The pore system and engineering properties of hardened cement paste

The work described in this thesis is an attempt to elucidate the relationships between the pore system and a number of engineering properties of hardened cement paste, particularly tensile strength and resistances to carbonation and ionic penetration. By examining aspects such as the rate of carbonisation, the pore size distribution, the concentration of ions in the pore solution and the phase composition of cement pastes, relationships between the pore system (pores and pore solution) and the resistance to carbonation were investigated. The study was carried out in two parts. First, cement pastes with different pore systems were compared, whilst secondly comparisons were made between the pore systems of cement pastes with different degrees of carbonation. Relationships between the pore structure and ionic penetration were studied by comparing kinetic data relating to the diffusion of various ions in cement pastes with different pore systems. Diffusion coefficients and activation energies for the diffusion process of Cl- and Na+ ions in carbonated and non-carbonated cement pastes were determined by a quasi-steady state technique. The effect of the geometry of pores on ionic diffusion was studied by comparing the mechanisms of ionic diffusion for ions with different radii. In order to investigate the possible relationship between tensile strength and macroporosity, cement paste specimens with cross sectional areas less than 1mm2 were produced so that the chance of a macropore existing within them was low. The tensile strengths of such specimens were then compared with those of larger specimens.

Pore structure and diffusional properties of hardened cement pastes

This study has investigated the inclusion of pulverised fuel ash (PFA) and blast furnace slag (BFS) into hardened cement pastes (HCP) in retarding the ingress of chloride ions and oxygen molecules from the external environment. The influence of environmental factors such as drying and carbonation on the pore structure and diffusional properties of OPC, OPC/30%PFA and OPC/65%BFS hardened pastes was investigated. Specimens were desorbed from a saturated surface dry condition to a near constant weight at 65% relative humidity (RH) while others were simultaneously exposed to a 65% RH atmosphere and a carbon dioxide atmosphere of up to 5% by volume until there were fully carbonated. The presence of the interfacial zone at the cement paste-aggregate interface was critically reviewed and identified. The influence of the interfacial zone on porosity and chloride ingress in assumed periodic composites of glass bead mortars was also studied. The investigations have demonstrated the following: (a) The use of fly ash and slag in blended cement pastes has resulted in a marked reduction in capillary porosity and rate of chloride ingress. (b) The ratio of oxygen to chloride diffusion coefficients increased from values close to 1 in permeable pastes, to values of around 15 in low-permeability blended fly ash and slag pastes. This supports the view that the diffusion of chloride ions is retarded by the surface charge of the hydrated cement gel in low-permeability pastes. (c) Compared with plain OPC pastes, the carbonation of blended fly ash and slag pastes resulted in a marked increase in the coarse capillary porosity and a corresponding increase in the oxygen and chloride diffusion rates.

New horizons in mouse immunoinformatics:reliable in silico prediction of mouse class I histocompatibility major complex peptide binding affinity

Quantitative structure–activity relationship (QSAR) analysis is a main cornerstone of modern informatic disciplines. Predictive computational models, based on QSAR technology, of peptide-major histocompatibility complex (MHC) binding affinity have now become a vital component of modern day computational immunovaccinology. Historically, such approaches have been built around semi-qualitative, classification methods, but these are now giving way to quantitative regression methods. The additive method, an established immunoinformatics technique for the quantitative prediction of peptide–protein affinity, was used here to identify the sequence dependence of peptide binding specificity for three mouse class I MHC alleles: H2–Db, H2–Kb and H2–Kk. As we show, in terms of reliability the resulting models represent a significant advance on existing methods. They can be used for the accurate prediction of T-cell epitopes and are freely available online (http://www.jenner.ac.uk/MHCPred).

Horizons régionaux et variations océaniennes des territoires français

« L’identité régionale […] repose sur une réalité concrète : la mer est aussi réelle que vous et moi […]. Je ne fais que constater qu’elle forge le caractère de cette planète, qu’elle est une source majeure de notre subsistance et que nous l’avons tous en partage, où que nous soyons en Océanie. Mais au-delà des épreuves quotidiennes, la mer nous lie les uns aux autres. Elle est source de sagesse infinie. La mer est notre métaphore la plus puissante. L’océan est en nous. » (Hau’Ofa, 2015 [1997] : 55-56). Souvent présentés de manière séparée, les territoires français dans le Pacifique Sud, objets de ce dossier, possèdent cependant des horizons régionaux intéressants qui mettent en exergue la variété des écosystèmes politiques de l’espace océanien1. Les facettes multidimensionnelles des évolutions humaines montrent une « mer d’îles » océaniennes en mouvement, selon l’intellectuel tongien Epeli Hau’Ofa (2008 [1993]). Sa pensée alimente la formation d’une identité régionale océanienne, à p... « Regional identity […] has been constructed on a foundation of concrete reality. That the sea is as real as you and I […], that it shapes the character of this planet, that it is a major source of our sustenance, that it is something that we all share in common wherever we are in Oceania – all of these are statements of fact. Yet beyond that level of everyday experience, the sea is our pathway to each other and to everyone else, the sea is our endless saga, the sea is our most powerful metaphor, the ocean is in us. » (Hau’Ofa, 2015 [1997]: 55-56). Often conceived of as separate entities, French overseas territories in the South Pacific, as the subject of this special issue, nevertheless possess interesting regional horizons, which highlight the variety of political ecosystems of Oceania. The multidimensional facets of human evolution show an Oceanian “Sea of Islands” in constant movement, according to the Tongan intellectual Epeli Hau’Ofa (2008 [1993]). His philosophy contributes to...