Modulus of elasticity of concrete: what is it and how to determine it?

A lot of people are interested in how different force impacts and loads affect the concrete structures. Concrete is a solid body, which tends to deform under the influence of external forces. It is the ability to elastic deformation (temporary nature) reflects the modulus of elasticity of concrete.

The amount of elasticity is determined when testing various specimens for resistance to stretching or compression. However, one should know that concrete, which does not contain reinforcement, is unstable to stretching. Based on the test results, a plot is constructed of the dependence of the arising deformations on the forces applied to the material. Visibility contributes to better understanding. It is also necessary to know the initial modulus of elasticity of concrete and the amount of deformation.

Under load, the increase in deformation is due to the fact that concrete has the property of creep. First, at a certain pressure, an elastic deformation occurs in it. It is a phenomenon in which a body that is deformed from a load returns to its original shape after it disappears. Then, under further loading, irreversible (plastic) deformations begin to occur in the material. However, it is extremely difficult to separate plastic and elastic changes. Because the instantaneous shape change depends on the speed of the load increase. Because of this, the deformation during the time of load increase is called elastic, and the further increase in the shape change is plastic. It occurs because of the creep of the concrete. Further deformation is already the destruction of the object. This modulus of elasticity of concrete is often called the modulus of deformation. It is determined by different methods.

The initial modulus of elasticity of concrete is very difficult to determine. However, its approximate value can be determined indirectly. On many graphs, the secant line to the curve reflecting the dependence of stress on deformation is very often, although not always, parallel to the tangent that passes through the origin.

Relatively true is the assertion that the modulus of elasticity of concrete increases in direct proportion to the root of its strength. However, this is true only for the main part on the graph (strain-strain) and depends on the environment and the test conditions. As an example, water-saturated types of material in tests have a greater modulus of elastic modulus than dry samples. Although their strength properties are similar.

The modulus of elasticity is strongly influenced by the quality of the large filler. This relationship is straightforward. Naturally, the index of lightweight concrete will be lower than that of heavy samples. Elasticity also increases with the age of the materials. For example, the modulus of elasticity of concrete in 25, after one year will be higher than initially, and after 10 years it will increase even more. To determine the elasticity index, there is a special table, where the approximate initial modules of the material of each brand are indicated.