Numerical modelling of effective thermal conductivity of hardened cement paste

Cheng Liu, Qiang Liu, Jianming Gao and Yunsheng Zhang

Abstract

In this study, a 3D microstructure-based model is established to simulate the effective thermal conductivity of cement paste, covering varying influencing factors associated with microstructure and thermal transfer mechanisms. The virtual cement paste divided into colloidal C-S-H and heterogeneous paste are reconstructed based on its structural attributes. Using the twolevel hierarchical cement pastes as inputs, a lattice Boltzmann model for heat conduction is presented to predict the thermal conductivity. The results suggest that due to the Knudsen effect induced by the nanoscale pore, the thermal conductivity of air in C-S-H gel pore is significantly decreased, maximumly accounting for 3.3% thermal conductivity of air at the macroscale. In the cement paste, the thermal conductivities of dried and saturated cement pastes are stable at the curing age larger than 100 h. The high water-to-cement ratio can decrease the thermal conductivity of cement paste.

Key Words

hierarchical structure; Knudsen effect; Lattice Boltzmann method; microstructure-based model; thermal conductivity

Address

Cheng Liu, Qiang Liu and Jianming Gao: Jiangsu Key Laboratory for Construction Materials, School of Materials Science and Engineering, Southeast University, Nanjing 211189, China Yunsheng Zhang: 1) Jiangsu Key Laboratory for Construction Materials, School of Materials Science and Engineering, Southeast University, Nanjing 211189, China, 2) Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou 730050, China

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