Investigation of the usability of biochars obtained from the pyrolysis of different biomasses in bitumen and bituminous hot mixtures

Economic and environmental problems caused by using nonrenewable and fossil-based materials led to the need for utilizing various alternative material and additives in the highway industry in terms of sustainability. Biomass, which is one of the largest and renewable energy sources in the world, has the potential to be used as bitumen additive materials thanks to its hydrocarbon structure provided by the application of various thermochemical methods. The additive product obtained from the pyrolysis process is called biochar. In this thesis study, the usability of biochar obtained from ground apricot seed shell, ground walnut shell and sawdust pyrolysis, which are abundant in Turkey and have low economic value, was investigated as a bitumen additive material to improve the performance of highway pavements, and it was aimed to provide economic benefits from these waste materials in a different field. In the study, biomasses were firstly subjected to the pyrolysis process in different conditions and the biochars obtained were used as bitumen additive materials. The dynamic shear rheometer test was conducted on the manufactured binders to determine optimum pyrolysis temperature and the most suitable ratio for additive. Modified bitumens were prepared by using biochars prepared under the designated conditions and traditional and Superpave binder tests were conducted on pure and modified binders. Marshall stability and flow, tensile strength ratio, indirect tensile stiffness modulus, indirect tensile fatigue, resistance to crack propagation and dynamic creep tests were conducted on hot mix asphalt (HMA) specimens manufactured by using these binders to evaluate the effects of biochars on HMAs' mechanical properties in a wide range. Based on the results obtained, it was determined that the use of biochars in bitumen modification improved the high-temperature performance of bituminous binders and did not affect low-temperature behavior significantly. As a result of mixture tests, it was determined that using biochar-modified bitumen improved the stability, stiffness, fatigue life, crack propagation and resistance to permanent deformation of hot mix asphalt and diminished resistance to moisture damage.