Free autogenous strain of early-age cement paste: metrological development and critical analysis

The objective of this paper is to analyse and compare the results obtained with three different experimental methods used for the measurement of autogenous deformation of hydrating cement-based materials. Two (horizontal and vertical) linear measurement systems and a rotary volumetric device, especially designed for the study of very early-age strain, have been developed. The tests were performed on Portland cement pastes with three different water-to-cement ratios (w/c) equal to 025, 030 and 040. The effects of bleeding on both the linear and the volumetric results and of immersion liquid absorption on the volumetric results have been highlighted. The critical analysis of these results yields the conclusion that, among the three test methods used and in the range of w/c ratios investigated, the dynamic volumetric method is the most adapted for the measurement of very early-age autogenous strain even if some improvements have to be made in the choice of the immersion liquid.