---
title: "Compressive and diagonal shear tests of masonry"
subject: "Concrete Technology and Masonry Structure"
chapter: 10
key: "semester_5/concrete_technology_and_masonry_structure:compressive-diagonal-shear-tests"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/compressive-diagonal-shear-tests
site: BCT Engineering
---

# Compressive and diagonal shear tests of masonry

Concrete Technology and Masonry Structure · Chapter 10: Testing of masonry elements

- Asked in: 2074 Ashwin, 3+3 marks; 2071 Shrawan, 6 marks (asked 2 times)
- Video: [compression vs diagonal test](https://www.youtube.com/watch?v=2VWFwfkZ1eg) — DIPAK  MANDAL
- 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/compressive-diagonal-shear-tests
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-10

## Question

Explain the compressive and diagonal shear tests in masonry structures (with the basic difference between these two tests).

## Short answer

In the compressive test, a prism (h/t 2-5) is axially loaded to vertical splitting; fm = (P/A)*k, basic stress=0.25fm. The diagonal shear test applies diagonal compression to a 1.2 m square panel, producing diagonal tension cracking; shear strength τ = 0.707P/An, ft=0.5P/An, with An=(w+h)t/2. The compressive test determines gravity-load strength, while the diagonal shear test gives in-plane lateral shear strength.

## Answer

#### Compressive strength test

- A wall panel or prism (at least 400 mm high, $h/t$ between 2 and 5) is loaded vertically in a compression machine till failure.
- $f_m = \dfrac{P}{A}\times k$, with $k$ from IS 1905 Table 12; basic compressive stress $f_b=0.25f_m$.
- Failure mode: vertical splitting cracks in units. Gives compressive strength and modulus of elasticity.

```text
   P                    P (along diagonal)
   v                     \
 +-----+               +--\--+
 |     |               |    \|
 |prism|               |wall /|
 +-----+               +----/+
 compressive test      diagonal shear test
```

#### Diagonal shear test

- A square wall panel (about 1.2 m $\times$ 1.2 m) is loaded in compression along one diagonal through steel shoes at opposite corners.
- Shear strength $\tau = \dfrac{0.707P}{A_n}$, with $A_n=\dfrac{w+h}{2}t$; diagonal tensile strength $f_t=0.5P/A_n$.
- Failure mode: diagonal tension cracking along the loaded diagonal.

#### Basic difference

| Point | Compressive test | Diagonal shear test |
|---|---|---|
| Property found | Compressive strength, modulus | Shear (diagonal tensile) strength, shear modulus |
| Specimen | Prism or wall, $h/t$ 2 to 5 | Square panel about 1.2 m $\times$ 1.2 m |
| Load direction | Perpendicular to bed joints (vertical) | Along the diagonal |
| Stress state | Uniform compression | Pure shear, principal tension perpendicular to the diagonal |
| Failure | Vertical splitting of units | Diagonal crack through joints/units |
| Use | Gravity load design ($f_b$) | Lateral (in-plane) shear design |

## Check yourself

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

1. What is the basic difference in load direction?
   A. Compressive: perpendicular to bed joints; diagonal shear: along the diagonal
   B. Both along the diagonal
   C. Compressive: horizontal; shear: vertical
   D. Both act parallel to bed joints
   Answer: A. Compressive test loads vertically on the prism, the shear test loads along a panel diagonal. (Key point: Load direction)

2. The diagonal shear test gives which property?
   A. Compressive strength
   B. Shear (diagonal tensile) strength and shear modulus
   C. Modulus of rupture
   D. Water absorption
   Answer: B. It is used for lateral in-plane shear design. (Key point: Property found)

3. Which pairing of failure is correct?
   A. Compression: vertical splitting; shear: diagonal crack
   B. Compression: diagonal crack; shear: vertical splitting
   C. Both: horizontal sliding
   D. Both: crushing of mortar only
   Answer: A. Compression splits units vertically; shear produces diagonal tension cracks. (Key point: Failure modes)

4. Which specimen pairing is right?
   A. Prism with h/t 2 to 5; square panel about 1.2 m
   B. Square panel for compression; prism for shear
   C. Single brick for both
   D. Both 400 mm cubes
   Answer: A. Compression uses a prism (h/t 2 to 5); diagonal shear uses a 1.2 m x 1.2 m panel. (Key point: Specimens)

## Related in Concrete Technology and Masonry Structure

- [Diagonal shear test of masonry wall](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Adiagonal-shear-test) — Concrete Technology and Masonry Structure, chapter 10, asked 6×
- [Diagonal shear and push shear tests](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Adiagonal-shear-push-shear) — Concrete Technology and Masonry Structure, chapter 10, asked 6×
- [Tests for compressive and tensile strength](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Astrength-tests-compression-tension) — Concrete Technology and Masonry Structure, chapter 5, asked 4×
- [Compressive strength test of masonry prism](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Acompressive-test-masonry-prism) — Concrete Technology and Masonry Structure, chapter 10, asked 2×
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- [Destructive and non-destructive tests in masonry](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Adestructive-ndt-masonry-list) — Concrete Technology and Masonry Structure, chapter 10

## Related in other subjects

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- [Permissible compressive stress of masonry as per IS 1905](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Amasonry-permissible-stress-factors-code) — Design of Timber and Masonry Structures, chapter 5
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