Differences in the Ageing Behavior of Asphalt Pavements with Porous and Stone Mastic Asphalt Mixtures

The degradation of bituminous materials as a result of ageing has a significant effect on asphalt pavement performance. In this study, one porous asphalt (PA) section and one stone mastic asphalt (SMA) asphalt pavement section were designed and constructed in 2014 and exposed to the actual environmental condition. To study the change in the pavement’s mechanical properties, asphalt cores were collected from both test sections annually. The change in stiffness modulus was determined via cyclic indirect tensile tests. To investigate the ageing behavior across the pavement depth, the bitumen was extracted and recovered from 13 mm slices along the depths of the cores. The chemical composition and rheological properties of the field-recovered bitumen, and that of original bitumen aged in standard short- and long-term ageing protocols, were investigated by means of the Fourier Transform Infrared (FTIR) spectrometer and Dynamic Shear Rheometer. The results show that the effect of mineral aggregate packing, and therefore of air-void distribution and connectivity, on the ageing sensitivity of the pavements with time was significant, as the changes in the stiffness of the PA mixture were greater than that of SMA mixture. In addition, the results of field-recovered bitumen show that there is an ageing gradient inside the porous asphalt layer, however, the ageing of SMA mainly happens on the surface of the layer. Finally, the field-recovered and laboratory-aged bitumen results demonstrate a weak relation between field and standard laboratory ageing protocols.

Photoacoustics for listening to Metal Nanoparticles Super-Aggregates

Photoacoustic detection signal has been used to build a new strategy to determine the mesoscale self-assembly of metal nanoparticles in terms of size distribution and aggregate packing density (metal nanoparticles...

Effect of Aggregate Packing on Strength of Reactive Powder Concrete: Modeling and Experimental Evaluation

This research investigates the effects of aggregate packing degree on the strength of Reactive Powder Concrete (RPC) mixtures on the basis of the Toufar model. To optimize the packing degree of sand for strength development of RPC, various sand blends with the combination of different fraction size were used. In addition, 10 different blends that showed best packing degree were chosen to investigate the compressive strength of RPC. It was found that experimental verification results conform to Toufar model calculations. The test result shows that packing degree had a significant effect on the strength of RPC: Mixtures with higher packing degree can achieve higher compressive strength. Furthermore, Results indicate the Toufar model can predict packing degree of aggregate blends.