Deriving and Characterising Alternative Bitumen from Waste Plastics

This study presents research on laboratory production and experimental characterisation of an alternative bitumen using municipal waste plastics. Six different waste plastics (A1 - A6) produced by a local waste recycling manufacturers were selected and characterised to investigate their feasibility in modifying the bitumen binders. Thermal characteristics were firstly obtained using Differential Scanning Calorimetry (DSC) device and the chemical functional groups were identified by Fourier Transform Infrared Spectroscopy (FT-IR) test to determine the plastic types existing in the recycled plastics. Then the rheological properties of the bitumen modified with two nominated plastic waste (A1 and A2) were examined using the Dynamic Shear Rheometer (DSR) device by conducting frequency sweep tests. Additionally, the engineering performance of waste plastics-derived bitumen was also obtained and compared against the control bitumen, including fatigue, rutting and healing performance using Time Sweep (TS) test, Multiple Stress Creep and Recovery (MSCR) test and Healing test, respectively. Results show that A1and A2 consist of low-density polyethene (LDPE) and polypropylene (PP), respectively. The recycled waste plastic A5 and A6 (both classified under the same category but collected from different plants and batches) are mainly consisting of LDPE. Whereas, other recycled plastics (A3 and A4) consist of a variety of materials and impurities. Thus, A1 and A2 were chosen as bitumen binder extenders. A1-modified bitumen exhibited more elastic and less viscous behaviour than the control bitumen, showed by increased shear modulus and reduced phase angle. Whereas, A2 (consisting of PP) caused a significant drop in the shear modulus. Both recycled LDPE and PP-modified bitumen had a substantially improved resistance to rutting and fatigue cracking compared to the control bitumen. Furthermore, waste LDPE-modified bitumen sustained increased healing potential compared to waste PP-modified bitumen, where the latter did not show noticeable improvement to the healing performance

Pyrolysis of polyolefin plastic waste and potential applications in asphalt road construction: A technical review

Pressures on the current plastic waste management infrastructure has made the growth of new sustainable recycling capacities crucial. Pyrolysis is an emerging thermochemical technology that may be utilised at a large scale to aid in reaching the EU 2030 targets for plastic waste. Plastic valorisation via this process could gain increased competitiveness with conventional methods through the use of concepts such as ‘Design for Recycling’, identifying further marketable applications for pyrolysis end co-products. This paper presents a review on the pyrolysis of the most abundant plastic waste polyolefins, low-density polyethylene (LDPE), high-density polyethylene (HDPE) and polypropylene (PP), with a focus on the heavy wax products. A sizeable research gap in its known applications outside of the petrochemical and chemical feedstock industries was identified. Furthermore, its potential use in the hot mix asphalt (HMA) layers of flexible roads as an alternative binder material and aggregate is discussed. A plastic-derived bitumen modifier could be a viable solution to the current limitations associated with plastic bitumen modifiers (PMB), while producing asphalt with enhanced rheological properties and failure resistances. Consequently, future trends in research may include obtaining a full understanding of the capacity for pyrolysis products from waste polyolefins in bitumen modification. The key relationships between pyrolysis process parameters and the subsequent product properties, modification mechanisms and binder performance may also be explored. This application pairing process for pyrolysis products from plastic wastes may also be more extensively adopted in sustainable infrastructure, as well as other industries

A fundamental study into wet process modification of paving binders and mixtures by crumb rubber from used tyres

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Mechanical and healing properties of asphalt mixes reinforced with different types of waste and commercial metal particles

Improper disposal of metal waste in landfills is one of the primary means by which metals, mainly produced in different industrial sectors, reach the soil and ground water. These can migrate to surrounding ecosystems and bio-magnify in plants and animals endangering human food chain. At the same time, the addition of metal particles in asphalt mixes produces a series of beneficial effects, such as enhancing their mechanical performance, durability and electrical conductivity making possible applications, such as ice/snow melting and cracks healing by electromagnetic induction. The present investigation assesses and compares the use of two different types of waste metal fibres (recovered from old tyres and shavings from machining industry) and two other types of commercial particles (steel wool and steel grit) regarding their effect on volumetric, mechanical and healing properties of asphalt mixes. Results showed that, with a proper design, the improvement in such properties by using waste metals is comparable to that obtained by using commercial particles. It was also found that fibres from old tyres are especially suitable for low structural layers (base and sub-base), while the use of metal shavings is particularly recommendable in superficial course layers

Investigation of high-density polyethylene pyrolyzed wax for asphalt binder modification: Mechanism, thermal properties, and ageing performance

The thermal pyrolysis of high-density polyethylene in a fixed bed reactor has been studied in the temperature range of 450–550 °C with two different nitrogen carrier gas flowrates, 2 and 4nullLnullmin−1, to study the effect of these process parameters as well as the resultant vapour residence times on the formation of wax and its chemical and thermal properties. The technology had a high selectivity to waxes, with a yield of up to 91.87% wax from high-density polyethylene at 500 °C using a nitrogen carrier gas flowrate of 4nullLnullmin−1 and subsequent 1.76 second vapour residence time, calculated using the ideal gas law. The waxes were characterised using techniques including gas-chromatography-mass spectroscopy (GC-MS), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The process operating temperature especially and its subsequent effect on vapour residence times within the reactor had a considerable impact on both the chemical and thermal properties of the waxes. Higher operating temperatures yielded more olefinic waxes due to the promotion of degradation radical mechanisms such as β-scission. They were observed to have higher melting points and thermal stability. An investigation was conducted to assess the thermal properties and ageing performance of the waxes. Thermal conditioning in an ashing oven at 170 °C for 0–6 hours was conducted with a detailed analysis of GC-MS and FTIR at each stage of thermal exposure to further support thermal characterisation results. The changes in chemical composition were attributed mainly to oxidation and polymerization ageing reactions and were seen to be more prominent in the more unsaturated waxes produced at higher pyrolysis temperatures. The wax produced at 550 °C was determined the optimal wax for binder modification in hot-mix asphalt pavement design due to lower volatile/mass loss. A lower temperature range was suggested for optimal blending conditions to further reduce loss of volatiles with initial blending and storage