Mechanical properties of asphalts containing styrenic block copolymers and properties of dense-graded asphalt concrete produced from these binders are presented. Materials studied include unmodified AC-5 and AC-20 asphalts and AC-5 containing 3 and 6% styrenic block copolymers.

Dynamic rheology of the binders was studied as a function of temperature and deformation rate. Complex viscosity of the polymer-modified asphalts exhibits less temperature susceptibility than that of control asphalts from 0°C (32°F) to 93°C (200°F) and slightly higher temperature susceptibility above 93°C (200°F). The modified asphalts are viscoelastic throughout the pavement operating temperature range with a significant elastic component. However, the unmodified asphalts are essentially nonelastic above 38°C (100°F).

Increases in polymer content increase viscosity, ductility, toughness, tenacity, and elasticity of the materials tested. However, shear-thinning characteristics of the polymer-modified asphalts allow handling by familiar techniques at conventional temperatures. Asphalt concrete was evaluated by resilient modulus and indirect tension over a range of temperatures. Results indicate tensile modulus is lowered at low temperatures and raised at high temperatures by addition of the polymer.