowels was generally the best of all the sections in terms of load transfer efficiency (LTE) and joint deflection. Three dowels per wheelpath was substantially worse than the other test sections that had four dowels per wheelpath in terms of load transfer efficiency (LTE), however, it was substantially better than before DBR. Joint deflections were substantially better for four epoxy-coated steel dowels per wheelpath than for the other sections. HVS results show that for each of the DBR alternatives, LTE was not substantially affected by heavy HVS loading and that the slabs failed by fatigue cracking before LTE dropped substantially.

FWD Tests: The primary performance criteria are LTE and vertical deflection of the joints. Larger joint vertical deflections and lower LTE are strongly correlated with increased rate of faulting and roughness development. FWD deflection measurements agree with those under HVS wheel loading, showing that LTE was substantially improved by DBR and was not substantially affected by HVS trafficking. Results are presented showing sensitivity of deflections and LTE to dowel type, number of dowels per wheelpath, and slab temperature based on FWD measurements.

Construction and materials: Observations about DBR construction and materials presented indicate variability in depth of dowel bar placement, overall good condition of the slots and grout, and test results showing that the grout met Caltrans specifications for flexural and compressive strength.