Frédéric Grondin

Improved measurement methods for autogenous shrinkage of cement mortars at very early age

This paper presents improved test methods for the measurement of autogenous shrinkage of cement-based materials at very early age (0 to 48h). These five test methods enable the measurement of chemical shrinkage, volumetric autogenous shrinkage, linear autogenous shrinkage in horizontal and vertical directions and restrained autogenous deformations leading to early-age cracking of the material. The first experimental results are discussed and analyzed. It was shown that the presence of granular inclusions slightly accelerates the evolution of mortar chemical shrinkage. The rotary test device for the measurement of volumetric autogenous shrinkage makes it possible to eliminate bleeding and segregation problems related to medium or high water-to-cement ratio (W/C). The use of non-contact and waterproof eddy current sensors permits to quantify uniaxial autogenous deformations of the cementitious matrices since the casting of the material, in quasi-isothermal conditions. Finally, it is shown from ring test results that the age of cracking decreases when the temperature increases, but the cracking appears at nearly the same hydration degree.