The work presented in this thesis deals with the development of self-consolidating high performance concrete (SCHPC) incorporating rice husk ash (RHA) as a supplementary cementing material. Various SCHPCs were produced using the water-binder (W/B) ratios of 0.30, 0.35, 0.40 and 0.50, and RHA content in the range of 0 to 30% of cement by weight. In addition, a number of pastes and mortars formulated from the concretes were prepared and tested for the filling ability. The paste and mortar filling abilities were tested with respect to flow time and flow spread, respectively, at various dosages of high-range water reducer (HRWR). Also, the mortars were tested for the air content at various dosages of air-entraining admixture (AEA). It was observed that the flow time of the pastes increased with lower W/B ratio and higher RHA content, whereas the flow spread of the mortars decreased with higher W/B ratio and greater RHA content. Both paste and mortar filling abilities increased with higher HRWR dosages. In addition, the air content of the mortars decreased with lower W/B ratio and higher RHA content for given AEA dosages. The fresh SCHPCs were tested for filling ability, passing ability, air-void stability, segregation resistance, unit weight and air content. The filling ability was determined with respect to slump and slump flow, inverted slump cone flow time and spread, and orimet flow time and spread. The passing ability was measured with regard to slump and slump flow with J-ring, inverted slump cone flow spread with J-ring, and orimet flow spread with J-ring. The air-void stability in several fresh SCHPC mixtures was investigated with respect to re-mixing of concrete and subsequent measurement of air content at different test stages. The test results obtained for the fresh properties showed that the inverted slump cone and orimet flow times increased with lower W/B ratio and greater RHA content. In addition, the slump flow, inverted slump cone flow spread, and orimet flow spread with and without J-ring increased considerably with lower W/B ratio and greater RHA content. However, the increases in slump with and without J-ring at lower W/B ratio and higher RHA content were not significant. The unit weight of concrete slightly decreased with higher W/B ratio and greater RHA content, and with higher air content. Achieving the target air content required greater AEA dosages for lower W/B ratio and higher RHA content. However, the presence of RHA had no adverse effect on the air-void stability of concrete. The segregation resistance of various SCHPCs was investigated by visual inspection of concrete in mixer pan, and during and after different flow tests. Slight bleeding and a thick layer of paste were noticed in mixer pan for several concretes. The dynamic segregation in the form of discontinuity or blockage of flow did not occur during the orimet and inverted slump cone flow tests for any concrete. No aggregate pile appeared in the slump flow, and orimet and inverted slump cone flow spreads of any concrete. But minor to severe mortar halos were noticed in the periphery of the flow spread of several concretes, particularly in the presence of high RHA content. The results of visual inspection suggest that both lower W/B ratio and greater RHA content improved the dynamic segregation resistance of concrete. In contrast, the higher RHA content resulted in a lower static segregation resistance, which was overcome in the presence of viscosity-enhancing admixture (VEA). The static segregation resistance of several SCHPCs was quantitatively determined by sieve and column apparatus. The segregation index given by the sieve increased with lower W/B ratio and higher RHA content, thus indicating a reduced static segregation resistance. In contrast, the segregation factor given by the column apparatus decreased with lower W/B ratio suggesting an increased static segregation resistance. However, the segregation factor increased with higher RHA content, and thus revealed a reduction in static segregation resistance. In the presence of VEA, both segregation index and segregation factor decreased significantly, indicating an improvement in the static segregation resistance of concrete. The hardened SCHPCs were tested for compressive strength, ultrasonic pulse velocity, water absorption, total porosity and electrical resistivity. Test results revealed that the compressive strength, ultrasonic pulse velocity and true electrical resistivity increased, whereas the water absorption and total porosity decreased with lower W/B ratio and higher RHA content. The entrained air-voids decreased the compressive strength, ultrasonic pulse velocity, water absorption and total porosity, but slightly increased the electrical resistivity of concrete. In general, the hardened properties indicated good durability of the concretes. The empirical models for the filling ability (slump flow) and compressive strength of SCHPC were derived and verified with test data from this study and other data taken from the literature. The slump flow and compressive strength computed from the models were coherent with the measured values. Both filling ability and strength models were useful to develop a mixture design method for SCHPC with and without RHA.

