🏗️ Freeze/thaw resistance of coarse aggregate — 10 cycles of freezing to −17.5 °C under water and thawing in a bath at about 20 °C

Construction PN-EN 1367-1

Overview

The standard specifies a test method which gives information on how an aggregate behaves when subjected to the cyclic action of freezing and thawing. The result makes it possible to assess the resistance of the aggregate to this form of weathering. The test is applied to aggregates with particle sizes from 4 mm to 63 mm. The standard notes that the stresses in the aggregate caused by frost depend among other things on the degree of water saturation and on the rate of cooling.

The freeze/thaw resistance of aggregate translates directly into the durability of concrete. Frost-resistant aggregate is used in order to obtain concrete resistant to the aggressive action of freezing and thawing, corresponding to the exposure classes from XF1 to XF4. In pavement concrete, because of the de-icing agents used in the winter maintenance of roads, aggregate resistant to frost also in the presence of salt is used — that test is described separately by Part 6 of the same series, and the result is denoted by the symbol FEC. Freeze/thaw resistance determined according to Part 1 is denoted by the symbol F.

The test consists of two parts: soaking at atmospheric pressure and storage in water in order to achieve full saturation, and exposure to the action of frost under water.

Method principle

Specimens of single-sized aggregate, previously soaked in water at atmospheric pressure, are subjected to ten cycles of freezing and thawing. A cycle consists in cooling the aggregate under water to −17.5 °C and then thawing it in a water bath at a temperature of about 20 °C. After the cycles have been completed the aggregate is examined for changes: the formation of cracks, the loss of mass and, where appropriate, changes in strength. The mass loss is calculated as the quotient of the difference of the masses before and after the test to the initial mass, expressed as a percentage, where the initial mass is the combined mass of three dried specimens and the final mass is the combined mass of those specimens remaining on a specified sieve.

Applications

• Qualification of aggregate for concrete exposed to freezing and thawing (exposure classes XF1–XF4)
• Choice of aggregate for pavement and bridge concrete
• Acceptance testing of aggregates in road construction
• Factory production control at the aggregate producer’s works
• Assessment of the suitability of aggregate from a new deposit

Key parameters

Standard

Standard number

PN-EN 1367-1:2007

Title (PL)

Badania właściwości cieplnych i odporności kruszyw na działanie czynników atmosferycznych — Część 1: Oznaczanie mrozoodporności

Title (EN)

Tests for thermal and weathering properties of aggregates — Part 1: Determination of resistance to freezing and thawing

Step-by-step procedure

1. Preparing the specimens

   Prepare three specimens of aggregate by reducing a sample taken from single-sized aggregate, after removing oversize and undersize particles. The recommended fraction is 8/16 mm with a mass of 2000 g ± 5 %; also admissible are 4/8 mm with a mass of 1000 g ± 5 %, 16/32 mm with a mass of 4000 g ± 5 % and 32/63 mm with a mass of 6000 g ± 5 %.

2. Washing, drying and weighing

   Wash the specimens and clean them of adhering particles, dry them at a temperature of 110 °C ± 5 °C to constant mass, cool them to ambient temperature and weigh them. Carry out the weighing to an accuracy of ±0.2 g for aggregate of a size up to 16 mm and to ±0.5 g above 16 mm.

3. Soaking

   Keep the specimens in the containers for 24 h ± 1 h at a temperature of 20 °C ± 5 °C in distilled or deionised water, at atmospheric pressure.

   ⏱ Time: 24 h ± 1 h

4. Placing in the cabinet

   Place the closed containers with the specimens in the low-temperature cabinet and subject them to ten cycles of freezing and thawing.

5. Cooling to zero

   Reduce the temperature from 20 °C ± 5 °C to 0 °C ± 1 °C within 150 min ± 60 min and hold 0 °C ± 1 °C for 210 min ± 90 min.

   🌡 Temperature: 0 °C ± 1 °C

6. Freezing

   Reduce the temperature from 0 °C ± 1 °C to −17.5 °C ± 2.5 °C within 150 min ± 60 min and hold −17.5 °C ± 2.5 °C for at least 240 min.

   🌡 Temperature: −17.5 °C ± 2.5 °C

7. Thawing

   Thaw the specimens in water at a temperature of about 20 °C until the temperature of the specimen reaches 20 °C ± 3 °C. After the end of each thawing stage leave the container in water at a temperature of 20 °C ± 3 °C for at most 10 hours. Carry out each full cycle within 24 hours.

8. Assessment and calculation

   After the ten cycles assess the macroscopic changes in the aggregate: the formation of fissures and cracks and the loss of mass, and where necessary changes in strength. Calculate the mass loss F as the ratio of the difference of the masses to the initial mass, as a percentage, where the initial mass is the combined mass of the three dried specimens and the final mass their combined mass remaining on a specified sieve. In the test report give the result together with the fraction tested.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The low-temperature cabinet works at −17.5 °C — gloves protecting against frostbite when taking out the containers
• Containers with water and aggregate of several kilograms — care when lifting, a risk of flooding the working place
• A drying oven heated to 110 °C — thermal gloves, tongs for taking out the vessels
• Aggregate after the cycles is sometimes cracked and sharp — gloves when sieving and weighing
• Mineral dust when washing and sieving — respiratory protection, wet working

Frequently asked questions