This paper presents the results of an experimental research on the effects of “Fischer Tropsch-Paraffin” (Sasobit) content on physical and rheological properties of Sasobit modified bitumen at various operational temperatures. For this purpose, bitumen with a Performance Grade (PG) of 58–22 is selected as the base and later it is modified with 1, 2, 2.5, 3, and 4 weight percent of FT-Paraffin (Sasobit). The performance of modified bitumen at high, intermediate, and low temperatures is evaluated based on Strategic Highway Research Program (SHRP) Superpave tests. Results of the study show that FT-paraffin improves the performance of bitumen at high temperatures in addition to increasing the resistance of mixture against permanent deformation. Despite the advantages of FT-paraffin on bitumen performance at high temperatures, it does not show a considerable influence on the intermediate and low temperature performance of bitumen. The effect of FT-paraffin content on the viscosity of modified bitumen is also investigated using Brookfield Viscometer Apparatus. Results show that increasing the additive content lowers the viscosity of modified bitumen. This in return can reduce the mixing and compaction temperature of asphalt mixtures.

No abstract

The purpose of this study is to evaluate and compare the properties of control and modified asphalt mixtures. Two polymers such as styrene butadiene styrene (SBS) and ethylene vinyl acetate (EVA) were used as modifiers, and mixes with different percentages of polymers were prepared by mixing with 60/70 penetration grade unmodified bitumen. Marshall samples were prepared using the modified and unmodified binders and the effect of SBS and EVA on the mechanical properties of the hot mix asphalt has been determined in terms of stability, flow, indirect tensile strength, and rutting resistance. Test results indicated that the polymer modification improved the conventional properties such as penetration, softening point, and temperature susceptibility. It was also conducted that the stability values related to SBS modified specimens increased with an increase in SBS content compared to the control specimens. While, the stability values for EVA modified specimens are smaller than the stability values of the control specimens. Finally, it was observed that the rutting resistance of the modified mixtures for both of polymer modified binders were higher than the control mixtures

Increasing the etching rate is one of the main optimization targets in the chemical machining (CM). Traditionally, this target is fulfilled by some costly techniques like selecting stronger etchants and increasing the etchant concentration. Also, other methods like increasing the etchant temperature and stirring the etchants by agitators are employed for increasing the etching rate.One of the advantages of these methods is reduction of the consumption of acidic etchants which results in the cost reduction and making an eco-friendley process.In this article, a systematic experimental study is performed on vibration-assisted CM of copper. In this technique, the workpiece vibrates in the etchant during the CM. For evaluating the performance of machining, effects of amplitude and frequency of vibrations, along with the temperature and concentration of acidic etchant, on material removal rate, surface roughness and machining undercut are studied experimentally. The experiments are designed by Central Composite Design (CCD) in Response Surface Methodology (RSM). Also, multi-objective optimization is performed by defining a desirability function. The optimal vibroassisted process parameters are temperature 60 ̊C, etchant concentration 600 g/l, vibration frequency 25 Hz, and vibration amplitude 1.5 mm, to get optimal outputs on the desired parameters.