Concrete is characterized above all by its high compressive strength and resilience. Since the composite building material also has a high density, the weight of concrete is not insignificant. However, not all concrete is equally heavy and there are differences in the weight of the concrete.
Not all concrete is equally heavy
Concrete consists of the three basic ingredients cement, aggregate (aggregate) and water. Starting from this, one can already guess the heavy weight that concrete must have. However, there are significant differences in the weight of concrete. So you can already distinguish three types of concrete by weight according to the ingredients:
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- Lightweight concrete: 1.000 to 2.000 kg / m³
- Normal concrete: 2.000 to 2.600 kg / m³
- Heavy concrete: from 2.600 kg / m³
The weight of concrete is based on the dry bulk density
However, the data mentioned does not relate exclusively to the weight of concrete. These data also make the respective density of concrete visible. Specified as dry bulk density, i.e. the density of dry hardened concrete, provides information about the specific composition of the concrete in question.
Theoretically, concrete can be produced from 300 kg / m³
Even if we use lightweight concrete from 1.000 kg / m³, it is also worth mentioning that lightweight concrete can at least theoretically be significantly lighter, namely from 300 kilograms per cubic meter. However, this concrete would be so unstable that there would be no or only very limited uses for it in the regular construction industry.
Effects of concrete reinforcement
Now further factors in the concrete weight have to be considered. For example, concrets are usually reinforced, so equipped with monoungers or steel mats to increase stability (flexibility and tensile strength). However, the reinforcement has a further increase in the weight of concrete. Each cubic meter reinforced concrete can be added again 100 kg weight to the dry rolling density.
Weight changes about the selection of the rock grain
The weight of concrete is therefore determined by the raw density. Since the density of water and cement can not be changed, the weight difference and thus the different raw density must be made by the rocking body (obsolete surcharge). In fact, it is so that the raw density of lightweight concrete is so low because here is a porous rocking granulation.
Special features of light and heavy concrete
Particularly with lightweight concrete, however, a distinction can also be made, since aggregate with a closed structure (LBG) or open-pore structure (LBH) is used. By the way, aerated or aerated concrete is not one of the lightweight concretes, since this building material is not concrete because, among other things, no cement is used. But even with heavy concrete, the final weight is determined by the density of the aggregate. Blast furnace slag, for example lead or chrome slag, is often used for heavy concrete.
Reducing weight with the help of random packings
The bulk density and thus the weight can also be influenced by other additives. Plastic balls are also used as so-called fillers and added to the concrete. In particular, they are intended to reduce the weight of concrete.
Up until the 1990s, concrete modified with such fillers was used relatively frequently. In the meantime, however, it has been recognized that this concrete is more susceptible to external influences and thus tends to be more damaged. With very high-quality concrete structures one has therefore abandoned it.
The load-bearing capacity and other weight-related properties of the concrete
That the weight is also related to the bulk density of concrete can be deduced from this: the lighter a concrete becomes, the more unstable it is. For example, lightweight concretes have so little load-bearing capacity that they cannot be used for load-bearing components and walls. On the other hand, lightweight concrete is characterized by other advantages such as a more favorable coefficient of thermal conductivity. Due to the porosity, the thermal conductivity of conventional concrete is significantly lower than that of lightweight concrete.Tips & Tricks When calculating concrete, the gross density of the aggregate is also of great importance. However, the calculation formulas for this are so complex that do-it-yourselfers usually mix concrete using simple rules of thumb.