Utilization of Pyrolized Carbon Black from Waste Tire in Asphalt Concrete
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Waste tire considered as a serious environmental solid waste problem worldwide. However, this type of waste tire cannot be treated in a landfill nor burned in the atmosphere, because it releases toxic gases. Accordingly several methods have been proposed for waste tire treatment. Among these methods waste tire pyrolysis is considered the most favorable. Pyrolysis is a process of converting waste tire into gases, fuel oil, steel and a by-product, which is pyrolized carbon black (PCB). However, gas and oil can be sold out in local market as well as steel, while PCB that contains 30-35 wt% of the waste tire product becomes another solid waste problem. In this project we aimed at employing PCB in asphalt concrete used in road pavement. Accordingly, a PCB sample was obtained from a local pyrolized waste tire plant; this was used as received without any chemical purification. The following variables were tested to investigate the effect of adding PCB to asphalt concrete, namely: PCB concentration, PCB particle size and PCB as a replacement to asphalt filler in different percentage. The effectiveness of the aforementioned variable was tested using Marshall test following the ASTM method. Further, the same variables were tested on the virgin bitumen matrix to investigate their impact on the softening point, flash and fire points, penetration and ductility. For asphalt concrete, results showed an increase in the stability and stiffness values by decreasing PCB particle size and increasing both PCB concentration and filler percentage until reach the optimum value then it behaves negatively. Furthermore, the impacts of PCB concentration, PCB particle size and PCB as filler on the flow test have values within the standard, while the effects of these variables were insignificant for the specific gravity. Also air voids increase with the increase of PCB particle sizes and decrease of its concentration, until reach the optimum value. As for the virgin bitumen matrix, the effect of PCB concentration are sufficient in the flash and fire point, softening point and penetration, while it is insignificant for the ductility. Increasing the PCB particle size resulted in a positive influence on penetration and softening point, while it has a negative effect for both the ductility, flash and fire points, but for the latter it was still in the standard range. These results showed that PCB could be employed successfully in enhancing the asphalt concrete, which resulted in an environmentally friendly, waste tire pyrolysis process as well as improving its economical value.