# 106.3.2.51 TM-51, Determination of Bitumen in Bituminous Paving Mixtures

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This method describes a procedure for determining the percent bitumen in bituminous paving mixtures.

## 106.3.2.51.1 Reagents and Apparatus

a) Microwave oven with adjustable heating rate.

b) Extraction apparatus as described in AASHTO T164-86, Method A, except that the extraction bowls shall be large enough to contain a sample of at least 2000 g.

c) Centrifuge capable of a minimum centrifugal force of 770 g.

d) Balance with a minimum of 5000 g capacity capable of weighing to 0.l g.

e) Centrifuge tubes with a minimum capacity of l00 ml.

f) Graduated cylinders, 2000 ml and l00 ml capacity.

g) Containers for drying aggregate. These must be of a material suitable for microwave ovens, and of a size to contain at least 2000 g of aggregate.

## 106.3.2.51.2 Procedure

Place the sample as received in a microwave oven and adjust the oven so that the sample heats to a maximum temperature of 115° C and is workable. Weigh a minimum of 2000 g of the sample into an extraction bowl and record the weight (S) to the nearest 0.l g. Cover the sample with trichloroethylene and allow to stand until the sample has disintegrated (not more than 1 hour). Place the bowl in the extraction apparatus. Determine the dry weight of a filter ring and place it around the edge of the bowl. Clamp the cover on the bowl and place a suitable container under the drain to collect the extract and washings.

Start the centrifuge revolving slowly, gradually increase the speed to approximately 3000 rpm and maintain that speed until solvent ceases to flow from the drain. Wash the sample with 200 ml additions of trichloroethylene until the extract is a light straw color (not less than three additions).

Add the washings to the extract and set aside for determination of mineral matter.

Remove the filter ring from the bowl and carefully transfer all the aggregate to a suitable container. Dry the aggregate and filter ring to constant weight in a microwave oven. The weight of the extracted aggregate (A) is equal to the weight of the aggregate in the container plus the increase in weight of the filter ring.

Measure the volume of the total extract that was set aside above. Stir thoroughly and measure an aliquot of at least 100 ml. Place the aliquot in a centrifuge tube which has been weighed to the nearest 0.1 g. Centrifuge for 20 minutes at a force of 770 g. Decant the liquid and add 50 ml of trichloroethylene. Stir well and repeat the centrifuging. Subtract the original weight of the centrifuge tube to get the weight of the mineral matter. This weight multiplied by the aliquot factor equals the weight of mineral matter in the sample (M).

## 106.3.2.51.3 Calculation

Calculation for type B and type C mixes

% Bitumen = ${\displaystyle 100\times {\frac {S-(A+M)}{S}}}$

Calculation for bituminous base and bituminous pavement mixes

% Bitumen = ${\displaystyle 100\times {\frac {S-(A+M)}{A+M}}}$

Where:

S = Weight of sample
A = Weight of extracted aggregate
M = Weight of extracted mineral matter