Microwave method and apparatus for heating loose paving materials

In a hot-mix plant, the combination comprising:

• a rotary drum-mixer having a first stage with a new aggregates receiving port and a second stage with a reclaimed material port for receiving fragmented old asphaltic concrete or the like for intermixing with material heated in said first stage,
• means for establishing a hot gas flow within said drum-mixer,
• means for selectively feeding new aggregates into said new aggregates receiving port,
• a sorter for separating large fragments of said old asphaltic concrete or the like that exceed a predetermined size from small fragments which are of lesser size,
• a microwave heating chamber, and
• a conveyor system interconnecting said drum-mixer and said sorter and said microwave heating chamber and having means for carrying said small fragments from said sorter to said reclaimed material port of said drum-mixer, means for carrying said large fragments from said sorter to said microwave heating chamber, and means for recombining said large fragments with said small fragments following heating of said large fragments in said microwave heating chamber.

A recycler for heating and remixing reclaimed asphaltic concrete fragments or the like, comprising:

• a housing having a first heating chamber and a second heating chamber therein, said first heating chamber being below said second heating chamber,
• first heating means for establishing a hot gas flow in said first heating chamber,
• second heating means for directing microwave energy into materials within said second heating chamber,
• a sorting screen having openings which pass ones of said fragments that are smaller than a predetermined size, said screen being positioned in said housing to receive said fragments of asphaltic concrete or the like and to pass said smaller fragments to said first heating chamber while directing larger fragments to said second heating chamber,
• inlet structure secured to said housing in position to receive said fragments and to direct said fragments to said sorting screen, and a mixing device having an inlet communicated with both said first heating chamber and said second heating chamber to receive and mix heated material from each thereof.

Apparatus for heating fragmented paving material that includes loose fragments of different sizes, comprising:

• first heating means for heating fragments within a first heating chamber at least predominately by applying externally produced heat to the surfaces of the fragments within the first heating chamber,
• means for generating microwave energy,
• second heating means for generating heat internally within fragments in a second heating chamber by directing at least most of said microwave energy into said second heating chamber,
• sorting means for separating large fragments that exceed a predetermined size from small fragments of lesser size,
• means for transferring said small fragments from said sorting means to said first heating chamber and for transferring said large fragments from said sorting means to said second heating chamber,
• means for recombining said large fragments with said small fragments following microwave heating of said large fragments in said second heating chamber, and
• mixing means for remixing the recombined large and small fragments.