In this work, the chloride transport related properties of slag concrete have been studied. For this, traditional experiments and an innovative computational method were applied to novel mixes with a low carbon footprint. In part 1 combination of Ground Granulated Blast Furnace Slag and Steel Basic Oxygen Slag activated using ordinary Portland cement, waste cement industrial residues and recycled Plasterboard Gypsum were studied. In order to characterize these blended binders, the compressive strength, the volume stability, the mineralogical changes due to hydration and the setting times were measured. In part 2 the chloride penetration was simulated to study the transport properties using a multi-species model. In this, the ionic species flow is given by the Nernst– Planck equation; however, due to ion–ion interactions there are ionic fields that affect the final flux producing an additional voltage known as the membrane potential. In order to calculate the inputs of the model a neural network methodology was developed to find the fundamental properties of concrete including the diffusion coefficients In part 3 a range of traditional transport chloride related experimental tests were carried out on concrete mixtures developed in part 1. These tests were workability, compressive strength, open porosity, initial water absorption capacity (sorptivity), carbonation, chloride migration and self diffusion, electrical resistivity, water permeability, and corrosion. Additionally, the methods developed in part 2 were used to calculate the chloride transport related properties of those mixes.

O uso de concreto de alto desempenho constitui tendência irreversível, devido às vantagens que apresenta em relação aos concretos de resistência usual, principalmente na execução de pilares de edifícios, pois as áreas das seções transversais podem ser reduzidas. Este trabalho trata da obtenção e do estudo teórico e experimental de pilares de concreto de alto desempenho, analisando o comportamento de modelos, solicitados à compressão centrada e flexão normal composta. Foram analisados pilares de seções transversais quadradas de 20cm x 20cm e retangulares de 15cm x 30cm e 12cm x 30cm, dimensões que representam pilares usuais em estruturas de edifícios. Na compressão centrada ficou caracterizado que o estado limite último foi atingido por ruptura da seção mais solicitada e comprovado que a ruptura ocorreu quando o núcleo, definido pelo perímetro considerado pelos eixos dos estribos, se rompeu. Nos ensaios de flexão normal composta os resultados mostraram que as hipóteses de distribuição de tensões, utilizadas para os concretos de resistências usuais, não devem ser consideradas para concreto de alta resistência. As forças normais experimentais e as teóricas, calculadas por um modelo proposto pelo Autor, ficaram iguais enquanto que, para os momentos fletores, os valores experimentais ficaram muito acima dos teóricos. / The use of high performance concrete is an irreversible tendency in structural design due to the advantages it presents, compared to the concrete of usual strength, these advantages can be seen mainly in the execution of buildings columns as the cross sections can be reduced. This thesis is about the theoretical and experimental study to obtain high performance concrete columns. The behaviour of models subjected to axial load and bending plus axial load was analysed. Columns with the square (20cm x 20cm) and rectangular (15cm x 30cm and 12cm x 30cm) cross sections were studied, because they are the usual buildings columns dimensions. As far as axial load is concerned, the ultimate state limit was reached when the mostly demanded section broke. It was proven that the rupture occurred when the core, defined by the perimeter considered by the axial stirrups, broke. The results of bending plus axial load tests have shown that the distribution of stress hypotheses used for concrete of usual strength must not be considered for high strength concrete. The experimental axial forces and the internal ones calculated by a given model were the same, whereas the experimental values for the internal moments were much higher.

The decommissioning of nuclear power stations will lead to the production of a number of contaminated components. The materials produced will consist of process and structural wasteforms. Before this waste can be disposed it will be necessary to obtain a full inventory of those radionuclides contained in those wastes. This will be necessary to ensure that the waste is handled in a suitable manner and that full information is available so that reliable risk assessment can be carried out on the proposed disposal site. A number of radionuclides have been highlighted as significant in terms if their halflife, terrestrial mobility and predicted levels in decommissioning wastes. A selection of these radionuclides have been investigated, and methods developed for their determination in concrete. It was a requirement of this work that the methods developed were robust and that the minimum detectable amount was below that of the de minimis of O.4Bq g-1.

O uso de concreto de alto desempenho constitui tendência irreversível, devido às vantagens que apresenta em relação aos concretos de resistência usual, principalmente na execução de pilares de edifícios, pois as áreas das seções transversais podem ser reduzidas. Este trabalho trata da obtenção e do estudo teórico e experimental de pilares de concreto de alto desempenho, analisando o comportamento de modelos, solicitados à compressão centrada e flexão normal composta. Foram analisados pilares de seções transversais quadradas de 20cm x 20cm e retangulares de 15cm x 30cm e 12cm x 30cm, dimensões que representam pilares usuais em estruturas de edifícios. Na compressão centrada ficou caracterizado que o estado limite último foi atingido por ruptura da seção mais solicitada e comprovado que a ruptura ocorreu quando o núcleo, definido pelo perímetro considerado pelos eixos dos estribos, se rompeu. Nos ensaios de flexão normal composta os resultados mostraram que as hipóteses de distribuição de tensões, utilizadas para os concretos de resistências usuais, não devem ser consideradas para concreto de alta resistência. As forças normais experimentais e as teóricas, calculadas por um modelo proposto pelo Autor, ficaram iguais enquanto que, para os momentos fletores, os valores experimentais ficaram muito acima dos teóricos. / The use of high performance concrete is an irreversible tendency in structural design due to the advantages it presents, compared to the concrete of usual strength, these advantages can be seen mainly in the execution of buildings columns as the cross sections can be reduced. This thesis is about the theoretical and experimental study to obtain high performance concrete columns. The behaviour of models subjected to axial load and bending plus axial load was analysed. Columns with the square (20cm x 20cm) and rectangular (15cm x 30cm and 12cm x 30cm) cross sections were studied, because they are the usual buildings columns dimensions. As far as axial load is concerned, the ultimate state limit was reached when the mostly demanded section broke. It was proven that the rupture occurred when the core, defined by the perimeter considered by the axial stirrups, broke. The results of bending plus axial load tests have shown that the distribution of stress hypotheses used for concrete of usual strength must not be considered for high strength concrete. The experimental axial forces and the internal ones calculated by a given model were the same, whereas the experimental values for the internal moments were much higher.

