The introduction of fiber reinforced plastic (FRP) dowels as possible alternatives to the epoxy-coated and stainless-steel dowels, was contemporaneous with a paucity of knowledge of their long-term performance. Although various isolated efforts had examined them on a short-term basis and produced some qualitative results or long-term predictive models, actual long-term performance in service was still unknown and unanalyzed. An experiment at the MnROAD Research facility placed FRP dowels in 2000 in some of the jointed plain concrete pavement (JPCP) panels of test Cell 52 and used epoxy-coated dowels in the remaining panels of this cell. The contiguity of this test cell with Cell 53, a JPCP high-performance concrete cell built in 2008 with stainless steel dowels, and Cell 54, a taconite JPCP cell with epoxy-coated dowels in built in 2004, facilitated a comparative analysis of performance of the 3 dowel types particularly in load transfer efficiency (LTE) and ride quality. The difference in the inception of the cells constrained a performance over time and encouraged a time-series autoregressive integrated moving average (ARIMA) analysis. Projections to 30 years showed that LTE and ride quality of FRP dowels were no different from those of the epoxy-coated dowels and the stainless-steel dowels although Cell 53 was designed and built with thicker concrete (12-in. thick) compared to 7.5-in in cells 52 and 54.

This study provided for a continuation of the long-term performance evaluation of 1.5-in (38-mm) diameter FRP dowels and Type 304 stainless steel solid dowels or mortar-filled tubes compared to epoxy-coated dowels. This primarily included an evaluation of load transfer efficiency (LTE) based on FWD testing, but also included a limited evaluation of faulting and ride. In addition, some FWD testing and coring was conducted on older projects (15 to 30+ years old) to evaluate the long-term corrosion protection provided by epoxy coatings. The 1.5-in (38 mm) FRP dowels with polyester resin and E-glass exhibited generally low LTE values, and are not providing performance comparable to that of the 1.5-in (38-mm) epoxy-coated mild steel dowel bars. The evaluation of alternative stainless steel clad dowels and concrete filled stainless steel tubes or pipes (Type 304 or Type 316) was inconclusive due to the small sample and the relatively short (14 years maximum) evaluation period, but it appears that they will perform satisfactorily in excess of 30 years given the minimal deterioration observed. Based on the coring of the older pavement projects, the life of the epoxy coating on mild steel dowels evaluated in Ohio and Wisconsin appears to be in the 25 to 30-year range. Many of the epoxy-coated dowels retrieved from in-service pavements revealed that the epoxy coating was debonded from the mild steel dowel and the surface of the mild steel dowel under the coating was pitted and rusted. In most cases, however, there was no significant loss of cross section. A review of two older projects in Ohio constructed with plastic-coated dowels indicated that those dowels were in excellent condition after 33 years. The overall condition of these projects was also very good, with little if any visible joint deterioration. Because plastic-coated dowels are similar to epoxy-coated dowels in terms of costs, they appear to be a cost-effective alternative to conventional epoxy-coated dowels.

Effective load transfer across Portland cement concrete pavement joints significantly decreases pavement deterioration. Areas of concern with using dowel bars include high costs, due to the labor-intensive procedure of retrofitting, and corrosion associated with standard mild steel epoxy-coated dowels. This research addresses these problems by evaluating four dowel bar details tested in an accelerated manner. Retrofit testing was performed using mild-steel epoxy coated dowels and fiber reinforced polymer (FRP) dowels. The details tested provide comparisons among dowel bar materials, depth of placement, number of dowels used, and dowel diameter. Verification testing of previously tested details is also presented.

Abstract: An investigation of the structural behavior and corrosion resistance of hybrid fiber reinforced polymer (FRP) wrapped steel reinforcement bars for use in reinforced concrete structures. The investigation is comprised of a bar analytical model using laminate theory, an in-depth analytical model for reinforced concrete sections, and a series of experimental tests to assess the structural performance and corrosion resistance of the composite bars. A comparison between the analytical model and experimental results was conducted and general design guidelines developed. Using these guidelines, sample designs were completed using hybrid bars, stainless steel bars, and standard epoxy coated steel reinforcing bars. The designs were compared and a life cycle cost (LCC) analysis was performed to assess the economic advantages or disadvantages of the hybrid bars. Conclusions and recommendations for standard practice and design and future research are then presented.