A stone is rejected if it absorbs water more than
💧 Why Water Absorption Matters
Water absorption is one of the most critical indicators of a stone's quality and durability. It refers to the amount of water a stone can soak up into its internal pores, expressed as a percentage of its dry weight.
Low water absorption is desirable because:
- It indicates low porosity: A dense stone with few pores is inherently stronger and more durable.
- It prevents frost damage: In cold climates, water trapped in pores can freeze, expand, and crack the stone.
- It maintains strength: Many stones are weaker when saturated with water.
- It resists staining: A less porous stone is less likely to absorb stains.
🔬 Detailed Analysis of the Absorption Limits
B. 10%
This is the correct answer. While the benchmark for a "good quality" stone is to absorb less than 5% water, the absolute upper limit for a stone to be considered usable in construction is generally 10%. If a stone's water absorption exceeds 10%, it is typically rejected as it indicates high porosity, low strength, and poor durability. Such a stone would be highly susceptible to weathering and would not perform well over time.
A. 5%
This is the limit for a good quality stone. A stone that absorbs less than 5% water is considered high quality, but a stone that absorbs 6% or 7% is not automatically rejected; it is just considered of lower quality.
C. and D. 15% and 20%
These values are far above the acceptable limit. A stone that absorbs this much water is extremely porous and weak and would be completely unsuitable for any construction purpose.
📊 Water Absorption Quality Standards
| Water Absorption (%) | Quality Classification | Suitability |
|---|---|---|
| < 5% | Good / Excellent | Suitable for all construction purposes. |
| 5% - 10% | Acceptable / Medium | May be suitable for some uses, but requires caution. |
| > 10% | Poor / Unsuitable | Should be rejected for use as a building stone. |
💡 Study Tips
- Two Key Numbers: Remember the two most important percentages: 5% is the target for a "good" stone, and 10% is the "rejection" limit.
- Think of a Test Score: Getting below 5% is like an 'A' grade. Getting between 5% and 10% is like a 'C' or 'D' - it passes, but it's not great. Getting above 10% is a failing grade.
- Porosity is the Enemy: High water absorption means high porosity (many internal holes). Porous stones are weak and don't last long.