Improvement of performance properties of flexible pavements by synthetic metal and polyboron additives

Various pavement types having different features are used to provide highway transportation. These structures are usually divided into three groups as flexible, rigid and composite. Among these, flexible pavements are preferred today depending on their properties.In flexible pavements distresses can be formed by the effects of traffic-environment-climate. In order to improve the quality of highway transportion, prevention or minimization of those distresses is necessary. Although bitumen ratio available in structure is so low comparing with aggregate, the properties of bitumen closely effect the resistance ability of pavement against distresses.In this study, it is aimed to improve the flexible pavement performance by enhancing properties of bitumen by modification with additives. Nine different additives are used in bitumen modification. These additives are new materials obtained by synthesising at laboratory conditions with a simple equipment group. Each additive is named in most general form as organically based metallic compound or ethylene glicol based polyboron compound according to materials used in its synthesis. Viscosity tests, softening point tests, ductility tests, dynamic shear rheometer (DSR) tests, bending beam rheometer (BBR) tests are applied to the original bitumen samples and the bitumen samples modified by the additives which are produced in the scope of this study. The effects of modification to the bitumen-aggregate mixtures are also investigated by Marshall tests and Nicholson stripping tests.Depending on the test results it is determined that each additive improve flexible pavement performance by creating effective changes on the properties of bitumen and bituminous mixtures (bitumen-aggregate mixtures). Accordingly, rutting resistance, low temperature cracking resistance and stripping resistance of flexible pavements increased by using the suitable additive synthesised in the scope of the study. Moreover; in the production and application processes of bituminous hot mixtures, additives provided energy saving, decrease in short term aging of bitumen and increase in workability