Evolution of Coefficient of Thermal Expansion of Concrete at Early Ages

Abstract

Together with drying shrinkage and autogenous deformations, thermal strain is one of the driving force of cracking of cement-based materials at early ages. However, current understanding of these early-age deformations remains unsystematic and further studies are needed. In this paper, evolution of thermal strain and coefficient of thermal expansion (CTE) are reviewed. Based on a newly built test setup at The University of Queensland, the development of the CTE of concrete at early ages was measured and investigated. It is found that CTE shows a clear rising trend after setting, meaning that CTE cannot be seen as constant even though this has often been done for modelling and design purpose. Based on newly-measured CTE, the separation process of self-desiccation shrinkage and thermal strain was studied. It is noted that the separation process is rather complicated due to the effects of delayed thermal strain. Through literature review, it is demonstrated that the delayed thermal strain is closely linked to relative humidity change inside concrete. Since the development of self-desiccation shrinkage is also affected by such relative humidity change, there appears a coupling effect between self-desiccation shrinkage and delayed thermal strain, which should be further studied in the future.