## 4 Factors Affecting the Successful Introduction of New-Age Nanotechnologies in Pavement Engineering
### Hydrophobic Characteristics of an Alkoxy-Silane Modification and/or Treatment
#### 4.7.2 Compatibility with the Mineralogy of Materials  
Some available nano-silane products are indeed only effective in the presence of large quantities of silica and have severe limitations in the presence of secondary minerals. It follows that any mineralogy investigations need to determine both the primary as well as the secondary minerals present in naturally available materials to ensure that the most applicable alkoxy-silane or HCT-modified product is applied to the available materials. This requirement is a basic pre-requisite to the successful application of any applicable nano-scale product, to be successfully applied as a modification to any stabilising agent used in material design in pavement engineering [16; 17]. The influence of minerals in the successful application of nano-silane products as protective coatings of various stone types was already recognised in the 1800's [1; 18]. For example, at the time, the application of silica-ester to acidic materials was observed to result in the successful formation of a protective gel while an alkaline sub-stratum will result in the formation of a \"useless\" gel when treated with silica-ester [18].  
It is of importance to note that at the most basic of geology terms, materials can be classified as either acidic, i.e., silicon-based minerals or basic, i.e., calcite that forms the basis of carbonate (CaCO\({}_{3}\)) (alkaline) based minerals. Acidic rocks are normally considered to contain in excess of 50 per cent of acid components, i.e., SiO\({}_{2}\) and CO\({}_{2}\)[5]. In the absence of silicon and the presence of calcite minerals, different nano-silicon technologies need to be applied.  
For example, calcite forms few if any hydroxyl (HO) groups with which alkoxy-silanes can react to form bonds (Figure 1). Hence, complementary nanotechnologies have to be added with stone/aggregate/soils exhibiting high percentages of calcite. The problem with a lack of HO groups on the surface particles of materials can be resolved by chemically altering the surfacing of the material using approaches such as a Hydroxy ConversionTreatment (HCT) [19]. The HCT will convert the surface of a crystal of calcite to produce hydroxyl (OH) groups (Figure 6a) that facilitates alkoxy-silane bonds. The chemical combination of the alkoxy-silane with the HCT and alkaline sub-strata to for a hydrophobic surface, expelling water as a by-product, is demonstrated in Figure 6a-d.  
The development of coupling agents and the ability to attach to different sub-strata are continuously being improved to create new products that cater for a wide spectrum of different minerals. In practice (not only in pavement engineering), it's important to be aware of limitations that do exist in the nano-silane technologies that are commercially available to be used. Both the designer and contractor must ensure that the nano-silane technology specified/used is effective and compatible with the naturally available materials to be treated and stabilised.