BINDER CONTENT OF PAVING MIXTURES.
( SP : 11 – 1976 )
Object:
To determine the binder content in the mix by cold solvent extraction.
Apparatus:
a) Centrifugal extraction machine electrically operated.
b) Balance – 15 kg capacity – sensitivity 0.1gm.
c) Cold solvent – Commercial grade of Benzene.
d) Filter paper – Wat 60.
e) Oven.
Procedure:
A representative sample about 1000gm is exactly weighed and placed in the bowl of the extraction apparatus and covered with commercial grade of benzene. Sufficient time (not more than 1 hour) is allowed for the solvent to disintegrate the sample before running the centrifuge.
The filter paper of the extractor is dried, weighed and then fitted around the edge of the bowl. The cover of the bowl is clamped tightly. A beaker placed under to collect the extract.
The machine is revolved slowly and then gradually increases the speed, maximum of 3600 rpm. This speed is maintained till the solvent ceases to flow from the drain. The machine is allowed to stop and 200ml of benzene is added and the above procedure is repeated. A number of 200ml solvent additions (not less than three) are used till the extract is clear and not darker than a light straw colour.
The filter paper removed from the bowl, dried in air then in oven to constant weight at 1150C and weighted the fine materials that might have passed through the filter paper are collected back from the extract preferably by centrifuging. The material is washed and dried to constant weight as before. The percentage of binder in the sample is calculated as below.
W1 – ( W2 + W3 ) + W4
W1
Where W1 = Weight of sample.
W2 = Weight of the sample after extraction.
W3 = Weight of Fine material recovered from the extract.
W4 = Increase in weight of the filter paper.
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