A full-scale experimental pavement was constructed to compare low temperature cracking performance of asphalt concrete containing two types of styrene block copolymers and an ethylene-based polymer each at two levels of concentration in a relatively soft asphalt cement. The experiment was designed to compare field performance with observed behavior in the laboratory.
Samples of all binders and mixtures were collected during construction and laboratory tests were conducted using actual materials placed in the field.
Mixture tests were limited to Marshall, resilient modulus, and ASTM D4867 moisture sensitivity. Results indicate a high resistance to water damage and relatively high Marshall stabilities for all mixtures evaluated. Marshall test results were highly variable and no apparent differences between materials could be resolved using Marshall parameters. Resilient modulus was conducted at three temperatures, but small differences in this property were not conclusive regarding effects of polymer modification on temperature susceptibility of the mixtures. Variability in resilient modulus measurements was high for certain mixtures.
Experience gained in the laboratory and field during design and construction of this experimental pavement has provided information regarding recommended practices when using certain polymer modifiers during construction of asphalt concrete. For example, conventional viscosity-temperature relationships developed with capillary viscometers were misleading regarding establishment of mixing and compaction temperatures. The predicted temperatures were higher than required for mixing and compaction of the polymer modified mixtures. This experience suggests that new techniques should be developed for establishing appropriate mixing, laydown and compaction temperatures for polymer modified asphalt mixtures.