What is the density of concrete?

2,400 kg/m³ (2,200–2,500), or 2.40 g/cm³.

No. At 2,400 kg/m³ it is denser than water.

Concrete

Density of concrete

2,400 kg/m³ (2,200–2,500)

2.40 g/cm³ · 149.8 lb/ft³

The tensile figure of 2-5 MPa is the important one and the one nobody quotes: concrete carries 25-40 MPa in compression and roughly a tenth of that in tension, which is why every span of it has steel in the bottom. It gains strength by hydration, not drying — concrete cured underwater is stronger than concrete left in the sun — and it keeps gaining slowly for years past the 28-day test figure. Its thermal expansion coefficient happens to match steel almost exactly, which is the quiet coincidence that makes reinforced concrete possible at all.

Properties

Density: 2,400 kg/m³ (2,200–2,500) — 2.40 g/cm³
Tensile strength: 2–5 MPa
Young's modulus: 30 GPa
Thermal conductivity: 1.4 W/(m·K)
Thermal expansion: 10 µm/(m·K)
Floats in water: No
Magnetic: No

What it is used for

Foundations, slabs and footings
Blockwork and paving
Dams and retaining walls
Precast pipes and lintels

How it compares

Water is 1,000 kg/m³. Anything with a shorter bar than water floats in it.

air 1.2 kg/m³

expanded polystyrene foam 20 kg/m³

rigid polyurethane foam 40 kg/m³

Water — the float line 1,000 kg/m³

concrete 2,400 kg/m³

tungsten 19,250 kg/m³

gold 19,300 kg/m³

platinum 21,450 kg/m³

Water is 1,000 kg/m³. Anything below that floats.
Material	Density	Relative to water
rigid polyurethane foam	40 kg/m³	0.04×
expanded polystyrene foam	20 kg/m³	0.02×
air	1.2 kg/m³	0.00×
concrete ←	2,400 kg/m³	2.40×
platinum	21,450 kg/m³	21.45×
gold	19,300 kg/m³	19.30×
tungsten	19,250 kg/m³	19.25×

Does it rust?

Concrete contains no iron, so it cannot rust. Whether it degrades depends on the material, not on oxidation.

Is it magnetic?

Concrete is not a metal and has no ferromagnetic response.

Common questions

What is the density of concrete?: 2,400 kg/m³ (2,200–2,500), or 2.40 g/cm³.
Does concrete float?: No. At 2,400 kg/m³ it is denser than water.
Is concrete magnetic?: Concrete is not a metal and has no ferromagnetic response.

Does concrete float? No
Brick 1,900 kg/m³
Gypsum board (drywall) 700 kg/m³
Tungsten carbide 14,900 kg/m³
Reinforced concrete 2,500 kg/m³
Graphite 2,200 kg/m³
Porcelain 2,400 kg/m³
Plaster 1,100 kg/m³
Silicon carbide 3,210 kg/m³

Sources

Typical range compiled from manufacturer specifications — At One Place

How these figures are compiled and checked