The density of normal concrete is about 145 pounds per cubic foot. The density of concrete is determined largely by the type of aggregate used in the mixture. The density of the cement used in the mix can also affect density, with compressed, vibrated cement creating a denser concrete mix.
The amount of air trapped into the concrete also changes the density of the material. The more air pumped into the concrete mix, the lower the density. Lightweight aggregates other than stone can also be added to the mix, reducing the density. Lightweight concrete, for example, has a density of only 115 pounds per cubic foot.