Which statement fits stone as a masonry unit?

Very strong in compression and durable, but heavy, hard to dress and weak in tension

Low strength but high water absorption

Made from soil with cement and pressed, no firing

What are hollow blocks mainly used for?

Light partitions and framed buildings, since they are light and large

The highest-strength load-bearing walls

Which is true of compressed earth blocks (CEB)?

They need no firing and use little energy, but must be protected from water

They are burnt at high temperature

They have the highest strength of all units

They are waterproof without plaster

Which is a brick quality test, and what do all masonry units share?

Water absorption not above 20 percent; all are strong in compression but weak in tension and shear

Colour only; all are strong in tension

Water absorption above 30 percent; all are weak in compression

Efflorescence is desirable; all are strong in shear

Practice · 6 marks

Comparison of masonry units

Short answer

Burnt clay bricks: 3.5–20+ N/mm², heavy, high energy. Stone: 20–100+ N/mm², durable but heavy. Solid concrete blocks: 4–10 N/mm². Hollow blocks: 3–8 N/mm², light, can be reinforced. Compressed earth blocks (CEB): 2–6 N/mm², low energy, needs water protection.

Differentiate between brick, stone, concrete block, hollow block and compressed earth block as masonry units, giving their characteristics and typical uses.

Property	Burnt clay brick	Stone	Solid concrete block	Hollow block	Compressed earth block (CEB)
Material	Clay moulded and burnt	Natural rock (granite, sandstone, limestone)	Cement, sand, aggregate	Same as concrete, with cores	Soil with 5–10% cement/lime, pressed
Compressive strength	3.5–20+ N/mm²	20–100+ N/mm²	4–10 N/mm²	3–8 N/mm² (net-area basis)	2–6 N/mm²
Density	1700–1900 kg/m³	2300–2800 kg/m³	2000–2300 kg/m³	1400–1800 kg/m³	1800–2000 kg/m³
Water absorption	up to 20%	Low (1–5%)	5–10%	5–10%	Higher, needs protection
Weight and ease	Handy, light	Heavy, hard to dress	Heavy	Light, large unit, quick	Medium
Energy	High (burning)	Quarrying and dressing	Cement energy	Lower	Very low (no burning)
Typical use	Load-bearing and partition walls	Foundations, retaining walls, hill houses	Load-bearing walls	Partitions, framed buildings	Low-cost housing

Notes

Brick quality is judged by compressive strength, water absorption (not above 20 percent), efflorescence and a ringing sound when struck.
Stone is durable and strong in compression, but heavy and weak in tension; it needs mortar and good bonding with through stones.
Hollow blocks have cores (voids more than 25 percent of the gross area); they are light, reduce dead load and can be reinforced and grouted for seismic resistance.
CEB is environment friendly, needs no firing and has good thermal behaviour, but it must be protected from water and erosion by plaster and projecting eaves.
All masonry units are strong in compression but weak in tension and shear, so masonry is mainly used for gravity load-bearing walls.

✓ Answer checked by Claude Sonnet 5.5

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Comparison of masonry units

Notes

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