Volume 39, Issue 6 (November 2011)
Modified Ignition Oven Test Procedure for Determination of Binder Content in Hot Mix Asphalt Containing Dolomite Aggregate
The binder content of hot mix asphalt (HMA) is most commonly determined either by solvent extraction or ignition oven (IO) methods. Generally, the IO method has worked well with various HMA mixtures except those containing certain types of high mass loss (decomposing) aggregates, especially dolomite. For these aggregates, the high temperatures experienced during the ignition process initiate chemical changes within the aggregate particles, which result in variable mass losses. This, in turn, causes difficulties in calculating a consistent correction factor and determining a repeatable binder content. This paper presents a modified IO binder content determination method, which involves lowering the test temperature to 427°C and reducing the sample mass by half. In addition, only the bottom material basket of the typical IO test setup is used to avoid errors in the results due to temperature differentials that develop when, upon ignition, mixture from the lower basket starts heating the mixture in the upper basket. The proposed method was successfully verified by using six different plant-produced mixtures.