QUANTIFICATION OF CAPILLARY PORES AND HADLEY GRAINS IN CEMENT PASTE USING FIB-NANOTOMOGRAPHY

Abstract

Based on high resolution 3D-microsturctural data from FIB-nanotomography the pore structure in the sub-m range can now be described quantitatively. This is demonstrated for a 28 days old cement paste. In contrast to the discontinuous pore size distribution (PSD) which results from mercury intrusion porosimetry, the data from FIB-3D-analysis reveals an exponential PSD at radii larger than 50 nm. Using extended image analysis techniques, porosity in hadley grains and the capillary pore network in the interstitial groundmass can be distinguished and the connectivity between them can be quantified. In the 28 days old cement paste, 34% of the total pore volume are located within the hadley grains. The connection with the capillary pores in the groundmass is dominated by numerous but small pathways (intersections). The average radius of these intersections is below 100 nm. The average intersection density is 0.75 intersections per m(2) of phaenograin surface. The intersections occupy only 2% of the interface between the phaenograins and the groundmass. In summary, the new 3D-microscopy technique not only provides information about pore size distribution of the bulk microstructure, but it also enables to distinguish different types of pores and to characterize the connectivity between them. This information is considered to be a prerequisite for establishing microstructural models that can predict permeability properties in cement pastes.