Unbound Aggregates for Roads

Unbound (or uncoated) aggregate is widely used in the construction of roads. It is mainly used in the UK for the subbase (see Fig. 8.1), but may also be used in the capping layer. Uncoated roadstone may also be used for the road-base and, in the case of low volume roads, for the complete structure. 

The role of the uncoated roadstone layer(s) may be one or more of the following  

The principle features which determine the suitability of an aggregate for use in the unboimd state are its resistance to  

Specifications vary widely from country to country and reflect the local climate, traffic conditions and economic constraints. 

In the UK, BS 63 [8.3] specifies requirements for single-sized aggregates (50, 40, 28, 20, 14,10, 6 and 3 mm) for general purposes and for surface dressing (although limestone is rarely used for surface dressing). The single sizes may be recombined to produce the particle size distribution required for a particular application. 

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Hydraulic bound and unbound aggregates for road layer construction... 

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