4. Microstructure Development of Cement Paste Phases

This chapter covers the modelling of cement hydration, cement paste microstructure, and the nanostructure of C-S-H. The models and techniques described in this chapter are in the process of revolutionizing the study of the microstructure- property relationships of cement-based materials at the cement paste level.

This section covers the scanning electron microscopy and image processing techniques used to obtain starting 2-D images of cement-based materials (cement powder, fly ash, etc.) dispersed in an epoxy resin. 

(1a) SEM/X-ray imaging of cement-based materials

(1b) SEM Analysis and Computer Modelling of Hydration of Portland Cement Particles

This section covers the modelling of the hydration of cement phases and the development of cement paste microstructure at the micrometer level. 

(2a) Modelling of cement hydration and microstructure development

See also, in conjunction with this section, the following manuals:

(2b) CEMHYD3D: A Three-Dimensional Cement Hydration and Microstructure Development Modelling Package. Version 2.0 (4/2000)

(2c) Incorporation of Fly Ash into a 3-D Cement Hydration Microstructure Model

(2d) A three-dimensional cement hydration and microstructure program. I. Hydration rate, heat of hydration, and chemical shrinkage

(2e) A three-dimensional computer simulation of portland cement hydration and microstructure development

(2f) Estimation of the degree of hydration of blended cement pastes by a scanning electron microscope point-counting procedure

This section describes the application of the CEMHYD3D model to analysis of CCRL Proficiency Cements 135 and 136 issued in January of 2000.

(3) Analysis of CCRL Proficiency Cements 135 and 136 Using CEMHYD3D

This section contains an education module that uses 2-D PC and Macintosh-based algorithms to teach basic concepts of cement hydration.

(4a) Computational Materials Science of Cement-Based Materials: An Education Module (United States Department of Commerce, Technology Administration, National Institute of Standards and Technology, NIST Technical Note 1405 (1993).)

Some of the physics and chemistry of an earlier version of the portland cement hydration model is discussed, and ultrasonic shear wave data is compared to percolation predictions from the model. Possible applications to predicting oil-well cement thickening times are also discussed.

(4b) Cellular automaton simulations of cement hydration and microstructure development (Modelling and Simulation in Materials Science and Engineering, 2, 783-808, (1994).)

This section discusses curing of cement paste, comparing experimental and model-derived measures of hydration, and making use of percolation concepts for cement paste. 

(5) Hydration of portland cement: The effect of curing conditions

This section discusses the modelling of C-S-H at the nanometer level. A nanostructural level model is developed and compared to experiment using simulations of pore size as measured by different molecular species, and by simulations of absorption and desorption of water vapor. 

(6) Modelling drying shrinkage of cement paste and mortar: Part 1. Structural models from nanometers to millimeters

This section discusses the application of scanning electron microscopy and image analysis to help determine the development of porosity and calcium hydroxide in cement pastes where silica fume is present. There is no modelling in this section, but the results are of great use for hydration and microstructure modelling of cement paste with silica fume. 

(7) Evolution of porosity and calcium hydroxide in laboratory concretes containing silica fume (D.P. Bentz and P.E. Stutzman, Cement and Concrete Research 24, 1044-1050, 1994.)

This section discusses the preliminary application of specialized x-ray absorption equipment to monitor the movement of water during curing of various cement pastes (a) and the modelling of this phenomena using CEMHYD3D along with further experimental observations (b). 

(8a) Preliminary observations of water movement in cement pastes during curing using x-ray absorption

(8b) Drying/Hydration in Cement Pastes During Curing

X-ray absorption (or more properly, x-ray attenuation) techniques have been applied to study the moisture movement in and moisture content of materials like cement paste, mortar, and wood. An increase in the number of x-ray counts with time at a location in a specimen may indicate a decrease in moisture content. The uncertainty of measurements from an x-ray absorption system, which must be known to properly interpret the data, is often assumed to be the square root of the number of counts, as in a Poisson process. No detailed studies have theretofore been conducted to determine the uncertainty of x-ray absorption measurements or the effect of averaging data on the uncertainty.

(8c) Determining the Uncertainty of X-Ray Absorption Measurements

This section contains the article that Dale Bentz wrote that covers his RILEM l'Hermite medal lecture, discussing some of the philosophy behind the cement hydration model and the use of digital methods to model cement-based materials. 

(9) Modelling cement microstructure: Pixels, particles, and property prediction

This section contains an article exploring the possibility of replacing the coarse cement particles in a low w/c ratio concrete by inert fillers. 

