After the concrete is poured, the hardening process begins. Knowing its strength for a given day, you can make a decision to remove the formwork and start construction. Using the calculator, you will calculate what hardness the concrete gained during the time elapsed since it was poured at a temperature of 15 ° C.
To make it clear, let’s look at how the calculation is carried out and what data is used. But first, let’s define what is considered concrete.
What is concrete
Concrete is a mixture of cement, water, sand, crushed stone or gravel, etc. By changing the proportions of materials, concrete of different strength is obtained. The prepared solution is poured into the mold, where the hydration process begins. As a result of this process, the solution hardens with the transformation into calcium hydrosilicate.
The gained hardness of concrete shows how many percent the transformation of the mixture into calcium hydrosilicate was completed. The standard duration of the hardening process is considered to be 28 days. In everyday life, we say the drying of concrete, which is not entirely true.
The main factors affecting the rate of hardening are:
- time elapsed since filling;
- temperature;
- brand of concrete;
- added hardening accelerators.
Formula for calculating hardness
The calculation uses the formula with the empirical dependence of Bolomey-Skramtaev:
- Rb(n) is the strength of concrete for day n.
- R28 – grade strength of cement.
The formula shows that the more time has passed since the mortar was laid, the greater the strength. But temperature has the greatest influence on the rate of hardening. The above graph for concrete shows how quickly the strength of concrete goes with increasing temperature.
At temperatures below 10 ° C, the hardening process slows down, and in frost it stops altogether. In this case, 28 days is not enough to gain hardness. And if at a temperature of 5-10 ° C you just need to increase the holding time of the concrete mass, then at a negative temperature it is necessary to provide additional heating.
The set of hardness of the concrete structure depends on other factors:
- ratio of water and cement;
- method of laying and sealing;
- cement quality;
- moisture intensity.
The calculator gives values close to real hardness values. But there are enough of them to decide whether it is possible to start building. To get an accurate result, more complex calculations are used. Accurate data is needed when building apartment buildings or bridges. In private construction, such accuracy is not needed.