Environmental assessment of asphalt mastics containing plastic bottles and jet grouting waste

Apart from the pressing problems of global warming due to outputs of atmospheric gases, the global society is increasingly troubled by the tasks of managing solid waste. In this regard, innovative solutions have been advanced for the reuse of solid waste in non-traditional sectors, including in road asphalt production. The present study investigates the potential production of sustainable superior-performing asphalt mastics (neat bitumen and filler), in which the filler is obtained through procedures of reusing shredded waste plastic (WP) and jet grouting waste (JGW) recovered from soil consolidation activities, rather than traditional limestone filler. A first phase of the study involved the production and the comparison of three asphalt mastics: a mastic containing JGW (JGWM) with a filler over bitumen ratio (f/b) of 0.29, a limestone mastic (LM) blended with an f/b ratio of 0.30 and a mastic containing WP (WPM) made up with an f/b ratio of 0.10. The mechanical characterization was carried out by use of a dynamic shear rheometer for analysis of the rheological performance of the three mastics in terms of rigidity, elasticity and resistance to permanent deformation. A life cycle assessment was conducted using the eighteen impact category indicators of the ReCiPe method, as a means of determining the human and environmental benefits of the innovative hot asphalt mastics. The main results from the mechanical point of view were that, compared to traditional LM: a) at temperatures from 0 to 30 °C, the use of JGW achieved an average 30% greater stiffness; b) at 40 and 50 °C, the WPM reduced permanent deformation by 56%. The most significant outcomes of the environmental analysis were: a) the use of JGWM achieved lower terrestrial ecotoxicity and freshwater eutrophication, respectively 53% and up to 97% less than with LM; b) the WPM achieved 33% and 38% reductions in effects on global warming and fossil resource scarcity, respectively.