ABSTRACT
Concrete diers in many ways from other engineering materials, exhibiting not only several unique benecial characteristics but also some detrimental ones. e advantages of this material are (1) it can be made from local components in almost all parts of the world; (2) it can be cast into complex shapes at ambient temperatures; (3) it does not require any post-casting treatment other than being kept moist for a few days; and (4) the cost of its production is signicantly lower than any alternative material, such as steel. On the other hand, the micro-and macrostructures of concrete, consisting of natural stone bonded together with a more or less porous, highly alkaline, multiphase cement paste, can lead to a variability of properties unless the components, mixture proportions, and construction procedures are carefully controlled. ese same characteristics also lead to the susceptibility of concrete to environmental degradation. e alkalinity means that the paste component is vulnerable to dissolution in acidic media. e solution-lled porosity allows ingress of deleterious species and leaching of soluble components of the cement paste. In those parts of the world that experience repeated freezing and thawing, the expansion of the pore solution on freezing can lead to cracking of the concrete and, where de-icing salts are used, scaling of the surface. Nevertheless, as mentioned earlier, appropriate mixture design and proportioning, careful placement, compaction, and sucient curing can minimize the risk of premature deterioration. Together with the use of chemical admixtures to counteract some of these weaknesses, the concrete industry is able to produce a material tailored to the local environment and able to withstand the forces of both man and nature for its specied service life.
