## 2 Background  
The use of nano-scale products for the stabilisation of granular materials in the construction of the pavement layers is nothing new. Per definition, products such as cement, lime as well as bitumen emulsion all incorporate nano-scale particles and can be considered as nanotechnology products, i.e., containing particles of which at least one dimension is between 1 and 100 nm in size [10]. The use of nanotechnology as a science only became of interest after the development of equipment enabling scientists (including chemists, physicians and engineers) to see and manipulate nano-scale particles at a molecular level in the 1980s/90s [11, 12]. This ability to manipulate nano-scale products has had an impact on all industries, including the built environment where silicon-based nanotechnology products are being used to improve building materials across basically all spheres of activity. However, nano-silane products have been developed, tested and used in the built environment to protect stone buildings in Europe since the 1860's [4]. The more than 150 years of \"lessons learnt\" from the built environment can assist pavement engineers to fast-track the implementation of these proven technologies to also protect and improve naturally available granular materials for use in the design and construction of roads. Experience in southern Africa [13] has shown that considerable savings are a reality through the implementation of nano-silane technologies used for the treatment and stabilisation of granular materials for all layers below the surfacing. Materials used in road pavements are traditionally classified using empirically derived criteria based on material indicator tests dating back more than a century [14]. These material classification systems often classify naturally available granular materials in climatic regions of the world associated with a high potential for chemical decomposition (high temperatures in combination with seasonal rainfall [15]) as \"non-standard,\" \"marginal\" or even \"sub-standard\" [16]). Available and applicable nanotechnologies that could enable the use of these materials at a low-risk in pavement structures could substantially reduce the unit costs of road infrastructure, specifically in these regions. Bitumen emulsion technology dates back to the early 1900s [17] when a nano-scale particle was discovered that enables an oil substance (e.g., bitumen) to be mixed with an aqueous substance (i.e., a water-based substance). This nano-scale particle is commonly referred to as an emulsifying agent (known in chemistry as a surfactant and in engineering practice commonly referred to as a \"soap\"). Bitumen emulsion technology enables a relatively low bitumen content to be mixed with granular materials at ambient temperatures to construct road pavement layers. Emulsion technology incorporates several advantages, including the ability to accommodate considerably higher tensile strains in comparison to the unstabilised granular material as well as cement-bound materials [14; 18]. However, similarly to the manufacturing of asphalt, it is still a requirement to use aggregate/stone/gravel granular materials of a relatively high quality together with the bitumen emulsion for the construction of a pavement layer meeting the required engineering specifications [19]. Similar to the manufacturing of asphalt for surfacings, the unmodified bitumen forms no chemical bonds with the granular aggregate/stone materials in the mix. Strength is only achieved through covalent bonds (relatively weak) and mechanical forces created through granular interlock and absorption of the bitumen into a porous surface of the aggregate [15]. For this reason, some aggregates containing a high silicon content, which usually result in relatively \"clean breaks\" during crushing, are notoriously difficult to use for the manufacturing of asphalt or bitumen emulsion stabilised layers meeting the engineering specifications.