## 3 Pavement Design Process Based on Scientific Principles
### Scientifically Based Material Properties of Naturally Available Materials  
#### 3.2.1 Mineralogy of Naturally Available Materials  
It is not the intention to replace the role of the geologist or to provide a comprehensive and detailed overview or description of all the various petrology and geology concepts as available in numerous sources. It is rather the intention to provide a simplistic approach with the emphasis on the basic concepts and understanding of the important role of mineralogy, in the successful implementation of proven and applicable nanotechnologies in the cost-effective use of naturally available materials in pavement engineering. The understanding of the roles of both the primary minerals (\"type of stone\") as well as the secondary minerals (\"condition of the stone\") are fundamental to the successful implementation of nanotechnologies through the incorporation of basic material science.  
Engineers traditionally assume that materials classified on the basis of various empirically derived tests stay unchanged during the design period of a pavement structure. However, due to the presence of moisture and temperature fluctuations, the chemical weathering of materials is a natural, continuous process, even within a pavement structure. The material chemical decomposition is independent of the role in which it is used as long as it has access to water (moisture or vapour) and subject to temperature variations during seasonal changes. These influences are more pronounced in areas around the world characterised by considerable fluctuation in temperature, humidity and rainfall, as mostly experienced between the Tropic of Cancer (North) and Tropic of Capricorn (South). Some primary minerals have a higher resistance to chemical weathering, and a basic knowledge and an understanding of these characteristics are of importance in the identification of material-compatible nanotechnology solutions.  
Figure 1: Recommended basic approach to road pavement materials design incorporating scientifically based concepts, developed for the selection of a material-compatible New-age (Nano) Modified Emulsion (NME) stabilising agent addressing the engineering requirements (physics) of a road pavement structure.  
The naturally available materials present between the two Tropics are usually the result of considerable chemical decomposition, representing a classification often more closely associated with soils than with the original geology. It follows that not only is the geology of importance but also the identification of soil-types. Geological and soils maps can be of great assistance to identify variations in the characteristics and the mineralogy of the materials that may be naturally available in any specific region [18]. The following factors all contributes to the mineralogy of the naturally available materials:  
* Original rock formation and primary minerals;
* Climatic factors including rainfall, temperature and humidity;
* Changes in the slope of the area and vegetation that both contribute to the removal of the top, most weathered materials through the flow of water;
* Human interference through deforestation and other activities.  
The variation in these factors has a considerable influence on the expected chemical weathering of the materials and changes in the expected fundamental mineral properties pavement materials engineers have to deal with, as summarized in Table 1 (summarised and based on [28]).