The Use of Atomic Force Microscopy in Evaluating Warm Mix Asphalt

In this thesis, atomic force microscopy (AFM) was used to investigate moisture damage and the healing characteristics of warm mix asphalt (WMA) and compare it to those of hot mix asphalt (HMA) at the nano-scale level. Furthermore, AASHTO T 283 test method was used to evaluate moisture damage in WMA and HMA mixtures at the macro-scale level. AFM Force spectroscopy technique was used to measure the cohesive and adhesive forces in the asphalt mix using a group of chemically functionalized AFM tips under dry and wet conditions while tapping mode imaging technique was used to obtain topographic and phase images for the asphalt binders. Two types of performance grade binders were evaluated in this study: a neat asphalt binder PG 64-22 and a polymer modified binder PG 70-22M. Four WMA technologies were investigated: Advera, Sasobit, Evotherm Advera, and foamed WMA. The results of the AFM imaging showed “bee- like” structures in most of the tested samples. Sasobit additive was the only WMA technology that significantly affected the “bee-like” structures by increasing their lengths and reducing their widths. In addition, Sasobit resulted in increasing the relative stiffness of dispersed domains containing the ‘bee-like’ structure in comparison with the flat asphalt matrix for both types of binders. Based on the force spectroscopy tests the polymer modified PG 70-22M HMA and WMA samples were found to be less susceptible to moisture damage compared to the PG 64-22 samples. The inclusion of WMA additives improved the adhesive forces for both types of binders while its effect on the cohesive forces was less significant. Sasobit had the least improvement on the adhesive forces and resulted in reducing the cohesive forces in both types of binders this could be related to the lower indirect tensile strength that were obtained for the Sasobit mixtures. The adhesive forces were reduced after conditioning of the control and WMA PG 64-22 binders. Sasobit and Advera had the highest reduction which could be related to the inferior tensile strength ratio obtained from their mixtures. However, Evotherm and control PG 64-22 adhesive and cohesive forces were not significantly affected by conditioning. AFM results also showed a good correlation between the adhesive force results and AASHTO T 283 results. The healing experiments showed that most WMA processes improved the healing rate except Sasobit which reduced the crack closure rate. Finally, this study provides a new approach for evaluating the healing characteristics of asphalt binder and a better understanding of the WMA characteristics at a nano-scale level. In addition, it demonstrated the capability of the AFM to characterize and examine the nano-structural properties of asphalt paving materials.

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Civil Engineering (Engineering and Technology)

Grantor dc:publisher

Ohio University

Year dc:date

2013

Author dc:creator

• Abu Qtaish, Lana

Contributors dc:contributor

• Nazzal, Munir

• Civil Engineering
• warm mix asphalt
• atomic force microscopy
• moisture damage
• healing
• force spectroscopy
• AASHTO T 283

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1357317910

OAI identifier oai:identifier

oai:etd.ohiolink.edu:ohiou1357317910