Process for making asphalt concrete

Abstract

A process for making asphalt concrete comprises mixing starting materials including aggregate and binder material and optionally, other additives, to a final temperature of about 60° C. to about 150° C. in an indirectly heated mixing chamber which is sealed. The moisture content of the asphalt concrete mixture is controlled as a function of the moisture content of the starting materials. Apparatus for performing the process in a continuous or batch operation is also set forth.

I claim: 
     
       1. A process for making asphalt concrete comprising: (a) selectively sealing a mixture of starting materials comprising aggregate and binder, such that said mixture does not communicate with the atmosphere,   (b) mixing and indirectly heating said mixture while so sealed, and   (c) controlling the moisture content of said mixture to a predetermined amount by either removing moisture from said mixture in the form of water vapor when said moisture content is greater than said predetermined amount until said moisture content equals said predetermined amount, or adding water into said mixture when said moisture content is less than said predetermined amount until said moisture content equals said predetermined amount.   
     
     
       2. A process in accordance with claim 1 wherein said binder material is selected from the group consisting of asphalt cement, asphalt cement-water emulsions, sulfur, and mixtures thereof. 
     
     
       3. A process in accordance with claim 1 including adding a surfactant to said mixing chamber. 
     
     
       4. A process in accordance with claim 1 including the further step of detecting the moisture content of the starting materials prior to said mixing and indirect heating thereof. 
     
     
       5. A process in accordance with claim 1 wherein said aggregate is selected from the group consisting of raw virgin aggregate, recycled aggregate, and mixtures thereof. 
     
     
       6. A process in accordance with claim 1 wherein said mixture is heated to a final temperature in the range of between about 60° C. and about 150° C. 
     
     
       7. A process in accordance with claim 1 wherein said moisture content of said mixture is adjusted to a moisture content in the range of between about 0.1% and about 10%. 
     
     
       8. A process in accordance with claim 1 including heating said mixture to a temperature in excess of 100° C., and removing moisture from said mixture in the form of water vapor by virtue of the vapor pressure of said water vapor. 
     
     
       9. A process in accordance with claim 1 which further comprises condensing said water vapor when moisture is removed. 
     
     
       10. A process in accordance with claim 9 further comprising the step of recycling gases back to said mixture after condensing said water vapor. .Iadd.11. In a process for making asphalt concrete (a) selectively sealing a mixture of starting materials including aggregate in a mixing chamber such that said mixture does not communicate with the atmosphere,   (b) indirectly heating said mixture while so sealed,   (c) evaporating some moisture from said mixture to form water vapor,   (d) condensing said water vapor by indirectly exchanging the heat in said water vapor to at least one of said starting materials which heats said starting material prior to the sealing of said mixture in said mixing chamber. .Iaddend. .Iadd.12. A process for making asphalt concrete comprising:   (a) selectively sealing a mixture of starting materials comprising aggregate and binder, such that said mixture does not communicate with the atmosphere,   (b) mixing and indirectly heating said mixture while so sealed,   (c) evaporating some moisture from said mixture to form water vapor,   (d) condensing said water vapor by indirectly exchanging the heat in said water vapor to at least one of said starting materials which heats said   
     
     
        starting material prior to said mixing step. .Iaddend. .Iadd.13.  A process in accordance with claim 12 further comprising heating said mixture to a temperature in excess of 100° C. .Iaddend. .Iadd.14. A process in accordance with claim 13 further comprising heating said mixture to a temperature at which a positive vapor pressure is created sufficient to cause said water vapor to migrate under its own pressure from a mixing means in which said mixture is mixed to a condensing means in which said water vapor is condensed. .Iaddend. .Iadd.15. A process in accordance with claim 12 wherein said moisture is evaporated until said mixture has a moisture content in the range of between about 0.1% and about 10%. .Iaddend. .Iadd.16. A process for making asphalt concrete comprising: (a) selectively sealing a mixture of starting materials comprising aggregate and binder, such that said mixture does not communicate with the atmosphere,   (b) mixing and indirectly heating said mixture while so sealed,   (c) evaporating pollutants and some moisture from said mixture to form gases and water vapor,   (d) condensing said gases and said water vapor by indirectly transferring heat contained therein to at least one of said starting materials. .Iaddend. .Iadd.17. A process in accordance with claim 16 further comprising removing pollutants from said condensed gases and water vapor. .Iaddend. .Iadd.18. A process in accordance with claim 16 further comprising heating said mixture to a temperature in excess of 100° C. .Iaddend. .Iadd.19. A process in accordance with claim 18 further comprising heating said mixture to a temperature at which a positive vapor pressure is created sufficient to cause said gases and said water vapor to migrate under their own pressure from a mixing means in which said mixture is mixed to a condensing means in which said gases and said water vapor is condensed. .Iaddend. .Iadd.20. A process in accordance with claim 16 wherein said moisture is evaporated until said mixture has a moisture content in the range of between about 0.1% and about 10%. .Iaddend.