Evaluation of wma healing properties using atomic force microscopy

Abstract

Warm Mix Asphalt (WMA) technology has received considerable attention in past few years due to its benefits in reducing energy consumption and pollutant emissions during production and placement of asphalt mixtures, widening the paving season, and increasing the pace of the construction process. However, many concerns and questions are still unanswered regarding its long-term performance. One of those questions is the effect of using WMA technology on the healing characteristics of asphalt materials, which has significant impact on their performance. The fundamental understanding and evaluation of the healing characteristics of WMA requires careful consideration of the micro-mechanisms that influence the adhesive bonds between the asphalt binder and the aggregate, and the cohesive bonds within the asphalt binder. However, all standard laboratory tests that have been used to evaluate the WMA examine their integral, macro-scale behavior only. Therefore, those tests are limited in their ability to validate the healing mechanisms in an asphalt system, as they cannot examine and deconvolve factors contributing to its response at the micro-scale. In this study, an Atomic Force Microscopy (AFM) based approach was developed and used to evaluate the effect of two types of WMA additives on the healing characteristics of an asphalt binder. The considered WMA additives included Sasobit and Advera. The results of this paper indicated that the use of WMA additives enhances the adhesive intrinsic healing characteristics of the selected asphalt binder. However, the two considered WMA additives showed adverse effects on the cohesive intrinsic healing behavior of that binder. Finally, the Sasobit was found to decrease the rate of crack closure in an asphalt binder. © RILEM 2012.