Mechanical Behavior Of Nanoclay Modified Asphalt Mixtures PDF Download

Asphalt pavement is subject to stresses induced by heavy traffic loading and thermal variations during its service life. Nowadays, increasing the permissible axle loads along with the impact of climate change have caused premature failure in the flexible pavement. Enhancing the properties of asphalt binders can reduce these distresses. Among the available options, finding a cost-effective alternative for improving the used binders is a challenge to overcome. Asphalt binder modification using nano-size materials has attracted attentions in recent years. Based on this study, nanoclays can improve the properties of asphalt binders, increase the resistance of asphalt to ageing, cracking and rutting, and extend the pavement's service life cycle. The objectives of this work were to investigate the rheological and mechanical properties of nanoclay modified asphalt binders and mixtures. The behaviour of a PG 64-28 asphalt binder modified with 2% and 4% concentration of two organo-montmorillonites was studied. Furthermore, the impact of using nanoclays was investigated in asphalt mixtures' performance. The nanoclays were mixed with the asphalt using a high shear mixer, and their dispersions were analyzed by employing a Scanning Electron Microscope (SEM) device. A SARA test was conducted on the modified and unmodified binders to examine the fraction composition of saturates, asphaltenes, resins and aromatics before and after the addition of nanoclays. Also, the neat binder and the nanoclay modified binders were subjected to short-term ageing using a rolling thin-film oven (RTFO) and long-term aged using a pressure ageing vessel (PAV). The following rheological properties of the asphalt binders were investigated: (1) High-temperature performance grading of unaged samples using a dynamic shear rheometer (DSR), (2) High-temperature performance grading of RTFO-aged samples using a DSR, (3) Intermediate temperature grading of PAV-aged samples using a DSR, (5) Low-temperature performance grading using a bending beam rheometer (BBR), (4) Two-piece healing test using a DSR, (6) Frequency-Sweep tests using a DSR, (7) Mixing and Compaction temperatures using a rotational viscometer, and (8) Mixing and compaction temperatures of modified asphalt binders using a DSR. Additionally, the mechanical properties of the asphalt mixtures that were analyzed are as follows: (1) Flow and Stability and stability test, (2) Bulk specific gravity test, (3) Theoretical maximum specific gravity on loose mixtures, (4) Fatigue and healing behaviour using a four-point bending test and (5) Dynamic Modulus test on Superpave samples. The results obtained from the high-temperature grading showed that the addition of 4% organo-montmorillonites increases the high-temperature grade from 64 to 70. Also, no change was observed in the low-temperature performance of the modified samples. The two-piece healing test showed promising results for nano-modified samples, with significant improvements in the initial healing proportional to the concentration of nanoclays in the binder. The Frequency-sweep analysis, utilizing a master curve, showed an improvement in ageing resistance by adding Montmorillonites. Furthermore, the SARA test results indicated that the nanoclay modified mixtures were storage stable. The asphalt mixture samples demonstrated, by repeated flexural bending using a four-point bending apparatus, increased stiffness and life cycles of the organo-montmorillonite modified asphalt mixtures.