Surface dressings and thin surfacings are used to improve the surface characteristics of a pavement and/or to seal and, hence, protect the underlying structure from environmental factors. However, the full effectiveness of these maintenance treatments is, as yet, unsubstantiated. A literature review and an investigation into a number of existing sites where these surface treatments have been used were carried out. The aim was to establish the effectiveness of both surface dressing and thin surfacing treatments in protecting, preventing and/or controlling pavement deterioration and hence prolonging the service life of pavements. The investigation found that surface dressings and thin surfacings have little or no direct strengthening effect on the structural performance of a highway pavement. However, on suitably drained sites, these treatments may have an indirect stiffening effect on the pavement structure by virtue of sealing the surface and, therefore, restricting the ingress of moisture to the foundation layers. On poorly drained sites or sites where water can enter the pavement from below, the application of a surface layer has little effect on structural performance. Nevetheless, these treatments are very useful in restoring the surface characteristics. (A)

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