Fracture insights on notched calcium silicate hydrate (C-S-H) and silica interface in concrete using reactive molecular dynamics simulations

M Gupta and S Bhowmik, CONSTRUCTION AND BUILDING MATERIALS, 499, 144081 (2025).

DOI: 10.1016/j.conbuildmat.2025.144081

The interfacial transition zone in concrete with an inherent defect as represented by calcium silicate hydrate (C-S-H) and silica interface has been explored from the perspective of fracture mechanics principles using the reactive molecular dynamics (MD) simulations. All the models are developed according to relevant literature and demonstrate high accuracy and computational efficiency. A uniaxial tensile loading is applied to the model for estimating the mechanical and fracture properties of interface failure. A rigorous parametric study of fracture parameters has been carried out to achieve a precise understanding on the effect of model size, notch location, notch length, and strain rate. The size effect trend has been accurately captured at nanoscale with 13% and 73% decrease in brittleness index. The notch location study emphasizes that the probability of aggregate rupture is very low and the model shows a quasi-brittle response in all the cases. Additionally, the detrimental effects of larger defects have been captured on fracture parameters. The results reveal that the brittleness index increases from 0.49 to 0.53 to 0.72 with increase in notch length. The fracture toughness and energy show an increasing trend with enhanced characteristic length for decreasing strain rates. All the obtained resulting trends are in well agreement with the available literature under similar conditions at macroscale. Overall, the simulations successfully capture the large-scale trends in concrete fracture highlighting the potential of MD simulations for fracture characterization. The obtained results can serve as a basis for homogenizing the fracture parameters to estimate multiscale properties.

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