Thermally activated viscoelasticity of cement paste: Minute-long creep tests and micromechanical link to molecular properties

The stiffness of cementitious materials decreases with increasing temperature. Herein, macroscopic samples of mature cement pastes are subjected at 20, 30, and 45 degrees C, respectively, to three-minutes-long creep compression experiments. The test evaluation is based on the linear theory of viscoelasticity and Boltzmann's superposition principle. This yields macroscopic elastic and creep moduli as a function of temperature. A state-of-the-art multiscale model for creep homogenization of cement paste is extended to account for temperature-dependent elastic and creep moduli of the hydrate gel. This extension is based on results from published molecular simulations. Temperature-independent stiffness is assumed for cement clinker. Upscaling to the macroscale of cement paste yields elastic and creep moduli which agree well with the aforementioned experimental results. The Arrhenius-type activation energy of the creep modulus is found to be independent of scale, composition, and maturity, because of ineffective stress redistributions from creeping to non-creeping constituents.

Automated summary

The stiffness of cementitious materials decreases with increasing temperature. Macroscopic samples of mature cement pastes were subjected to creep compression experiments at different temperatures, and the results were evaluated based on the theory of viscoelasticity and Boltzmann's superposition principle. A multiscale model for creep homogenization of cement paste, accounting for temperature-dependent elastic and creep moduli, was developed based on molecular simulations. The model successfully predicted the experimental results, and the activation energy of the creep modulus was found to be independent of scale, composition, and maturity.