ABSTRACT
ART. 12.1 . INTRODUCTION R e i n f o r c e d concrete is widely used for water-retaining structures of all kinds, such as tanks, water-towers and reservoirs. In Article 2.4 it is explained that the impermeability of concrete is not absolute: but provided the aggregates are well chosen and the water/cement ratio is successfully controlled, and provided the concrete is mechanically vibrated and subsequently cured in the best manner, concrete can be made near enough impermeable to water for most industrial purposes without the need for a separate waterproof lining. This is not true of liquids of low viscosity and high penetrating power such as petrol; nor is it true of nonaqueous liquids, which will allow the concrete to dry out com pletely, causing shrinkage cracks. Other liquids, such as certain vegetable oils and sugar solutions, and certain natural waters containing sulphates or other acids, may attack the concrete or corrode the steel, and in such cases it may be necessary to increase the cement content of the mix, or use special cements, or provide some form of lining to protect the concrete. This is discussed in Article 2.2.
