Common uses of fireclay bricks: select the most appropriate set of applications from the list provided.

Introduction / Context:
Fireclay bricks are versatile alumino-silicate refractories with moderate cost and good performance. They are widely used in general-purpose linings where temperatures and atmospheres are within their capability and where intermittent operation may occur.

Given Data / Assumptions:

• Fireclay has reasonable thermal shock resistance compared with silica bricks.
• They are appropriate for flues and chimneys that see hot gases and cycling.
• They are not intended for the most aggressive slag lines or ultra-high-temperature crowns.

Concept / Approach:
The three listed applications — intermittent furnaces, flues, and chimney linings — align well with fireclay’s property profile: adequate refractoriness, fair resistance to thermal shock, and acceptable corrosion resistance in many combustion atmospheres. For severe basic slags or extreme temperatures, high alumina, basic bricks, or special products are preferred instead.

Step-by-Step Solution:
Evaluate each application against fireclay capabilities.Intermittent operation: fireclay handles cycling better than silica.Flues/chimneys: compatible with hot-gas service at moderate temperatures.Therefore, choose “All (a), (b) and (c)”.

Verification / Alternative check:
Standard lining schedules list fireclay for flues, stacks, small reheating furnaces, and ovens, with higher-grade materials reserved for more severe zones.

Why Other Options Are Wrong:
Individual picks miss the broader, established usage pattern; all three are correct together.

Common Pitfalls:
Overapplying fireclay to zones requiring high alumina or basic refractories; always match chemistry and duty.

Final Answer:
All (a), (b) and (c)