<p>This PhD thesis is divided into two parts. Part one dealswith the development of the material and the mechanicalproperties of Steel Fibrous Cement Based Composites (SFCBC) forimproving bridge design and construction. It familiarizes thehydration mechanisms of the high performance concrete with thehelp of Powers´ and Jensen´s models. Concretes withdifferent water-cement ratio were compared with each other withrespect to degree of hydration and hydration products. Thisanalysis showed that high performance concrete has higherstrengths not because it has more gel solid, but due to ithaving less porosity and higher filler content compared toordinary concrete.</p><p>A number of experiments were performed to achieve a mixdesign method for a SFCBC, which has good workability, highearly and long-term strength and good durabilitycharacteristics. A Self-compacting and self-leveling fibrouscomposite, which has ultra high strengths (Compressive strength<i>f</i><i>c</i>= 180 ~ 220MPa and flexural tensile strength<i>f</i><i>föi</i>= 14 ~ 32MPa depending on the volumefraction of fibers) was produced. This composite was alsotested under different curing conditions in order toinvestigate the effect of curing on hydration andself-desiccation shrinkage. These tests showed that SFCBCshould not be water-cured under a long period andself-desiccation influences the compressive strengthnegatively. Test of scaling at freezing showed that SFCBC hasvery good durability characteristics.</p><p>Part two deals with the behavior of SFCBC in the anchoragezones of prestressed bridges. The prismatic composite specimenswere tested for different volume fractions of fibers underdifferent concentrations ratios of strip loading. The resultsof these tests showed that the ultimate strength of the SFCBCspecimens was approximately twice that of ordinary concretewith the same size (<i>f</i><i>c</i>= 60MPa reinforced with stirrups). Therefore,SFCBC has good possibility to replace the traditional rebars inthe anchorage zones of prestressed bridges.</p><p>This composite has different behavior than the traditionalconcrete e.g. crack formation, failure criteria, effectivestrength and angle of friction. A vertical crack on thecenterline was occurred while wedge developed under the loadingplate. In contrast to ordinary concrete, the cracks could notreach to the bottom of the blocks.</p><p>The tests results gave the ideas of that this material actslike metals or plastics in the high fiber content. Thismaterial is neither very brittle as concrete nor very ductileas metals but it is somewhere between them.</p><p>Upper-bound plasticity solutions were utilized for modelingthe bearing capacity of SFCBC. Predictions of this method aregood enough to estimate the bearing capacity of SFCBC in theanchorage zones of prestressed bridges.</p><p><b>Keywords:</b>Process improvement of bridges, Prestressedconcrete, High performance concrete, Ultra high performanceconcrete, Hydration, Cement based composites, Fibers,Self-compacting concrete, Bearing capacity, Anchorage zones,Tests</p>

The concrete technology has during the last century changed dramatically where the concept of high strength concrete has gone from 30MPa to well over 100MPa. UHPC has many areas of application and is used more and more frequently in all manner of structures. It is also a suitable concrete in areas and environments that are demanding and harsh for the concrete due to its overall excellent durability properties which suggest lifespans of reinforced structure elements that far exceeds what is economically available to design for today with a low cost of maintenance. The aim of this research was to produce Ultra High-Performance Concrete using mostly locally available materials. Tests were made on the binary materials where the particle packing was optimized through the Punkte method. A series of smaller mortar mixes was made where the effect of different proportions of i.e. silica fume, flyash, superplasticizer had on the concrete mix. The fresh and hardened properties of the mix as mini cone flow, slump flow, density, compressive strength and flexural strength was evaluated to obtain a mix which exhibited the properties sought for, high strength and good workability. The results showed that it is difficult to find an optimum mixture since the design of a recipe always has compromises and rarely all criteria’s can be met fully. The concrete produced had a W to C ratio between 0,21, 20wt% of silica fume, 4,5wt% of superplasticizer and max filler size of 1mm. Some mixes of the concrete were also produced with flyash replacement and with steel fibers. This resulted in concretes exhibiting compressive strength over 140MPa, flexural strength of 18MPa without fiber reinforcement and with self-consolidating properties. The replacement of cement with 30wt% of flyash resulted in better workability and long term(1year) compressive strength almost equaled the concrete without flyash replacement.

