The mixing degree of virgin and aged asphalt binders is one of the main factors that can significantly affect the performance of reclaimed asphalt pavement (RAP). On the other hand, an important factor that contributes to the mixing is diffusion, which dominantly determines the general performance of asphalt mixtures with RAP. In this study, twelve different lab-mixing conditions were deliberately adopted to investigate the impact on the diffusion between virgin and aged bitumen binders, including three mixing temperatures (110°C, 130°C, 150°C) and four mixing times (30 s, 60 s, 120 s, 240 s). Specially fabricated cubic aggregates were designed and deposited for collecting pure binders, so that virgin or aged binders can be tracked and the effect of chemical reagents be avoided. Based on the Dynamic Shear Rheometer (DSR) and Fourier Transform Infrared Spectroscopy (FTIR) tests, the performance and blending rate of binders under various conditions were clearly shown. The results show that blending temperature can play a more crucial role in diffusion than mixing duration, which means the higher temperature is capable of accelerating the inter-diffusion rate between virgin and aged bitumen binders, thus increasing the efficiency of recycling ulteriorly. The blending degree investigated in this study could not achieve the complete mixed state with the highest value being around 50%. Furthermore, the Asymmetric Gaussian Model is proposed to mathematically describe the change of blending rate with the mixing time.

This paper investigates the effect of jacking two groups of open-ended prestressed high-strength concrete (PHC) piles on an existing highway embankment based on field measurements of excess pore pressure and lateral soil displacement. Excess pore pressure due to pile jacking increased with depth and decreased with increasing distance from the pile; the influence reached a distance of 43 pile diameters from the pile axis. For pile groups, the amount of excess pore pressure dissipated decreased with increasing depth and varied from 54% to 100% in 20 days. Lateral soil displacement and excess pore pressure continued to increase for a period of time after the end of pile jacking, and this could have resulted in significant inclination of piles if pile installation was too quick and pile spacing was too small. Lateral soil displacement due to pile group decreased with decreasing distance to the existing embankment as a result of higher soil stiffness and strength produced by the embankment loading. The effect of pile group installation on the existing embankment was negligible.

Bitumen, like many other organic substances, is affected by the presence of oxygen, ultraviolet radiation, and by changes in temperature. These external influences result in the phenomenon known as “aging” and cause changes in the chemical composition and therefore the rheological and mechanical properties of the bitumen. Aging is primarily associated with the loss of volatile components and oxidation of the bitumen during asphalt mixture production (short-term aging) and progressive oxidation of the in-place material in the field (long-term aging). Both factors cause an increase in viscosity (or stiffness) of the bitumen and consequential stiffening of the asphalt mixture. Aging at moderate levels is generally accepted and can even enhance performance, but at significant levels results in embrittlement of the bitumen, significantly affecting its adhesive characteristics and usually resulting in reduced cracking resistance of the asphalt mixture under repeated loading. It has long been recognized that the characteristics of bitumens are affected by the mineral aggregate with which they come into contact and that age hardening is influenced by both the bitumen and the mineral aggregate as reported by Bell and Sosnovske in 1994. This paper investigates the influence of aggregate type and aging procedure on the rheological and chemical fractional properties of aged bitumen. Asphalt mixtures comprising limestone or granite aggregate have been artificially aged in the laboratory and the rheological properties and chemical composition of the recovered bitumen from the mixtures determined after different durations of aging. In addition, the influence of bulk aging versus thin film aging has been assessed on the same bitumen aged in the presence of aggregate.