PORTLAND CEMENT CONCRETE - Materials for Civil and Construction Engineers - page 242

T ABLE 7.3 Maximum Water-Cementitious Material Ratios and Minimum Design Strengths
for Various Exposure Conditions*

Maximum Water-Cementitious
Material Ratio by Mass for Minimum Design Compressive

f œ ,

Exposure Condition Concrete Strength, MPa (psi)

Concrete protected from Select water-cementitious Select strength based on

exposure to freezing and material ratio on basis of structural requirements

thawing, application of strength, workability, and

deicing chemicals, or finishing needs

aggressive substances
Concrete intended to 0.50 28 (4000)

have low permeability
when exposed to water
Concrete exposed to 0.45 31 (4500)

freezing and thawing in
a moist condition or
deicers
For corrosion protection 0.40 35 (5000)

for reinforced concrete
exposed to chlorides from
deicing salts, salt water,
brackish water, seawater,
or spray from these sources

*American Concrete Institute (ACI 318), 1999.

meter of mix. Round aggregates require less water than angular aggregates for
an equal workability.
The maximum allowable aggregate size is limited by the dimensions of
the structure and the capabilities of the construction equipment. The largest
maximum aggregate size practical under job conditions that satisfies the size
limits in the table should be used.

Situation Maximum Aggregate Size

Form dimensions 1/5 of minimum clear distance

Clear space between reinforcement or
prestressing tendons 3/4 of minimum clear space

Clear space between reinforcement and form 3/4 of minimum clear space

Unreinforced slab 1/3 of thickness