---
title: "Hollow blocks and compressed earth blocks"
subject: "Concrete Technology and Masonry Structure"
chapter: 7
key: "semester_5/concrete_technology_and_masonry_structure:hollow-block-compressed-earth-block"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/hollow-block-compressed-earth-block
site: BCT Engineering
---

# Hollow blocks and compressed earth blocks

Concrete Technology and Masonry Structure · Chapter 7: Introduction to masonry structures

- Asked in: 2079 Bhadra, 4 marks
- Video: [Compressed Earth Blocks for House Build](https://www.youtube.com/watch?v=EEdUm0-LLms) — Lee's Living Out Of The Norm
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/hollow-block-compressed-earth-block
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-7

## Question

Explain the uses and advantages of Hollow Blocks and Compressed Earth Blocks.

## Short answer

Hollow blocks provide faster construction, lighter weight, thermal insulation, and reinforced cores for seismic resistance. Compressed earth blocks are made from local soil with stabiliser, requiring no firing, offering low cost, low energy, good thermal mass, and suitable for low-rise rural buildings.

## Answer

#### Hollow blocks (concrete or clay)

**Uses:** walls of buildings (load-bearing up to 2 or 3 storeys), partitions, infill, boundary walls and reinforced masonry (cores filled with grout and bars).

**Advantages:**
- Larger size than brick, so faster construction and less mortar.
- Lighter, so a lower dead load and smaller foundation.
- Good thermal and sound insulation from the voids.
- Uniform size gives plumb, straight walls; pipes and conduit can run through cores.
- Cores can be reinforced, giving good earthquake resistance.

#### Compressed earth blocks (CEB)

Blocks made by compressing a moist mix of soil, sand and a little stabiliser (cement or lime, 5 to 10 percent) in a manual or mechanical press, then curing but not burning.

**Uses:** load-bearing walls of low-rise rural houses, schools and health posts; infill and boundary walls.

**Advantages:**
- Made from local soil on site: low cost and low transport.
- No firing, so very low energy and no fuel; environmentally friendly.
- Accurate shape and size, strong and durable when stabilised; needs little mortar.
- Good thermal comfort (high thermal mass).
- Interlocking CEBs reduce mortar and skilled labour.

Limitations: must be protected from continuous moisture and erosion (good plinth, roof overhang, plaster).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why do hollow blocks give faster construction?
   A. They are larger than bricks and need less mortar
   B. They are smaller than bricks
   C. They need firing
   D. They need formwork
   Answer: A. Larger size means fewer units and joints. (Key point: Hollow block advantage)

2. How are compressed earth blocks made?
   A. By firing in a kiln
   B. By compressing moist soil, sand and 5 to 10 percent stabiliser, cured but not burnt
   C. By casting with high-grade cement only
   D. By sun-drying plain mud
   Answer: B. No firing means very low energy use. (Key point: CEB making)

3. Why are CEBs environmentally friendly?
   A. They use burnt coal
   B. They need imported soil
   C. No firing, so no fuel is needed, and they use local soil
   D. They use steel
   Answer: C. Local soil and no fuel lower energy and transport. (Key point: CEB environment)

4. What protection do CEBs need?
   A. Protection from air
   B. Burning
   C. No protection
   D. Protection from continuous moisture and erosion
   Answer: D. Good plinth, roof overhang and plaster help. (Key point: CEB limitation)

## Related in other subjects

- [Anchored sheet pile, free earth procedure](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aanchored-sheet-pile-free-earth-procedure) — Foundation Engineering, chapter 5
- [Comparison of masonry units](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Amasonry-units-comparison) — Design of Timber and Masonry Structures, chapter 4