01033783

Component

http://www.trb.org/Publications/Blurbs/156750.aspx

Many of the asphalt concrete mixtures designed using the Superpave mix design system are relatively stiff and difficult to compact. In order to properly densify these types of mixtures, it is necessary to keep the rollers directly behind the paver in order to apply the compactive effort while the mix is hot. Several different roller patterns can be employed, but the most efficient roller pattern typically uses a pneumatic tire roller for initial compaction followed by a double drum vibratory roller for intermediate, and often finish, rolling. Some Superpave designed mixtures, however, are very tender and move under the compactive effort of the rollers. These tender mixes shove in both the longitudinal and transverse direction and often check or crack while being compacted. For tender mixtures, three temperature zones typically exist--both an upper and a lower temperature zone where density can be obtained and an intermediate temperature zone where de-compaction of the mix occurs during the rolling process. For tender mixes, it is necessary to alter the roller patterns in order to achieve the required level of density in the upper temperature zone--before the mix starts to move and shove. The use of two double-drum vibratory (DDV) rollers operated in echelon directly behind the paver is the most efficient and effective method to achieve the desired level of density in such mixtures. The purpose of this paper is to review some of the possible causes for both stiff and tender asphalt concrete mixtures and to discuss how to properly compact each type of mix. For mixtures which exhibit tender characteristics, the contractor must be aware of the three temperature zones which typically exist during the rolling process.

01033774

English

pp 69-83

2006-9

Transportation Research Circular

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Photos (5) ; References (8)

Asphalt concrete; Compaction; Hot mix asphalt; Road rollers; Superpave; Temperature; Vibratory compaction

Stiff mixes; Tender mixes

Construction; Highways; Materials; I31: Bituminous Binders and Materials; I52: Construction of Pavements and Surfacings

TRIS, TRB

Sep 29 2006 11:31AM

• Basics of Longitudinal Joint Compaction
• Constructing Longitudinal Joints with Lower Voids
• Construction of Durable Longitudinal Joints
• Field Testing of the Zero-Shear Viscosity Method
• Fundamentals of Percent Within Limits and Quality Control–Quality Assurance Compaction Specifications
• Impact of Incentives on In-Place Air Voids
• Measurement of Longitudinal Joint Density in Asphalt Pavements Using Nuclear and Nonnuclear Gauges
• Oscillatory Compaction of Hot-Mix Asphalt
• Percent Within Limits Experience on a Design–Build Project
• Prediction of Compaction Temperatures Using Binder Rheology
• State-of-the-Practice for Cold-Weather Compaction of Hot-Mix Asphalt Pavements
• Vibratory Pneumatic Tire Roller
• Vibratory Rollers