Report rep025 : Early Age Cracking in Cementitious Systems - Report of RILEM Technical Committee 181-EAS - Early age shrinkage induced stresses and cracking in cementitious systems

Early age cracking sensitivity is a well-known phenomenon, which is associated with drying shrinkage. In special structures and concretes this can be aggravated by thermal effects. The cracking sensitivity induced by drying can occur before or at the onset of setting (plastic shrinkage cracking) or at the period of few days after beginning of setting and hardening.
The advent of modern concrete technology renewed the interest in this issue from several points of view: application of new means to control cracking (e.g. fiber reinforcement and shrinkage reducing admixtures) and the development of a variety of new concretes of superior performance in the fresh and hardened state, that may be more sensitive to early age cracking (e.g. high strength concretes of low water/binder ratio).
In order to optimize the use and design with such concretes and admixtures, there is a need for a comprehensive understanding and treatment of early age cracking. Such an approach is much more complex than the simplistic treatment where cracking sensitivity is quantified in terms of free shrinkage only. It is essential to evaluate, test and model the systems under restrained conditions, to take into account the stresses developed and assess the risk of cracking by considering fracture criteria.
With this in mind, the RILEM technical committee TC 181-EAS was established, to develop and advance the required comprehensive treatment outlined above, to cover basic mechanisms, engineering and design considerations, as well as testing procedures. The present report is a compilation of the State of the Art produced by the committee, addressing the basic scientific principles and upon them expands the treatment towards various engineering aspects. The State of the Art covers a variety of topics required for a comprehensive treatment of early age cracking risks and their mitigation: driving forces and microstructural aspects, engineering properties, modeling, testing and implementation of the concepts in special cementitious systems.

Contents

Chapter 1: Introduction: Overview of early age cracking

Chapter 2: Terminology and definitions

Chapter 3: Driving forces and microstructural aspects

Chapter 4: Engineering properties

Chapter 5: Modeling concepts

Chapter 6: Testing

Chapter 7: Special cementitious systems