Date of Award
Master of Science (MS)
Modification of asphalt binders is essential to improve the physical and rheological properties of asphalt and to reduce the aging effect. The use of polymers to modify asphalt is the most common approach in asphalt modification. Force ductility test has been a challenging topic as an indicator of asphalt performance, especially for the modified asphalt binders. The significance of the force ductility test as a measure of fatigue and thermal cracking has been debated because of its low reproducibility, empirical nature and the unclear relationship with the fundamental asphalt properties, especially with modified asphalt binders . Extensional deformations tests where converging flows occur have been used by many for polymer characterizations (2). In this study, the extensional deformation behavior of binders Performance Graded 58-28, PG 64-22, and PG 76-22 and its parameters including geometry and temperature were investigated through an extensional rheological approach using a DSR-based Sentmanat Extensional Rheometer (SER). Furthermore, a test method and a sample preparation procedure especially for asphalt binders were developed as a replacement to the conventional force ductility test. The sample preparation method has been simplified and detailed in a way that it can be performed in all asphalt labs. A detailed analysis indicates that the average second peak and first peak elongation forces increase due to the increase of the sample’s area, with ܴ ଶ values of 0.85 and 0.84, respectively. However, the same areas with different dimensions derived different values of elongation force that is due to the dominant role of the width. The elongation force of all samples with the same area but different dimensions increases due to the width’s increment even though the thickness decreases.
Based on this study, the recommended test specifications are as follows: the selected geometry is 9 mm x 0.72 mm (width x thickness). The second peak elongation force F2 value was chosen as a recommended force ductility parameter. The minimum ܨଶ value recommended is 14 N, which was lower than the lowest limit of 99% confidence interval (14.45N – 15.99 N). Also, the minimum ratio of the second peak elongation force over the first peak elongation force ܨଶ/ܨଵ of 1.25 is recommended for PG 76-22. This is also lower than the lowest value of 99% confidence interval (1.29-1.51). The recommended temperature is 4ºC, the recommended strain rate is 0.1ݏ ିଵ , and the recommended final strain is 3.4 rad. Therefore, with a more reproducible, significantly less material and time consuming, and with a more mechanistic approach, the developed novel method can help improve the durability of modified asphalt pavements.
Omer, Waleed M., "" (2018). Thesis. 11.