Effects of Rubber Additives on Properties of Asphaltic

EFFECTS OF RUBBER ADDITIVES ON PROPERTIES OF ASPHALTIC MATERIALS by JOHN ALBERT ALEXANDER Submitted to the Department of Civil Engineering on August 17, 1968, in partial fulfillment of the requirements for the degree of Master of Science in Civil Engineering. This study investigated the modification of asphalt with various rubbers and the effect of this modification on the values of fracture toughness at low temperature. Test results indicated that the fracture toughness of asphalt can be substantially increased by modification with a small percent of either a suitable rubber in latex form or with a low molecular weight liquid rubber that is crosslinked after dispersion by the use of an epoxy and hardener. The effects of an accelerated aging procedure on the modified asphalts revealed that the prolonged exposure to high temperature further increased the fracture toughness while fracture toughness of unmodified asphalt was lowered by exposure to the same aging procedure. Addition of mineral filler increased the flexural strength of the test beams but did not significantly change the fracture toughness of the modified asphalt. A brief study of the various modifications at the magnifications provided by the optical microscope revealed a strong relationship between the fineness of the rubbery second phase and the values of critical strain energy release rate. Thesis Supervisor: Fred Moavenzadeh, Ph.D. Title: Associate Professor of Civil Engineering