Rutting is one of the main issue in pavement engineering [1
]. Rutting, also referred to as permanent deformation is a common occurrence in the North West of Australia where pavement is subjected to higher trafficable loading from an increase usage of road trains under hot climatic conditions [2
]. The main cause for rutting is apparent when a binder becomes sensitive to stress at high temperatures due to the softness of the binder [3
]. Thus, it is important to investigate the temperature vulnerability of a binder in order to address rutting resistance [4
Polymer Modified Binder’s (PMBs) are a popular way to enhance the binder’s performance against both fatigue and rutting. The application of polymer-modified bitumen enhances the pavement’s service life length, especially in severe conditions such as parking areas tolerating heavy traffic loads, deformed road base, and stress-relieving interlayer. However, a modified binder is by no means a new phenomenon. It has been proven to meet the requirements for optimal performance in modern pavement construction and coatings; also, it appears to be a practical, logical, and economical approach compared to other approaches [3
Polymer modified bituminous mixture has an extensive choice of applications nowadays in most countries around the world. Adding polymer to the bituminous mixture increases its stiffness and improves its non-susceptibility to temperature fluctuations in different regions and climates. This feature, in turn, raises the level of resistance of the mixture to rutting. Additionally, it is believed that high polymer content in asphalt modification could provide more benefits in terms of improving the performance properties of pavement [5
]. In Western Australia, the polymer of choice commonly used is either SBS or crumb rubber where its elastomeric properties have been proven to enhance a binders resistance against fatigue [2
]. However, literature suggested that elastomeric polymers do not adequately rectify the temperature vulnerability of a binder compare to plastomer type polymers such as Ethylene-vinyl acetate (EVA) which is a popular choice to enhance resistance against rutting. However, it is good to be noted that polymers from virgin origins are expensive to produce and have its obvious negative impacts on the environment [6
Majority of Australia’s bitumen is sourced from international suppliers [11
], where over 80% is imported from East Asian markets [12
]. Several studies have indicated the loss of quality of bitumen from international markets in comparison with Australian manufactured bitumen [13
]. The loss of quality is primarily due to the reduction of the asphaltene content throughout the bituminous medium resulting in a lower viscous bitumen and hence a ‘softer’ bitumen [15
]. Therefore, one can say the reduction of quality has been a contributing factor to making the need to use PMBs inevitable.
AGPT/T190, The Australian PMB specification, consistency 6% at 60 °C is used for Elastometer test parameter, to rank the rutting resistance of a PMB. Although, the Elastometer parameter has been verified by several studies [1
], it is of the Authors opinion that the parameter will be limited at high service temperatures to measure and predict the temperature susceptibility of PMB. Recent developments with the U.S. Superpave specifications has recently adopted the Multiple Stress Creep Recovery (MSCR) test to evaluate a binder and grade its in-situ rutting performance [17
]. The MSCR test specification, listed as AASHTO M332, provides a high temperature binder specification that has been proven to assess the temperature susceptibility and hence the rutting resistance against the non-recoverable compliance parameter (Jnr
). Previous research has indicated that the Jnr
correlates better to in-situ rutting resistance in comparison to the Strategic Highway Research Program (SHRP) rutting parameter (G*/sin δ) [18
Alternatively, international studies have shown positive results to enhancing the performance of a binder that often matches if not improving the performance of virgin polymers [8
]. Costa et al. [9
] had highlighted positive results in using waste HDPE to modify a binder’s resistance against rutting. However, it is worth noting Costa et al. [9
] emphasized that HDPE modified binder caused with poor elastic recovery that may lead to potential cracking from fatigue failure. Research in Waste Polymer Modified Binder (WPMB) in Australia is limited, test work to validate the compatibility of using waste HDPE polymer is required prior to implementing in the road networks of Australia.
Most importantly using a waste polymer has environmental benefits [35
]. With the recent prohibition of export of plastic from China [36
], Australia’s recycling rate is on the decline where exports to China has previously accounted for roughly one-third of the total recycled plastics [37
]. Highlighting the quantity of plastic waste by polymer type, Statistics shows that HDPE is a dominant waste plastic, providing a substantial available resource as a WPMB [35
The previous research of WPMBs provided this test work the guidance selecting the polymer type and mixing requirements. Mixing requirements have been noted to be critical to the performance of a WPMB [32
]. In addition it was highlighted by Kalantar et al. [7
] that the mixing temperature and duration will depend on the type of polymer. A summary of the previous research that has undertaken waste HDPE polymer is listed Table 1
corresponding to the resulting outcome. It is worthy to note that previous research indicates improved performance from smaller particle size, long mixing duration, high mixing velocity at high temperatures.
As shown in the Table 1
, that there are different condition mix (time, temperature and rpm speed mix) due to the difference in the bitumen type and application of mixtures, as well as type of polymer. The studies in Table 1
indicated that the longer mix duration of 6 h results in poor dispersion, however, mixing time of 30–90 min could essentially provide modified binder with better rutting resistance.
The novelty of the current work is that using local WA plastic waste to improve the binder properties before and after aging. Also, the study focuses on filling the gap of knowledge related to rutting performance based on the modified binder characterises using bitumen grade C170. Most importantly that the study is novel in term of there is no current study has been conducted to improve the C170, which is primarily used for spray sealing applications, using waste HDPE. Using waste plastic has its visible environmental profits together with the reduction of cost for PMB application. On the other hand, it cannot be expected that waste HDPE plastic would be well-suited with bitumen modification in Australia without conducting laboratory afford investigating the rheological test and modified binder performance.