Field conditioning of superpave asphalt mixes

Failing volumetric properties (low air voids and voids in mineral aggregate) have been a common occurrence in the production of Superpave mixes in Florida and nationally. There are several potential causes of this problem including the effect of asphalt absorption as related to conditioning time. Research was done to determine (a) whether the 2-h force-draft oven conditioning adequately simulates actual roadway conditions and (b) how actual roadway conditions can best be simulated when the asphalt mixture is sampled and tested immediately following production at the plant. The results indicate the following: (a) 3 h of conditioning during design best correlated with roadway conditions; (b) a 1-h conditioning time at the asphalt plant resulted in maximum specific gravity values that best correlated with roadway conditions; (c) 1 h of conditioning at the asphalt plant increased the air voids of the mix by 0.5 percent for absorptive materials and 0.25 percent for nonabsorptive materials; and (d) conditioning had minimal effect on bulk density values.