## 3 Defining Marginal Materials
(* Typical examples of recommended pavement structures taken from the draft TRR [22] with material classification according to TRH14 [23] [A = Aguhal CS = Chip-seal; C = Cement stabilisation; G = Granular materials (Figure 1); NME = New-age Modified Emulsions (Figures 3 and 4)]. Figure 3: References [6;7]: Minimum recommended standard specifications for New-age (Nano) Modified (NME) stabilised materials, addressing four different classifications in terms of engineering requirements. Figure 4: Reference [27]: Minimum recommended standard specifications for New-age (Nano) Modified (NME) stabilised materials, addressing Low-volume Roads (LVR) and access roads to remote communities as well as in villages/townships. From the comparative design catalogue (Figure 2), it is seen that for the higher-order roads using conventional designs, a high-quality crushed stone (G1, G2, and G3 (Figure 1)) material is prescribed for the construction of the base-layer (as an alternative to full-depth asphalt designs) [28]. These materials are usually only available from commercial sources at a considerable cost which, in addition, is also associated with haulage costs that could be substantial depending on the availability of the material relative to the distance from the construction site. Haulage costs may be a major factor in areas between the tropics close to the equator and in desert areas where sources of high-quality crushed stone may be a scarce commodity. In comparison, naturally available materials (gravels of a G4 to G9 quality (refer Figure 1) or sand of various gradings) may be more readily available close to construction sites. The use of the naturally available granular materials, together with a material-compatible anionic NME stabilising agent, may result in considerable savings in material costs as a basic input into a probabilistic life-cycle cost analysis approach [29], taking into account the associated risks. Naturally available materials close to but not meeting the classification criteria/ properties of freshly crushed stone usually still contain a solid core of primary minerals with some presence (relatively small percentages) of secondary minerals which developed as a result of some chemical weathering [6; 7]. The neutralisation of any possible negative effect of these secondary minerals, using applicable nanotechnologies, are relatively easy to achieve by following the recommended materials design method [6]. The opposite is the case with materials of very poor quality as defined for use in road pavement structures (these materials may be classified as very good for purposes such as agriculture). In these cases, the bulk of the naturally available material may consist of secondary minerals with the structure of the particles of the primary minerals already compromised due to the process of chemical weathering [6]. It follows that the crushing strength of the primary minerals present in the naturally available materials may already have been compromised. Although more complicated, the characteristics of these materials can also substantially be improved using applicable nanotechnologies [6; 7; 12]. In these cases, the material may be improved for use in the upper layers (base and/or sub-base of roads with design traffic loading up the 10 million E80s [16; 17; 18; 27]) or in the supporting layers of pavement structures with higher design traffic loadings. G3 to G6 (Figure 1) materials are considered marginal or unacceptable for use in base-layers of roads with a design loading in excess of 3 million E80s. However, in combination with a material-compatible anionic NME stabilisation agent, the quality of such material can chemically be improved to be suitable for use in the base and sub-base-layers of these roads.