Water Calculations in Concrete Mix 1

[fastrex]

When calculating the water to cement ratio for a mix, is the water calculated by determining the free water in the aggregates as including the water necessary to bring the aggregate from Oven Dry Condition to Saturated Surface Dry (SSD) condition?

i.e:
Is the water an aggregate contributes to a mix when calculating the water to cement ratio (W/C):
Water = Weight of Aggregate - Weight of Agg. in Oven Dry condition

or:

Water = Weight of Aggregate - Weight of Aggregate in SSD

 

[samay]

In most of the mix designs the free water in aggregates do not account for water cement ratio. But I do believe that it should account both the free water and absorption of aggregates in the same manner as the cementitious materials do. If not, the amount of water and w/c ratio will differ from material to material for the same class of concrete.

http://concrete.union.edu/design.htm

based on the ACI code do not include the free water in the ratio.

 

[bimr]

The concrete supplier must ensure that the amount of free-water in the mix does not vary from that called for in the mix design. Batch plant operators monitor aggregate moisture to determine if there is any free-water in the aggregate or if the aggregate is so dry that it will absorb water that is added to the mix. It is rare to have aggregate at the batch plant that is in the saturated surface dry condition where the amount of add-water would equal the amount of free-water called for in the mix. Batch plant operators have to compute the amount of add-water by subtracting the amount of aggregate free-water from the amount of free-water shown on the mix design. The equation for this is:

Add water = free-water shown on the mix design – aggregate free-water

ftp://ftp-fc.sc.egov.usda.gov/NEDC/pdf/concrete.pdf