Single surface dressing

The upper size of chippings is usually 6.3 or 10 mm. The rate of spread of chippings should be such to achieve 100% to 105% shoulder-to-shoulder coverage (Heslop et al. 1982), as measured by CEN EN 12272-1 (2002). 

The single surface dressing has the least number of operations and requires the least quantities of material (chippings and binder) than the rest of the types of surface dressing. The quantities of material required mainly depend, as in all cases, on the condition of the pavement surface (mainly hardness), traffic category and size of chippings. 

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The stress-absorbing membrane (SAM) technique is similar to the single surface dressing. The only differences are that the quantity of the bituminous material sprayed is higher and the bituminous binder is exclusively modified bitumen. 

Figure 15.23 Types of surface dressing, (a) Single surface dressing (b) racked-in surface dressing (c) double dressing (d) inverted double dressing and (e) sandwich dressing (example of pre-chippIng dressing). (Reproduced from CEN EN 12271, Surface dressing - Requirements, Brussels CEN, 2006. With permission [ CEN].)...

The pre-chipping layer consists of large-size chippings (usually 14 mm) and the chippings of the single surface dressing consist of small-size chippings (usually 6 mm). 

Table IS.3 Recommended nominal size of chippings and target rates of spread binder at spraying temperature for single surface dressings...

The amount of 10 mm or larger aggregates required in single surface dressings (sprayed seals) is based on the ALD value of the aggregate. 

The determination of the design binder application rate for the first application is carried out in a similar way as for a single surface dressing (single seal) described above. 

In particular, the basic binder application rate for first application for conventional bitumen, B, i> is determined first and then the design binder application rate for first application for conventional bitumen, considering allowances for surface texture, aggregate embedment and so on, as for single surface dressing. 

When instead of conventional bitumen, another type of binder such as polymer-modified bitumen, bitumen emulsion, or polymer-modified emulsion is used, the design binder application rate for the first and second application is determined in a similar way as above but considering first the polymer factor and emulsion factor, as explained in single surface dressing. 

Table 15.14 Quantities of emulsion and aggregate for single surface dressing...

The sequence of single surface dressing construction may be summarised as follows ... 

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