Laboratory simulation and mechanical performance of asphalt materials under the action of saline

Abstract

Conventional asphalt mixture performs well in most asphalt pavement applications. However, blistering, which is a common phenomenon in semi-arid areas, is one distress mechanism caused by various detrimental salts resulting in the loss of adhesion at the interface of aggregates and bitumen. When moisture reaches this delaminated interface, it can lead to blistering under the action of heat and thermal expansion. There is heightened interest in the semi-arid areas to modify bitumen and enhance the mechanical properties of asphalt mixtures to address durability and cost-effectiveness issues. One of the approaches being investigated includes using renewable additives to promote a more environmentally friendly production of asphalt mixtures. In this study, two bitumens of penetration grades 40/60 and 50/70 were modified with various percentages of Teak (TK) fibre contents to prolong the service life of asphalt pavements in the semi-arid areas. The properties, including rheological information of base and TK fibre-modified bitumens, were obtained through rutting, penetration, thermal conductivity, and multiple stress creep recovery (MSCR) tests. Base and TK fibre-modified bitumens were soaked in different sodium hydrogen carbonate (NaHCO3) solution concentrations for varying durations. The MSCR test was used to investigate the mechanical performance of the bitumen and binder mastics under salt action. TK fibre modified bitumens demonstrated better rutting resistance, reduced penetration and lower thermal conductivity. The test results indicated that all binder mastics with TK fibres had reduced shear strain, higher recovery, and higher non-recoverable creep compliance than the base bitumen. The TK fibre-modified binders showed better resistance to the action of salt than the base bitumen but exhibited an increase in shear strain, reduction in recovery and increase in non-recoverable creep compliance for soaked samples with increasing salt content. Both base bitumens exhibited excessive softening and showed negative recovery at stress levels from 0.5 kPa with increased soaking duration and salt content. These results show that the optimum level of TK fibres was 2% by weight of bitumen. The results from this study are encouraging for the potential use of TK fibres to improve the performance of asphalt mixtures in semi-arid field conditions where the presence of salt, and specifically NaHCO3, is expected.