O presente trabalho fornece uma visão geral sobre a aplicação, o dimensionamento e o detalhamento de pilares confeccionados com concreto de alto desempenho (CAD), cujo principal atributo analisado é a resistência do concreto à compressão. A ênfase do estudo é dada à aplicação do CAD em pilares de edifícios. São apresentadas as principais diferenças entre pilares de CAD e pilares confeccionados com concretos de baixa resistência (fck < 40 MPa), sendo abordados, com base em códigos vigentes e em resultados experimentais, os diagramas tensão-deformação mais indicados, as formas de consideração das não-linearidades física e geométrica, as excentricidades a serem consideradas no dimensionamento, as causas e a forma de prevenção do fenômeno da perda do cobrimento (característico de pilares de CAD), a importância e a forma de consideração do confinamento e algumas disposições construtivas necessárias para o bom desempenho do pilar. Procurou-se, sempre que possível, apresentar os aspectos que não necessitam de alterações, ou seja, que podem ser considerados da mesma forma para concretos de baixa e de alta resistência. Finaliza-se com a apresentação de alguns exemplos de dimensionamento de pilares de CAD, abordando os tópicos analisados ao longo do texto. / The present work provides an overview of use and design of columns made with high performance concrete (HPC), whose main analyzed attribute is the compression strength of the concrete. The emphasis of the study is given to the application of HPC in columns of buildings. The main differences are presented among columns of HPC and columns made with low strength concrete (fck < 40 MPa), being approached, on base in effective codes and in experimental results, the more suitable stress-strain diagrams, the forms of consideration of the physical and geometrical non-linearities, the eccentricities to be considered in the design, the causes and the form of prevention of the phenomenon of the spalling of the concrete cover (characteristic of HPC columns), the importance and the form of consideration of the confinement and some necessary constructive dispositions for the good performance of the column. It was sought, whenever possible, to present the aspects that don\'t need alterations, that is to say, that can be considered in the same way for low and high strength concretes. It concludes with the presentation of some examples of design of HPC columns, approaching the topics analyzed along the text.

Do ponto de vista reológico, o concreto fresco flui como um líquido. Sendo assim, o seu comportamento no estado fresco deve ser estudado a partir dos conceitos da reologia, ciência voltada para o estudo das deformações e escoamento de um fluido sob a influência de tensões. As estruturas bem planejadas, dependendo do processo adotado para sua confecção, são executadas em tempo muito pequeno após a mistura dos materiais que irão constituir os concretos. Assim, a trabalhabilidade do concreto é um parâmetro importante a ser estudado, tanto por facilitar o lançamento do material quanto pelas decisões relacionadas com a forma desse lançamento. Tradicionalmente, a trabalhabilidade do concreto está associada à sua consistência, expressa em termos de abatimento obtido no ensaio de tronco de cone, que, apesar de ser um método de ensaio bastante utilizado, não a quantifica totalmente. Isto porque o concreto se comporta como um fluido binghamiano, sendo, então, caracterizado por dois parâmetros reológicos: a tensão de escoamento e a viscosidade plástica. Assim, o presente trabalho determina alguns parâmetros de medida, a partir de conceitos reológicos, para a verificação do comportamento de alguns tipos de concreto de alto desempenho no estado fresco, com adição de sílica ativa. Para isso, foram usados tanto os métodos de ensaios tradicionais - ensaio de abatimento de tronco de cone e consistômetro de Ve-Be - quanto equipamentos mais modernos - reômetro. Uma modificação do ensaio de abatimento tradicional também foi usada como uma tentativa de simplificar a determinação dos parâmetros reológicos que caracterizam o comportamento dos concretos frescos. A capacidade dos concretos escoarem sob influência do seu peso próprio foi avaliada através do ensaio da caixa L. A identificação da natureza reológica dos concretos foi feita com o auxílio de um reômetro. A trabalhabilidade dos concretos foi avaliada a partir dos métodos de ensaio que medem os dois parâmetros reológicos e sua perda ao longo do tempo foi associada à evolução dos parâmetros medidos. Apesar de terem sido classificadas como misturas fluidas, nenhum concreto apresentou escoamento suficiente que o caracterizasse como um material auto-adensável, porém apresentou bom escoamento sob a energia de um vibrador. A natureza reológica dos concretos foi identificada como sendo realmente semelhante a um fluido binghamiano. A trabalhabilidade, bem como sua perda ao longo do tempo, foram associadas à evolução dos parâmetros reológicos: observou-se um aumento da tensão de escoamento (ou torque de escoamento), enquanto a viscosidade plástica (ou viscosidade de torque) permaneceu praticamente constante durante os 60 minutos em que o comportamento foi acompanhado. Conclui-se que para a trabalhabilidade dos CAD, há inúmeros outros fatores importantes a serem considerados no prosseguimento da pesquisa, os quais deverão levar em conta parâmetros associados à produção, ao transporte e ao lançamento do material. / From the rheological point of view, the fresh concrete flows as a liquid. In such case, its fresh behavior should be studied from the concepts of rheology, the science which concerns the study of deformation and flow of a fluid under stress influence. The well designed structures, depending on the process considered in their production, are performed in a very short time after the mixture of the materials that will constitute the concretes. Thus, the concrete workability is an important parameter to be studied, even for facilitating the material placement and for the decisions related with the method of this process. Traditionally, the concrete workability is associated to its consistency, expressed in terms of the slump value measured by the slump test that, in spite of being a quite used test, does not quantify it totally. It happens because the concrete behaves as a Bingham fluid, being described by two rheological parameters: the yield stress and the plastic viscosity. Thus, the present research determines some measure parameters from rheological concepts to verify the behavior of some types of fresh high performance concrete (with silica fume addition). For this, both traditional test methods - slump test and Vebe consistometer - and more recent equipments - rheometer - were used. A modification of the traditional slump test was also used as an attempt to simplify the determination of the rheological parameters that describe the fresh concretes behaviors. The capacity of the concretes flow under the influence of their own weight was evaluated by the L-box test. The identification of the concretes rheological behavior was made with a rheometer. The concretes workability was evaluated from test methods that measure the two rheological parameters and its loss over time was associated to the evolution of the measured parameters. In spite of being classified as fluid mixtures, none of the concretes presented enough flow to describe it as a self-compacting material; however they presented a good flow under vibration energy. The concrete rheological behavior was identified as being similar to a Bingham fluid. The workability, as its loss over time, was associated to the evolution of the rheological parameters: an increase of the yield stress (or flow resistance) was observed, while the plastic viscosity (or torque viscosity) stayed practically constant during the 60 minutes in which the behavior was followed. It is concluded that for the high performance concretes workability, there are other several important factors to be considered in the research pursuit, which should consider the parameters associated to the material\'s production, transport and placement.

