The aim of this work was to develop the method for the determination of the superperplasticizers (SP) content in the water solution. The method developed was then applied to study the SP adsorption on the individual components used for high-performance concrete and the influence of the temperature and pH values over this adsorption. Furthermore the influence of the water to binder ratio, SP, finely grounded granulated blast furnace slag, fly ash, silica fume, finely ground silica sand and bauxite on the hydration process was studied by means of isoperibolic, isothermal and solution calorimetry. The compressive and flexural strength of most samples used in calorimetric experiments was also determined.

Ultra-high performance concrete (UHPC) has progressively gained interest because of its favorable strength and durability properties. Literature shows that curing temperature has a significant effect on the resultant mechanical properties of UHPC, generally resulting in increased compressive strength. However, limited datasets are currently available to ascertain the degree of change related to compressive strength as a function of curing temperature and conditions. This study investigates the effect of isothermal and submerged curing temperature conditions, ranging from 10°C to 90°C, on the compressive strength and elastic modulus development of UHPC and generates a numerical model to capture these effects. The extent and rate of compressive strength development in Cor-Tuf UHPC was found to increase with curing temperature, while only the rate of elastic modulus development increased with curing temperature. The numerical model shows reasonable agreement when compared with the experimental results and was successfully implemented in finite element analysis software.

[pt] A utilização dos concretos de alto desempenho na indústria da construção civil está se tornando muito freqüente ultimamente. Este fato impõe cada vez mais a necessidade de um melhor conhecimento sobre o comportamento deste material relativamente novo, visando principalmente manter os níveis de segurança adequados nas estruturas. As vantagens apresentadas por tal material, notadamente a sua resistência à compressão, permitiram uma melhoria generalizada nos processos construtivos e conseqüente aumento nos vãos dos elementos estruturais. Somado o fato de que os concretos de alto desempenho apresentam um comportamento reconhecidamente mais frágil, começou-se recentemente a aplicar conceitos da teoria da Mecânica da Fratura para a análise do comportamento destas estruturas, já que passa a haver a necessidade de se considerar adequadamente o efeito de escala no dimensionamento. Portanto, o objetivo principal do presente estudo é verificar experimentalmente a ocorrência do efeito de escala em concretos de alto desempenho e comparar estes resultados com resultados numéricos encontrados na literatura. Objetiva-se também estudar o comportamento dos referidos concretos nos ensaios à flexão em três pontos e calcular a sua energia de fraturamento através de dois métodos diferentes. Durante o estudo foram executados ensaios à flexão em três pontos em vigas de concreto simples com entalhe, de acordo com as especificações dadas pela recomendação do comitê RILEM 50-FMC. As vigas foram moldadas no Laboratório de Estruturas da PUC-Rio e os ensaios realizados no Instituto de Tecnologia (ITUC) desta Universidade. Os ensaios foram executados em uma máquina Instron com controle de deslocamentos. Ao todo foram ensaiadas 60 vigas, em 4 tamanhos diferentes, com alturas variando de 38mm a 304mm. Os concretos utilizados apresentaram fator água/cimento variando entre 0.37 e 0.25 e resistência à compressão entre 64 MPa e 88 MPa. / [en] The use of high performance concrete as a construction material is becoming very common lately. This fact imposes the need of a better knowledge of this material, aiming to keep the structural design with an appropriate safety level. The advantages provided by this material, specially its compressive strength, allowed a generalized improvement in the building processes e the consequent increase in the structural members size. Added the fact that the high performance concrete has a recognizably more brittle behavior, it`s started to apply some Fracture Mechanics theory concepts to analyze the structures behavior. Then, the fracture mechanics size effect should be suitably considered in design. Therefore, the main objective of this study is to verify experimentally the occurrence of the size effect phenomenon on high performance concrete and to carry out a comparison with numerical results found in the literature. It`s also objectified to study the behavior of the referred concrete in three point bent tests and to calculate its fracture energy by means of two different methods. During this study three point bend tests in notched beams made with unreinforced concrete were carried out. These tests comply with the specifications given by RILEM 50-FMC committee. The specimens were cast at the PUC- Rio Structures Laboratory and the tests were conducted at the Technology Institute (ITUC) of this university. The tests were performed in a servo-controlled materials testing system. It were tested 60 specimens, with 4 different sizes and with heights varying from 38mm to 304mm. The concrete had a water/cement ratio varying from 0.37 to 0.25 and a compressive strength between 64 MPa and 88MPa. / [es] La utilización de los concretos de alto desempeño en la industria de la construción civil se ha hecho frecuente en los últimos tiempos. Este hecho impone cada vez más la necesidad de un mayor conocimiento sobre el comportamiento de este material relativamente nuevo, con el objetivo de mantener los níveles de seguridad adecuados en las extructuras. Las ventajas presentadas por dicho material, notadamente su resistencia a la compresión, permitirán una mejoría generalizada en los procesos. Sumando el hecho de que los concretos de alto desempeño presentan un comportamiento reconocidamente más frágil, se comenzó recientemente a aplicar conceptos de la teoría de la Mecánica de la Fractura para el análisis del comportamiento de estas extructuras, debido a la necesidad de considerar adecuadamente el efecto de escala en el dimensionamiento. Por lo tanto, el objetivo principal del presente estudio es verificar experimentalmente la ocurrencia del efecto de escala en concretos de alto desempeño y comparar estos resultados con los resultados numéricos encontrados en la literatura. Se trata también de estudiar el comportamiento de los referidos concretos en los ensayos a la flexión en tres puntos y calcular su energía de fractura a través de dos métodos diferentes. Durante el estudio se ejecutaron ensayos a la flexión en tres puntos en vigas de concreto simple con entalladura, de acuerdo con las especificaciones dadas por la recomendación del comité RILEN 50-FMC. Las vigas fueron moldeadas en el Laboratorio de Extructuras de la PUC-Rio y los ensayos realizados en el Instituto de Tecnología (ITUC) de esta Universidad. Los ensayos fueron ejecutados en una máquina Instron con control de desplazamientos. Fueron ensayadas 60 vigas, en 4 tamaños diferentes, con alturas variando de 38mm la 304mm. Los concretos utilizados presentaran factor agua/cemento variando entre 0.37 y 0.25 y resistencia a la compresión entre 64 MPa y 88 MPa.

