Evaluation of selected warm mix asphalt additives Nishant Mukeshkumar Sheth , University of Iowa Follow

[摘要] Warm mix asphalt (WMA) is an emerging technology that can allow asphalt to be produced and compacted at a significantly lower temperature. In the past, a number of researchers evaluated various WMA mixtures using select testing procedures in the laboratory. However, none of them evaluated all four major WMA products and compared them against both control HMA and WMA mixtures without an additive using a comprehensive set of testing protocols. This thesis presents a comprehensive evaluation result of four major WMA additives regarding their tensile strength, moisture sensitivity, dynamic modulus and flow number. The WMA specimens exhibited similar air voids as HMA specimens which indicate that WMA additives are effective in compacting asphalt mixtures at a lower temperature. The indirect tensile strengths and tensile strength ratio (TSR) values of all WMA specimens were lower than that of HMA specimens. This result indicates that WMA mixtures could be susceptible to moisture damage. The only WMA mixture with CECABSE RT® exhibited the higher dynamic modulus at 37.8°C than the control HMA mixture. All WMA specimens, except Advera WMA and CECABASE RT®, passed the requirement of 10,000 cycles of repeated loading. Particularly, the WMA mixture with granular Aspha-min® exhibited the lowest permanent deformation followed by the control HMA mixture. The nano-scale images of additives with asphalt were also taken to study the characterization and interaction of WMA additives with asphalt. A shape resembling bee was observed in all asphalt images which has been criticized by the researchers. However, bee structures were disappeared in those images of asphalt with CECABASE RT® additive. At nano-scale, height and phase angle of all additive were found greater than the asphalt which proves them highly viscous than the asphalt.