ABSTRACT
The most important parameter is the tensile strength of the concrete. It is a time dependent material property which can be calculated according to the following equation.
βcc,t = es· (
1− √
(1)
(where 0, 20 ≤ s ≤ 0, 38, function of cement-type) Therefore it is important to know at what time crack-
ing will occur. In many cases, such as where the dominant imposed deformation arises from dissipation of the heat of hydration, it is sufficient to consider 2-5 days old concrete (e.g. many ground supported slabs). This leads to an effective tensile strength of ca. 50% of the values at 28 days. When the time of cracking cannot be established with confidence as being less than 28 days, the tensile strength of hardened concrete has to be taken into account (e.g. inner walls of underground parking lots).
