Portland cement concrete pavement (PCCP) with favorable as-constructed smoothness and lower rates of roughness progression is expected to have a longer service life. This study was done to quantify the effect of as-constructed smoothness and other design, construction, traffic, and climatic variables on the rate of roughness progression on concrete pavements in Kansas. Selected inventory, construction, climatic, and annual roughness data were obtained for 21 PCCP projects constructed after 1992. From the annual roughness data in terms of international roughness index (IRI), collected by the South Dakota-type profilometers, the rate of roughness progression was obtained through regression analysis. Multiple linear regression analysis was then done to find the functional relationships between the rate of roughness progression and the independent variables selected. The results show that the concrete modulus of rupture, subgrade material, number of wet days, and initial IRI roughness (roughness measured during the first-year network-level survey after construction) significantly affect the rate of roughness progression. Higher flexural strength tends to help retain as-constructed smoothness longer on some projects. Some pavements with high initial IRI roughness tend to become smoother as traffic passes over them, presumably because of smoothening of minor surface irregularities and stabilization of subgrade soil moisture during early years of pavement life. Finally, a trend analysis of annual IRI roughness data showed that the as-constructed smoothness tends to wear out in about 3 to 5 years and thus does not influence future roughness development.
Abstract