Significance of Thermal Eigenstresses on the Risk of Cracking due to Concrete Hardening with Focus on Ground-Slab Types

In times of climate change, responsible use of our natural resources is of great importance. For the optimization of concrete structures, the interdisciplinary cooperation of all parties involved is crucial already in the planning process. Through this cooperation, it is also possible to provide evidence of crack prevention as a result of hardening-induced restraint stressing, which enables significant savings in the minimum reinforcement for crack control. There are different existing verification formats, such as the cracking index, cracking probability or macrocrack index. The latter was developed primarily for the targeted assessment of the risk of macrocracks that cover the entire tensile zone, whereby only those restraint stresses that cause restraint forces are considered. The eigenstresses generated in the hydration process are not further assessed in the macrocrack index as they are assumed in engineering terms to reduce the risk of macrocracking. This paper questions this engineering assumption with special attention to the correct combination in time between restraint stresses due to restraint forces with the corresponding eigenstress profile using nonlinear thermomechanical FE investigations. The result of the research is a proposal for the consideration of eigenstresses for the assessment of the risk of cracking depending on the member type and thickness.