Comparison of autogenous shrinkage measurements by different methods in case of fast-hardening mortar

Autogenous shrinkage in the volume of cementitious materials results from changes in the microstructure and environmental conditions. These deformations can be sufficient to cause premature cracking of structures, especially the fast hardening materials or thin products with large exchange surfaces, such as paving, screeds and cement-glass composite. The appearance of cracks influences the quality and aesthetics of the works. The dimensional variations can be observed immediately after the cement and the water have been brought into contact during mixing. In this research, the endogenous shrinkages of a fast hardening mortar based on ettringite binder were studied with different methods. In this mortar, there is not only the shrinkage phenomenon but also the swelling relating to the early ettringite formation. Therefore, the understanding of the dimensional variation with different measurement methods is very important. The results indicate that the endogenous shrinkage measured by linear methods and volumetric methods are in good agreement. All measurement method well recorded both a quick shrinkage and a swelling phenomenon in the mortar.