Method and apparatus for analyzing asphalt content

An apparatus for pyrolysis of a bituminous paving mix containing aggregate and a combustible asphalt binder, said apparatus comprising:

• an oven having a bottom wall, a top wall, side walls and an access door defining a combustion chamber;
• a sample support provided within said combustion chamber;
• a sample container for receiving and supporting a sample of the paving mix, said sample container being positionable on said sample support;
• a weighing device operatively connected to said sample support for obtaining weight measurements of the sample during pyrolysis thereof;
• an infrared heater mounted within said oven oriented to direct infrared radiation at said sample support so as to heat the sample of paving mix to combustion by means of infrared radiation heat transfer;
• an air inlet positioned for admitting air into the combustion chamber;
• an outlet for discharging combustion gases from the combustion chamber, said outlet being positioned in spaced relation from said air inlet to thereby provide for the circulation of air and combustion gases generally through the combustion chamber;
• a plenum chamber mounted on the outside of said combustion chamber and communicating therewith via said outlet, an exhaust flue connected to said plenum chamber for discharging exhaust gases therefrom;
• and
• a blower mounted between said plenum chamber and said exhaust flue and operable for inducing a flow of air into the combustion chamber via said air inlet and for drawing exhaust gases from the combustion chamber into said plenum chamber via said outlet.

An apparatus for pyrolysis of a bituminous paving mix containing aggregate and a combustible asphalt binder, said apparatus comprising:

• an oven having a bottom wall, a top wall, side walls and an access door defining combustion chamber;
• a sample support provided within said combustion chamber;
• a multi-tier sample basket for receiving a sample of the bituminous paving mix and arranging the sample in a plurality of thin layers for pyrolysis, said sample basket being removably positionable within the oven on said sample support;
• an internal weighing device operatively connected to said sample support for obtaining weight measurements of the sample during pyrolysis thereof;
• an infrared heater mounted within said oven in an upper portion of said combustion chamber and oriented to direct infrared radiation generally downwardly at said sample support so as to heat the sample of paving mix to combustion by means of infrared radiation heat transfer;
• an air inlet positioned for admitting air into the combustion chamber at a location above said sample support;
• an outlet positioned for discharging combustion gases from the combustion chamber at a location below said air inlet to thereby provide for the circulation of air and combustion gases generally downwardly through the combustion chamber;
• and
• a blower located on the downstream side of said outlet and cooperating therewith for inducing a flow of air into the combustion chamber via said air inlet and for drawing exhaust gases from the combustion chamber via said outlet.

A method for assaying the asphalt content of a bituminous paving mix, said method comprising:

• placing a sample of a bituminous paving mix containing aggregate and a combustible asphalt binder in a sample container;
• placing the sample container with the sample of bituminous paving mix in a combustion chamber of an oven;
• exposing the sample to radiation from an infrared heater;
• heating the paving mix sample by infrared radiation heat transfer from the infrared heater to ignite and combust the asphalt binder;
• introducing airflow into the combustion chamber through an inlet to fuel the combustion of the asphalt binder;
• discharging combustion gases from the combustion chamber through an outlet;
• adjusting at least one of the temperature of the infrared heater and the rate of airflow through the combustion chamber during said heating step.

A method for assaying the asphalt content of a bituminous paving mix, said method comprising:

• placing a sample of a bituminous paving mix containing aggregate and a combustible asphalt binder in a sample container;
• placing the sample container with the sample of bituminous paving mix a combustion chamber of an oven;
• exposing the sample to radiation from an infrared heater;
• heating the paving mix sample by radiating heat transfer from the infrared heater to ignite and combust the asphalt binder;
• introducing airflow into the combustion chamber through an inlet to fuel the combustion of the asphalt binder;
• discharging combustion gases from the combustion chamber through an outlet;
• maintaining the airflow through the combustion chamber at an initial relatively low rate;
• sensing the onset of combusting of the asphalt binder;
• and in response thereto increasing the rate of airflow through the combustion chamber during a subsequent period.

A method for assaying the asphalt content of a bituminous paving mix by combustion in an oven, said method comprising:

• measuring the weight of an empty sample container using an external weighing device;
• placing a sample of a bituminous paving mix containing aggregate and a combustible asphalt binder in the sample container;
• measuring the filled weight of the sample container using a weighing device located external to the oven;
• determining a first initial weight of the sample using the weight of the empty sample container and the externally-measured filled weight of the sample container;
• placing the sample container with the sample of bituminous paving mix in a combustion chamber of the oven;
• measuring the filled weight of the sample container using an internal weighing device operatively positioned within the oven;
• determining a second initial weight of the sample using the weight of the empty sample container and the internally-measured filled weight of the sample container;
• determining the difference between the first initial weight and the second initial weight, the difference being a weight loss correction factor;
• exposing the sample to radiation from an infrared heater;
• heating the paving mix sample by radiation heat transfer from the infrared heater to ignite and combust the asphalt binder;
• introducing airflow into the combustion chamber through an inlet to fuel the combustion of the asphalt binder;
• discharging combustion gases from the combustion chamber through an outlet;
• measuring the final weight of the paving mix after combustion of the asphalt binder using the internal weighing device;
• and
• applying the weight loss correction factor to the measured final weight to obtain a corrected final weight.