## 5 Effect of RAS on Performance Properties of Asphalt Binders and Mixtures  
Overall, RAS addition to asphalt binders or asphalt mixtures generally increases the stiffness and strength of bituminous materials. As a result, RAS-modified flexible pavements perform relatively better in warmer regions. However, RAS-modified mixtures can be characterized by relatively low fatigue and thermal cracking resistance due to reduced ductility. In this regard, the addition of some recycling agents or specific additives can improve the cracking resistance [24; 33; 34]. In this section, the effects of RAS (either on asphalt binders or asphalt mixtures) on high-/low-temperature resistance, fatigue, and moisture susceptibility are summarized from existing research studies. The main findings related to RAS-modified asphalt blends are summarized in Tables 1 and 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Reference** & **RAS Type and** & **RAS Mixing Details** & **RAS Dosage (\% by** & **Mixing Method** & **Asphalt Mixture Type** \\ \hline
[1] & TOSS \(\leq\) 12.5 mm & N/G & 5, 6\% by aggregate & N/G & HMA \\ \hline
[8] & TOSS extracted binder &
\begin{tabular}{c} Mixing at 3600 rpm \\ for 30 min \\ \end{tabular} & 5\% by binder & Wet & Binder only \\ \hline
[11] & TOSS \(<\) 12.5 mm & N/G &
\begin{tabular}{c} 4\% only by aggregate \\ (aggregate replacement) \\ \end{tabular} & Dry & WMA, HMA \\ \hline
[12] & TOSS binder & N/G & N/G & Wet & Binder only \\ \hline
[13] & TOSS \(<\) 9.5 mm & N/G & \
\begin{tabular}{c} 2.5, 5, 7.5, 10, 12.5\% by \\ mixture \\ \end{tabular} & Dry &
\begin{tabular}{c} HMA \\ WMA \\ \end{tabular} \\ \hline
[14] & TOSS \(<\) 13 mm & N/G &
\begin{tabular}{c} 1, 2, 3, 4, 5, 6\% by aggregate \\ weight \\ \end{tabular} & Dry & HMA \\ \hline
[15] & TOSS \(<\) 12.5 mm & N/G & N/G & N/G & HMA \\ \hline
[16] & MWSS, TOSS binder & N/G & 15, 30, 100\% by binder & Wet & Binder only \\ \hline
[17] & TOSS 70\% \(<\) 1 mm &
\begin{tabular}{c} Mixing at 750 rpm, \\ 30 min, 135 \({}^{\circ}\)C to \\ obtain BMAS \\ \end{tabular} & 5, 15, 30, 40\% by binder & Wet & Binder only \\ \hline
[18] & TOSS \(<\) 0.075 mm &
\begin{tabular}{c} Mixing 30 min at \\ 180–200 \({}^{\circ}\)C \\ \end{tabular} & N/G & Both & HMA \\ \hline
[19] & TOSS binder & N/G & 5\% by binder & Wet & Binder only \\ \hline
[20] & TOSS binder & N/G & 20\% by binder & Wet & HMA, WMA \\ \hline
[30] & TOSS \(<\) 9.5 mm &
\begin{tabular}{c} Mixing at 180 \({}^{\circ}\)C, \\ 1 h, 450 rpm \\ \end{tabular} & 5, 15, 30, and 40\% by binder & Wet & Binder only \\ \hline
[31] & MWSS, TOSS \(<\) 9 mm &
\begin{tabular}{c} Mixed with binder \\ (1.5-2 h) \\ \end{tabular} & 0.6–1.5\% by mix & Wet & HMA \\ \hline
[24] & MWSS and TOSS & \
\begin{tabular}{c} Virgin and extracted \\ bindered for \\ 7 min \\ \end{tabular} &
\begin{tabular}{c} 5, 10, 15, 30, 45, 60, 80, 100\% \\ by binder \\ \end{tabular} & Wet & Binder only \\ \hline
[32] & TOSS \(\leq\) 2.36 mm &
\begin{tabular}{c} 5 min mixing with \\ aggregate before \\ adding binder \\ \end{tabular} & 5\% by mix & Dry & WMA \\ \hline
[34] & MWSS and TOSS &
\begin{tabular}{c} N/G \\ extracted binder \\ \end{tabular} & 5, 10, 15, 20\% by binder & Wet & Binder only \\ \hline
[35] & MWSS \(<\) 12.5 mm & N/G & 3, 5, 7, 10\% of total mix & Dry & HMA \\ \hline
[36] & RAS \(<\) 12.5 mm & N/G & 3, 5\% by aggregate & Dry & HMA \\ \hline
[37] & MWSS and TOSS Both & N/G & 3, 5\% by binder & Dry & HMA \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Previous research studies on RAS-modified asphalt materials: summary of methods and experimental conditions.