The adverse weather conditions such as shrinkage and welling, freezing and thawing, heating and cooling, exposure to high temperature and other environments such as acids and sulphates during selection of material and method of placing etc.
1) Consideration of secondary stress:
Due to the conditions such as uneven drying and wetting, heating and cooling etc; the stresses are produced and the magnitude of that depends upon element size, relative humidity and ambient temperature. Hence for consideration of these stresses, the various methods as well as codal provisions should be followed in the design of the concrete.
For instance, if mass concreting is done, it is good to use aggregate of low thermal expansion coefficient to lower thermal strain in concrete because the coefficient of thermal expansion of concrete as directly proportional to that of aggregate used.
2) Appropriate selection of constituents:
- Capillary pores present in hydrated cement paste phase are very critical in shrinkage and swelling of concrete element due to drying and wetting. Stresses are developed when the water is absorbed during wetting and evaporated during drying. Hence to minimize this, proper grades of aggregates, smaller sized aggregate and low water cement ratio is used.
- In order to minimize the effect of the temperature stresses in the restrained condition the aggregate having low coefficient of thermal expansion (e.g. limestone) is used.
- To minimize the cyclic stresses developed in concrete due to freezing and thawing air entraining agents are used and special mix design methods are followed for use of these admixtures.
3) Lastly, the Selection of appropriate reliant methods for concreting and curing in hot and cold climatic conditions should be done.