Impact of dowel bar number and location on pavement performance in a low volume road
In jointed concrete pavements, dowel bars are typically used to transfer loads between adjacent slabs. These dowels are typically made of steel and are spaced 12 inches on center for the full length of a transverse joint. The objective of this research was to evaluate the impact of the number of dowel bars and dowel location on pavement performance and joint performance. Consequently, four dowel arrangements were evaluated: 1) zero dowels, 2) three dowels in the outside wheel path, 3) four dowels in the outside wheel path, and 4) full basket of dowels (twelve). In addition, two test sites were prepared with two different subgrades, one with a compacted soil subgrade (Rural site) another with a built up asphalt surface treatment subgrade (Urban site). Evaluations of the test sections were performed biannually (early fall or late summer and early spring) over a five-year testing period. In addition, a soil investigation was performed using in-situ soil classification from soil borings and consultation of US Department of Agriculture soil survey. Biannual evaluation of both the Urban and Rural sites consisted of: 1) visual distress surveys, 2) joint opening measurements, 3) joint faulting measurements, and 4) deflection measurements using an Iowa DOT (Department of Transportation) Road Rater. Analysis of the biannual testing indicated that the stiffness of a subgrade magnifies the effect of dowel arrangement on a pavement. It was recommended for pavements with a weak subgrade (dynamic k-values less than 200) to use the standard (full) dowel compliment. For pavements with a strong/stiff subgrade (dynamic k-values greater than 220), three or four dowels in the outside wheel path will suffice. Additional investigation is needed to recommend a dowel bar arrangement for moderately weak to moderately strong subgrades, possibly with dowels in the inside wheel path.