Hybrid micromechanical modelling and experiments on temperature-dependent thermal conductivity of graphene reinforced porous cement composites

Dispersing graphene and its derivatives into traditional cement matrix to develop highperformance and multifunctional construction materials has attracted great attention. Pores and temperature are evidenced to have significant effects on the thermal properties of graphene nanoplatelets (GNPs) reinforced cement composites (GNPRCCs). Accurate prediction of the thermal property of the GNPRCCs with considering pores and temperature is crucial for their engineering application. In this work, the GNPRCCs samples with different GNPs volume fractions are prepared, characterized, and tested for their thermal conductivity. A hybrid micromechanical model (HMM), employing effective medium theory (EMT) with Mori-Tanaka (MT) approach is developed for the thermal conductivity of the porous GNPRCCs. Particularly, a phonon physical model is incorporated into the model to capture the temperature-dependency of the thermal conductivity. The model is validated by comparing present results with experimental data. The obtained results show that the thermal conductivity of the GNPRCCs with 1 wt% GNPs decreases by 19.79% as the temperature increases from 300 K to 350 K. The increase in porosity results in the blockage of phonon heat transport and the decrease in the thermal conductivity of the GNPRCCs. It is observed that the thermal conductivity of GNPRCCs with 1 wt% GNPs decreases by 14.78% as the porosity increases by 10%. Spherical pores are found to be more favorable for heat flow transport and enhancement of the thermal conductivity. In contrast, the needle-like GNPs with larger size promote the formation of heat transport network and enhance the thermal conductivity of the samples more effectively. For example, the thermal conductivity of the GNPRCCs with 1 wt% GNPs increases by 20.75% as the size of the GNPs increases from 15 mu m to 30 mu m. The developed model for the thermal conductivity of the cement composites is envisaged to provide useful guidelines for their potential engineering applications in snow melting, de -icing and geothermal structures.