This research report presents a literature review on the topic of long-life pavements and provides details of an assessment of heavy duty structural asphalt pavements in New Zealand, carried out in 2001-2002.
Long-life pavements are structural asphalt pavements which maintain their strength or become stronger with time. This is caused by curing of the binder and results in a pavement which is expected to remain structurally sound for an indefinite period.
Three structural asphalt pavements were identified in the Auckland region from which cores were extracted for testing. These cores were taken from the inside wheel track and between the wheel tracks of the left-hand lane. They were tested to assess the changes in properties of the bitumen and asphalt mix with time, and the effects of traffic loading.
No significant difference was recorded in results between the core samples extracted from in the wheel tracks compared with those taken from between the wheel tracks. This suggests that traffic has little effect on the properties of the asphalt mix. Viscosity of the recovered binder and the resilient modulus of the asphalt mix both increased with age. Cores from cracked sections of pavement were extracted and the cracks were found to initiate at the surface. The reasons for top-down cracking are discussed.
A whole-of-life cost assessment showed that the current Transfund New Zealand project evaluation procedure favours structural asphalt, rather than conventional unbound granular options, for an existing pavement that requires rehabilitation. Because of high initial costs, this evaluation process does not however favour the long-life pavement over the thinner structural asphalt pavement.
Keywords: asphalt, bitumen, long-life, New Zealand, pavement, road, top-down cracking, transport