new hampshire superpave experience - university of … rawson_oct08.pdf · new hampshire superpave...

New Hampshire SuperpaveExperience

New Hampshire Superpave Experience

First Two Projects —1997

Fully Implemented — 2003

Don’t Forget What You Know!


Prior to Superpave; Marshall Design StateSouth - AC 20North - AC 1012.5 mm Wearing SurfaceRutting - not an issueEnvironmental Cracking - biggest concern


Started Using New Hampshire Superpave Binders in circa 1996

Primary Grade PG 64-28

Secondary Grade PG58-28; PG58-34


Poor durability on early Superpave mixes!Early distress crackingRavelingLongitudinal joints crackedHard to compact with high in-place voidsHighly permeableLow asphalt content & very coarse


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


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


Don’t forget what you know!

new hampshire superpave experience - university of … rawson_oct08.pdf · new hampshire superpave...

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