Sandwich surface dressing

Sandwich surface dressing is used in situations where the pavement surface is binder rich and works are carried out during hot weather. 

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). 

The rate of spread of chippings is as for double surface dressing. 

It is the most complete surface dressing design methodology that may also be used outside the United Kingdom with minor modifications. 

The input parameters required for determining the binder spread rate related to chipping size, road hardness and traffic category are as follows  

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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].)...

Finally, in the case of sandwich dressing, the large-size chippings are spread on the clean surface first and then steps (b) to (e) follow. 

The purpose of antimicrobials in medical textiles such as wound dressings is to eithCT prevent infection from occurring or to contribute to the healing of infected wounds, and odour control is a subsidiary effect whereas, the inclusion of activated charcoal in wound dressings is specifically to manage odour. Activated charcoal cloth (ACC) is sandwiched/encapsulated between two layers of a polyamide nonwoven fabric. The ACC with silver has to be in close contact with the wound s surface in order for the silver ions to react with the bacteria causing the infection (Mcqueen, 2011). 

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