Friday, 11 September 2015

Soundness of cement

It is very important cement after setting shall not undergo ant appreciable change of volume. The determination of soundness of cement is necessary to ensure that the cement does not show any appreciable subsequent expansion.

The unsoundness in cement is due to % of excess of lime than that could be combined with acidic oxide at the kiln, excess of magnesia or excessive proportion of sulphates.

Soundness of cement is determined  by Lechatelier-Test.

It consists of small split cylinder of brass 0.5mm thick.This forms a mould 30mm. Internal diameter and 30mm high. On each side of split is attached an indicator having pointed end of each indication is 165mm.

The cement paste having 0.78P water filled in Lechatelier apparatus and covered by glass plate at both end and kept in water for 24hrs.

Measure the distance between indicator in mm. Again keep the assembly in boiling water for an hour.

Allow it to cool and measure the distance between the indicator in mm.

The difference between 1st and this reading gives the soundness of cement.

It should not exceed 10mm.