## 5 The Clay Problem
Using traditional material classification systems, the indicator material test results shown in Figure 9 would have identified the material to be unsuitable for use in any load-bearing layers of a pavement structure, even for low-volume roads. However, the stabilisation results gave confidence to the use of the material in the sub-base with 1 percent anionic NME stabilising agent (highest results in terms of tensile strength) and with 1.5 percent in the base layer (highest Retained Compressive Strength (RCS) of 71 percent). A high RCS can be related to high resistance to possible damage due to water-ingress from the top in the case of a compromised surfacing layer. This pavement structure constructed with the anionic NME stabilisation as indicated was evaluated using Accelerated Pavement Tests (APT) [8; 9]. The design traffic loading of 3 Million Standard 80 kN dual-wheel single axle loads (E80s) was surpassed with ease with an estimated load-bearing capacity of at least three times that of the design traffic loading in terms of applicable pavement deformation performance criteria [36]. The stabilised materials have also shown remarkable resilience against overloading with a damage co-efficient of n < 2 (normally assumed to be 4.2 [37]). It follows that road pavement structures containing anionic NME stabilised base and sub-base layers will be ideally suited for the construction of roads where law enforcement in terms of vehicle over-loading is limited or even totally absent. Available nanotechnologies have been used under laboratory conditions to achieve acceptable engineering results on materials of considerably poorer quality than shown in Figure 9. Figure 10 shows the exposed surface of a material sample crushed during an ITS\({}_{\text{wet}}\) test of relatively poor laterite. This material contained almost 50 percent of fines passing through the 0.075 mm sieve size, of which almost 70 percent was identified through XRD scans as kaolinite clay particles. In this case, a material compatible HCT modified high-quality sub-nano size silane was used with a nano-polymer to stabilise the material. The crushed sample shown in Figure 10 was tested to have an ITS\({}_{\text{wet}}\) of 80 kN with good hydrophobicity achieved throughout the sample as shown by the beading [7] effect of the water sprayed onto the exposed surface of the broken sample after testing. These anionic NME treated materials will be suitable for use in the upper load-bearing layers of some low-volume roads (refer criteria [38]). The sub-nano size silane and nano-polymer needed to be carried into the material using water as a carrier and thoroughly mixed. As well known, high percentages of clay in a wet condition present considerable challenges in terms of workability in the field. In practice, workability may need to be addressed by mixing a percentage of material such as sand or naturally available gravel into the material to practically enable the material to be workable when adding the modified stabilising agent into the material using water as a carrier. The material shown in Figure 10 may be considered to be an extreme example of a granular material not to be considered for use in traditionally accepted pavement engineering. However, such materials are all too common in areas close to the equator, associated with high humidity and high-temperature conditions. Granular materials of similar characteristics (shown in Figure 10) may be the only material available over considerable distances. Hence, any improved use of granular materials of very poor quality, similar to that demonstrated in Figure 10, may be of considerable cost benefit to any road project [39]. The use of materials of such a poor quality may be unthinkable in traditional pavement engineering.