Tie bars are used in jointed portland cement concrete pavements to provide load transfer between longitudinal slabs and to prevent lane separation. Tie bars are located within the middle third of the pavement and span the longitudinal joint of two slabs. Tie bars are placed by staking or baskets prior to the placement of the concrete or during paving via automatic inserters. Inspection of South Dakota pavements after construction using ground penetrating radar (GPR) has revealed that many bars were misaligned or missing. More bars were reported missing or misaligned when automatic inserters were used. Many states, including South Dakota, have banned the use of automatic inserters based on a lack of confidence regarding the placement of tie bars. The long-term effect on the pavement from misaligned or missing bars is unknown, but it can be assumed that additional maintenance costs and reduced pavement life are both possible. While tie bars are considered necessary for long-lasting pavements, only a few states have set tolerances for placement. Specifications that have been established may lack engineering or economic basis, making it is impossible to know whether they are too lax or too stringent. Specifications may be unrealistically difficult to construct or verify. In the absence of an engineering or economic basis for the specifications, it is difficult to judge what corrective actions are warranted when they are not met.

1) Characterize specifications and construction practices currently used regarding tie bars in portland cement concrete pavement. 2) Determine the extent and significance of having missing or misaligned tie bars. 3) Develop structural analysis of tie bars that provides a basis for design and placement tolerances. 4) Develop specifications, inspection criteria, and contractor penalties for tie bar placement.

1) Meet with the technical panel to review project scope and work plan. 2) Review literature and survey state transportation departments regarding tie bar placement specifications, construction practices, inspection methods, corrective actions, and impact on pavement performance and maintenance costs. 3) Conduct a structural engineering analysis of the pavement/tie bar system to define requirements for tie bar placement. 4) Verify the validity of the engineering analysis through targeted laboratory testing. 5) Meet with technical panel to review results of laboratory and finite element testing. 6) Based on results of surveys, laboratory testing, and finite element testing, develop specifications, inspection criteria, and contractor penalties for tie bar placement. 7) Prepare a final report and executive summary of the research methodology, findings, conclusions, and recommendations.

Tie bar placement tolerances developed in this study would constitute a model specification for PCC paving projects. The model specification would provide guidance to states for more rational and effective specifications and would establish a common level of expectation in the concrete paving industry for tie bar placement by any method.