Este trabalho fornece uma visão geral sobre a aplicação, o dimensionamento e o detalhamento de elementos fletidos de concreto de alto desempenho (CAD), armados ou protendidos, com particular atenção para estes últimos. Procurou-se, sempre que possível, realçar as situações nas quais os atuais procedimentos normalizados permanecem válidos, ou não, para o cálculo das vigas de CAD. Na introdução, apresenta-se a viabilidade econômica da aplicação do concreto de alto desempenho nas vigas. No capítulo referente à retração e à fluência, abordam-se procedimentos válidos para o CAD, os quais apresentam melhor correlação com os resultados experimentais que a obtida através do ACI 209 (1982) ou do CEB-FIP (1990). No que se refere à flexão, apresenta-se um diagrama tensão-deformação retangular, e comparam-se os seus resultados para concretos usuais e de alto desempenho, com os obtidos pelo diagrama parábola-retângulo, em termos de consumo de armadura. No capítulo referente ao cisalhamento, apresentam-se recomendações para a utilização do Método Padrão e do Modelo de Treliças de Diagonais de Inclinação Variável para o cálculo da armadura transversal em vigas de CAD. Para o cálculo dos deslocamentos causados por ações de curta duração, confirma-se a validade da metodologia de Branson para as vigas de CAD. Os deslocamentos adicionais causados por ações de longa duração também são considerados, incluindo-se metodologias para as vigas de concreto armado e para as pré-moldadas protendidas. Exemplos de dimensionamento são feitos para todos os itens apresentados, considerando-se uma viga pré-moldada de 30 m de comprimento, seção \"T\", com pós-tensão e fck = 70 MPa. / This work provides an overview of use and design of the high performance concrete (HPC) flexural members, reinforced or prestressed, with particular attention for the last ones. Cases in which procedures of the modern codes for calculation of HPC beams remain valid were enhanced. In the introduction, the economic viability of high performance concrete beams is presented. In the chapter about shrinkage and creep, valid procedures for HPC are presented. These procedures have better correlation with the actual results than those relative to ACI 209 (1982) or CEB-FIP (1990). A rectangular stress block is presented, and its results for usual and high performance concrete are compared with those from the parabolic-rectangular stress block, in terms of consume of steel. In the chapter about shear, recommendations for use of Standard Method and Variable Angle Truss Model for HPC beams are presented. For the calculation of short term deflections, the validity of Branson\'s Method for high performance concrete beams is confirmed. Sustained load deflections are also considered, and including procedures for reinforced beams and for precast prestressed ones. For all the considered topics, examples are presented for a 30 m span precast post-tensioned beam, \"T\" cross section and fck = 70 MPa.

