The relationship between humidity and water content in a hydrating cement paste is largely controlled by the nanostructure of the C–S–H gel. Current hydration models do not describe this nanostructure, thus sorption isotherms and self-desiccation are given as constitutive inputs instead of being predicted from microstructural evolution. To address this limitation, this work combines a C–S–H gel description from nanoscale simulations with evolving capillary pore size distributions from a simple hydration model. Results show that a progressive densification of the C–S–H gel must be considered in order to explain the self-desiccation of low-alkali pastes. The impact of C–S–H densification on the evolution of microstructure and sorption isotherms is then discussed, including the effect of water-to-cement ratio, cement powder fineness, and curing temperature. Overall, this work identifies an area where nanoscale simulations can integrate larger-scale models of cement hydration and poromechanics.

C–S–H gel densification: The impact of the nanoscale on self-desiccation and sorption isotherms

Di Luzio, Giovanni
2018

Abstract

The relationship between humidity and water content in a hydrating cement paste is largely controlled by the nanostructure of the C–S–H gel. Current hydration models do not describe this nanostructure, thus sorption isotherms and self-desiccation are given as constitutive inputs instead of being predicted from microstructural evolution. To address this limitation, this work combines a C–S–H gel description from nanoscale simulations with evolving capillary pore size distributions from a simple hydration model. Results show that a progressive densification of the C–S–H gel must be considered in order to explain the self-desiccation of low-alkali pastes. The impact of C–S–H densification on the evolution of microstructure and sorption isotherms is then discussed, including the effect of water-to-cement ratio, cement powder fineness, and curing temperature. Overall, this work identifies an area where nanoscale simulations can integrate larger-scale models of cement hydration and poromechanics.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11311/1056563
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