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.

The inclusion of steel dowel bars to transfer forces across sawed or formed transverse joints from one concrete pavement slab to another while permitting expansion and contraction movements of the concrete has been a basic design practice in most U.S. state departments of transportation (DOTs) for many decades. However, corrosion of the steel dowels remains a common problem, especially in states that use salt and other caustic deicing chemicals for snow and ice control. Significant corrosion reduces the effective diameter of the dowel bar in the joint, often to the point where the dowel bar will fail in shear when loaded, resulting in faulting of the pavement slab. Furthermore, the corrosion can also "lock" the dowel bar into the concrete, preventing movement of the concrete during expansion and contraction and thereby leading to the development of cracking in the adjoining slabs. In the mid-1970s, state DOTs began to require that steel dowel bars be coated with epoxy or other materials to prevent corrosion, and epoxy-coated dowels became the standard for most states. Recently, a number of different alternative dowel bar materials have emerged, seeking to combine effective load transfer capabilities with enhanced corrosion resistance. While the corrosion resistance of some alternative materials have been well documented in laboratory examinations, other performance characteristics affecting service life remain to be fully evaluated, particularly in representative field installations and over meaningful time periods.

The objective of this research was to evaluate the impact of the number of dowel bars and dowel location on joint performance and ultimately on pavement performance. For this research, test sections were designed, constructed, and tested in actual field service pavement. Test sections were developed to include areas with load transfer assemblies having three and four dowels in the outer wheel path only, areas with no joint reinforcement whatsoever, and full lane dowel basket assemblies as the control. Two adjacent paving projects provided both rural and urban settings and differing base materials. This report documents the approach to implementing the study and provides discussion and suggestions based on the results of the research.