Size Characterisation of Pore Structure for Estimating Transport Properties of Cement Paste

The conventional experimental approaches to assessing pore structure characteristics (e.g. mercury intrusion porosimetry) in cement paste have difficulties in providing reliable results. This problem can be approached by geometrical statistical and mathematical methods, e.g. stereological analysis and mathematical morphological measurements. This paper deals with the application of these methods to section images of cement paste specimens and presents a representative set of results of size characterization of pore structure in cement pastes with various water cement ratios and degrees of maturity. The size characterization of pore space allows direct prediction of paste permeability with empirical relationships. However, only porosity, pore size, and eventually porosity connectivity (i.e. connected fraction of porosity) are taken into account in the conventional models for estimating permeability of cement pastes, such as the Kozeny-Carman equation and the Katz-Thompson equation. These simplified models cannot provide accurate estimation of paste permeability without significant improvements. Accurate predictions of cement paste permeability and of other transport properties require incorporating information on how the pores are interconnected, i.e., on topology characteristics of pore structure. This requirement can be fulfilled by pore network modelling, which reflects pore size distribution and the complex situation of connectivity in pore space. Potential applications of mathematical morphology methods for constructing the pore network model and thereby estimating transport properties of cement paste are also discussed in this contribution. Key words: Size characterisation, pore structure, transport properties.