# Chapter 5. Cement paste percolation, transport, and elastic properties

This chapter covers the percolation, transport, and elastic properties of cement paste. The results of model studies are used to understand how the pore structure of cement paste is controlled by its percolation properties, and how this pore structure helps determine transport and elastic properties.

This section covers the percolation properties of cement paste, covering capillary porosity, C-S-H, and CH. The C3S hydration model is used to explore the percolation thresholds in hydrating cement paste. Later on, the section on the electrical properties of frozen cement paste gives experimental evidence for the correctness of the C-S-H percolation threshold. Note that a realistic cement particle size distribution was not used, so that the capillary porosity percolation threshold is somewhat low, 18 % instead of 20% to 22 %.

This section updates the percolation properties of the cement hydration model for portland cement chemistry and more realistic cement particle size distributions, and in addition, discusses the effect of various numerical uncertainties on the results of the model. Transport properties (fluid permeability vs. ionic diffusivity) are also discussed and updated for the model.

This section discusses the modelling of the diffusivity of cement paste, using the C3S model. Percolation theory and composite theory are used to interpret the results and develop a general equation for cement paste diffusivity as a function of capillary porosity. This equation is then used later in the full multi-scale model for concrete diffusivity.

The equation for diffusivity as a function of porosity was updated via experimental data and simulations that were conducted on a complete portland cement hydration model (including silica fume).

This section describes direct comparisons, at room temperature, between experiment and simulation for the DC conductivity of white cement paste.

This section describes more direct comparisons, at room temperature, between experiment and simulation for the DC conductivity of portland cement paste. The experimental technique used is impedance spectroscopy.

This section describes direct comparisons, at room temperature, between experiment and simulation for the dielectric properties of portland cement paste. The experimental technique used is impedance spectroscopy. The dielectric properties are considered in the low frequency limit.

This section describes direct comparisons, at -40C, between experiment and simulation for the DC electrical conductivity of portland cement paste. The experimental technique used is impedance spectroscopy.

The linear elastic moduli of cement paste are key parameters, along with the cement paste compressive and tensile strengths, for characterizing the mechanical response of mortar and concrete. Predicting these moduli is difficult, as these materials are random, complex, multiscale composites. This paper describes how finite element procedures combined with knowledge of individual phase moduli are used, in combination with a cement paste microstructure development model, to quantitatively predict elastic moduli as a function of degree of hydration, as measured by loss on ignition.

This section presents an argument for the usage of coarser cements in high performance concretes based on microstructural modelling of cement paste microstructure and analysis of hydration progress and pore space percolation.

This section presents a more detailed study of the effects of cement particle size distribution on numerous physical properties of cement-based materials, using microstructural modelling and computer-based prediction of properties.

(11a) Transient Plane Source Measurements of the Thermal Properties of Hydrating Cement Pastes

### Go to 6. Mortar and concrete microstructureGo back to 4. Microstructure development of cement paste phases

References

(1a) D.P. Bentz and E.J. Garboczi, Cement and Concrete Research 21, 325-344 (1991).
(1b) E.J. Garboczi and D.P. Bentz, Cement and Concrete Research 31 (10), 1501-1514 (2001).
(1c) D.P. Bentz, Cement and Concrete Composites 28 (5), 427-4331 (2006).
(1d) D.P. Bentz, Advances in Cement Research 18 (2), 65-70 (2006).
(1e) D.P. Bentz, Journal of the American Ceramic Society 89 (8) 2606-2611 (2006).
(2a) E.J. Garboczi and D.P. Bentz, Journal of Materials Science 27, 2083-2092 (1992).
(2b) D.P. Bentz, O.M. Jensen, A.M. Coats, F.P. Glasser, Cement and Concrete Research 30, 953-962 (2000).
(3) B.J. Christensen, T.O. Mason, D.P. Bentz, and E.J. Garboczi, in Advanced Cementitious Systems: Mechanisms and Properties, edited by F.P. Glasser, G.J. McCarthy, J.F. Young, T.O. Mason, and P.L. Pratt (Materials Research Society Symposium Proceedings Vol. 245, Pittsburgh, 1992), pp. 259-264.
(4) R.T. Coverdale, B.J. Christensen, T.O. Mason, H.M. Jennings, E.J. Garboczi, and D.P. Bentz, Journal of Materials Science 30, 712-719 (1995).
(5) R.T. Coverdale, B.J. Christensen, T.O. Mason, H.M. Jennings, and E.J. Garboczi, Journal of Materials Science 29 (19), 4984-4992 (1994).
(6) R.A. Olson, B.J. Christensen, R.T. Coverdale, S.J. Ford, G.M. Moss, H.M. Jennings, T.O. Mason, and E.J. Garboczi, Journal of Materials Science 30, 5078-5086 (1995).
(7) C.-J. Haecker, E.J. Garboczi, J.W. Bullard, R.B. Bohn, Z. Sun, S.P. Shah, and T. Voight, to be published in Cement and Concrete Research (2005).
(8) D.P. Bentz and C.J. Haecker, Cement and Concrete Research 29 (4), 615-618 (1999).
(9a) D.P. Bentz, E.J. Garboczi, C.J. Haecker, and O.M. Jensen, Cement and Concrete Research 29 (10), 1663-1671 (1999).
(9b) D.P. Bentz, published in Self-Desiccation and Its Importance in Concrete Technology II, eds: B. Persson and G. Fagerlund, Lund University, 127-134 (1999).
(10a) D.P. Bentz, C.J. Haecker, X.P. Feng, and P.E. Stutzman, Proceedings of the 5th International VDZ Congress "Process Technology of Cement Manufacturing", Düsseldorf, Germany, September 23-27, 2002 (2003).
(10b) D.P. Bentz, Materials and Structures 40(4), 397-404 (2007).
(11a) D.P. Bentz, accepted by Materials and Structures, (2007).