ABSTRACT
Abstract Thermal dilation (TD) and autogenous shrinkage (AS) generate stresses in concrete members hardening under restraint. The sum of TD and AS may readily be determined in the laboratory for realistic temperature histories, and may serve as an accurate basis for stress calculations in structures. However, for general calculation programs it is desirable to have individual material models for TD and AS. An experimental strategy is proposed to obtain a basis for such models. Preliminary results are given, which demonstrate that AS depends strongly on temperature history, and cannot be realistically estimated from isothermal tests. Keywords: Autogenous shrinkage, high performance concrete, temperature dependence, thermal dilation
1 Introduction and background
Hardening concrete will generate stresses if the movements caused by hydration reactions are restrained. There are two active mechanisms producing movements: Thermal Dilation (TD) and Autogenous Shrinkage (AS). Traditionally, only thermally induced stresses have been considered when estimating cracking risk in young concrete. However, with increased use of high performance concrete (water-to-binder ratio below 0.45) it has become clear that AS may contribute significantly to stress generation, and any serious approach to estimate cracking risk by calculations must take both TD and AS into account as "driving forces" to stress generation.
