Water-Cement Ratio

w / c = W_{w} / W_{c} (mass)

Abrams' law: lower w/c → higher strength and lower permeability, provided the mix is workable and well cured. Typical structural w/c ≈ 0.40–0.50. Durability (chloride, freeze-thaw) often caps w/c (e.g. 0.45). Do not confuse w/c with slump (workability also depends on admixtures and aggregate).

$w / c$: Water-cement mass ratio
$W_{w}$: Mass of mixing water
$W_{c}$: Mass of cement

Step-by-step solved example

Cement 400 kg, water 180 kg. w/c? If water increases 20 kg with cement fixed, new w/c?

Water vs cement in the paste — the water occupies volume in the mix.

1. Original
w/c = 180/400 = 0.45.
2. New
200/400 = 0.50. Strength expected to drop.

Answer: 0.45 then 0.50

10 practice questions

0/10 correct

1.w/c is a ratio of

2.Lower w/c, well compacted, generally gives

3.A durability spec of w/c ≤ 0.45 is typically for

4.Water 160 lb, cement 400 lb. w/c =

5.High-range water reducer (superplasticizer) lets you

6.w/cm uses

7.If cement is doubled and water is doubled, w/c

8.Bleed water increases when

9.Curing is still required at low w/c because

10.Typical structural w/c is nearest