Unit Weight of Concrete

Reference

Self weight is the first load on every concrete structure, and this is the number it comes from: what a cubic meter of concrete actually weighs, plain, reinforced and lightweight.

24 kN per cubic meter (reinforced, normal weight)
Plain concrete, normal weight2300 to 2400 kg/m3
Reinforced concrete2400 to 2500 kg/m3
Design values, Eurocode24 plain, 25 reinforced kN per cubic meter
Design values, US practice145 plain, 150 reinforced lb per cubic foot
Structural lightweight1450 to 1850 kg/m3
Fresh concreteabout 1 percent above the hardened value

Notes for design and site

Two things move the number: the aggregate and the steel. Limestone and granite aggregates land a plain mix near 2300 to 2400 kg/m3, heavier trap rock pushes past it, and structural lightweight aggregate drops the whole mix below 1850. Reinforcement then adds its share, which is why codes quote a separate reinforced value: Eurocode uses 24 kN per cubic meter for plain concrete and 25 once the bars are in, while North American practice runs on 145 and 150 lb per cubic foot.

Self weight is usually the biggest single load in a concrete structure, so the choice matters. A 200 mm slab at 24 kN per cubic meter is 4.8 kPa of dead load before anything is built on it, more than the residential live load in many codes. Rounding 24 up to 25 moves every moment and reaction in the takedown by about 4 percent, cheap insurance on a transfer element, wasted concrete on a long ramp.

For ordering, think in tonnes: a 7.5 cubic meter pour of normal weight concrete weighs about 18 tonnes, which is also why pump lines and formwork see the pressures they do. Fresh concrete runs about one percent heavier than the hardened value until the bleed water leaves.

Related Calculators and Reference