Resources

The NZ Transport Agency (NZTA) engaged MWH to conduct analysis of the attained life of certain chipseal resurfacing types. This followed some preliminary work as reported at the NZTA / NZIHT 14th annual conference held in Auckland, November 2013, following which refinement of the analysis selection criteria was made at a meeting between the NTZA, MWH and Alan Stevens representing Roading NZ members.

The key selection criteria were as follows:

• Minimum life increased from 60 days to 4½ years in order to exclude any polishing effect
• Exclusion of ramps since the focus was on rural highways
• Use of HCV ranges in lieu of the road traffic R1 to R4 ranges
• Ignoring the size of the second chip for two coat chipseals (specifically 2CHIP and RACK)

The RAMM surface types reported in the national summary were 1CHIP (single coat chipseal), 2CHIP (two coat chipseal) and RACK (racked in two coat chipseal) for first chip grades 2, 3 and 4 for each of the four HCV daily (carriageway) flow ranges and for each of the three levels of horizontal curvature stress (low, mid or medium, high). The analyses were conducted for bituminous and emulsion binder types (Bxxx and Exxx) only, with the additive type adjustment applied to ensure that PMB and EMP (PME) were excluded.