Evaluation of microclimate effects on surfacing seal performance

Abstract

Surfacing seals consist of a combination of bitumen and aggregate, and are used to provide an all-weather surfacing to protect underlying layers and provide safe access to vehicles traveling on a road. Analysis of a number of sections in Gauteng, South Africa, has shown that surfacing seals lost a large proportion of their aggregate where the road was crossed by a bridge. As all original properties of the seal components as well as the traffic on the road were similar, it was deduced that the micro-climate where the road traveled underneath the bridge should have caused this localized failure condition. In this paper the phenomenon is investigated through analysis of the micro-climate underneath the bridge, the material properties of the surfacing seal, and the combined effect of these factors on the performance of the seal. It is shown that the micro-climate can affect the performance of an otherwise suitable surfacing seal to such an extent that the performance of the seal is severely compromised. A procedure for the analysis of potential micro-climate effects is described in the paper.