Porosity characterisation of intact concrete specimens.

The chemical durability of concrete is largely dependent on the chemical reactivity of the silicate aggregates to alkaline pore water. Concrete irradiated at sufficient neutron fluences results in the breakdown of the Si-tetrahedron connected to 4 Si-atoms (Q⁴) to produce Q³ species, which is significantly more soluble in aqueous media. This leads to the alkali silica reaction (ASR), which is the most important degradation process in radiation-damaged concrete. For biological shielding concrete the occurrence of ASR has two ramifications: loss of mechanical strength (which shortens service life), and changes to the pore structure and reactive surface that play a role in the sorption characteristics and transport of radionuclides (neutron activated species or fission products from leaked reactor cooling water). Most investigations on the porosity of materials are conducted on pulverized specimens. We employ intact specimens. In order to achieve the highest possible resolution via μ-computed tomography (μ-CT), small cylindrical cores (0.15±0.01 g) were examined. The connected porosity of these specimens is examined using mercury intrusion porosimetry.