Abstract
Rubberised bitumen obtained through a swelling process, has widely proved to be a successful technology for asphalt pavement applications and a solution to reduce the dismantling of tyre rubber on landfills. However, this technology presents two main operative issues which need the adoption of costly special equipment. First, significant high value of high-temperature viscosity (HTV), which imposes mixing and compaction difficulties, leads to increased energy consumption and emissions. Furthermore, during the hot storage period, phase separation between rubber particles and the base bitumen could occur. Developing recycled tyre rubber-modified bitumen (RTR-MB) with improved storage stability and reduced values of HTV could allow using this technology in standard asphalt plants, resulting in an environmental-friendly and cost-effective option of standard polymer-modified bitumen. In this study, two different pre-treated and one straight ambient recycled rubbers were used to produce RTR-MB. The first RTR was pre-treated by special oil and warm-mix additives and the second was partly de-vulcanised. Also, two base binders were selected with large differences in mechanical properties in order to identify the effect of base binder. The HTV was successfully reduced by using pre-treated RTR. The use of RTR together with Fischer–Tropsch wax (Sasobit®) in bitumen technology offered superior high in-service temperature properties and reduced value of HTV, and thus can be the preferred option over styrene–butadiene–styrene modification.
Highlights
Incorporating Recycled Tyre Rubber (RTR) into flexible pavement applications by the means of wet process could solve a serious waste problem, save energy and materials, and enhance pavement life and performance
Manufacturing RTR-MBs The rubber percentage mass was kept constant for all RTR-MBs combinations, 18% by bitumen weight which is equal to 15.25% of total blend
The following gravimetric procedure was used to determine the RTRs that dissolved into the bitumen (Ghavibazoo and Abdelrahman 2013): 1. Approximately 3g of RTR-MB was transferred into an Erlenmeyer flask and the mass of the sample determined to the nearest 1 mg
Summary
Incorporating RTR into flexible pavement applications by the means of wet process could solve a serious waste problem, save energy and materials, and enhance pavement life and performance. The RTR-MBs were manufactured by utilising simple laboratory tools, Brookfield Viscometer with a modified impeller (Dual Helical Impeller DHI), see Figure 1 These tools allow to practical investigation many variables associated in manufacturing the RTR-MBs. The tools can precisely control the temperature, continuously monitor the viscosity measurements in real-time, keep the rubber uniformly distributed within the blend by creating a convective like flow, and consume as little as 10-15 g of material (Celauro et al 2012, Lo Presti et al 2014, Lo Presti & Airey 2013)
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