---
code: "ISO 679"
title: "Cement — Test methods — Determination of strength"
institution: "ISO"
category: "testing-analysis-systems"
revision: "2013"
scope: "International mortar prism strength method — mixer, jolting table, triple moulds, RH cabinet, water cure, then flexure at 50 ± 10 N/s and compression at 2400 ± 200 N/s. Aligned with EN 196-1 in European laboratories."
testMethod: "40 × 40 × 160 mm prisms; w/c 0.50, cement:sand 1:3; timed mixing ±1 s; 120 jolts; wet flexure then compression on 40 × 40 mm platens; six results with ±10 % outlier rule."
specimenRequirements: "Per triple mould: 450 ± 2 g cement, 1350 ± 5 g CEN sand, 225 ± 1 g water; mould 160.0 × 40.0 × 40.1 mm; climate per mixing room, cabinet, and tank."
url: "https://vectorbtc.com.tr/resources/standards/iso-679/"
---

# ISO 679 — Determination of strength

## Cement mortar flexural and compressive strength

*European laboratories typically apply the same technical requirements through [EN 196-1](/resources/standards/en-196-1/) (2016), which is harmonized with ISO 679.*

---

> **Legal notice**
>
> The information on this page is a summary prepared by Vector Scientific Testing Devices based on a review of the applicable standard; it does not replace the official standard. For the authoritative, complete text, obtain ISO 679 from ISO or your national standards body through official channels. Vector accepts no liability for direct or indirect loss arising from reliance on this summary.

---

## 1. Purpose and principle

**Purpose:** Determine **flexural** and **compressive** strength of cement mortar at defined cure ages (commonly **2, 7, and 28 days**).

**Principle:** Prepare **plastic mortar** from cement, **CEN reference sand**, and water; cast **40 mm × 40 mm × 160 mm** prisms. Test **flexure** first (prism breaks in two), then **compression** on each half.

**Mass proportions:**

- Water / cement = **0.50**
- Cement / sand = **1 / 3**

**Batch for one triple mould:**

| Component | Mass |
|-----------|------|
| Cement | **450 ± 2 g** |
| CEN standard sand | **1350 ± 5 g** |
| Water (distilled/deionized for reference tests) | **225 ± 1 g** |

---

## 2. Laboratory climate

| Zone | Temperature | Relative humidity | Notes |
|------|-------------|-------------------|--------|
| **Mixing and moulding** | **20 ± 2 °C** | **≥ 50 %** | Log room T and RH **≥ once per day** |
| **Mould storage (first 24 h)** | **20 ± 1 °C** | **≥ 90 %** | Log cabinet T and RH **every 4 h** |
| **Water curing tank** | **20 ± 1 °C** | — | Still water; specimens fully submerged, not touching each other or the floor |

Materials and apparatus at **room temperature** before use.

---

## 3. Apparatus — the ISO 679 laboratory set

ISO 679 defines a **coordinated set**, not a single machine:

| Role | Requirement summary | Vector equipment |
|------|---------------------|------------------|
| **Mortar mixer** | Planetary motion; low/high speeds; clearance **3 ± 1 mm** | [Cement mortar mixer](/products/testing-analysis-systems/mixers/cement-mortar-mixer/) VTR-1017 |
| **Jolting table** | **20.0 ± 0.5 kg** moving mass; **15.0 ± 0.3 mm** drop; **60 jolts** per run | [Jolting table](/products/testing-analysis-systems/jolting-table/) VTR-1024 |
| **Triple prism moulds** | **160.0 × 40.0 × 40.1 mm** internal; wall **≥ 10 mm**; faces **≥ 200 HV** | User-supplied steel moulds per standard |
| **RH cabinet** | **20 ± 1 °C**, **≥ 90 % RH** for first **24 h** | [Curing cabinet](/products/testing-analysis-systems/cement-curing-cabinet/) VTR-1025S / VTR-1025D |
| **Strength press** | Flexure **50 ± 10 N/s**; compression **2400 ± 200 N/s** on **40 × 40 mm** platens | [Cement test press](/products/testing-analysis-systems/cement-test-press/) VTR-1026S / VTR-1026D |

### 3.1 Mortar mixer

| Speed | Blade spin (rpm) | Planetary orbit (rpm) |
|-------|------------------|------------------------|
| **Low** | **140 ± 5** | **62 ± 5** |
| **High** | **285 ± 10** | **125 ± 10** |

- **~5 L** stainless bowl; matched blade set.
- Blade–bowl clearance **3 ± 1 mm**, checked periodically (monthly in EN 196-1 practice).

