ABSTRACT
Concrete can be produced in a large variety of forms, with strengths up to 150N/mm2 and densities from 500 to 4000 kg/m3. However, where durability is concerned it is suggested that in essence there are 5 main options for protecting concrete,
• Ordinarycrete • Supercrete • Coatedcrete • Coatedrebarcrete • Efficientcrete
Ordinarycrete is produced to current specifications but is likely to require repairs and maintenance at intervals to restore serviceability, as shown in Figure 8. Ordinarycrete is all too often a result of inadequate site practices and is therefore unlikely to comply with the design life requirements of a structure without additional expenditure. Supercrete is produced to current specifications, satisfying durability requirements but is otherwise greatly in excess of structural requirements. This can be produced by specifying a high cement content, say >400 kg/m3 and low water/cement ratio, say <0.4. This, depending on curing, is likely to give in-situ strengths in excess of 50N/mm2. Problems may, however, arise due to heat of hydration associated with the high cement content.
