Assessment of Leather Solid Waste as Partial Replacement of Asphalt Binder

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Addis Ababa University


Asphalt binder is considered as the most expensive part of hot mix asphalt pavement material. Leather industry has been categorized as one of highly polluting industries and it has adverse impact on environment because of its generation of liquid, solid and gaseous wastes. Solid wastes generated from tanning industries contain different chemicals which are used during leather manufacturing process. Chrome Buffing Dust (CBD) is a solid waste generated during leather making process at the finishing operation. This research study evaluated partial replacement of asphalt binder with CBD. It compares neat asphalt binder and asphalt binder mixed with CBD using laboratory tests including conventional (penetration, softening point and ductility) and rheological tests (Amplitude Sweep Test, Frequency Sweep Test, Performance Grading and Multiple Stress Creep and Recovery Tests). Six asphalt binders were obtained by mixing the asphalt binder (penetration grade 60/70) with five different percentages of CBD by weight of asphalt binder (2%, 4%, 6%, 8% and 10%). The conventional test results of asphalt binder mixed with CBD revealed better performance improvement. In general, as percentage of CBD increases penetration decreases and softening point increases, while ductility property showed dramatic decrease as CBD percentage increases. Rheological asphalt binder tests were conducted using a Dynamic Shear Rheometer (DSR). Four rheological tests were conducted namely Amplitude Sweep Test (AST), Frequency Sweep Test (FST), Performance Grade (PG) test and Multiple Stress Creep and Recovery (MSCR) Test. The AST was conducted to determine the Linear Viscoelastic (LVE) Range, FST was conducted to construct the master curve and the MSCR test was conducted to determine the rut parameter called non-recoverable creep compliance (Jnr). The AST and FST were conducted at three temperatures (21.1°C, 37.8°C, and 54.4°C) while the MSCR tests were conducted at three temperatures (52°C, 58°C and 64°C). Performance Grade (PG) tests were also conducted at higher temperatures. From FST tests, CBD affected the property of asphalt binder at higher temperature ranges in improving its potential for resistance of permanent deformation. From MSCR test result analysis, addition of CBD has resulted in better improvement on the rut resistance (decrease in Jnr value up to 30%) of asphalt binders. In conclusion, partial replacement of asphalt binder with CBD improves the stiffness and rut resisting performance of asphalt binders at high temperature ranges. Overall, the research shows promising results that it is feasible to partially replace asphalt binder with CBD up to 6%.



Asphalt Binder, Rheology, CBD, Stiffness, Rutting