Effect of porosity and temperature on thermal conductivity of jennite: A molecular dynamics study

Despite growing interest of cement materials in design and construction of green buildings, their thermal properties are not well understood at atomic scale. In this work, we reported the thermal conductivity of porous jennite, the major component of cement paste, and its porosity and temperature dependences, using molecular dynamics simulations with ClayFF force field. With molecular modeling for the porous jennite with different porosities by removing atoms within the sphere with a certain radius, we mostly applied the non-equilibrium Miiller-Plathe method to the porous jennite models, using the sufficiently extended simulation boxes along the heat flux direction and divided into numbers of plane slices. Our calculations revealed that the volumetric thermal conductivity of porous jennite decreases from 1.141 to 0.144 W/m.K as increasing the porosity from 0 to 72% at room temperature, which follows the empirical coherent potential model when the pore is filled with air. Moreover, as temperature increases, their thermal conductivities were observed to increase first and gradually decrease after certain temperature. We compared the calculation data with our measurement and other available experiments, confirming reasonable agreement between our calculation and experiment.