(10a) Computer modelling of the replacement of coarse cement particles by inert fillers in low w/c ratio concretes: Hydration and strength

(10b) Replacement of "Coarse" Cement Particles by Inert Fillers in Low W/C Ratio Concretes II: Experimental Validation

(10c) Modeling the Influence of Limestone Filler on Cement Hydration Using CEMHYD3D

Self-desiccation shrinkage

This section contains an article examining the effects of shrinkage-reducing admixtures on early age desiccation of cement pastes and mortars. Experimental data is gathered using the new x-ray absorption device for measuring water movement in porous materials. 

(11) Shrinkage-reducing admixtures and early age desiccation in cement pastes and mortars

(12) On the Mitigation of Early Age Cracking 

Hydration Kinetics

(13) Influence of Water-to-Cement Ratio on Hydration Kinetics: Simple Models Based on Spatial Considerations 

Go to Chapter 5. Cement paste percolation, transport, and elastic properties

Go back to Chapter 3. Cement and concrete characterization

References

(1a) D.P. Bentz, P.E. Stutzman, C.J. Haecker, and S. Remond, Proc. of the 7th Euroseminar on Microscopy Applied to Building Materials, Eds: H.S. Pietersen, J.A. Larbi, and H.H.A. Janssen, Delft University of Technology, pp. 457-466 (1999).
(1b) D.P. Bentz, and P.E. Stutzman, SEM Analysis and Computer Modelling of Hydration of Portland Cement Particles, Petrography of Cementitious Materials, ASTM STP 1215, Sharon M. DeHayes and David Stark, Eds., American Society for Testing and Materials, Philadelphia, pp. 60-73, 1994. 
(2a) D.P. Bentz, an original Web document
(2b) D.P. Bentz, National Institute of Standards and Technology Internal Report, NISTIR 6485, U.S. Department of Commerce, April 2000. 
(2c) D.P. Bentz and S. Remond, National Institute of Standards and Technology Internal Report, NISTIR 6050, U.S. Department of Commerce, August 1997. 
(2d) D.P. Bentz, National Institute of Standards and Technology Internal Report, NISTIR 5756, U.S. Department of Commerce, November 1995.
(2e) D.P. Bentz, J. Amer. Ceram. Soc., 80, 3-21 (1997).
(2f) X. Feng, E.J. Garboczi, D.P. Bentz, P.E. Stutzman and T.O. Mason, Cement and Concrete Research 34 (10), 1787-1793 (2004).
(3) D.P. Bentz, X. Feng, C.-J. Haecker, P.E. Stutzman, National Institute of Standards and Technology, NISTIR 6545, U.S. Department of Commerce, August, 2000.
(4a) U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology, Technical Note 1405 (1993). 
(4b) D.P. Bentz, P.V. Coveney, E.J. Garboczi, M.F. Kleyn, and P.E. Stutzman, Modelling Simul. Mater. Sci. Eng., 2, 783-808 (1994).
(5) Dale P. Bentz, Kenneth A. Snyder, and Paul E. Stutzman, Proceedings of the 10th International Congress on the Chemistry of Cement, Vol. 2, Gothenburg, Sweden, edited by H. Justnes (Amarkai AB and Congrex Goteborg AB, Goteburg, 1997).
(6) D.P. Bentz, D.A. Quenard, V. Baroghel-Boouny, E.J. Garboczi, and H.M. Jennings, Materials and Structures 28, 450-458 (1995).
(7) D.P. Bentz and P.E. Stutzman, Cement and Concrete Research 24, 1044-1050 (1994).
(8a) D.P. Bentz and K.K. Hansen, Cement and Concrete Research 30 (7), 1157-1168 (2000).
(8b) D.P. Bentz, K.K. Hansen, H.D. Madsen, F. Vallee, E.J. Griesel, Materials and Structures, 34, 557-565 (2000).
(8c) G.S. Wojcik, Journal of Research of the National Institute of Standards and Technology, 109 (5), 479-496 (2004).
(9) D.P. Bentz, Materials and Structures 32, 187-195 (1999). 
(10a) D.P. Bentz and J.T. Conway, Cement and Concrete Research, 31 (3), 503-506 (2001). 
(10b) D.P. Bentz, Cement and Concrete Research, 35 (1), 185-188 (2005).
(10c) D.P. Bentz, Cement and Concrete Composities, 28 (2), 124-129 (2006).
(11) D.P. Bentz, M.R. Geiker, and K.K. Hansen, Cement and Concrete Research, 31, 1075-1085 (2001). 
(12) D.P. Bentz, M. Geiker, and O.M. Jensen, International Seminar on Self-Desiccation, Lund, Sweden (2002). 
(13) D.P. Bentz, Cement and Concrete Research, 36 (2), 238-244 (2006).

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