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New Hampshire Superpave Experience
First Two Projects —1997
Fully Implemented — 2003
Don’t Forget What You Know!
New Hampshire Superpave Experience
Prior to Superpave; Marshall Design StateSouth - AC 20North - AC 1012.5 mm Wearing SurfaceRutting - not an issueEnvironmental Cracking - biggest concern
New Hampshire Superpave Experience
Started Using New Hampshire Superpave Binders in circa 1996
Primary Grade PG 64-28
Secondary Grade PG58-28; PG58-34
New Hampshire Superpave Experience
Poor durability on early Superpave mixes!Early distress crackingRavelingLongitudinal joints crackedHard to compact with high in-place voidsHighly permeableLow asphalt content & very coarse
New Hampshire Superpave Experience
Changes to improve durability of Superpave mixes in 2003 & 2004:
Don’t use 125 & 100 gyration mixesEliminated restricted zoneMinimum asphalt content; 12.5 mm surface mix onlyFiner Gradations; More passing the #8 (2.36mm) sieve Developed 50 gyration mixesRecently developed 75 gyration, 9.5 mm mixUse raised longitudinal joint & joint adhesive
New Hampshire Superpave Experience
Today---Pleased with Superpave mixesRutting; not a problemNot porousHave not observed paver segregationEasier to compact; in-place voids 5 to 6.5%DOT Highway Maintenance, DOT Construction & Contractors like these mixes Less salt usage & easier to get ice pack offLong term durability looks good