Micromechanical shear modulus modeling of activated crumb rubber modified asphalt cements

The rheological properties of three asphalt cements containing reacted and activated rubber (RAR) are evaluated to quantify the relative effects of swelling, splitting, and absorption. Rheological testing and electron microscopy are used to measure the dynamic shear modulus, |G∗|, and rubber particle changes respectively. It is found that |G∗| increased for all RAR and that particles swell 15.8-49.3% with those in softer asphalt showing the greatest swelling. Micromechanical models are used to predict |G∗| of the materials. The Hashin and Christensen models are found to accurately predict the measured moduli after accounting for the swelling, splitting, and absorption.