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

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Many people are interested in how concrete structures are affected by various forces and loads. Concrete is a solid body that tends to succumb to deformation when exposed to external forces. It is the ability to elastic deformation (of a temporary nature) that reflects the modulus of elasticity of concrete.

The value of elasticity is determined when testing various samples for resistance to tension or compression. However, you should be aware that concrete that does not contain reinforcement is unstable in tension. Based on the test results, a graph of the dependence of the resulting deformations on the forces applied to the material is constructed. Visualization promotes 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 such a property as creep. First, at a certain pressure,elastic deformation. It is a phenomenon in which a body that has been deformed by a load returns to its original shape after it has disappeared. Then, with 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 rate of load increase. Because of this, the deformation during the increase in load is called elastic, and a further increase in shape change is called plastic. It is due to the creep of concrete. Further deformation is already the destruction of the object. This modulus of elasticity of concrete is often also called the modulus of deformation. It is determined using different methods.

The initial modulus of elasticity of concrete is very difficult to determine. However, its approximate value can be established indirectly. In many graphs, the secant line to the stress-strain curve is very often, though not always, a parallel tangent that goes through the origin.

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

The modulus of elasticity is strongly affectedcoarse filler quality. This relationship is straight forward. Naturally, the indicator of light concretes will be lower than that of heavy samples. The elasticity also increases with the age of the materials. For example, the modulus of elasticity of concrete v25, after one year will be higher than initially, and after 10 years it will increase even more. To determine the elasticity, there is a special table, which indicates the approximate initial modules of the material of each brand.