Measured Aggregate Absorption ('as is')

The percentage by weight of the water, which the aggregate would lose if dried in its condition at the time of the mixing of the concrete, should be entered. The percentage is equal to

100(Wasis – Wdry)/Wdry

where:

Wasis = weight of given quantity of aggregate in the ‘as is’ condition.

Wdry = weight of same quantity of dry aggregate.

If the ‘as is’ absorption is less than the ‘at set’ absorption, Firstmix assumes that the difference between the ‘at set’ absorption and the ‘as is’ absorption represents the amount of water absorbed by the aggregate in the period between the mixing and the setting of the concrete. It therefore indicates the difference between the quantity of mix water and the free water content.

If on the other hand the ‘as is’ absorption is greater than the ‘at set’ absorption, Firstmix assumes that the difference between the ‘as is’ absorption and the ‘at set’ absorption represents the amount of surface water on the aggregate which will be added to the free water content.