| dc.description.abstract | The objectives of this project is to demonstrate whether the Surface Free Energy (SFE) concept reported by Cheng et al. (2002) can be utilized to characterize the moisture-induced damage potential of selected asphalt binders and aggregates that are widely used in Oklahoma. Pursuit of this objective, the SFE components of two selected binders, PG 64-22 and PG 70-28 from Valero Refinery, Oklahoma, were evaluated with and without anti-strip additives in Phase II - Year 1. Two anti-strip additives, AD-here HP Plus and Redicote E-6 from Arr-Maz, Florida and Akzo Noble, Texas respectively, were used at three percentages 0.25o/o, 0. 75% and 1.5%. The total SFE of PG 64-22 and PG 70-28 increases with an increase in additive content. 1.5% AD-Here HP Plus and 1.5% Redicote E-6 increased the total SFE of PG 64-22 by 67% and 208%. The corresponding increases in total SFE of PG 70-28 are 23.6% and 24.4%, respectively. The acid component of PG 64-22 and PG 70-28 are 2.9 dyne/cm2 and 2.5 dyne/cm2, respectively whereas, the corresponding base components is 0.4 dyne/cm2 for both. Basic chemicals in the form of anti-strip additives (such as amines) can reduce the acid component and increase the basic components of asphalt binder. With the addition of 1.5% Redicote E-6 in PG 64-22, the acid component of asphalt binder decreases by 92% and the base component increases by 1141 %. The SFE components of aggregates were evaluated by a Universal Sorption Device (USD) using water, methyl propyl ketone and n-hexane. The SFE of limestone and chat are 166.6 ergslcm2 and 132.2 ergslcm2, respectively. The higher surface energy oflimestone provides better adhesion strength between limestone and asphalt binder. The basic component of SFE of limestone and chat are 390.8 ergslcm2 and 219 ergslcm2, respectively. It is evident that limestone is more basic than chat. It was observed that both the anti-strip additives have detrimental effect on limestone and chat in the presence of water. Comparatively, both the anti-strip additives have improved the free energy of adhesion in the presence of water between Georgia granite and asphalt binders (both PG 64-22 and PG 70-28). This is due to the fact that Goergia granite is a highly acidic aggregate. Therefore, liquid anti-strip additives can improve the adhesion between highly acidic aggregate such as granite and asphalt binders (based on their SFE characteristics). Finally, it can be concluded that SFE method is an excellent tool for measuring acid-base characteristics of aggregates and asphalt binders with and without anti-strip additives. | |