Este trabalho apresenta uma análise do comportamento da frente de carbonatação em vigas de concreto armado sob tensão, em escala natural e reduzida, com a máxima condição de subarmação. As vigas foram construídas com e sem adição da sílica da casca de arroz e sílica de ferro silício ou silício metálico. Para cada viga em escala natural (agregado graúdo com D máx. = 19 mm) foi moldada uma em escala reduzida com o mesmo traço de concreto para estabelecer os mesmos parâmetros de comparação. As vigas foram curadas durante 7 dias e posteriormente submetidas à flexão, com o carregamento aplicado nos terços (L/3 da viga). Realizou-se o pré-condicionamento para a estabilização da umidade interna das vigas que foram expostas durante 28 dias em um ambiente com concentração de 50% de dióxido de carbono, umidade relativa de 65 \'+ OU -\' 5% e temperatura ambiente. Foram determinados: resistências à compressão simples axial, resistência à tração por compressão diametral, módulos de elasticidade e profundidade da frente de carbonatação em corpos-de-prova cilíndricos. A profundidade da frente de carbonatação em corpos-de-prova foi determinada para diferentes concentrações de dióxido de carbono. Também foi verificada a carbonatação ao longo das vigas em escala natural e reduzida e nas posições das fissuras. Para a previsão da profundidade da frente de carbonatação nas vigas, foram ajustadas equações para a representação da carbonatação na região das fissuras. Os resultados obtidos mostraram a eficiência da espessura do cobrimento, a eficácia dos modelos físicos reduzidos para realizar estudos de carbonatação e a tendência da carbonatação em elementos estruturais na condição de serviço. A frente de carbonatação difere na posição das fissuras, evidenciando um comportamento diferente quando comparado com corpos-de-prova. A análise microestrutural ilustrou o comportamento da frente de carbonatação em vigas de concreto armado, complementando o estudo experimental. Com base nos resultados obtidos pode-se afirmar que a simples adoção de concretos de alto desempenho para construção de elementos estruturais não é suficiente nas peças que contenham fissuras e que sejam submetidas a atmosferas ambientais agressivas. / This work reports on the behavior of carbonation in reinforced concrete beams under stress regime on full and small scales having the lowest possible frame. The beams were made with and without adding silica from rice husk and silica fume (Fe-Si). For each beam on a full scale (coarse aggregate with D máx. = 19 mm) another beam on a small scale was made with the same mix of concrete to maintain the same comparison parameter. The beams were cured for 7 days and subsequently submitted to flexure by applying a two-point loading (L/3 of beam). Humidity stabilization to stabilize internal humidity of beams exposed for 28 days in an environment with a concentration of 50% carbon dioxide, 65 \'+ OR -\' 5% of relative humidity and room temperature was carried out. The following was determined: axial compression strength, tensile splitting strength, young\'s modulus and carbonation depth in cylindrical specimens. The carbonation depth was determined in specimens with unlike carbon dioxide concentration. Moreover, carbonation along beams on full and small scales and in cracks was observed. To estimate the carbonation depth of the beams, equations were adjusted to represent the carbonation in cracks. The results show the efficiency in the thickness of the cover, efficiency of small-scale models for studies concerning carbonation and behavior of carbonation in the serviceability of structural elements. The carbonation depth differs in the position of cracks, showing behavior which is unlike the one compared to specimens. The microstructure analyses show the behavior of carbonation depth in reinforced concrete beams complementing the experimental study. The results show that it is not sufficient to use high performance concretes in structural elements for elements with cracks and in aggressive atmospheres.

Existing and novel laboratory techniques and equipment are used to produce comprehensive information on the liquefaction mitigation provided by granular drainage columnar inclusions in loose sand. Extensive use is made of bender-element testing techniques and the frequency dependence of such measurements is examined. Phase-sensitive detection is proposed as a new method to obtain the frequency response of the element data. The applicability of this technique is extended to provide a convenient and accurate method for determination of the time-of-flight of a shear-wave in sand. This technique is employed to measure the load share between sand and columnar components during triaxial testing. A novel low cost, high loading frequency, triaxial testing system is developed and preliminary testing is carried out on both pure sand samples and composite columnar samples. The testing programme examines aspects of liquefaction mitigation due to the rigidity of the columnar inclusions and due to the increased permeability of the columns. The laboratory results are verified by the application of existing analytical models. The equipment and techniques are used to investigate the feasibility of using recycled aggregates in place of stone backfill.

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