💧 Water Absorption of Masonry Units
In short
Determination of water absorption (absorptivity) of bricks and calcium silicate units by immersion method. The test is performed according to PN-EN 772-21:2011; Typical range: 5–25% (ceramic bricks). The procedure comprises 6 steps (about 2 days 1 h 35 min–4 days 1 h 35 min in total); it is used for: Quality control of ceramic bricks (manufacturer), Acceptance of masonry materials on construction site, Qualification of bricks for facades (class F2 — frost resistance).
At a glance
- Standard: PN-EN 772-21:2011
- Category: Construction
- Procedure steps: 6
- Total time of stages: 2 days 1 h 35 min–4 days 1 h 35 min
- Drying temperature: 105 ± 5°C
- Immersion time: 24 ± 0.5 h
- Water temperature: 20 ± 5°C
Overview
Water absorption is a measure of the ability of building material to absorb water and is expressed as percentage ratio of absorbed water mass to dry specimen mass. It is one of basic parameters for assessing quality and durability of masonry units (bricks, calcium silicate blocks).
High water absorption reduces frost resistance (water in pores freezing increases volume by ~9%, causing material destruction), deteriorates thermal insulation and increases risk of efflorescence. For facade bricks, water absorption should not exceed 16% (class F2 — full frost resistance).
Testing involves drying specimens at 105°C to constant mass, immersion in water for 24 h, and reweighing. Mass difference expressed as percentage gives water absorption.
Method principle
Specimens (whole bricks or their halves) are dried in oven at 105±5°C until reaching constant mass (ms) — difference between two consecutive weightings every 24 h not greater than 0.1% mass. Dried specimens are immersed in water at temperature 20±5°C for 24±0.5 h. After removal from water, excess moisture is removed (cloth) and weighed (mw).
Water absorption W = (mw - ms) / ms × 100 [%]
Applications
- Quality control of ceramic bricks (manufacturer)
- Acceptance of masonry materials on construction site
- Qualification of bricks for facades (class F2 — frost resistance)
- Testing calcium silicate and lime-sand blocks
- Assessment of durability of historic ceramic materials (conservation)
- Certification of masonry units (CE marking)
Key parameters
| Parameter | Value |
|---|---|
| Drying temperature | 105 ± 5°C |
| Immersion time | 24 ± 0.5 h |
| Water temperature | 20 ± 5°C |
| Limit for facades (F2) | ≤16% |
| Typical range | 5–25% (ceramic bricks) |
| Number of specimens | Min. 6 units from batch |
Standard
- Standard number
- PN-EN 772-21:2011
- Title (PL)
- Metody badań elementów murowych — Część 21: Określanie absorpcji wody ceramicznych i silikatowych elementów murowych przez zanurzenie w zimnej wodzie
- Title (EN)
- Methods of test for masonry units — Part 21: Determination of water absorption of clay and calcium silicate masonry units by cold water absorption
Step-by-step procedure
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Specimen preparation
Select min. 6 bricks randomly from batch. Clean of loose particles. Mark each specimen.
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Drying
Place in oven 105±5°C. Dry min. 24 h. Weigh every 24 h until constant mass (difference <0.1%).
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Dry weighing (ms)
Cool in laboratory room. Weigh each specimen with accuracy 0.1 g. Record ms.
-
Immersion
Immerse specimens in water 20±5°C so that water covers them min. 25 mm. Maintain 24±0.5 h.
-
Wet weighing (mw)
Remove from water. Remove excess water with damp cloth. Weigh immediately (max 1 min from removal).
-
Calculations
W = (mw - ms) / ms × 100%. Calculate for each specimen and series average. Round to 0.1%.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Laboratory oven | Binder FD 115, POL-EKO SLW 115, Memmert UF110 | 5,000–15,000 PLN |
| Laboratory balance | Radwag WLC 30, range 30 kg, accuracy 0.1 g | 3,000–6,000 PLN |
| Immersion tank | PE or steel, with supporting rack | 500–2,000 PLN |
| Damp cloth | For removing excess water from surface | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Tap water | — | Temperature 20±5°C, for immersing specimens |
Health and safety (OHS)
- Oven 105°C — burn risk, thermal insulation gloves
- Specimen weight (bricks ~3 kg) — watch feet
- Brick edges — sharp, work gloves
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN 772-21:2011 — “Methods of test for masonry units — Part 21: Determination of water absorption of clay and calcium silicate masonry units by cold water absorption”.
How does this method work?
Specimens (whole bricks or their halves) are dried in oven at 105±5°C until reaching constant mass (ms) — difference between two consecutive weightings every 24 h not greater than 0.1% mass.
What is the measuring range and accuracy?
Drying temperature: 105 ± 5°C; Immersion time: 24 ± 0.5 h; Water temperature: 20 ± 5°C; Limit for facades (F2): ≤16%.
How long does the test take?
The times given for the individual stages add up to approximately 2 days 1 h 35 min–4 days 1 h 35 min. The procedure comprises 6 steps.
What equipment is required?
Laboratory oven, Laboratory balance, Immersion tank, Damp cloth. Indicative cost of the core instrument (Laboratory oven): 5,000–15,000 PLN.
Where is this test used?
Quality control of ceramic bricks (manufacturer); Acceptance of masonry materials on construction site; Qualification of bricks for facades (class F2 — frost resistance); Testing calcium silicate and lime-sand blocks; Assessment of durability of historic ceramic materials (conservation); Certification of masonry units (CE marking).
What safety precautions apply?
Oven 105°C — burn risk, thermal insulation gloves; Specimen weight (bricks ~3 kg) — watch feet; Brick edges — sharp, work gloves.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN 772-21.