## 3 Pavement Design Process Based on Scientific Principles
### Scientifically Based Material Properties of Naturally Available Materials
#### 3.2.2 Primary Minerals Defining the Type of Stone  
Stone/gravel/soil/clay consists of numerous minerals that are influenced in different ways through the differences in climatic variations. More than 4000 minerals have been identified by scientists within the crust of the Earth, resulting in countless variations and permutations that could influence material behaviour [29]. However, the understanding of mineralogy can be considerably simplified through the identification of the minerals that are in abundance and form most of the crust of the Earth. It follows that these minerals will also be of particular importance in the identification of material-compatible nano-silane technologies to be used together with an appropriate stabilising agent. Only a few elements form the bulk of these minerals (Table 2[30]). A generalised composition of Igneous rocks (solidification of lava materials) found in the crust of the earth is shown in Figure 2 (Compiled from various similar figures in public domain (e.g., [31]). \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Climatic Conditions** & **Cold Regions (Little Decomposition)** & **Warm Regions (Considerable Decomposition)** \\ \hline
**Property** & Materials: Conventional (Crushed rock base, river gravels, glacier outwash) & Materials: Pedogenic (laterites, calcretes, ferricretes, silcretes, etc.) \\ \hline
**Climate** & Temperate to cold & Arid, tropical, warm temperate \\ \hline
**Material Composition** & Natural or crushed &
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline
**Material Chemical Reactivity** & Inert \\ \end{tabular} & Reactive \\ \hline
**Material Variability** & Homogeneous & Extremely variable \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Generalised material properties associated with different climatic regions of the world due to the effect of chemical weathering (based on [28]). Figure 2: Generalised composition of Igneous rocks found in the crust of the Earth (based on and compiled from various similar figures in public domain, e.g., [31]). \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Estimated \% by Weight** & **Estimated Atomic \%** & **Estimated Volume \%** \\ \hline
**Oxygen (O)** & \textasci{-}46.6–49.5 & \textasci{-}62.3–66.2 & \textasci{-}92–94 \\ \hline
**Silicon (Si)** & \textasci{-}25.3–27.7 & \textasci{-}19.4–21.2 & \textasci{-}8–6 \\ \hline
**Aluminium (Al)** & \textasci{-}7.5–8.1 & \textasci{-}6.0–6.5 & \\ \hline
**Iron (Fe)** & \textasci{-}4.2–5.1 & \textasci{-}1.6–1.9 & \\ \hline
**Calcium (Ca)** & \textasci{-}3.2–3.6 & \textasci{-}1.7–1.9 & \\ \hline
**Sodium (Na)** & \textasci{-}2.4–2.9 & \textasci{-}2.0–2.4 & \\ \hline
**Potassium (K)** & \textasci{-}2.3 - 2.6 & \textasci{-}1.2–1.4 & \\ \hline
**Magnesium (Mg)** & \textasci{-}1.9–2.1 & \textasci{-}1.6–1.8 & \\ \hline
**All Others** & \textasci{-}2.5 & \textasci{-}0.5 & \\ \hline
**Total** & **100** & **100** & **100** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Estimated percentages of the main elements found in the crust of the Earth that constitutes most of the materials (estimates based on [30])—some significant variances are present around the globe. Due to the abundance of the Silicon (Si) and Oxygen (O) elements (Table 2), more than 90 per cent of the materials found in the crust of the earth are defined as Silcretes. Hence, materials are generally defined as Silicate minerals and non-Silicate minerals (e.g., Carbonates, Oxides Sulphates and Halite). Since the Si-O bonds are some of the strongest in nature [11], it could easily be assumed that any modified stabilising agent compatible with Silicate materials should be effective and able to form strong bonds with most of the naturally available materials. However, such a generalised deduction is erroneous and could have severe detrimental consequences. Figure 3 give an indication of the Silicon versus Carbon-dioxide content of some of the more well-known commonly found naturally available materials.