Refractory bricks — how are bricks classified based on chemical behavior with slags and environments? Choose the most complete answer.

Introduction / Context:
Refractories are selected not only for temperature resistance but also for chemical compatibility with slags, fluxes, and atmospheres. A standard classification divides refractories into acid, basic, and neutral types depending on their reactions with acidic or basic slags. This question checks familiarity with that foundational classification.

Given Data / Assumptions:

• Examples: silica (acid), magnesia/dolomite (basic), chromite/alumina (often neutral or amphoteric).
• Service conditions vary across furnaces, converters, kilns.
• We are classifying categories, not specific brands.

Concept / Approach:
Acid refractories resist acidic slags but react with basic ones; basic refractories resist basic slags; neutral refractories have good resistance to both and are used where slag chemistry varies. Hence all three categories exist and are used according to process requirements.

Step-by-Step Solution:

Verification / Alternative check:
Refractory handbooks adopt this tripartite classification, guiding lining choices for steelmaking, glass furnaces, and cement kilns.

Why Other Options Are Wrong:
Listing only one class omits the others, giving an incomplete classification.

Common Pitfalls:
Confusing temperature rating with chemical compatibility; both must be satisfied for durable linings.

Final Answer:
All of the above