In refractory technology, “grog” refers to which of the following material descriptions?

Introduction / Context:
Grog is a widely used term in ceramics and refractories. It affects drying, firing shrinkage, and thermal shock behavior of clay bodies and refractories. Understanding what grog is and why it is added helps explain body formulation and performance under heat.

Given Data / Assumptions:

• Grog derives from previously fired (calcined) material.
• Intended to reduce plasticity and shrinkage, improve thermal shock resistance.
• Typically alumino-silicate composition from crushed firebrick or calcined clays.

Concept / Approach:

Grog is non-plastic, pre-fired aggregate (often crushed firebrick), usually containing alumina and silica. Adding grog to a plastic clay body reduces drying/firing shrinkage, controls cracking, and can improve permeability and thermal shock performance by interrupting continuous clay matrix shrinkage paths.

Step-by-Step Solution:

Verification / Alternative check:

Ceramics processing references consistently describe grog as non-plastic, calcined aggregate used to temper bodies and reduce shrinkage.

Why Other Options Are Wrong:

Each individual statement is true; hence the inclusive option (all of the above) is correct.

Common Pitfalls:

Assuming grog is raw clay or a chemical additive; overlooking its pre-fired, non-plastic nature.

Final Answer:

All of the above