Which property of brick and block units influences their water absorption and frost resistance?

• A. Porosity/absorption rate.
• B. Color hue.
• C. Surface roughness.
• D. Thermal conductivity.

Answer: (A)

Water absorption and frost resistance come down to porosity and how much water the unit can take in. The pore structure of brick and block controls how easily moisture moves into the material and how much water it can store. When temperatures drop, that trapped water freezes and expands, creating internal pressures that can crack the brick or mortar and degrade the wall over time. So, a unit with appropriate porosity—not too high to take in excess moisture, and with a pore structure that limits rapid water uptake—will resist freeze-thaw damage better.

Color hue is about appearance and pigments, not moisture handling. Surface roughness affects how mortar bonds to the face and may influence aesthetic texture, but it doesn’t determine how much water the unit can absorb. Thermal conductivity deals with heat flow, which affects temperature changes but not the fundamental capacity of the brick or block to absorb water or withstand freezing.