Quick setting cement is produced by adding .....
ā±ļø Understanding Quick Setting Cement
Quick Setting Cement is engineered to set very fast once mixed with water. Its primary application is for construction in running water or underwater, where the concrete needs to stiffen quickly before it can be washed away. Its initial setting time is about 5 minutes and its final setting time is about 30 minutes.
This property is achieved by accelerating the natural "flash set" tendency of cement, which is normally controlled in OPC.
š Detailed Analysis of the Options
(a) less amount of gypsum in very fine powdered form
This is the correct answer. In Ordinary Portland Cement, gypsum is added to retard the setting time. To make a quick-setting cement, the amount of this retarder (gypsum) is significantly reduced. This allows the highly reactive Tricalcium Aluminate (CāA) to hydrate very quickly, causing the cement to set fast. Grinding the cement finer also contributes to this rapid reaction.
(b) more amount of gypsum in very fine powdered form
This is incorrect. Adding more gypsum would have the opposite effect, creating a slow-setting or extra-rapid-hardening cement, not a quick-setting one.
(c) aluminium sulphate in very fine powdered form
This is a plausible distractor. Aluminium sulphate does act as an accelerator, speeding up the setting process. However, the primary method of *producing* quick setting cement from standard clinker is by reducing the amount of the retarder (gypsum), not by adding an accelerator. Accelerators are typically added as admixtures to normal concrete, whereas quick setting cement is a distinct manufactured product.
(d) pozzolana in very fine powdered form
This is incorrect. Pozzolana is added to produce Portland Pozzolana Cement (PPC). It generally slows down the rate of hydration and early strength gain.
š OPC vs. Quick Setting Cement: Key Differences
| Property | Ordinary Portland Cement (OPC) | Quick Setting Cement |
|---|---|---|
| Gypsum Content | Normal (~2-3%) | Reduced Amount |
| Initial Setting Time | > 30 minutes | ~ 5 minutes |
| Final Setting Time | < 10 hours | ~ 30 minutes |
| Primary Use | General Construction | Underwater / Running Water Construction |
š” Study Tips
- Quick Set = Less Gypsum: This is the fundamental principle. To make cement set faster, you reduce the amount of the substance that slows it down (the retarder, gypsum).
- Setting vs. Hardening: Do not confuse Quick Setting Cement with Rapid Hardening Cement. Quick setting refers to the speed of stiffening. Rapid hardening refers to the speed of strength gain. Their manufacturing processes and uses are different.
- Think "Emergency Repairs": The main use for quick setting cement is in situations where you need the concrete to become solid very fast, like plugging a leak or working in a flowing stream.