For magnesite (MgO) bricks, the maximum apparent porosity encountered in standard dense products is approximately what percentage?

Introduction / Context:
Apparent porosity affects corrosion resistance, slag penetration, and strength. For magnesite bricks, designers target a controlled porosity range to balance performance and cost in basic slag environments.

Given Data / Assumptions:

• Question asks for an approximate upper bound for standard dense grades, not insulating MgO products.
• Very high porosity (40%+) is atypical for dense MgO bricks.

Concept / Approach:
Dense magnesite bricks commonly exhibit apparent porosity values in the teens to low twenties (%). A reasonable “maximum” figure cited for dense commercial grades is around 24%, beyond which strength and slag resistance degrade rapidly.

Step-by-Step Solution:
Exclude very low extremes (2–8%) as best-case or specialty.Exclude 44–58% as characteristic of insulating or highly porous structures.Choose 24% as a sensible upper figure for dense MgO.

Verification / Alternative check:
Typical specification sheets list apparent porosity for dense MgO between ~15% and 22–24% depending on grade.

Why Other Options Are Wrong:
44/58%: far too high for dense MgO bricks.8%: unusually low and not an upper bound.

Common Pitfalls:
Confusing dense bricks with insulating grades that intentionally raise porosity.

Final Answer:
24