In US practice one sack is 94 lb of portland cement, about one loose cubic foot, and flatwork and residential orders state cement content in sacks per cubic yard. A five-sack mix carries 470 lb of cement per yard and a six-sack mix 564 lb, roughly the step from light residential flatwork to a sturdier commercial mix. Engineered specs call for strength and w/cm instead, while crews and small contractors order by the sack.
Just send me a six-sack with fiber, it's a driveway, not a bridge deck.
Sack count describes cement content, not strength, so a six-sack mix with too much water can still break low.
Also heard as
- bag
- six-sack
- five-and-a-half sack
Related terms
Portland cement
The gray powder that reacts with water to bind sand and stone together into concrete.
Mix design
The recipe for a concrete mix: the weights of cement, SCMs, water, aggregates and admixtures per cubic yard.
Yard
One cubic yard of concrete, 27 cubic feet, the unit used for every US ready-mix order and invoice.
w/cm
Water-to-cementitious-materials ratio: the weight of mix water divided by the weight of cement plus SCMs.