# How to input compressive strength value of concrete in construction stage?

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$$If you measure the development of parameters of concrete in time, you can specify their absolute values in the construction stage of prestressing in IDEA StatiCa Beam. The software automatically calculates the equivalent time for a given concrete parameter. This allows us to prestress concrete members with age under 3 days with the fast development of compressive strength or elastic modulus according to paragraph 3.1.2 (5).Once you tick the checkbox for fck, you will be able to input its user-specified value. On the other hand, one can specify the elastic modulus value at that stage. These values can not be combined and overrule each other.$$