## 3 Traditional Use of Nanotechnology Products in Road Pavement Engineering
### Chemistry of Organofunctional Nano-Silanes for Application in Pavement Engineering
At the same time, through creating the appropriate bonds, the surface of these materials will become water repellent, negating the negative impact that water has on the durability of materials through the prevention of (or at least limiting) weathering due to chemical decomposition (a pre-requisite of the process of weathering of materials through chemical decomposition (chemical change) and the formation of resultant secondary minerals in the presence of and access to water [15]). In pavement engineering design analyses, it is usually assumed that material mineral properties will stay unchanged during the design period. This basic assumption is incorrect, and even over a design period of 20 to 40 years, dramatic changes can occur (even in freshly crushed stone--given conducive environmental conditions [15]), which will influence the design assumptions considerably. This aspect alone shows the potential benefit of the use of organofunctional nano-silane products in pavement engineering as a protective agent for high-value, freshly crushed stone against chemical decomposition and deterioration over its design life (e.g., a 20-year normal design period). Rehabilitation investigations conducted on major freeways in the Gauteng province of South Africa have shown that high-quality newly constructed stone G1 (Figure 6) [32] base-course material can deteriorate over a period of 22 years to an equivalent G4 to G6 quality material. Similarly, secondary roads in the Gauteng region of South Africa have shown that a cement-treated base-course layer can deteriorate from a cement-treated layer (Unconfined Compressive Strength (UCS) between 750 to 1500 kPa) quality layer to an equivalent G7/8 quality material [32], over a period of 20 years (rehabilitation investigations undertaken in the Gauteng Province of South Africa by the main author). Figure 6: Classification of granular materials (comparative summarisation of some characteristics of the material classification [32]) (refer CBR compaction [33; 34]). Modification of Nano-Silanes through Hydroxy Conversion Treatments (HCT) Based on the Mineralogy of the Granular Material Sub-Strata  
Although approximately 60 percent of the crust of the earth contains Si-O bonds, not all naturally available granular materials are silicon-rich. Non-silicate materials include carbonate materials such as calcretes and dolerites that are predominant in certain areas of the world and laterites (abundant in warm/humid conditions conducive to chemical weathering and the leaching-out of silicate materials). In such cases (e.g., with calcretes, dolomites, etc. ), very little or even no silicon may be available in the material to create the Si-O-Si bonds, as explained in the example. The part of the earth conducive to weathering due to chemical decomposition is situated in areas associated with the presentence of moisture (humid conditions) and high variations in seasonal temperature variations. These environmental conditions are especially pronounced between the Tropics of Capricorn and Cancer. The mineralogy of the naturally available materials (especially in areas close to the Equator), may be deprived of readily available silicon and may not be able to form Si-O bonds with the nano-silanes, as shown in Figure 5. In these areas, the nano-silanes need to be complemented with a material compatible nano-particle conversion to created strong chemical bonds with the minerals in the available granular materials. This conversion of a nano-silane is generally referred to as a Hydroxy Conversion Treatment (HCT), which is best characterised by its ability to form bonds with the available minerals in the granular materials (stone/gravel/soil). For example, in the case of carbonate-rich materials (e.g., dolomites and calcretes), the nano-particle added to the nano-silane in the form of an HCT must be able to form strong chemical bonds with the Calcium-carbonates (Ca(CO\({}_{3}\))) in the material.