# A Review of Nanomaterials' Effect on Mechanical Performance and Aging of Asphal Mixtures
## 3 Effect of the Modification with Nanomaterials in the Asphalt Binder  
Some studies about the use of nanomaterials in asphalt binders have already been done, with special attention to nanosilica and nanoclays. Regarding the effects of the modification with nanomaterials in the properties of the asphalt binder, few recent reviews address this topic. [PERSON] et al. [5] presented a review about the asphalt binder modification covering several types of modifiers, such as, polymers, chemical modifiers (including nanocomposite modifiers), and warm mix technology. The review of [PERSON] and [PERSON] [51] focused on the use of nanoclays. [PERSON] et al. [52] presented a review covering a wide range of nanomaterials, such as, nanocarbon, nanoclay, nanofiber, nanosilica, and nanottanium. [PERSON] and [PERSON] [76] presented a state-of-the-art about the use of carbon and graphene family nanomaterials in asphalt modification. The following paragraphs present a brief description of the effects of the modifications with nanomaterials in the properties of the asphalt binder, as well as, some additional details found in literature. In brief, the nanosilica-modified binder presented a decrease in penetration, increase in viscosity, and increase in softening point [10; 18; 25; 27; 77; 78]. Regarding the rheological behavior, evaluated using the dynamic shear rheometer (DSR), the modified binders present higher complex modulus and lower phase angle [18; 64; 77; 79]. Authors evaluating the binder fatigue with DSR tests, concluded that the nanosilica modifications showed superior fatigue resistance [80; 81; 22]. At the level of fundamental characterization, the nanoclay-modified binder presented a decrease in penetration, increase in softening point, and increase in viscosity [10; 25; 27; 79; 35; 39; 41; 55; 79; 82; 83; 84; 85; 86; 87; 88; 89]. And consistently, regarding rheology, the nanoclay modified binders present an increase in complex shear modulus and decrease in phase angle [34; 38; 41; 42; 55; 86; 87; 90]. The existing studies mostly focused on organically modified montmorillonite, due to the expectation of obtaining exfoliated structures in the modified binders and higher performance improvements. The raw nanoclays, in their hydrophilic natural form, may form only intercalated structures, although, some authors studying raw nanoclays [38; 41; 42; 91; 92] also obtained considerable performance improvements. The type of nanoclay used in the modification has an important effect in results, i.e., in the modified binder performance. Although the overall trends were the same, the authors that studied more than one nanoclay type obtained different results, regardless of using the same control binder. A study [41] about the modification of 60/70 asphalt binder with nanoclays, sodium bentonite (BT) and organically modified sodium bentonite (OBT), revealed that both modifications caused reduction of the phase angle and increased viscosity, softening point, and complex shear modulus. The effects were correlated with the dosage of nanoclay introduced and, in all cases, the effects of the organically modified clay were stronger. The exfoliated structure of the organically modified nanoclay, that promotes a better dispersion in the asphalt matrix, can explain these effects. On the other hand, in another study [55], the authors studied the modification of a PG 64-28 with two organically modified nanoclays with similar structure (nanoclay A and nanoclay B) and observed different effects. For example, regarding viscosity, the modifications caused an increase of 41% and 112% with 2% of nanoclay A and 2% of nanoclay B, respectively, and regarding complex shear modulus, the modifications caused an increase of 66% and 184% with 2% of nanoclay A and 2% of nanoclay B, respectively. [PERSON] and [PERSON] [34] studied the effects of two organically modified nanoclays (Nanofil-15 and Cloisite-15A) on the properties of the 60/70 asphalt binder and, found the effects of the second stronger than those of the first.