A Multiscale Microstructure Model of Cement Paste Sulfate Attack by Crystallization Pressure

Published

September 20, 2017

Author(s)

Pan Feng, Jeffrey W. Bullard, Edward Garboczi, Pan Feng

Abstract

A recent microstructural model for simulating near-surface external sulfate attack on cement paste is modified to incorporate diffusive ionic transport between the surface and the interior of a macroscopic specimen. The model calculates the driving force for local expansive growth of the AFt phase in terms of crystallization pressure, and the strain and stress fields are tracked within the microstructure with micrometer-scale resolution using a linear elastic finite element model. Damage induced by expansion modifies both the local effective transport properties and linear elastic properties of each microstructure at different depths, and thereby potentially alters the rates of sulfate ingress and expansion. Therefore, the progress of phase transformations and expansion from the surface to the interior of the porous material is dictated by the rate of ingress of concentration fronts of both sulfate ions and pH, which do not necessarily coincide. Predictions are made of the macroscopic expansion due to ingress by sodium sulfate solutions with different concentration, which are compared with previous models and published experimental data. The model demonstrates what has previously been assumed in sulfate attack models, namely that volumetric expansion of macroscopic paste samples in the early stages of sulfate attack is a linear function of the mass of AFt phase precipitated. In addition, the model captures the evolution of local elastic and transport properties within a macroscopic paste sample, showing an apparently parabolic dependence on depth of the local Young's modulus and local formation factor.

Citation

Modelling and Simulation in Materials Science and Engineering

Pub Type

Journals

Keywords

computer modeling, microstructure, cement, sulfate attack

Citation

Feng, P. , Bullard, J. , Garboczi, E. and Feng, P. (2017), A Multiscale Microstructure Model of Cement Paste Sulfate Attack by Crystallization Pressure, Modelling and Simulation in Materials Science and Engineering (Accessed July 18, 2024)