University of Baghdad Hosts Master’s Thesis Defense on Enhancing Moisture Resistance in Local Asphalt Pavements

The College of Engineering at the University of Baghdad hosted the public defense of the Master’s student Noor Najah Adwar from the Civil Engineering Department for the thesis titled ” Contributory Factors Related To Moisture Damage Of Local Asphalt Pavements” December 18, 2024, in Dr. Khalid Shaker Hall in the Civil Engineering Department, under the supervision of Professor Dr. Amjad Hamad Khalil Albayati.
The aim of this study was to examine numerous variables in asphalt concrete mixtures to assess their impact on moisture damage resistance. Mix design parameters such as the asphalt content (AC); optimum asphalt content, and optimum asphalt content ±0.5%, as well as three aggregate gradations with passing sieve No.4 (PNo.4) equal to mid-range gradation, mid-range−6% (coarse gradation), and mid-range+6% (fine gradation), were considered as variables during this study. Additionally, hydrated lime (HL) was utilized as a partial substitute for limestone dust (LS) filler at 1.5%, 2%, and 2.5% by weight of the aggregate in asphalt concrete mixtures for the surface layer. This study also investigated the potential enhancement of traditional asphalt binders and mixtures by adding nano-additives, specifically nano-silica oxide (NS) and nano-titanium dioxide (NT), at rates ranging from 0% to 6% by weight of the asphalt binder.
The results indicated that the variations in the mix design variables significantly affected the moisture damage resistance of the asphalt concrete mixtures. The maximum improvement values were obtained at (OAC) and fine gradation (mid-range + 6%) with TSR values of 80.45 and 82.46 and IRS values of 74.39 and 77.14, respectively. Modifying asphalt concrete mixtures with HL resulted in improved moisture resistance compared with mixtures without HL (0% HL) at each PNo.4 level, reaching superior performance at 2.5%HL+ PNo.4 (mid-range + 6) by 8.37% and 8.59% in the TSR and IRS tests, respectively. Additionally, both NS and NT enhanced the physical properties of the asphalt binder, leading to substantial enhancements in asphalt concrete mixture performance against moisture damage. A 6% dosage of NS and NT showed the best performance, with NS performing slightly better than NT. TSR was increased by 14.72% and 11.55% and IRS by 15.60% and 12.75%, respectively, with 6% NS and NT compared with mixtures without nanomaterials (0% NM).
Based on the results of this study, some recommendations were proposed for future research