For a reinforced concrete structure, subjected to freezing and thawing cycles, the most critical property of the aggregate is
- ASpecific gravity
- BWater absorptionCorrect
- CThermal conductivity
- DBulk density
Solution
Concept
Aggregate with high water absorption (high porosity) gets saturated and is damaged by freeze-thaw cycles.
Step-by-step solution
1. In freezing, water inside pores turns to ice. 2. Ice has about 9% more volume than water. 3. This creates internal pressure in the aggregate and the concrete. 4. Aggregate with high water absorption holds more water, so damage is more. 5. So water absorption (porosity) is the most critical property.
Explanation
Freeze-thaw damage happens when water in pores freezes and expands. Porous aggregate with high water absorption holds more water and cracks easily. So low water absorption and low porosity aggregate is needed for frost resistance.
Why the other options are wrong
A: Specific gravity does not directly control frost damage. C: Thermal conductivity has only a small effect. D: Bulk density is related to packing, not to frost resistance.
Shortcut
Freeze-thaw means water in pores, so choose water absorption or porosity.
Common mistake
Choosing specific gravity because it is linked with density and strength.
Correct answer: B) Water absorption