[pt] O presente trabalho avalia o efeito da utilização de concreto de ultra-alto desempenho (CUAD) em elementos estruturais, analisando seu comportamento à flexão e o impacto da utilização desse material no seu dimensionamento. Através de ensaios de caracterização do material, foram estudadas as suas propriedades mecânicas. Os resultados dos testes já apresentavam resistência à compressão de 104 MPa com 7 dias de idade e 142 MPa aos 28 dias de idade, além de um aumento na capacidade de carga e na ductilidade dos corpos de prova com o aumento da quantidade de fibras utilizadas no CUAD. Na escala estrutural, foram analisadas quatro vigas de concreto armado, onde duas foram produzidas com concreto de ultra-alto desempenho e duas com concreto convencional (CC), com taxa de armaduras de 0,44 por cento e 1,78 por cento. Primeiramente foi realizada uma análise comparativa dos resultados dos momentos obtidos experimentalmente e teoricamente (baseado nas normas NBR 6118:2014, ACI 544.4R-18 e Model Code 2010) não apresentando diferença significativa. Posteriormente, através dos resultados dos ensaios foi possível verificar que, a utilização do CUAD melhora, no geral, as propriedades mecânicas dos elementos analisados. A utilização do CUAD em vigas subarmadas apresenta resultados similares às vigas normalmente armadas com CC. Além disso, quando combinadas a utilização do CUAD com o aumento da taxa de armaduras, os resultados melhoram significativamente, apresentando, por exemplo um ganho na capacidade de carga de aproximadamente 40 por cento no aumento da taxa geométrica de armaduras e de 75 por cento com o aumento da taxa de armaduras combinada com a utilização do CUAD. / [en] The present work evaluates the effect of the use of ultra-high performance concrete (UHPC) in structural elements, analyzing its behavior to bending and the impact of the use of this material on its dimensioning. Through tests of characterization of the material, its mechanical properties were studied. The results of the tests already presented compressive strength of 104 Mpa at 7 days of age and 142 Mpa at 28 days of age, in addition to an increase in load capacity and ductility of the specimens with the increase in the amount of fibers used in the UHPC. In the structural scale, four reinforced concrete beams were analyzed, two of which were produced with ultra-high performance concrete and two with conventional concrete (CC), with an armor rate of 0.44 percent and 1.78 percent. First, a comparative analysis of the results of the moments obtained experimentally and theoretically (based on the norms NBR 6118:2014, ACI 544.4R-18 and Model Code 2010) was performed, with no significant difference. Subsequently, through the results of the tests it was possible to verify that the use of UHPC improves, in general, the mechanical properties of the analyzed elements. The use of UHPC in underarmed beams presents similar results to beams normally armed with CC. In addition, when combined with the use of UHPC with increased reinforcement rate, the results improve significantly, presenting, for example, a gain in load capacity of approximately 40 percent in the increase in the geometric rate of reinforcements and 75 percent with the increase in the reinforcement rate combined with the use of UHPC.

