  The effect of moisture and porosity on thermal conductivity of tobermorite 14
\AA~as the major component of cement paste is studied by using molecular
dynamics simulation with ClayFF potential. The calculated results show that the
thermal conductivity increases monotonically as the moisture content by mass
within the interior pores increases and the slope of the linear fitting
function decreases as the porosity increases. Meanwhile, the normalized thermal
conductivity is found to increase exponentially as increasing the moisture
content by volume. Phonon density of states of porous and moist tobermorite 14
\AA~is used to explain the contribution of individual atoms and molecules to
the thermal properties. The results can be potentially used to design higher
thermal insulating materials with cement and concrete for energy saving
buildings.
