## 1 Introduction  
Surfaced road networks, creating accessibility to markets and reducing transportation costs, have been shown to be a major stimulus for economic growth. Developing areas around the world, such as sub-Saharan Africa, compares poorly with the developed world in terms of, inter alia, the percentage surfaced road network [1]. The general lack of adequate funding in developing regions, together with relatively high road unit construction costs, makes it almost impossible for these regions to provide the road network required to stimulate economic growth [2]. The high road unit construction costs are often associated with traditional use of material classification systems dating back many decades. These material classification systems generally exclude the use of naturally available materials in the upper load-bearing layers of a pavement structure [1]. Hence, high-quality, high-cost crushed stone, normally, has to be imported to construct road infrastructure. The material classification systems used, in many cases, are based on empirically derived tests, some dating back more than a century. These empirically derived tests were developed to limit the risks associated with the chemical weathering of materials and the formation of secondary minerals (e.g., clay) within the materials. However, material-compatible nanotechnology solutions are able to neutralise any negative influence of secondary (or some primary) minerals. These technologies have been proven scientifically, in laboratories and in practice, using accelerated pavement testing (APT) with materials traditionally classified as marginal, or even unsuitable [1], stabilised with anionic New-age (nano) Modified Emulsions (NMEs) to be able to meet required engineering properties [3; 4; 5]. Enabling the use of naturally available materials in all structural road pavement layers can considerably reduce the construction costs of roads. However, to ensure success and limits the risks associated with the introduction of new technologies, implementation needs to be based on sound, scientifically based principles and fundamental engineering design methods [6; 7; 8]. To fully realise cost savings, the anionic NME-stabilised naturally available materials in the upper pavement layers must be suitable for use with relatively thin, durable surfacings such as various chip seals. The cost-effectiveness of these surfacings has been proven on roads constructed with traditionally classified materials all over the world, e.g., [9; 10]. However, the traditional use of bitumen emulsion stabilisation in base layers, together with thin chip seal surfacings, has often proved problematic, with punching of the stone into the base. This leads to early distress in terms of severe bleeding of the binder, associated with rut deformation and early failure of the top of the base layer. These failures are invariably associated with high moisture build-up just below the surfacing, which can also result in detachment of the surfacing. With traditional emulsion stabilisation, moisture is only relieved from the layer through evaporation. The general specification and use of some modified binders known to restrict the evaporation of moisture from base and sub-base layers [11] entraps moisture and increases the risk of moisture build-up underneath the surfacing. This problem is not only restricted to emulsion-treated layers but also can be associated with any base and sub-base layer that will release moisture directly after construction, before reaching a state of equilibrium, such as granular and/or cemented layers. An equilibrium state within pavement layers is usually only reached after one to two seasons under traffic loading. The introduction of material-compatible anionic NME stabilisation has the advantage that over and above evaporation, water is effectively repelled from the stabilised layer through a chemical reaction between the minerals of the materials and the material-compatible modifying agent applied to the emulsion.