MOLECULAR DYNAMICS SIMULATION OF CSH UNDER VARIOUS LOADING AND THERMAL CONDITIONS

Abstract

In this research we adopt the molecular dynamics simulation techniques to study the mechanical and thermal properties of the chosen C-S-H atomistic model The chemical composition of the C-S-H model is (CaO)1 60(SiO2)(H2O)1 63 and its density is about 2 32 g/cm3 The interatomic potential is the CSHFF which is a new version of ClayFF applying Coulombic electrostatic potential function as long-range interactions and take Lennard-Jones potential function as shortrange interactions Tension compression shear torsion bending and indentation simulations were conducted to correlate properties with microstructures The C-S-H model exhibits clear layered structure at room temperature but the layered structure becomes more homogeneous at high temperature indicating thermal energy causing large fluctuation in atom positions At room temperature our calculated Q1:Q2:Q3 ratio is about 15 : 50 : 35 consistent with literature data At high temperature Q1 is almost constant and dominant Q2 decreases and Q0 increases This change in Q’s affects the mechanical properties of C-S-H significantly In tensile compressive and shear tests the layer structure and silicate chains affect fracture mechanisms At high temperatures the C-S-H loses its strength and toughness significantly Based on our calculations the largest shear modulus is about 18 30 GPa from the torsion test and largest Young’s modulus is about 75 00 GPa from the bending test The C-S-H exhibits ultimate tensile stresses between 1 5~2 5 GPa in responses to various loading directions From indentation tests the hardness is about 7 33 GPa and the indentation modulus is about 64 19 GPa The calculated coefficient of thermal conductivity is 10 852 W/mK by the Green-Kubo equilibrium method

Date of Award	2017 Aug 1
Original language	English
Supervisor	Yun-Che Wang (Supervisor)