## 4 Performance of Waste-Plastic-Modified Bitumen Binder and Mixture
### Characteristics of Plastic-Modified Bituminous Mixtures
#### 4.2.1 Mechanical and Durability Performance  
Recent research presented a chemically recycled PET additive synthesized using aminolysis, which considerably enhanced rutting resistance, moisture resistance, and low-temperature cracking performance, particularly at a 2% dose. Nonetheless, the optimal dynamic creep resistance was seen at a 1% additive concentration, suggesting that the optimal dosage may vary with performance criteria [50]. The results were statistically \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**References**} & **Plastic** & **Dosage** & **Particle** & **Mixing** & **Shear** & **Key** & **Compatibility/** \\  & **Type** & **(wt\%)** & **Size** & **Temp (\({}^{\circ}\)C)** & **Rate/Time** & **Impacts** & **Aging** \\ \hline \hline \multirow{4}{*}{[39; 41]} & \multirow{4}{*}{LDPE} & Up to 5\% & \multirow{4}{*}{\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{160–180} & \(\uparrow\) Softening point (57–68.5 \({}^{\circ}\)C), \(\downarrow\) penetration (up to 63\%), \(\uparrow\) viscosity, \(\downarrow\) penetration (up to 63\%), \(\uparrow\) viscosity, \(\downarrow\) particle size and dosage \\  & & & & & \\ \cline{1-1}  & & & & & & \\ \cline{1-1}  & & & & & & \\ \cline{1-1}  & & & & & & \\ \hline \hline \multirow{4}{*}{[39]} & \multirow{4}{*}{HDPE} & Up to 5\% & \multirow{4}{*}{\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{160–180} & \(\uparrow\) Softening point (51–79 \({}^{\circ}\)C), \(\downarrow\) penetration (up to 63\%), \(\uparrow\) viscosity, \(\downarrow\) particle size and dosage \\  & & & & & & \\ \cline{1-1}  & & & & & & \\ \cline{1-1}  & & & & & & \\ \hline \hline \multirow{4}{*}{[41]} & \multirow{4}{*}{\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{Not} & Not specified & \multirow{4}{*}{170} & \(\uparrow\) G\({}^{\star}\)/sin\(\delta\), \(\uparrow\) stiffness, \(\uparrow\) compatibility (500 rpm/ 60 min & Elevated 60 min & Elevated 60 min & Elevated 60 min & Elevated 60 min \\  & & & & & & \\ \cline{1-1}  & & & & & & \\ \cline{1-1}  & & & & & & \\ \hline \hline \multirow{4}{*}{[40]} & \multirow{4}{*}{\
\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{
\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{170} & \(\uparrow\) & Optimized low-temp (500 rpm/ 60 min & Effective 60 symergistic \\  & & & & & & \\ \cline{1-1}  & & & & & & \\ \cline{1-1}  & & & & & & \\ \cline{1-1}  & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Performance of plastic-modified bitumen binder (note: percentages represent plastic dosage by weight relative to the base binder unless otherwise specified). validated by Analysis of Variance (ANOVA) [50]. Recent findings from Balanced Mix Design (BMD) experiments indicate that the addition of 0.25-1.0% LDPE or LLDPE by weight of aggregate enhances rutting resistance and cracking performance relative to control mixes. LLDPE exhibited superior cracking tolerance (CTIndex), although LDPE had enhanced moisture resistance [51]. Longer (18 mm), rough-surfaced PET fibres significantly enhanced the cracking resistance and hardness of asphalt mixtures at both ambient and sub-zero temperatures, as assessed by the Semi-Circular Bending (SCB) test. The advantages became more apparent as the loading rate of the SCB test was reduced, indicating the necessity for protocol enhancement in evaluating crack performance [52]. Field trial evidence confirms this, as illustrated in Ontario, Canada, where PET fibres utilized in cold climates exhibited enhanced low-temperature crack resistance compared to mixed plastics [53]. Ref. [54] assessed dry-processed plastic and rubber-modified composites subjected to ageing and moisture conditioning. Short-term ageing enhanced tensile strength and stiffness in all mixtures; however, long-term ageing produced an uneven effect benefiting plastic-modified asphalt but degrading the properties of rubberized mixtures.