SQUEEZING LIFE INTO ROAD SURFACES

Compaction improves the strength, stability and durability of a bituminous mix and reduces permeability, resulting in a higher density, which can give a significant improvement in pavement performance. It is vital that adequate compaction is applied before the mix has cooled; the critical minimum temperature depends upon air temperature and wind speed as well as the type and grade of bitumen and bituminous mix. Higher stability mixes require more care in compaction and possibly a higher compactive effort if their full potential is to be realised. Compaction should be monitored quickly for compliance checks with a density specification appropriate for the bitumen mix used and its service requirements. Nuclear density meters, if used closely after the roller, can indicate areas where additional rolling is needed in good time. The time-consuming measurements of density by the taking of cores should be confined to areas where compliance is in question. Good compaction depends upon an appreciation of the factors affecting compaction, it need not be expensive and can be effective in terms of costs and performance. (TRRL)