The College of Engineering at the University of Baghdad hosted the public defense of the Master’s student Ghufran Abd Al-Mohsen Hussein from the Civil Engineering Department for his thesis titled ” Evaluating the Rutting Resistance of Asphalt Mixtures Containing Waste Steel and Recycled Concrete Aggregate” on Monday, December 23, 2024, in Dr. Khalid Shaker Hall in the Civil Engineering Department, under the supervision of Professor Dr. Mohammed Qadir Ismael.
The aim this thesis was the impact of using RCA in several percentages: 25%, 50%, and 75% reinforced by three dosages of waste steel: 0.3%, 0.6%, and 0.9% added as a proportion of mixture weight. The RCA was immersed in a 0.1 M hydrochloric acid solution for one day. The assessment was carried out in a laboratory using the Marshall test to determine the optimal quantity of asphalt contents, the volumetric characteristics of asphalt mixes, and the wheel tracking test. The study involved sixteen rectangular slabs measuring (300×400×50) mm, subjected to repeated wheel loads of 700 at 55 °C to assess their rut resistance.
Results indicated an increase in Marshall stability by 45.18; however, adding waste steel and RCA did not significantly alter the volumetric properties of the asphalt mixes. The mix containing 75% RCA and 0.9% waste steel exhibited a remarkable improvement in Marshall stability, increasing by 45.18% compared to the control mixture. The rutting performance decreased with the addition of RCA and rose with the inclusion of waste steel. The results indicate that adding waste steel to asphalt mixtures effectively increases the rutting resistance. The mixture with 50% RCA and 0.9% waste steel showed a minimal rutting depth, 25.57% less than the reference mixture.
Based on the results of this study, some recommendations were proposed for future research, including studying the effect of additional grades of asphalt binder on the properties of hot-mixed asphalt containing varying proportions of steel waste, as well as studying the effect of increasing proportions of steel waste on corrosion resistance, fatigue cracking, and resistance to moisture damage in asphalt mixtures. It was also noted that some RCA granules disintegrate during the compaction process, especially in mixtures containing 75% RCA. This issue should be taken into consideration, especially with regard to the circular surface of the sample base that contacts the compaction hammer.
After the scientific discussion by the esteemed members of the examination committee, listening to the researcher defense, and evaluating the thesis, the researcher was awarded a Master’s degree in Civil Engineering/Engineering Management.