[pt] O concreto de ultra-alto desempenho (CUAD) é um material cimentício avançado que possui excelente desempenho mecânico, ductilidade e durabilidade devido a uma elevada densidade de empacotamento e ao uso de fibras, promovendo benefícios à vida útil das estruturas. Grande parte das estruturas está sujeita a ações cíclicas, ou seja, variáveis com o tempo, resultando em danos de fadiga, como o surgimento e a propagação de trincas, que podem comprometer sua integridade. Assim, é essencial compreender o comportamento dos materiais sob fadiga para que sejam propostas diretrizes de projeto seguras e adequadas ao bom funcionamento das estruturas. Este trabalho visa, portanto, investigar o comportamento do concreto de ultra-alto desempenho pré-fissurado sob fadiga na flexão, quantificando sua degradação mecânica ao longo do carregamento cíclico a partir dos parâmetros de abertura de fissura (CMOD) e rigidez, contribuindo para o estudo desse tipo especial de concreto. Foram propostas equações para prever a vida à fadiga em relação ao limite superior de carga e estabelecer o limite de fadiga do concreto de ultra-alto desempenho, igual a 75,3 por cento, considerando o limite inferior igual a 30 cento do limite superior. Ainda, avaliou-se o comportamento pós-fadiga de amostras que não sofreram ruptura ao longo de 1.000.000 de ciclos, sendo possível observar que o mecanismo não gerou alterações no desempenho das amostras sob flexão para limites inferiores ao limite de fadiga. / [en] Ultra-high Performance Concrete (UHPC) is an advanced cementitious material that has excellent mechanical performance, ductility and durability due to a high packing density and the use of fibers, contributing to increase the structures lifespan. Most of the structures are subject to cyclic loads, which vary with time, resulting in fatigue damage such as the formation and propagation of cracks that could compromise its integrity. Thus, it is essential to understand the behavior of materials subjected to fatigue so that safe and proper design guidelines can be proposed for the appropriate performance of the structures. Therefore, this work aims to investigate the behavior of pre-cracked ultra-high performance concrete under flexural fatigue, quantifying its mechanical deterioration during cyclic loading through both crack mouth opening displacement (CMOD) and stiffness, which will contribute to the study of this special type of concrete. Equations were proposed to predict fatigue life according to the upper load limit during the cyclic loading and to establish the endurance limit of ultra-high performance concrete in 75,3 percent, considering the lower limit load equal to 30 percent of the upper limit. Also, when evaluating the post-fatigue behavior of samples that did not fail over 1,000,000 cycles it was possible to identify that the cyclic loading did not change the performance of the samples under bending, which was due to the use of upper loads below the endurance limit.

Non-contact lap splices placed within a single concrete placement are often used and have been studied in previous research projects. However, non-contact lap splices used with each bar in a different concrete placement such that there is a cold joint between the bars, have not been investigated. This situation is found in the repair of adjacent box beam bridges and in the construction of inverted T-beam systems, among others. It is vital to understand whether the same mechanisms are present across a cold joint with two different types of concrete as are present in traditional non-contact lap splices. In this research, eight T-beam specimens with non-contact lap splices were tested. The spacing between the bars, the splice bar blockout length, and presence of transverse bars were varied to study the effectiveness of the splices. The beams were tested in four point bending so that the splice region was under constant moment and the tension forces in the spliced bars were constant. End and midspan deflections were measured along with surface strain measurements at midspan and at the quarter span points, top and bottom. Gap openings were also measured at the ends of the blockouts. The main conclusions found from this research are that beams containing non-contact lap splices were able to develop nominal capacity with the bar spacing less than or equal to 4 in. and the blockout between 17 and 20 in. long. Extending the blockouts and adding transverse bars underneath the splices did not add to the capacity. / Master of Science

