Keywords: compressive strength, cement paste, multiscale model, C-S-H, microstructure, blended cement.

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.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £75 +P&P)