Investigation of the feasibility of using waste slags in self-healing asphalt concrete pavements via the microwave method

Within the scope of the thesis study, by using microwave heating radiation energy, it is aimed to design a thermally conductive asphalt pavement thanks to the rapid conversion of electromagnetic energy into thermal energy and to increase traffic safety by increasing the self-healing properties of the pavement and solving the icing formations on the road surface in cold climatic conditions. In this context, aluminum and ferrochrome slag wastes found in landfills were used to benefit from their conductive properties and increase sustainable transportation. In addition, steel fiber (SF) reinforcement was added to the mixture to increase conductivity efficiency. Aluminum dross powder (ADP) was used as filler substitute in three different proportions (33.3%, 66.6% and 100%), ferrochrome waste (FeCr) was brought to filler size and used in bitumen modification with binder in three different proportions (5%, 10% and 15%) and SF material was used in two different proportions (0.35% and 0.70%) of the total mix weight. Scanning electron microscopy (SEM) and Energy dispersive X-ray spectrometry (EDS) analysis were performed to determine the topographic structure and elemental properties of the materials. The properties of the modified binder were determined by standard bitumen tests and superpave binder performance tests such as dynamic shear rheometer (DSR), rotational thin film oven test (RTFOT), pressure aging vessel (PAV) and bending beam rheometer (BBR) tests. According to the Superpave volumetric mix design, the appropriate gradation was determined and the optimum bitumen ratios were determined for each mix separately. The moisture susceptibility of each mix group was determined by Modified Lottman test and the strength values were determined by indirect tensile test (IDT). Based on the strength values, tensile strength ratio (TSR) values were determined. Then, Hamburg wheel tracking test (HWTT) was applied to determine the rutting performance of the mixture specimens. The thermal diffusivity properties of the specimens on the surface were measured with a thermal camera after microwave heating for a total of 120 s at 30 s intervals and the average surface temperature values (AST) were determined. Then, IDT and semicircular bending test (SCB) were applied to determine the healing properties, which are important parameters of the thesis study. After the initial crushing process, the specimens were cured by heating under microwave heat energy and after the curing period, the specimens were subjected to crushing again and the curing properties were determined by crushing-heating cycle. After the curing processes, ice masses were formed on the samples in the laboratory environment under -20 °C temperature conditions and their deicing performances were examined under microwave heating energy for 120 s in total. As a result, microwave heating efficiency (MHE) values were determined by utilizing the ice melting speed (IMS), initial temperature, and final temperature of each mixture sample. In the thesis study, analyses were also conducted using machine learning algorithms, one of the artificial intelligence methods, based on the strength data sets of mixture designs containing ADP, FeCr, and SF separately. Finally, a cost analysis was performed to determine the costs associated with each mixture sample individually. As a result, it was determined that FeCr modification improved the performance properties of the binder. It was determined that the mix design with FeCr and SF material improved the strength and moisture susceptibility properties; the best strength conditions were found in 15% FeCr admixture with 0.70% CF, and the best TSR value was found in 10% FeCr mix with 0.70% SF. In the mixture combinations with ADP and SF, it was observed that the best strength value was in the 100% ADP sample, and the best TSR ratio was in the 66.6% ADP mixture, especially the 0.70% SF ratio, which decreased the strength and TSR values. In ADP, FeCr, and SF specimens, it was determined that while the SF additives showed a better improvement effect during 60 s heating time in the curing conditions by IDT method, the curing performances of the samples without SF additives were generally better at 120 s heating time. In ADP, FeCr, and SF mixtures, it was determined that the curing performances of SF doped materials were higher at 60 s and 120 s microwave heating conditions in the curing conditions by SCB method. It was determined that the AST values of ADP, FeCr, and SF doped mixture combinations reached higher temperature values than the reference mixtures, thus showing better thermal conductivity and increasing healing properties and deicing efficiency.