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Civil EngineeringWBPSC AE · SSC JE · RRB JE

Building Materials— Important Topics, Formulas & MCQs

Building Materials & Construction covers the properties and testing of cement, concrete, aggregates, bricks, timber, steel and other construction materials. It is a memory-based, high-yield subject ideal for quick scoring.

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Important topics in Building Materials

Cement — types, composition, tests, soundness
Aggregates — properties, grading, fineness modulus
Concrete — workability, strength, durability
Concrete admixtures — plasticisers, accelerators
Bricks & masonry
Timber & its defects
Lime, mortar & plaster
Steel & corrosion-resistant bars
Paints, varnishes & sealants
Building stones
Must-know

Key concepts & formulas — Building Materials

Cement unsoundness

Expansion caused by free lime and free magnesia; tested by Le Chatelier / autoclave.

Fineness modulus

FM ≈ 2.2–2.6 (fine), 2.6–2.9 (medium), 2.9–3.2 (coarse) sand.

Compaction factor

A workability test; its value is always less than 1 (theoretical max 1.0).

PPC vs OPC curing

PPC needs longer curing because the pozzolanic (secondary) reaction proceeds after primary hydration.

Exam relevance

5–7 questions in AE/JE papers; among the easiest marks if the standard facts are memorised.

Study tip

Make flashcards of cement/concrete test values and admixture doses — this subject rewards rote recall.

Worked example

Sample Building Materials MCQ

The unsoundness (delayed expansion) of cement is mainly caused by:

A. Free lime and magnesia
B. Tricalcium silicate
C. Gypsum
D. Fly ash
Answer: A. Excess free lime (CaO) and magnesia (MgO) hydrate slowly and expand, causing unsoundness; tested by the Le Chatelier and autoclave methods.

Common mistakes to avoid

OPC initial setting time ≥ 30 min and final setting time ≤ 600 min.
C₃S gives early strength; C₂S contributes to later-age strength.
Fineness modulus ranges: fine sand 2.2–2.6, coarse sand 2.9–3.2.
PPC needs longer curing than OPC because the pozzolanic reaction follows primary hydration.
Keep going

Related Civil Engineering subjects

Strength of Materials
RCC
Steel Structures
Soil Mechanics
Foundation Engineering
Surveying
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