Residual expansion deformation of high-speed railway steam-cured concrete: mechanism, modeling, and measurement

To clarify the volume deformation characteristics and residual expansion deformation formation mechanism of steam-cured concrete, the content of free water and air of fresh concrete before heating, and the hydration kinetics and mechanical characteristics evolution of concrete during the steam curing process were obtained by experiment and fitting. The residual expansion strain calculation model of steam-cured concrete was proposed and its accuracy was verified by a non-contact test. Results showed that: (i) the volume deformation characteristics of steam-cured concrete could be divided into two stages: rapid expansion in heating stage, then rapid shrinkage in constant temperature treating period and gentle shrinkage in cooling period; besides, an irrecoverable residual deformation was gained at the end of cooling period; (ii) the tested peak value of residual expansion strain of steam-cured concrete appeared at 0.5–1 h later than the fitting value, and the final tested residual expansion strain is lower than the fitting value; (iii) the higher the initial free water content and the lower the initial structural strength, the greater the final residual expansion deformation of steam-cured concrete. This paper aims to reveal the mechanism of residual expansion deformation and propose a method of restraining the deformation of high-speed railway steam-cured concrete. This paper could provide technical support for the production of steam-cured concrete prefabricated components and predict the residual expansion deformation.