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Application of Nanomaterials in Asphalt Modification
- Author / Creator
- Johnson, Thomas W
Canada has the 7th largest road network in the world with a total of 1.13 million kilometers (40% paved and 60% unpaved). Rise in traffic volumes, increased vehicle axle loading, extremely low air temperatures and seasonal freeze-thaw cycles have resulted in decreased performance of the asphalt layer and, consequently, pavement life. Modification of asphalt binder have been found to be a promising possibility for increasing the performance of asphalt pavements at extreme temperature ranges. Previous research suggests that the addition of nanoclay to asphalt binder can improve the rheological properties of asphalt cement and, consequently, affect its mechanical properties, such as tensile strain, flexural strength, and elasticity. Prior research also has shown that the addition of cellulose nanocrystals to asphalt binder can increase the shear modulus at high temperatures, increase asphalt cement toughness at low temperatures, and decrease thermal susceptibility.
The objective of this research is to investigate and compare the effects on the properties of PG 64-28 when each type of nanomaterial (i.e. bentonite nanoclay, halloysite nanoclay and cellulose nanocrystals) is added to it in 2 distinct proportions by weight of the binder (i.e. 3% and 6% for each of the nanoclays, and 0.5% and 1% for the cellulose nanocrystals). The research also investigated and compared the effects of the aforementioned modifications on the asphalt mixes produced therewith. The Superpave asphalt mixture design and analysis system was used and the properties evaluated were: (1) asphalt cement rheology at high and intermediate service temperatures using the dynamic shear rheometer (DSR) and at low service temperatures using the bending beam rheometer (BBR); (2) asphalt mix performance at high service temperatures using the Hamburg wheel tracker (HWT) permanent rutting test at 45°C; intermediate temperature fatigue resistance and cracking potential using the indirect tensile asphalt cracking test (IDEAL-CT); and low temperature cracking resistance using the indirect tensile strength (IDT) test and creep compliance at temperatures of 0, -10, and -20°C; (3) moisture sensitivity of asphalt mixes using the indirect tensile test (ITS) after freeze/thaw conditioning of asphalt mix samples and determination of the inflection points of asphalt mixes after conducting HWT tests; and (4) mixing method used to disperse the nanomaterials in the asphalt binder matrix.
The results of the Superpave testing protocols for the asphalt binder and the asphalt mixes indicated that there was a 28% to 40% increase in the stiffness of the modified asphalt binders which had a 29% to 75% increase in the rutting resistance the asphalt mixes produced therewith, as well as 55% to 93% increase in the resistance to moisture sensitivity. Although the increase in the stiffness, along with an increase in the mixing and compaction temperatures of the modified asphalt binders, showed no increase in the high temperature performance grade (PG), an increase in the high temperature continuous PG grade was observed. At low temperature, the results show a 2% to 23% increase in fracture energy of the modified specimens. There was also a 10% to 79% increase in the CT index at intermediate temperature for the modified specimens. Moreover, preliminary cost estimates indicate CNC is the most reasonable option in terms of cost and benefit. Finally, the foregoing results show that the high shear mixer-hot plate combo could be an effective tool for dispersing the nanomaterials in the asphalt matrix without causing aging of the asphalt binder.
- Graduation date
- Spring 2020
- Type of Item
- Master of Science
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