Positron lifetime spectroscopy as a probe of nanoporosity of cement-based materials

Hydrating cement pastes prepared with water-to-cement ratio equal to 0.5 in weight were investigated through positron annihilation lifetime spectrosco py over a period of 4 weeks. Two series of samples were prepared using diff erent pre-treatment procedures, in order to assess the influence of sample manipulations on positron annihilation measurements. The technique is sensi tive to changes in the pore structure with ageing time. Moreover, from the positron data an estimate of the first two moments of radii distribution of the nanopores was obtained. (C) 2000 Elsevier Science Ltd. All rights rese rved.