Water / Cement Ratio

[M40A]

Doesn't the absorbed water, in aggregate(s), effect the water/cement ratio?

The below definition would indicate not, but couldn't the absorbed water play a part in the total water/cement ratio?



As defined in ACI 2008:

Water-cement ratio - the ratio of the mass of water, exclusive only of that absorbed by the aggregates, to the mass of portland cement in concrete, mortar, or grout, stated as a decimal and abbreviated as w/c.

 

[bimr]

Aggregate moisture content must be accounted for because PCC productin does not require dried aggregate.

Aggregate moisture affects the following parameters:

Aggregate volumes are calculated based on oven dry unit weights, but aggregate is typically batched based on actual weight. Therefore, any moisture in the aggregate will increase its weight and stockpiled aggregates almost always contain some moisture. Without correcting for this, the batched aggregate volumes will be incorrect.

If the batched aggregate is anything but saturated surface dry it will absorb water (if oven dry or air dry) or give up water (if wet) to the cement paste. This causes a net change in the amount of water available in the mix and must be compensated for by adjusting the amount of mixing water added.

 

[M40A]

Understandable - that's what my thoughts were on the matter; but, where is it reference in ACI?

 

[Ron]

M40A...it is in ACI 304; however, "Design and Control of Concrete Mixes" published by the Portland Cement Association gives a good treatment of the subject as well.