The crushing strength (MPa) of good stone used for construction of a building must not be less than____.
💪 Understanding Crushing Strength
Crushing strength, also known as compressive strength, is the most important property for any stone used in a load-bearing capacity. It measures the maximum compressive load a stone can withstand before it fails (crushes).
In a building, stones in the walls and foundation must support the immense weight of the structure above them. If the stone's crushing strength is too low, it could fail under this load, leading to a structural collapse.
🔬 Detailed Analysis of the Standard and Test Procedure
C. 100 MPa
This is the correct answer. According to standard building codes and practices, a good quality building stone intended for structural use must have a minimum crushing strength of 100 MPa (MegaPascals). This ensures a high factor of safety and long-term durability for the structure.
How is Crushing Strength Tested?
The crushing strength of stone is determined in a laboratory using a Compression Testing Machine (CTM). The procedure is outlined in the Indian Standard code IS 1121 (Part 1) - 1974.
- Sample Preparation: A cube of stone is cut, typically with dimensions of 50 mm x 50 mm x 50 mm.
- Testing: The sample is placed in the CTM.
- Loading: A compressive load is applied at a constant rate of approximately 14 MPa per minute (or 140 kg/cm² per minute) until the stone sample crushes.
- Calculation: The maximum load at which the stone failed is divided by the surface area of the cube to get the crushing strength in MPa.
📊 Summary: Crushing Strength for Building Stones
| Crushing Strength (MPa) | Classification | Suitability for Building Construction |
|---|---|---|
| < 50 | Very Low | Unsuitable for any structural purpose. |
| 50 - 100 | Low to Medium | Not recommended for load-bearing structures. |
| > 100 | Good / High | Required minimum for structural use. |
💡 Study Tips
- 100 is the Gold Standard: Think of 100 MPa as the passing grade for a stone to be used in a building. Anything less is a failure.
- Mega Strength: "MegaPascals" (MPa) implies a high value is needed. 100 is a significant, round number to remember as the minimum.
- Test Cube: Remember the 50x50x50 mm cube for the test—it's a common size in materials testing.