## 5 Construction of NME Stabilised Granular Pavement Layers--Practical Aspects
### Central Plant Mixing and Construction of Pavement Layers Using Paving Equipment  
As discussed previously, the use of marginal materials and stabilisation/enhancement thereof is not restricted to lower-order roads. The use on crushed stone materials protected by the addition of small percentages of an anionic NME can be beneficial both in terms of durability (prevention of in situ chemical decomposition) as well as the energy required to achieve the specified high levels of compaction [21; 22; 23]. Naturally available granular materials stabilised with a material-compatible anionic NME stabilising agent as per a scientifically based materials design process can also, with relative ease, meet the design requirement for inter-city and other highways, designed to carry relatively high traffic loadings as shown in Figure 2[21], in association with Figure 3[6]. These roads are associated with a high required constructed riding quality, ideally suited for construction using equipment able to deliver these requirements at a low risk to contractors. The example shown involves the use of a central computerised mixing plant (Figure 7a) to prepare the granular material mixed with the construction water and an anionic NME stabilising agent. The central mixing plant automatically mixes the granular material (in this case, a G5/6 material--refer Figure 1) with a high degree of accuracy with the anionic NME stabilising agent (in the example--1.2 per cent, containing about 0.7 percent residual bitumen)) pre-mixed with the construction water to be delivered to trucks for transportation to the road under construction (Figure 7b). The water added to the mix should take into account any loss of moisture that may occur during the transportation of the mix to the construction site and the construction of the layer. In cases of a long haulage distance and/or high temperatures, it is standard procedure to cover the pre-mixed materials on the trucks to minimise the loss of moisture through evaporation during transportation. On this specific project, the sub-base was constructed using the same granular material stabilised with 0.7 percent anionic NME (\(\pm\)0.4 percent residual bitumen) using conventional equipment (to be demonstrated). Note the curbs put in place for the inter-city freeway that is being constructed. Figure 7b,c shows the delivery of the NME-mixed granular material prepared in the central plant for placement by paver with the various compaction rollers ready for the compaction of the 150 mm thick base-layer (the small roller is used for compaction next to the curb, while the smooth drum vibratory roller ensures that the density requirements are met and, in combination, the pneumatic wheel roller ensures that a high-quality surface texture is achieved). Figure 8a-c shows the compaction of the base-layer and the final high-quality finishing of the base-layer after compaction. The hydrophobic nature (water repellent characteristics of the anionic NME stabilisation of the base-layer) is shown by the speed at which the moisture is effectively repelled from the layer. Figure 7: (**a**) Central mixing plant mixing the granular material with the required construction water containing the anionic NME stabilising agent for transportation to site; (**b**) delivering material in a paper; and (**c**) compaction of base-layer. One week after construction of the base and sub-base (both exposed with no prime or surfacing was severely tested by nature). Within 48 h, more than 200 mm of rain was reported on site with the sub-base (Figure 9a) and base (Figure 9b) representing rivers. The general consensus among the seasoned contractors, consultants, and the  
Figure 8: (**a**) Compaction of base-layer behind paper. (**b**) Final compaction with pneumatic roller to a high level of tolerance. (**c**) Achieved base texture with G5/G6 material with 1.2% anionic NME stabilising agent (0.7% residual bitumen). client was that the pavement layers would have been damaged to such an extent that reconstruction would be inevitable.