Dirk Schlicke

Cracking Risk and Regulations

This chapter is focused on the cracking risk at early ages. After general considerations about cracking, the cracking risk prediction is discussed. Two main ways to assess this risk are considered: through an evaluation of the tensile stresses and through an evaluation of the strains. Finally, the evaluation of crack opening at early ages and the reinforcement design in regulations are presented.

On-site Monitoring of Mass Concrete

On-site monitoring of mass concrete offers several benefits. It may comprise a wide range of objectives from (i) the maintaining of adequate temperature conditions for the evolution of the desired concrete properties and to (ii) the determination of thermal and mechanical parameters for verification of the calculation models and assumptions applied for crack assessment of the considered structure. Next to very general information on monitoring of mass concrete, this chapter presents different levels of measures with regard to the purpose and expected insights into each level, available instruments and least requirements on practical application, as well as possibilities for result verification. The chapter focuses on both established techniques with comprehensive experiences in many applications and comparably new techniques available on the market. Finally, the presented techniques and approaches were exemplified on three different application examples with regard to different measurement systems as well as types of structures.

Crack Assessment of a Very Thick and Bloc-Like Concrete Member

Abstract This paper presents the results of recent research activities on the hardening-induced stresses and the risk of cracking in very thick concrete members. These activities focus on a very large member with bloc-like dimensions. In contrast to typical member types such as ground slabs or foundation walls, bloc-like members are dominated by temperature gradients in all three dimensions (height, width and length) at the same time. Besides, the comparably high stiffness of these members leads to very low external restraints in cases of common applications. In these cases the members considered show distinct eigenstresses (residual stresses or self-balanced stresses) but only low restraint forces and moments. The assessment of the hardening-induced cracking of such members therefore requires a detailed analysis of the temperature and stress fields. This contribution presents comprehensive investigations on the hardening-induced risk of cracking of a typical bloc-like concrete member in the form of an underwater foundation. The results of the simulation were compared with selected practical observations during the construction of the underwater foundation of a recently built bridge.