Porosity is the voids in concrete that allow water movement. Which option is correct?

• A. Permeability
• B. Absorption
• C. Porosity
• D. Sorption

Answer: (C)

Porosity refers to the volume fraction of voids in concrete—the empty spaces where water can reside and potentially move. When a description talks about voids that allow water movement, it points to porosity as the term for those void spaces themselves. Permeability, by contrast, is about how easily water can flow through the material, which depends not just on how many voids exist but on how well they are connected. Absorption describes how much water the material takes up, often through capillary action, and sorption covers both adsorption and absorption. So porosity is the correct term for the void spaces in concrete. Keep in mind that high porosity doesn’t always guarantee high permeability; pore connectivity plays a big role in flow.