TENDER MIXES--PROBABLE CAUSES, POSSIBLE REMEDIES

Many different factors have the potential for promoting tenderness in asphalt mixes. Potential tender mixes may be identified at the mix design stage by examining: (1) aggregate shape and texture; (2) mix gradation; (3) properties of the asphalt cement; and, (4) tensile or resilient modulus tests on laboratory mixes. Tender mixes may pose problems at the construction stage or the in-service performance stage or both. The potential causes are many, but the more likely reasons are: (1) aggregate shape and texture, excess sand and low filler contents in the mix; (2) moisture in the mix; (3) excess additives; (4) high rolling temperatures; (5) high ambient temperatures; (6) high asphalt cement content and (7) asphalt cement characteristics (high temperature susceptibility, slow setting, less than 10% asphaltenes, etc.). Most tender mixes eventually "set up" in due course, although they may tend to shove and rut under heavy traffic conditions. The biggest problem is evident at the construction stage for the contractor in that tender mixes are difficult to compact. Delaying rolling until the mix is stable enough to accommodate compaction equipment is suggested as a solution, but only if adequate density of compaction can be achieved. In this case, the vibratory roller should be operated initially in the static mode. The use of a lighter roller initially has also been recommended. Attempts to recompact with high pressure tire rolling may actually induce decompaction.

• Corporate Authors:

  National Asphalt Pavement Association (NAPA)

  5100 Forbes Boulevard
  Lanham, Maryland  United States  20706
• Authors:
  • Crawford, C
• Publication Date: 1986-3

Media Info

• Features: Figures; References;
• Pagination: 9 p.

Subject/Index Terms

• TRT Terms: Additives; Aggregate gradation; Aggregates; Asphalt cement; Asphalt mixtures; Compaction; Construction; Fillers (Materials); Mix design; Modulus of resilience; Moisture content; Performance; Rollers; Rolling; Temperature; Vibratory equipment
• Uncontrolled Terms: Causes; Tender mixes; Vibratory rollers
• Old TRIS Terms: Gradation; Remedies
• Subject Areas: Construction; Geotechnology; Highways; Materials; I31: Bituminous Binders and Materials;

Filing Info

• Accession Number: 00457639
• Record Type: Publication
• Report/Paper Numbers: QIP 108-3/86
• Files: TRIS
• Created Date: Aug 31 1986 12:00AM