Investigation of the effects of asphaltite on the mechanical properties of hot mix asphalt

In this dissertation study, the effects of using Silopi asphaltite in hot mix asphalt as a filler material were investigated. Silopi asphaltite was added into the mixtures at 5 different proportions from 1% to 5%. Designs of both the pure and asphaltite containing mixtures were carried out in accordance with the Superpave method. The tests were applied on short-term aged mixtures as well as long-term aged mixtures.It was found out that the stability, Marshall Quotient (MQ) and Retained Marshall Stability (RMQ) values increased in parallel with asphaltite content. The tensile strength ratio tests demonstrated that higher asphaltite contents enhanced the tensile strength and the tensile strength ratios (TSR). As a result of the indirect tensile stiffness modulus tests, the positive influence of higher asphaltite content on stiffness of the mixtures was also determined. The indirect tensile fatigue test showed that the fatigue life increased with asphaltite content, in addition to resulting in a more brittle type of cracking due to the reduction in deformation. As a result of the repeated creep tests, it was found that the resilient modulus, creep modulus and flow numbers increased with rising asphaltite content. It was determined from the fracture toughness tests that KIC values were similar in pure and modified mixtures up to 3% of asphaltite content, but decreased at 4% and 5% asphaltite. Jc values displayed that the mixtures possessed higher resistances against crack propagation at higher asphaltite content. In the study, images of the Jc tests were taken and subjected to digital image processing procedure to evaluate crack propagation with time. Finally, the relationships between the variables were modeled by linear regression analysis and stated in first order equations.In consideration of the test results, it was determined that as the asphaltite content increased, the stiffness and resistance of the mixtures against plastic deformation, fatigue cracks, moisture damage and crack propagation improved, although eventuating in a more brittle cracking in the mixtures. Taking volumetric design into account, it was concluded that the most appropriate asphaltite content in hot bituminous mixtures would be 3%.