# A Review of Nanomaterials' Effect on Mechanical Performance and Aging of Asphal Mixtures
## Nanomaterials
### Modification of the Asphalt Binder with Nanomaterials  
In the majority of the studies found in literature, the modification of asphalt mixtures with nanomaterials is initially done at the binder level, i.e., the asphalt binder is modified with the nanomaterials, and then, the modified binder is used to produce the asphalt mixture. The optimum dosage of nanomaterial in the asphalt binder will be dependent on the type of nanomaterial, type of asphalt binder, and the methodology used, i.e., type of testing selected. Generally, the nanomaterials \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Designation** & **Type** & **Modifier** &
\begin{tabular}{c} **Bulk Density** \\ **(g/cm\({}^{3}\))** \\ \end{tabular} & **Reference** \\ \hline \multirow{2}{*}{Cloisite-15A} & \multirow{2}{*}{Organophilic} & Methyl, tallow, & \multirow{2}{*}{0.230} & \multirow{2}{*}{[34]} \\  & & bis-2-hydroxyethyl, & & \\  & & quaternary ammonium & & \\ \hline \multirow{2}{*}{Nanofil-15} & \multirow{2}{*}{Organophilic} & Nanodispers layered silicate, & \multirow{2}{*}{0.190} & \multirow{2}{*}{[34]} \\  & & long chain hydrocarbon & & \\ \hline \multirow{2}{*}{Organophilic} & \multirow{2}{*}{Organophilic} & dimethyl ammonium with & \multirow{2}{*}{–} & \multirow{2}{*}{[35]} \\  & & two alkyl chains & & \\ \hline \multirow{2}{*}{Bentonite} & \multirow{2}{*}{Hydrophilic} & – & – & [36; 37] \\ \hline \multirow{2}{*}{NMN} & \multirow{2}{*}{Hydrophilic} & – & 0.678 & [38] \\ \hline \multirow{2}{*}{PMN} & \multirow{2}{*}{Organophilic} & Polysiloxane & 0.251 & [38] \\ \hline \multirow{2}{*}{Cloisite 15A} & \multirow{2}{*}{Organophilic} & Quaternary ammonium salt & – & [39] \\ \hline \multirow{2}{*}{Nanoclay A} & \multirow{2}{*}{Organophilic} & Na-activated; Dimethyl, & \multirow{2}{*}{–} & \multirow{2}{*}{[40]} \\  & & dehydrogenated tallow, & & \\  & & quaternary ammonium & & \\ \hline \multirow{2}{*}{Nanoclay B} & \multirow{2}{*}{Organophilic} & Na-activated; Methyl, tallow, & \multirow{2}{*}{–} & \multirow{2}{*}{[40]} \\  & & bis-2-hydroxyethyl, & & \\  & & quaternary ammonium & & \\ \hline \multirow{2}{*}{Nanoclay C} & \multirow{2}{*}{Organophilic} & Dimethyl, benzyl, & \multirow{2}{*}{–} & \multirow{2}{*}{[40]} \\  & & Na-activated; hydrogenated & & \\  & & tallow, quaternary ammonium & & \\ \hline \multirow{2}{*}{BT} & \multirow{2}{*}{Hydrophilic} & – & – & [41; 42] \\ \hline \multirow{2}{*}{OBT} & \multirow{2}{*}{Organophilic} & octadecylammonium salt & – & [41; 42] \\ \hline \multirow{2}{*}{Nanoclay} & \multirow{2}{*}{Organophilic} & Polysiloxane & 0.251 & [43] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Properties of nanoclay used by several authors. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type** & **Particle Size (nm)** & **Specific Surface Area (m\({}^{2}\)/g)** & **Purity (\%)** & **Reference** \\ \hline Fe & 50 & 25 & \(>\)80 & [36] \\ Fe\({}_{2}\)O\({}_{3}\) & 38 & – & – & [49] \\ Fe\({}_{2}\)O\({}_{3}\) & 20–40 & 40–60 & \(>\)98 & [50] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Properties of nanoiron used by several authors. are blended with asphalt binder in small percentages, around 2 to 6% by mass of asphalt binder [51]. In some cases, besides the nanomaterial, a polymer modification is also done, or the binder being modified is a polymer-modified binder (PMB). Generally, for the modification of the asphalt binder with nanomaterials in laboratory one out of two methods is used: The dry blending method or the solvent blending method [52; 53; 54; 55]. A recent review addresses more in depth the details of the polymer modification with nanoclay [56; 57]. The dry blending method consists of the use of high-speed stirring to disperse the nanomaterials in the asphalt binder matrix. In this method the asphalt binder is previously heated above the softening point temperature, generally, up to a temperature equal or near to the recommended asphalt mixture mixing temperature, the nanomaterial is added, and a shear mixing effect is applied for a specific time period.