Approximately 500 million tons of hot mix asphalt (HMA) are placed in the United States each year. With this large quantity of HMA, it is expected that some construction problems will occur from time to time. One problem that has been observed for years, on a small percentage of projects is tenderness of some mixtures during compaction. Tender mixtures are not stable under the roller and tend to move laterally when rolled. The lateral movement sometimes results in hair-line cracks, often referred to as checking. Most information indicates that for tender mixes the tenderness begins once the surface temperature of the mat drops to approximately 240 F and tenderness continues until the temperature drops to about 180-190 F and on some jobs as low as 150 F. This temperature range (150-240 F) in which the mix is tender has been referred to as the tender zone. The objective of this paper is to provide guidance on handling of mixes that may be tender during compaction. Information is provided for techniques to reduce mix tenderness and recommendations are made for preferred compaction techniques that continue to act tender. 15p.
Six different AC-20 asphalt cements were used in a Pennsylvania project in September 1976. Two of the six test pavements developed low-temperature cra...
According to Superpave mixture design, gyratory specimens are mixed and compacted at equiviscous binder temperatures corresponding to viscosities of 0...
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