In recent years, polymer-modified asphalt mixtures have been increasingly used in the construction of flexible pavements. These products have gained popularity because of their ability to increase pavement performance in both cold and hot environments. The increased elasticity from the polymer imparted to the mixtures at cold temperature increases the pavement's ability to resist thermal cracking. Theincreased stiffness, as well as the increased elasticity, of these mixtures at warm temperatures has shown an improved resistance to rutting. The increased resistance to rutting in warm climates was of particular interest for construction projects in the hot desert climate of southern nevada. To investigate the potential benefits of these polymer-modified materials, the nevada department of transportation (ndot) placed six polymer-modified experimental test sections between los vegas, nevada, and the arizona border in december 1989. The university of nevada, reno, in conjunction with ndot, developed a research program to rank the rutting potential of the various mixturesand the increased rutting potential in the presence of moisture. Conclusions from this research were that strains observed in creep testing depend on the location of instrumentation and boundary conditions imposed on the sample. Results showed that a ranking of the materials (lowest to highest strain) was the same for 8-in.-High samples instrumented over the center third or over full depth. A finite element analysis showed that the magnitude of strains observed depends on the area of instrumentation. End friction in the sample can give rise to substantial difference in the creep strain measurements made.Conclusions also indicate that the permanent strains after moistureconditioning appear to be a good indicator of possible moisture damage. This paper appears in transportation research record no. 1317, Asphalt mixtures: design, testing, and evaluation 1991.
Abstract