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Design manual for Roads and Bridges - Surfacing

4.1 The wet skidding resistance of a road is dependent

on the tyre interacting with the microtexture of the road

surfacing. On a concrete road, microtexture comes

primarily from the sand and fine aggregate in the

concrete surface layer. Microtexture is gradually

polished by traffic until an equilibrium level of skidding

resistance is reached. On a concrete road, the laitance

containing the fine aggregate may be worn away to

expose the coarse aggregate which may be unable to

maintain adequate microtexture. HD 28 (DMRB 7.3.1)

provides advice on standards for the skidding resistance

of in-service roads.

4.2 The ability of a surface to maintain adequate

skidding resistance at high speeds is governed by the

macrotexture of the surfacing. As a surfacing ages, the

level of macrotexture may fall as, for example, the

ridges created by brushing, are worn away. There may

also be inadequate or excessive brushing of the new

concrete surface such that the minimum or maximum

requirements for texture depth of a new road may not be


4.3 Retexturing is the mechanical reworking of a

sound road surface to restore either skidding resistance,

texture depth or both. However, on a concrete road the

coarse aggregate may play a significant part in

determining the suitability of retexturing treatments.