Other Durability considerations:
As stated previously, there are other performance characteristics of concrete related to durability such as
resistance to freezing and thawing, sulfate damage, permeability, and corrosion. The American
Concrete Institute (ACI) 318 Building Code Requirements for Structural Concrete uses the w/cm as the
primary concrete mixture parameter to achieve the minimum durability requirements for concrete in
buildings. It states “the licensed design professional shall assign exposure classes based on the severity
of the anticipated exposure of structural concrete members for each exposure category.” 6
ACI 318 then requires that concrete mixtures comply with the most restrictive requirements according to
a table in the document which lists limitations including a maximum water to cementitious materials ratio
(w/cm) and minimum specified compressive strength (f’c) for each exposure class of concrete. The ACI
318 table also includes additional minimum requirements of other parameters such as air content,
cementitious materials types and limitations regarding the types, the use of calcium chloride admixtures,
maximum water-soluble chloride ion content in concrete expressed as percent by weight of the cement,
and other related provisions.
While ACI 318 requires a maximum w/cm for durability, it has a companion specified compressive
strength, f’c for each level of w/cm. This is a recognition that w/cm cannot be reliably measured and
verified for conformance to the requirement, while compressive strength can. ACI 318 provides
commentary related to the requirement that concrete mixtures shall be proportioned to comply with the
maximum w/cm and the other requirements based upon the anticipated exposure classification of the
structural concrete.