Quantification of moisture sensitivity of warm mix asphalt using image analysis technique

Warm Mix Asphalt (WMA) is susceptible to moisture damage owing to its lower production temperature. Moisture can cause adhesion failure, hence stripping of asphalt binder from aggregates. This paper proposes a new method based on image analysis to estimate the adhesion failure due to moisture on fractured conditioned asphalt surfaces. A novel approach is used to identify the adhesion failure susceptibility due to moisture damage related to its mechanical strength in direct tension. The percent area failure due to adhesion is quantified more precisely via image analysis technique after the specimens were fractured in direct tension. The specimens under observation were evaluated for dry, 1 Freeze Thaw (F-T) cycle and 3 F-T cycles before being fractured by direct tensile force. The Environment for Visualizing Images (ENVI) Version 4.0 image analysis software tool was used to evaluate the extent of adhesion failure. The results from the image analysis showed that adhesion failure increased with the number of F-T cycles and mixtures prepared using PG-76 binder exhibited lower adhesion failure compared to PG-64 binder. The method enabled evaluation of adhesive failure of mixtures prepared using different binders and levels of laboratory moisture conditioning. This shows that the image analysis method can be used to quantify adhesive failure of warm mix asphalt and is a better alternative to the conventional method of visualization using the naked eye.