Investigation of the effect of organic based colemanite compound on the performance properties of bitumen and bituminous mixtures

In this thesis study, pure bitumen with a penetration grade of 50/70, supplied from Tüpraş Kırıkkale Refinery, was used as the primary binder. In the laboratory, a new additive was chemically synthesized using colemanite and monoethylene glycol, and this compound was named the "Organic Based Colemanite Compound (OEKB)." The OEKB was used as an additive for bitumen modification. During the modification process, OEKB was added to the bitumen in proportions of 1%, 2%, 3%, 5%, and 8% by weight. The modification was carried out at 150 °C for 20 minutes using a mechanical stirrer. Various tests based on both conventional and Superpave methods were conducted on the bitumen samples modified with OEKB. The conventional test methods included the viscosity test, penetration test, softening point test, force-ductility test, and elastic recovery test. As part of the Superpave performance tests, the Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), Rolling Thin Film Oven Test (RTFOT), and Pressure Aging Vessel (PAV) tests were performed. Additionally, bituminous mixtures prepared with the modified binders were subjected to the Marshall mix design, indirect tensile strength test, and Nicholson stripping test. As a result of the experiments, it was confirmed through penetration and softening point test results that the consistency of the bitumen increased when modified with OEKB compared to the pure bitumen. According to the viscosity test data, it was observed that the additive decreased the consistency of the bitumen at high temperatures. DSR test results indicated a significant improvement in rutting resistance of the modified bitumen, while the BBR test results demonstrated enhanced low-temperature performance. The addition of 2% OEKB to bitumen has enabled the development of high and low performance grades to a higher advanced level. In the Marshall mix design test, an increase in the stability of the mixture was observed due to the use of the additive. In the indirect tensile strength test performed at different temperatures, a notable increase was particularly observed at 40°C as 8.8%. Finally, the results of the Nicholson stripping test showed that the stripping resistance of the bituminous mixtures was improved significantly from 60 % to 80 % with the use of OEKB.