Percolation Description

Percolation in Cementitious Materials

In the Cementitious Materials Modelling Laboratory at the National Institute of Standards and Technology, researchers are using percolation theory to develop a basic understanding of microstructure-property relationships in cementitious materials. Percolation deals with the connectivity of one or more phases in a microstructure. Examples abound in cementitious materials: the commonly measured setting (set time) behavior of a cement paste is a measure of the percolation of solid cement particles by the C-S-H gel product. As hydration continues, the capillary porosity (original water-filled space) actually depercolates, which has large effects on transport coefficients. The connectivity of crystalline phases such as calcium hydroxide can be critical to durability, as these phases are often the most easily leached from the concrete. Thus, this leaching may reconnect a previously disconnected capillary pore system.

Percolation is also important when one considers concrete. Here, a key concern is whether the aggregate content and surface area is sufficient that the individual interfacial zones surrounding each aggregate will percolate across a concrete system. Since these interfacial zones are often weak links in terms of strength and durability, their percolation can have significant effects on the final properties of a concrete. This phenomena can be modelled using a hard core (aggregate)/ soft shell (interfacial zone) percolation model.

Publications

Garboczi, E.J., Thorpe, M.F., DeVries, M.S., and Day, A.R., "Universal Conductivity Curve for a Plane Containing Random Holes", Physical Review A, Vol. 43 (12), 6473-82, 1991.

Bentz, D.P., and Garboczi, E.J., "Percolation of Phases in a Three-Dimensional Cement Paste Microstructural Model", Cement and Concrete Research, Vol. 21 (2), 325-44, 1991.

Bentz, D.P., and Garboczi, E.J., "Modelling of the Leaching of Calcium Hydroxide from Cement Paste: Effects on Pore Space Percolation and Diffusivity", Materials and Structures, Vol. 25, 523-33, 1992.

Winslow, D.N., Cohen, M.D., Bentz, D.P., Snyder, K.A., and Garboczi, E.J., "Percolation and Pore Structure in Mortars and Concrete", Cement and Concrete Research, Vol. 24 (1), 25-37, 1994.

Lewis, J.A., Boyer, M., and Bentz, D.P., "Binder Distribution in Macro-Defect-Free Cement: Relation Between Percolative Properties and Moisture Absorption Kinetics", Journal of the American Ceramic Society, Vol. 77 (3), 711-16, 1994.

Garboczi, E.J., Schwartz, L.M., and Bentz, D.P., "Modelling the Influence of the Interfacial Zone on the D.C. Electrical Conductivity of Mortar", Journal of Advanced Cement-Based Materials, 2, 169-181, 1995.

Bentz, D.P., Hwang, J.T.G., Hagwood, C., Garboczi, E.J., Snyder, K.A., Buenfeld, N., and Scrivener, K.L., Interfacial Zone Percolation in Concrete: Effects of Interfacial Zone Thickness and Aggregate Shape, MRS Proceedings, Vol. 370, Microstructure of Cement-Based Systems/Bonding and Interfaces in Cementitous Materials, 437-442, 1995.

Bentz, D.P., Fibers, Percolation, and Spalling of High Performance Concrete, ACI Materials Journal, 97 (3), 351-359, 2000.

Bentz, D.P., Cement Hydration: Building Bridges and Dams at the Microstructure Level, Materials and Structures, 39, 2006.

Bentz, D.P., Capillary Porosity Depercolation/Repercolation in Hydrating Cement Pastes via Low Temperature Calorimetry Measurements and CEMHYD3D Computer Modeling, Journal of the American Ceramic Society, 89 (8), 2606-2611, 2006.