# A Review of Nanomaterials' Effect on Mechanical Performance and Aging of Asphal Mixtures
## 6 Cost Evaluation  
Asphalt pavement construction deals with large quantities of materials, in the range of tons, contrasting with the nanotechnology that syntheizes and manipulates few grams of a specific material. As the production of nanomaterials is oriented to deliver small quantities of highly controlled materials, i.e., purity levels \(\geq\)98%, the cost of these materials is relatively high compared to traditional paving materials. The costs are justified by the use of expensive equipment and technology involved, as well as, the fact that nanomaterials production is generally conducted by highly qualified personal. However, this cost has been decreasing over time and, the trend is for further decrease, pushed by an increasing demand and improvements in manufacturing technology. Generally, due to the costs associated with their synthesis, the price of the nanomaterials are highly dependent on the particle's size range and specific surface area. Products with high purity and narrow size range and high specific surface may demand higher processing efforts, thus having higher final costs. The prices for nanosilica particles can vary from 80 \(\upepsilon\)/kg to 1500 \(\upepsilon\)/kg. The products with smaller size and narrow range (5 nm to 20 nm) and high specific surface (up to 690 m\({}^{2}\)/g) can cost between 1000 \(\upepsilon\)/kg and 1500 \(\upepsilon\)/kg. On the other side, particles with a wider size range (15 nm to 70 nm) and higher variation on specific surface area (130 m\({}^{2}\)/g to 600 m\({}^{2}\)/g) can cost between 80 \(\upepsilon\)/kg to 150 \(\upepsilon\)/kg. Further modifications of the nanosilica, for example with silane coupling agents, also brings an increase to the costs. Silane modified silica nanoparticles can cost between 180 \(\upepsilon\)/kg to 450 \(\upepsilon\)/kg. Currently, the commercial price of nanoclays ranges from 100 \(\upepsilon\)/kg to 250 \(\upepsilon\)/kg, depending on the particle size and types of treatment/modification. Organically modified nanoclays are more expensive due to the additional surface treatment process. On the other side, raw nanoclays with natural hydrophilic behavior are cheaper. The prices of nanoinor particles are in the range of 100 \(\upepsilon\)/kg to 2600 \(\upepsilon\)/kg. Costs are dependent on purity level and size range. Nanoparticles of Fe\({}_{2}\)O\({}_{3}\) with average size 50 nm and purity around 98% cost can cost between 100 \(\upepsilon\)/kg to 300 \(\upepsilon\)/kg. The most expensive iron nanoparticles are 99.9% 5 nm Fe\({}_{2}\)O\({}_{3}\). The zero-valent nanoinor (50 nm) can cost nearly 120 \(\upepsilon\)/kg. The framework provided by [PERSON] et al. [137] was considered to perform a simple cost analysis regarding the construction of a 5 cm thick asphalt concrete (AC14 surf 35/50) wearing course. Using conventional materials (unmodified asphalt binder) the estimated cost was 6.8 \(\upepsilon\)/m\({}^{2}\). Regarding the nanomodified binders, the cost where estimated using the costs of the respective raw materials but not accounting with the possible costs of technology implementation for industrial scale refinery- or plan-modification. Considering the available nanosilica with the lower cost, the asphalt mixture cost was estimated to be 21.0 \(\upepsilon\)/m\({}^{2}\), 44.7 \(\upepsilon\)/m\({}^{2}\) and 38.9 \(\upepsilon\)/m\({}^{2}\) for the modifications with 3% nanosilica, 8% nanosilica, and 3% silane-nanosilica, respectively. The cost for nanoclay modifications was estimated to be 25.4 \(\upepsilon\)/m\({}^{2}\) and 51.4 \(\upepsilon\)/m\({}^{2}\), when using 3% non-modified nanoclay and 3% organically modified nanoclay (modified with quaternary ammonium), respectively. The cost for nanoinor modifications were estimated in 12.1 \(\upepsilon\)/m\({}^{2}\) and 35.3 \(\upepsilon\)/m\({}^{2}\) for the modifications with 0.9% nano-Fe\({}_{2}\)O\({}_{3}\) and 4% nano zero-valent iron. The low dosage required by the nano-Fe\({}_{2}\)O\({}_{3}\) modification indicated that it is competitive from the economic point of view.