The development of strength of cement and its fineness are...........
🔗 The Link Between Fineness and Hydration
Fineness refers to the particle size of the cement. Finer cement has a greater surface area per unit of mass (higher specific surface area).
Development of strength is the result of a chemical reaction called hydration, where cement particles react with water. The speed of this reaction determines how quickly the cement hardens and gains strength.
A fundamental principle of chemistry is that the rate of a reaction increases with the surface area of the reactants. More surface area means more sites for the reaction to occur simultaneously.
📝 Detailed Analysis of the Options
(a) Directly proportional
This is the correct answer. As the fineness of cement increases, its surface area increases. This larger surface area allows for a more rapid and complete hydration reaction with water. A faster hydration rate leads to a faster development of strength, especially in the early stages. Therefore, the rate of strength development is directly proportional to the fineness of the cement.
(b) Inversely proportional
This is incorrect. It would imply that coarser (less fine) cement gains strength faster, which is the opposite of what happens.
(c) Not related & (d) Randomly related
These are incorrect. There is a very clear and well-established physical and chemical relationship between the fineness of cement and its rate of strength gain.
📊 Effect of Increasing Fineness on Cement Properties
| Property | Effect of Higher Fineness |
|---|---|
| Rate of Hydration | Increases |
| Rate of Strength Development | Increases (especially early strength) |
| Heat of Hydration | Increases (more heat is released faster) |
| Workability | Decreases (requires more water for same consistency) |
| Shrinkage and Cracking | Increases (higher tendency for drying shrinkage) |
💡 Study Tips
- Finer = Faster: This is the key relationship to remember. Finer cement particles react faster, leading to faster strength gain.
- Think Sugar Cubes vs. Powdered Sugar: A sugar cube dissolves slowly in water, while powdered sugar dissolves almost instantly because of its huge surface area. Cement hydration works on a similar principle. -
- There's a Trade-off: While fineness increases the rate of strength gain, it's not without downsides. It also increases the heat generated and the potential for shrinkage, so there's an optimal level of fineness for different applications.