### 3.2 Jolting (compacting) table

- Moving mass (table, arms, empty mould, hopper, clamps): **20.0 ± 0.5 kg**.
- Lift **15.0 ± 0.3 mm**, free drop onto anvil.
- **1 drop per second**; **60 jolts** per layer in one automatic run.

### 3.3 Triple gang prism moulds

- **Steel** (or equivalent hard metal); inner faces **≥ 200 HV** (often **≥ 400 HV** in practice).
- Internal: **160.0 ± 0.8** × **40.0 ± 0.2** × **40.1 ± 0.1 mm**.
- Joints sealed against leakage; light mould release on inner faces.

### 3.4 Curing cabinet and water tank

- **24 h** at **≥ 90 % RH** after moulding (extend to **48 h** only if demoulding is impossible — document on the record).
- After demoulding, prisms cured **horizontally** in **20 ± 1 °C** water until test age.

### 3.5 Auxiliary equipment

- **Balance:** at least **1 g** readability for batching cement, sand, and water.
- **Straightedge** and **scraper** for strike-off and mixing scrape step.
- **Water tank** with stable **20 ± 1 °C** temperature monitoring.

---

## 4. Mixing procedure (timing ± 1 s)

| Time (s) | Action |
|----------|--------|
| **0–30** | Water and cement in bowl; start **low speed** |
| **30–60** | **Low speed**; add all sand over **30 s** |
| **60–90** | **High speed** **30 s** |
| **90–180** | **Stop**; **scrape** to centre in first **15 s**; **rest** **75 s** |
| **180–240** | **High speed** **60 s** |

---

## 5. Moulding and curing

1. Two layers in the clamped mould on the jolting table — **60 jolts per layer** (**120** total).
2. Strike off flush with a **metal straightedge**.
3. **24 h** in the RH cabinet.
4. Demould; store in the **water tank** until the test day.

---

## 6. Strength tests

Workflow: **mixer → jolting table → curing cabinet → water tank → test press**.

### 6.1 Flexural strength

- Test **wet** as removed from the tank (no drying).
- **Three-point bending**, span **100 mm**, mid-span loading.
- Rate **50 ± 10 N/s** until break.

### 6.2 Compressive strength

- Test both halves **immediately** after flexure.
- Load the **smooth mould side faces** (not the struck top face) against **40.0 × 40.0 mm** platens (**1600 mm²** area).
- Platens **≥ 600 HV**; rate **2400 ± 200 N/s**; record **Fmax**.

The [Vector cement test press](/products/testing-analysis-systems/cement-test-press/) provides flexure and compression fixtures with programmed rates for ISO 679 / EN 196-1 programmes.

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## 7. Calculation and validity

```text
Rc (MPa) = Fc / 1600
```

(Fc in N; platen area **1600 mm²**.)

1. Two compressive values per prism → **six** per triple mould set.
2. Mean of six.
3. If **one** result lies outside **± 10 %** of that mean, **exclude** it and report the mean of the remaining **five**.
4. If **more than one** result is outside **± 10 %**, **void the set** and repeat from mortar mixing.

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## 8. Relation to EN 196-1 and procurement

When a tender calls for an **“ISO 679 compliant cement strength laboratory”**, suppliers must deliver (or verify):

1. Programmable **planetary mixer** with the speed table above.  
2. **Jolting table** with controlled mass, stroke, and **60-jolt** automation.  
3. Qualified **triple moulds** and batching balance.  
4. **RH cabinet** and **thermostatic water tank** on the climate table.  
5. **Calibrated press** for flexure and compression rates.

Technical detail for European national implementation: [EN 196-1 summary](/resources/standards/en-196-1/).

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## 9. Practical notes

1. **One climate programme** across mixer room, cabinet, and tank — hydration errors show up as strength scatter, not press noise alone.
2. **Timing ± 1 s** on mixing is mandatory; do not shorten scrape or rest steps.
3. **Press calibration** and loading-rate checks at **50 N/s** and **2400 N/s** setpoints are part of ISO 679 conformity, not optional add-ons.
4. Vicat and setting-time work often shares the mixing room — see [EN 196-3](/resources/standards/en-196-3/).

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*Summary based on ISO 679:2013. Confirm the current edition at ISO.org before contractual or accreditation use.*