Dorry's testing machine is used for
🧪 Understanding Stone Testing Equipment
To ensure building stones meet quality standards, they undergo various laboratory tests. Each test measures a specific property and often requires a specialized machine. This question asks you to identify the purpose of the Dorry's testing machine.
🔬 Detailed Analysis of the Tests and Machines
B. Hardness Test of Stone
This is the correct answer. The Dorry's testing machine is specifically designed to determine the hardness of a stone, more accurately described as its resistance to abrasion (wear). This is especially important for stones used in flooring, pavements, and steps.
- Procedure: A cylindrical stone sample is weighed and then held under a constant pressure against a rotating metal disc. Standard sand is fed onto the disc to act as an abrasive. After a set number of revolutions, the sample is removed and weighed again.
- Result: The loss in weight is used to calculate the "Coefficient of Hardness". A smaller loss in weight indicates a harder, more abrasion-resistant stone.
A. Crushing Test of Stone
This test measures the compressive strength of a stone. It is performed using a Compression Testing Machine (CTM) or a Universal Testing Machine (UTM), not a Dorry's machine.
C. Impact Test of Stone
This test measures the toughness of a stone, or its ability to resist shock from sudden loads. It is performed using an Impact Testing Machine, where a hammer is dropped onto the sample from increasing heights.
D. Water Absorption Test
This test measures the porosity of a stone. It is a simple procedure that involves weighing a dry sample, soaking it in water for 24 hours, and then weighing it again. It does not require a specialized machine like the others.
📊 Summary of Common Stone Tests
| Property Measured | Test Name | Machine Used |
|---|---|---|
| Hardness / Abrasion | Hardness Test | Dorry's Testing Machine |
| Compressive Strength | Crushing Test | Compression Testing Machine (CTM) |
| Toughness | Impact Test | Impact Testing Machine |
| Porosity | Water Absorption Test | None (Balance and container) |
💡 Study Tips
- Dorry's = Abrasion/Hardness: Connect the name "Dorry's" specifically to the hardness test that measures abrasion.
- Think of "Grinding": The Dorry's machine works by grinding the stone with sand. Grinding tests for wear and hardness.
- Match the Test to the Machine:
- Dorry's = Hardness
- CTM = Crushing
- Impact Machine = Impact/Toughness