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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 108
PROCEEDINGS OF THE FIFTEENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING
Edited by: J. Kruis, Y. Tsompanakis and B.H.V. Topping
Paper 146

A Multiscale Model for Compressive Strength Evolution of Blended Cement Pastes

V. Šmilauer1, M. Hlobil1 and G. Chanvillard2

1Department of Mechanics, Faculty of Civil Engineering, Czech Technical University in Prague, Czech Republic
2Lafarge Centre de Recherche, St Quentin Fallavier, France

Full Bibliographic Reference for this paper
, "A Multiscale Model for Compressive Strength Evolution of Blended Cement Pastes", in J. Kruis, Y. Tsompanakis, B.H.V. Topping, (Editors), "Proceedings of the Fifteenth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 146, 2015. doi:10.4203/ccp.108.146
Keywords: compressive strength, cement paste, multiscale model, C-S-H, microstructure, blended cement.

Summary
This paper presents a new four-level micromechanical model for prediction of compressive strength of pure and blended cements. The model assumes that compressive strength of cement paste is governed by intrinsic tensile strength of C-S-H globules. Failure under compressive loading is associated with tensile stresses appearing on randomly inclined ellipsoidal inclusions within C-S-H which result in strain softening at all hierarchical levels. The addition of unhydrated clinker, supplementary cementitious materials, remaining hydration products, and entrapped / entrained air further decreases the compressive strength of cement paste.

The multiscale model uses relevant volume fractions of chemical phases on each homogenization level and encompasses a spatial gradient of C-S-H inbetween individual grains. Identification of the intrinsic tensile strength of C-S-H globules on 95 experimental compressive strength values showed this strength amounts to 320 MPa. Governing factors responsible for paste compressive strength evolution remain the newly proposed "C-S-H/space" ratio (analogous to the traditionally used "gel/space" ratio), followed by the volume of entrained or entrapped air, and the spatial gradient of C-S-H between individual grains.

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