Crack Formation under Hygral or Thermal Gradients

An approach towards the consideration of stresses induced by tem- perature or moisture distributions including diffusion analysis and cracking is succinctly described. The material properties required for the numerical analysis, which can be either determined experi- mentally in a direct way or obtained by means of inverse analysis, are also dealt with. Some applications of the developed model to the time-dependent behaviour of drying concrete members are pre- sented. It is shown that the length change of concrete specimens observed during shrinkage tests cannot be considered as a material property. Rather, it must be understood as the complex response the specimen to a time-dependent, highly non-linear state of eigen- stresses. The effect of the slab depth on the warping of members exposed to drying at their top surface as well as of the concrete qual- ity on the restraint reaction in dowelled slabs is also outlined. The main conclusion is that practical cases with requirements for high performance and the optimization of design or technological mea- sures can only be treated efficiently by means of a rational approach as the one presented this work. 1423 1 , while monitoring the daily and seasonal variations in the warping concrete pavements in California, Hveem (1951) reported on a particularly interesting profile: the one corresponding to a roadway lined with a grove of eucalyptus. The general lack of flat- ness recorded during the measurements was in this case much less pronounced than for the rest of the pavements. It was apparent for that the moisture drawn by the roots of the trees was the cause this improved performance. Many publications documenting today's state-of-the art in the design, evaluation and rehabilitation of concrete pavements empha- size the need for taking the stresses induced by temperature or moisture changes into consideration.