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Microstructure and Transport Properties of Concrete.


pdf icon Microstructure and Transport Properties of Concrete. (717 K)
Garboczi, E. J.

RILEM. Performance Criteria for Concrete Durability. Proceedings. State of the Art Report prepared by RILEM Technical Committee TC 116-PCD, Performance of Concrete as a Criterion of Its Durability. RILEM Report 12. Chapter 8. 1995, E & FN SPON, London,England, Kropp, J.; Hilsdorf, H. K., Editor(s)(s), 198-212 pp, 1995.

Keywords:

concretes; transport properties; cements; mortar; sand

Abstract:

Concrete is a composite material whose microstructure is random over a wide range of length scales. At the largest length scale, concrete can be considered to be a mortar-rock composite, where the randomness in the structure is on the order of centimeters, the size of a typical coarse aggregate. Mortar itself can be considered to be a cement paste-sand composite, with random structure on the order of millimeters. Cement paste can also be considered to be a random composite material, made up of unreacted cement, CSH, CH, capillary pores, and other chemical phases. The randomness in the cement paste microstructure is on the order of micrometers. Finally, CSH is itself a complex material, with random structure, as seen by neutron scattering, on the order of nanometers. This range of random structure, from nanometers (CSH) to centimeters (concrete) covers seven orders of magnitude in size! It is a large and difficult task to try to relate microstructure and properties theoretically for concrete. However, there are some simple, basic ideas that do provide a framework for this task, with the main difficulty being carrying these ideas through to specific application. This chapter attempts to outline the general principles that must be considered in trying to understand microstructure transport property relationships in concrete, or indeed any other random porous material. Specific applications to cement paste, mortar, and concrete will be considered. An earlier review, which mentions some of the ideas discussed in this chapter is also a helpful reference for some of the earlier transport property data and their interpretation in terms of pore structure.