Concept to predict crack initiation and crack development in fairfaced concrete screeds

Within a research project of the Laboratory of Solid Structures of the University of Luxemburg, a design concept to predict cracks in various concrete structures will be developed. The current paper presents the numerical investigation of crack initiation and crack development of an unreinforced cementitious fairfaced concrete floor. Thereby cracking of concrete is divided into cracking of an early stage and into cracking of a later stage. The present study deals with cracking of an early stage. Taking into account shrinkage and the chronological strength development of the used C20/25 concrete and with the use of the Element Failure Method (EFM) it will be possible to predict, within a Finite Element Analysis, a possible crack path spatial as well as temporal.
For this purpose a finite element model, based on a commercial FE-Software is developed. The program is tested on H-shaped concrete specimen with an unfavorable size ratio between surface and volume. Besides, shrinkage on this specimen is hindered so that unplanned restrain forces has to occur. Using an algorithm the finite element program is able to calculate the model gradually for several load steps within a loop. Furthermore the net dependency of the EFM can be excluded by the use of suitable load steps.