Process for recycling asphalt-aggregate compositions

Abstract

In recycled asphalt-aggregate compositions prepared by adding a suitable amount of make-up asphalt to pieces of the used composition and heating the mixture in a rotating cylindrical drum by tumbling the composition over heated pipes as it is gradually directed towards an output end of the drum, the improvement comprising adding an amount of petroleum hydrocarbon to achieve a laid down asphalt penetration of between 25 and 300 dmm at 77° F. A further embodiment of the improved process comprises venting a mixture of hydrocarbon gases and moisture vaporized from the hot composition mixture at the output end of the apparatus, condensing the moisture and removing it and returning the hydrocarbon gases to a combustion chamber for providing heat to the apparatus tubes. Still another improvement comprises an apparatus modification wherein a plurality of relatively short pipes are disposed in the forward ends of the heating tubes through a front plate displaced from the forward end wall of the drum with the open pipe ends exposed to the combustion chamber for providing heat to the interior of the heating tubes.

I claim 
     
       1. In a process for recycling used asphalt-aggregate composition comprising heating and mixing said composition in a heating and mixing chamber, the improvement comprising adding to said composition an amount of petroleum hydrocarbon having at least 55% aromatics.Iadd., and heating and mixing the composition at a temperature of at least about 200° F. .Iaddend.to achieve a product having a penetration of between about 25 and about 300 dmm at 77° F. 
     
     
       2. The process of claim 1 wherein said composition is heated to at least about 200° F. prior to adding said hydrocarbon, and mixing said composition and said hydrocarbon in said chamber to produce said product. 
     
     
       3. The process of claim 2 wherein said hydrocarbon has a flash point above about 300° F. 
     
     
       4. The process of claim 3 wherein said hydrocarbon has an initial boiling point above about 500° F. 
     
     
       5. A process for recycling used asphalt-aggregate composition comprising introducing said composition in a heating and mixing chamber, detecting the asphalt deficiency of the composition, adding an amount of make-up asphalt to said composition in response to the detected deficiency, gradually heating and mixing said composition and make-up asphalt in said chamber, and adding an amount of petroleum hydrocarbon having at least 55% aromatics to the mixture in the mixing chamber.Iadd., and heating and mixing the composition at a temperature of at least about 200° F. .Iaddend.to achieve a product having a penetration of between about 25 and about 300 dmm at 77° F. 
     
     
       6. The process of claim 5 wherein said hydrocarbon has a flash point above about 300° F. 
     
     
       7. The process of claim 6 wherein said hydrocarbon has an initial boiling point above about 500° F. 
     
     
       8. The process of claim 5 wherein said hydrocarbon is added to said mixture after it has been heated to above about 200° F. 
     
     
       9. The process of claim 1 wherein the asphalt of the product achieved has a ductility of at least 150 cm at 77° F. 
     
     
       10. The process of claim 5 wherein the asphalt of the product achieved has a ductility of at least 150 cm at 77° F.