As per building code, water cement ratio should be limited to 0.5 for Moderate Exposure and less than 0.45 for More Severe Exposure. To place and compact such a dry mix, use of plasticizer is very important. The compressive cylindrical strength of concrete should not less than 4000 psi for Moderate Exposure and 4500 psi for More Severe Exposures or it shall be as specified in the design. Depending on the purpose of use, the recommended slump for concrete is selected from table below.
| Type of Construction | Maximum Slump* | Minimum Slump |
|---|---|---|
| Reinforced Foundation Wall & Footing | 75 mm | 25 mm |
| Plain Footings, Caissons & Sub Structure Walls | 75 mm | 25 mm |
| Beams & Reinforced Walls | 100 mm | 25 mm |
| Building Columns | 100 mm | 25 mm |
| Pavements & Slabs | 75 mm | 25 mm |
| Mass Concrete | 75 mm | 25 mm |
Low permeability or water-tightness is the key to good concrete. The mix should be properly proportioned to achieve minimum porosity. Concrete should be properly consolidated and cured.
