Value-Added Use of Waste PET in Rubberized Asphalt Materials for Sustainable Pavement

Waste poly(ethylene terephthalate) (PET) drinking bottles and end-of-life scrap rubber tires are common municipal solid wastes discarded and produced every day, which are usually disposed of in landfills and stockpiles, occupying a great quantity of land and causing serious environmental issues. This study aims to first turn waste PET into two value-added derived additives under the chemical treatment of two amines, namely triethylenetetramine (TETA) and ethanolamine (EA), respectively, and then adopt them in association with crumb rubber (CR) to modify virgin bitumen for preparing various rubberized asphalt mixtures. Subsequently, the high- and low-temperature properties of the rubberized binder modified by PET additives (PET-TETA and PET-EA) were comparatively characterized through dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests, while the rutting resistance, fatigue resistance, and dynamic modulus of the further fabricated mixtures were evaluated and validated through mixture tests. The results obtained indicate that 2 wt.% PET-TETA and PET-EA contribute to increase the rutting failure temperature of asphalt rubber from 82.2 °C to 85.5 °C and 84.2 °C, respectively, retaining the high grade of PG 82; the low-temperature grade of asphalt rubber slightly decreased from PG-28 to PG-22 as the additive was added; the rut depth slightly changed from 3.10 mm to nearly 3.70 mm; and PET-TETA exhibits the potential to be capable of extending the fatigue life of asphalt rubber in contrast with PET-EA at different stress levels within 450 kPa. Based on the findings of this study, the developed recycling approach is considered to be applicable to not only alleviate the environmental concerns caused by the landfills and stockpiles of those wastes but also make them valuable for building more durable pavement.

Application of Acoustic Emissions Technique in Assessment of Cracking Performance of Asphalt Pavement Materials

This chapter focuses on various applications of acoustic emissions (AE) technique in evaluation of cracking in asphalt pavements including (1) assessment of low-temperature cracking of asphalt binders and mixtures and (2) quantitative characterization of rejuvenators’ efficiency in restoring aged asphalt pavements to their crack-resistant state. The AE-based embrittlement temperature results of 24 different asphalt materials consisting of eight different binders, each at three oxidative aging levels are presented. Results show that embrittlement temperatures correlated well with corresponding bending beam rheometer (BBR-based) critical cracking temperatures with R2 = 0.85. This chapter also presents application of AE for evaluation of rejuvenators’ efficiency on asphalt materials at various oxidative aging levels. The Geiger’s iterative source location method was employed to accurately determine embrittlement temperatures throughout the thickness of rejuvenator-treated asphalt samples. Results showed that the low temperature cracking properties of oxidative aged materials after 2 weeks of dwell time of rejuvenator have been recuperated. Moreover, it was observed that cracking characteristics of aged asphalt 6–8 weeks after applying rejuvenator far exceeded that of the virgin materials. The promising results suggest that the AE technique can be considered as a viable approach for the assessment of low temperature behavior of asphalt pavements.

Determining the Environmental Potentials of Urban Pavements by Applying the Cradle-to-Cradle LCA Approach for a Road Network of a Midscale German City

This study used a cradle-to-cradle Life Cycle Assessment (LCA) approach to evaluate the environmental potentials of urban pavements. For this purpose, the urban road network of the City of Münster (Germany) was selected as the case study, and comprehensive data for several phases were collected. The entire road network is composed of flexible pavements designed according to specific traffic loads and consists of main roads (MRs), main access roads (MARs), and residential roads (RSDTs). Asphalt materials, pavement structures, and maintenance strategies are predefined for each type of road and are referred to as “traditional” herein. Some pavement structures have two possible maintenance strategies, denoted by “A” and “B”, with distinguished periods of intervention. To evaluate the impact of using recycled materials, we considered alternative pavement structures composed of asphalt materials containing a greater amount of reclaimed asphalt pavement (RAP). The study was carried out considering analysis periods of 20, 50, 80, and 100 years and using two indicators: non-renewable cumulative energy demand (nr-CED) and global warming potential (GWP). The results show that the use of higher amounts of RAP can mitigate negative environmental impacts and that certain structures and maintenance strategies potentially enhance the environmental performance of road pavements. This article suggests initiatives that will facilitate the decision-making process of city administrators to achieve more sustainable road pavement constructions and provides an essential dataset inventory to support future environmental assessment studies, particularly for European cities.