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The physical origins of thermal properties of cement paste

Despite their impact on longevity, serviceability, and environmental footprint of our built infrastructure, the chemo-physical origins of nanoscale thermal properties of cement-based materials, and their link to macroscale properties still remain rather obscure. In this paper, we link atomic-scale equilibrium and non-equilibrium thermal properties of calcium-silicate phases in cement paste to those at macro-level. To this end, we analyze the vibrational density of states (VDOS) of a set of 150 calcium-silicate-hydrates (C-S-H) models with varying Ca/Si ratio, portlandite (CH), alite (C_3S) and belite (C_2S) in details. C-S-H exhibits common features of glassy materials such as Boson peak characterized by extra vibrational states at low frequencies (<2 THz). The specific heat capacities of different phases are measured from VDOS and molecular dynamics. Specific heat capacity of C-S-H is shown to scale linearly with Ca/Si ratio. Furthermore, full thermal conductivity tensors of all phases are calculated via the Green-Kubo approach. While C-S-H and CH exhibit distinct heat transport anisotropy, C_2S and C_3S show isotropic conductive properties. Finally, the macroscopic specific heat capacity and thermal conductivity of cement paste during the hydration process are calculated via mean-field homogenization approach. These results indicate that multiscale material design would ultimately pave the way to a novel route for optimization of macroscopic thermal properties of construction materials.

Author(s):

Mohammad Javad Abdolhosseini Qomi    
MIT
United States

Franz-Josef Ulm    
MIT
United States

Roland Pellenq    
MIT
United States