Supplementary cementitious materials (SCMs), are beneficial when used as partial replacement of cement in concrete mixtures for coastal concrete structures, blended with Portland cement (binary or ternary mixes), i.e., high-performance concrete provides improved properties when exposed to marine harsh environment. In order to characterize selected durability properties of different concrete mixtures, a testing program was established. The intent of this study consists of testing 10cm diameter x 20cm long concrete specimens prepared with a range of different mix designs. 1) to evaluate the rate of water absorption due to capillary suction, referred to as sorptivity, 2) to evaluate the concrete surface resistivity, 3) to evaluate and compare the total porosity of specimens with different mixes, and 4) to obtain correlations between resistivity and sorptivity. All of these experimental tests were carried out according to ASTM International Standards (Sorptivity, Porosity) and Florida Method of Test (Resistivity). The tests were performed on concrete samples at various ages. Moreover, The results provided a fast and reasonable approximation of the concrete durability over time. Ordinary portland cement was partially replaced with supplementary cementitious materials including: fly ash (20%), silica fume (8%) and blast furnace slag (50%). These SCMs are highly effective in creating more durable concrete design mixtures. The water-to-cementitious (w/cm) ratios of 0.41 and 0.35 were investigated. The concrete that contains pozzolanic materials has demonstrated progress in extending the time for initiation of corrosion. The test results obtained indicate that the concurrent inclusion of fly ash and silica fume greatly reduced water penetration. The mixes containing slag also showed lower porosity and water absorption result, when compared to specimens containing fly ash only. Ternary concrete mixtures specimens showed much higher surface resistivity values than binary mixture specimens. These results suggest that reducing w/cm ratio, adding SCMs to concrete mixtures improved the concrete durability. The possibilities for the risks of corrosion initiation would be minimized (delayed) by prescriptive and then performance-based concrete blends with SCM materials optimized for service exposure in aggressive environments. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

For this research, prestress losses were monitored in six HPC bridge girders. These measured losses were compared to predicted losses according to four sources. Prestress loss predictive methods considered for this research were: 1- AASHTO LRFD 2004, 2- AASHTO LRFD 2004 Refined, 3- AASHTO LRFD 2007, and 4- AASHTO LRFD Lump Sum method. On the other hand, the camber prediction methods used in the present research were: 1- Time dependent method described in NCHRP Report 496, 2- PCI multiplier method, and 3- Improved PCI Multiplier method. For the purpose of this research, long-term prestress losses were monitored in select girders from Bridge 669 located near Farmington, Utah. Bridge 669 is a three-span prestress concrete girder bridge. The three spans have lengths of 132.2, 108.5, and 82.2 feet long, respectively. Eleven AASHTO Type VI precast prestressed girders were used to support the deck in each span. The deflection of several girders from a three-span, prestressed, precast concrete girder bridge was monitored for 3 years. Fifteen bridge girders were fabricated for the three span-bridge. Ten girders from the exterior spans had span length of 80 feet, and five girders from the middle span had span length of 137 feet. From the results of this research, in both the 82- and 132-foot-long, the AASHTO LRFD 2004 Refined Method does a better job predicting the prestress loss and it can be concluded that all the prediction methods do a better job predicting the loss for the larger girders. The Lump Sum method predicted very accurately the long term prestress loss for the 132-foot-long girders.

Yes / This paper evaluates the influence of mineral admixtures partially replacing cement, sea sand replacing quartz, sea water replacing fresh water on ultra-high performance concrete (UHPC). The fluidity and mechanical properties were studied. Besides, the impermeability, chloride resistance and freeze-thaw resistance were investigated. Failure modes, scanning electron microscope (SEM) analysis, mass loss, relative dynamic modulus of elasticity and mechanical properties of UHPCs after freeze-thaw cycles were conducted. The results showed the fluidity of UHPC paste gradually increases with the improvement of water-binder ratio. It is recommended that the water-binder ratio of UHPC be set at 0.19. The fluidity also increases with the improvement of the content of slag, fly ash and water reducer, but decreases with the improvement of silica fume content. The flexural and compressive strengths of UHPC enhance with the improvement of the content of silica fume, but reduce with the improvement of the content of fly ash and slag. The UHPCs made of quartz sand, river sand and sea sand, all, achieve a high strength. UHPCs prepared at standard curing conditions, with or without steel fibers, mixed by artificial seawater and made of sea sand, exhibited excellent impermeability and chloride resistance. The frost resistant grade of all UHPC specimens prepared by standard curing are greater than F500 exhibiting excellent freeze-thaw resistance and sustainability.

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