Water-Cement Ratio (w/c)

The water-cement ratio (w/c) is the ratio of water weight to cement weight in a concrete mix, and it is the single biggest factor controlling strength, permeability, and durability. Lower ratios generally produce stronger, less permeable concrete but can reduce workability unless offset with admixtures.

Typical structural mixes fall in the 0.40–0.55 range; ACI 211 mix-design tables select a target w/c ratio based on the desired compressive strength.