2D-Correlation NMR relaxation analysis of pore-water interactions in cement materials: laboratory and in-situ analysis.

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Cements and concretes have been used for millennia and continue to be globally important. By any measure, they translate to billions of dollars per year (10% of European GDP is spent on buildings and infrastructure; circa 50% is spent on repairs; 270 million tonnes of cement delivered in 2003). However, and notwithstanding this vast scale, a detailed understanding of the evolution of pore micro-structure in cements, and of water dynamics at the nano / micro scale within cement-pores, remains singularly elusive. According to a major European industrial / academic consortium, NANOCEM, this lack of quantitative understanding is a key, cross-cutting, research problem facing the cement industry. On the one hand, it inhibits systematic progress by cement chemists and technologists creating new materials that offer better in-use performance, greater functionality and improved durability. Modellers face a dearth of numerical information. On the other hand, end-user consultant engineers require improved, quantitative methods to map water content and porosity in the outer layers (top 50 mm) of concrete - see e.g. CIRIA report C538 (2000). Failure of engineering structures is driven by several processes all of which depend on the presence and movement of water in surface layers. Decisions about expensive remedial work require knowledge of the pore structure and water near surface and at depth. Elsewhere, during build, technological failure results if concrete toppings are laid before substrates are properly cured , economic loss results if they are delayed. Again water mapping is needed.Magnetic resonance relaxation time analysis is a powerful means of characterising liquid filled porous media. It is used, for instance, by the oil industry down-bore-hole to investigate pore size distributions and oil content in oil-reservoirs rocks. Magnetic resonance imaging is the means by which similar information can be got with spatial resolution.Relaxation time analysis has recently been advanced considerably by the introduction of 2D-correlation-relaxometry. This has created new and exciting opportunities to address the needs of the cement community. The 2D-correlation-relaxometry promises major advances in measuring the correlation times which describe water adsorption to pore surfaces, water diffusion across pore surfaces, water exchange rates between pores and pore size distributions during the hydration of cement. The aim of this proposal is to realise these opportunities.The project will (i) provide the detailed numerical information on water dynamics required by cement technologists for a range of cements with and without additives, and (ii) the implementation of 2D correlation relaxometry on a portable magnetic resonance imaging system for consultant engineers so that thay can map water distributions and dynamics in the surface layers of new and existing construction non-destructively and in-situ.