Compliance Standards:
- ASTM D6307-98 and AASHTO T30
Brief Details:
- The Asphalt Content/Binder Furnace with internal automatic balance is an environmentally-friendly and cost-effective method for the accurate determination of asphalt content. Ignition method reduces testing time compared to solvent testing methods and automatic operation frees technicians for other tasks. Accurate internal balance monitors weights automatically throughout ignition. Easy operation- simply enter sample weight, calibration factor, load the sample, and push start, when unit beeps at test end, push stop, and sign receipt.
Why Aggregate Mineral Content Changes the Result
- Aggregate Mass Loss: High temperatures (typically at 538 C) or burn off the asphalt binder, but they also thermally degrade certain minerals in the stone aggregate.
- Chemical Breakdown: Minerals like calcium carbonate in limestone or chemically bound water in soft aggregates decompose and escape as gas.
- False Readings: The oven measures weight loss to determine asphalt content. It cannot distinguish between burned asphalt and vaporised aggregate minerals.
- Overestimated Binder: This unintended stone weight loss is incorrectly calculated as extra asphalt binder, leading to inaccurate quality control data.
The Solution: Aggregate Correction Factors
To counteract this limitation, laboratories must determine an Aggregate Correction Factor (ACF) for every specific mix design before testing production samples.
- Blank Testing: Technicians mix a known, precise amount of asphalt binder with the exact aggregate blend used on the project.
- Factor Calculation: The sample is burned in the ignition oven. The difference between the actual asphalt added and the oven's measured loss yields the correction factor.
- Application: This correction percentage is subtracted from all subsequent production test results to yield the true asphalt content.
- Re-Calibration: If the aggregate quarry source changes, or if the natural mineral percentages within the same quarry shift, a brand new correction factor must be established immediately.