7.1 General
A durable concrete is one that meets predetermined expectations under the working environment (exposure) conditions during its service life. The materials and mix proportions specified and used should be such as to maintain its integrity and, if applicable, to protect embedded metal from corrosion.
7.1.1 One of the main characteristics influencing the durability of concrete is its permeability to the ingress of water, oxygen, carbon dioxide, chloride, sulphate and other potentially deleterious substances. Impermeability is governed by the constituents and workmanship used in making the concrete. With normal-weight aggregates a suitably low permeability is achieved by having an adequate cement content, sufficiently low free water/cement ratio, by ensuring complete compaction of the concrete, and by adequate curing.
The factors influencing durability include,
a) the environment;
b) the cover to embedded steel;
c) the type and quality of constituent materials;
d) the cement content and water-cement ratio of the concrete;
e) workmanship, to obtain full compaction and efficient curing; and
f) the shape and size of the member.
The degree of exposure anticipated for the concrete during its service life together with other relevant factors relating to mix composition, workmanship, design and detailing should be considered. The concrete mix to provide adequate durability under these conditions should be chosen taking account of the accuracy of current testing regimes for control and compliance as described in this Subsection.