🏗️ Density of hardened concrete

Construction PN-EN 12390-7

Overview

The standard PN-EN 12390-7 specifies a method of determining the density of hardened lightweight, normal-weight and heavyweight concrete. It distinguishes three states of the specimen: as received, water-saturated and oven-dried — and three ways of determining the volume: by water displacement (the reference method), by calculation from the actual dimensions measured and, for cubes only, by calculation from checked declared dimensions. The precision depends on the method chosen for the volume: water displacement is the most accurate, then the measurement of the dimensions, and the declared dimensions the least accurate (the restriction to cubes follows from the wider length tolerances of other shapes in PN-EN 12390-1).

The minimum volume of the specimen is 0.785 l; where the Dmax of the aggregate exceeds 25 mm, the volume must not be smaller than 50·D³ mm³. The whole specimen as received is usually tested; where that is not possible, a smaller specimen may be broken or cut out. Specimens with a capping layer must not be tested.

The density is determined routinely alongside the strength — as a check on the compaction of the concrete. In pavements of cement concrete the WWiORB technical specifications of GDDKiA require the density to conform to the mix proportions within a tolerance of ± 3.0 %, tested by water displacement on specimens in the saturated state; in the proficiency tests of the Institute of Building Materials and Concrete Technology (IMBiTB) the density is determined on 150 mm cubes from checked declared dimensions and the mass in the saturated state.

Method principle

The mass and the volume of a specimen of hardened concrete are determined and the density is calculated. The mass as received mr: weighed with an error of ≤ 1 g. The saturated mass ms: immersion in water at (20 ± 2) °C until the mass changes by less than 0.2 % in 24 h (specimens cured in water for ≥ 72 h may be taken as saturated). The dried mass mo: drying in a ventilated oven at (105 ± 5) °C until the mass changes by less than 0.2 % in 24 h, with cooling before weighing in an airtight vessel or a desiccator. The volume by the reference method: the specimen in the saturated state is weighed on a cradle in water and in air, and the volume is calculated from the difference of the masses.

Applications

• Check on the compaction of concrete before strength tests (compression, flexure, splitting)
• Assessment of the conformity of the density of pavement concrete with the mix proportions (a tolerance of ± 3.0 % in the WWiORB technical specifications of GDDKiA)
• Classification of lightweight and heavyweight concretes by density
• Density of cores taken from structures (before capping)
• Proficiency testing of construction laboratories

Key parameters

Standard

Standard number

PN-EN 12390-7:2019-08

Title (PL)

Badania betonu — Część 7: Gęstość betonu

Title (EN)

Testing hardened concrete — Part 7: Density of hardened concrete

Step-by-step procedure

1. Choice of the specimen

   Use the whole specimen as received; the volume at least 0.785 l (with a Dmax > 25 mm ≥ 50·D³ mm³). If the shape or the size does not allow it, break or cut out a smaller specimen. Do not use specimens with a capping layer.

2. Mass as received

   Weigh the specimen mr with an error of not more than 1 g and record it in kg.

3. Mass in the saturated state

   Immerse the specimen in water at (20 ± 2) °C until the mass changes by less than 0.2 % in 24 h, wiping excess water from the surface before each weighing. Record ms in kg. Specimens cured in water for ≥ 72 h may be taken as saturated to constant mass.

   🌡 Temperature: 20 ± 2 °C

4. Mass in the dried state

   Dry in a ventilated oven at (105 ± 5) °C until the mass changes by less than 0.2 % in 24 h. Before each weighing cool to near room temperature in an airtight vessel or a desiccator. Record mo in kg.

   🌡 Temperature: 105 ± 5 °C

5. Volume by water displacement (the reference method)

   Make sure that the specimen is in the saturated state. Weigh the specimen on the cradle fully immersed in the tank with a constant water level and then in air, and calculate the volume from the difference of the masses.

6. Volume from the dimensions (alternatives)

   Calculate the volume from the actual dimensions measured (callipers, rules, error ≤ 0.5 %) or — for cubes only — from checked declared dimensions.

7. Calculation of the density

   Calculate the density as the mass in the chosen state divided by the volume; state in the test report the state of the specimen and the method used for the volume.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The specimens are heavy — take care when immersing them in the tank and taking them out, the cradle must be securely suspended
• The oven at 105 °C — carry hot specimens with heat-resistant gloves and cool them in a desiccator
• Breaking or cutting the specimens: safety goggles, wet cutting

Frequently asked questions