Admixtures may be defined as the materials other than the basic ingredients of concrete i.e., cement, aggregates and water added to the concrete mix immediately before or during the mixing process to modify one or more specific properties of concrete in fresh or hardened state. Whereas an additive is a material which is added at the time of grinding cements [...]
Pozzolanic materials are siliceous and aluminous materials, possessing little or no cementitious value by themselves, but in finely divided form and in the presence of moisture react chemically with calcium hydroxide liberated on hydration of cement at ordinary temperature to form compounds, possessing cementitious properties. The Silicious or aluminious compounds in a finely divided form react with calcium hydroxide to [...]
By nominal dosages of plasticizers or super plasticizers the improvement in the workability of very stiff or zero slump concrete has not been observed. A mix having 20 mm to 30 mm initial slump can only be fluidised by the use of plasticizers or super plasticizers. To fluidify a no slump concrete a high dosage is required. An improvement in [...]
The admixtures can be broadly classified according to their characteristic effect as follows: 1. Accelerating Admixtures 2. Accelerator Plasticizer 3. Retarders 4. Oil Wells 5. Retarding Plasticizer (Water Reducing Admixtures) 6. Air Entrainment 7. Air Contents 8. Gas Forming Agents 9. Damp and Water Proofing Admixtures 10. Workability Agents and a Few Others. 1. Accelerating Admixtures: Sometimes conditions require to [...]