Yes / Steel wire reinforced ultra-high performance concrete (SWRUHPC) offers exceptional resistance to impacts and blast, making it a promising construction material for infrastructure with blast-resistance demands. However, limited research has been conducted on the blast-resistance characteristics and design of SWRUHPC elements under blast loading, particularly in considering multiple influencing parameters and levels. Therefore, this study employed finite element simulation methods to investigate the influence of scaled distance (Z), reinforcement ratio (ρ) and slab thickness (D) as well as slab length (L) on the failure mode and maximum deflection of SWRUHPC slabs. Range analysis and variance analysis methods were used to quantitively analyze the effects of various factors on the blast resistance performance, culminating in the proposal of a design formula for SWRUHPC slabs. The results demonstrated that SWRUHPC exhibits superior blast resistance compared to ordinary concrete, effectively reducing the occurrence of concrete spalling and splashing, thus enhancing overall structural resilience in blast scenarios. Among the four factors analyzed, their influence on maximum deflection follows this order: D > Z > ρ > L. Notably, the maximum deflection decreases by 82% when the slab thickness increases from 40 mm to 90 mm. Additionally, the established design formula for SWRUHPC slabs under different scaled distances shows good agreement with the numerical simulation results, offering valuable design guidelines for SWRUHPC slabs in protective engineering structures. / National Science Foundation of China (52308236 and 52368031), and the Major Science and Technology Research Project of the China Building Materials Federation (2023JBGS10-02), Natural Science Joint Foundation of Liaoning Province (2023-BSBA-077), and the Fundamental Research Funds for the Central Universities (DUT24GJ202). / The full text will be available at the end of the publisher's embargo: 22nd July 2025

High performance concrete (HPC) provides a long lasting, durable concrete that is typically used in bridge decks due to its low permeability, high abrasion resistance, freeze-thaw resistance and strength. However, this type of concrete is highly susceptible to the deleterious effects of both autogenous and drying shrinkage. Both types of shrinkage occur when water leaves small pores , (< 50 nm) in the paste matrix to aid in hydration or is lost to the surrounding environment. Autogenous deformation (self-desiccation) occurs as the internal relative humidity decreases due to hydration of the cementitious material. Drying (and subsequent shrinkage) occurs when water is lost to the environment and continues until the internal relative humidity is equivalent to the ambient relative humidity. Typically, the magnitude of autogenous shrinkage is less than that of drying shrinkage. These two types of shrinkage do not act independently, and the total shrinkage is the aggregation of the two shrinkage mechanisms. It is imperative to minimize the amount of shrinkage in restrained members, such as bridge decks, to reduce the cracking potential. Various methods have been researched to minimize both types of shrinkage. Two methods to that have been reported to reduce shrinkage were selected for further research; internal curing using pre-soaked lightweight fine aggregate (LWFA) and shrinkage reducing admixtures (SRAs). The purpose of this study was to determine the long-term drying shrinkage performance of these two methods while reducing the external curing duration of 14 days for new bridge deck construction as specified by the Oregon Department of Transportation. In addition to monitoring drying shrinkage, durability testing was performed on concrete specimens to ensure these shrinkage mitigation methods performed at levels similar to concrete with the current mixture design. Freeze-thaw testing, permeability testing and restrained drying shrinkage testing were conducted. It was concluded that the combination of SRAs and pre-soaked LWFA was the most effective method to reduce longterm drying shrinkage for all curing durations (1, 7, and 14 day). Additionally, for durability testing, it was found that the use of SRAs performed the best in freeze-thaw testing, chloride permeability and restrained shrinkage. / Graduation date: 2012

For members and flat slabs without shear reinforcement, the shear and punching shear strength are often the determining design criteria. These failure modes are characterized by a fragile behaviour implying possible partial or total collapse of the structure. Despite extensive research in this field, shear and punching shear in reinforced and prestressed concrete structures, remain complex phenomena so much that the current approach is often empirical or simplified. The ability of Steel Fibre Reinforced Concrete (SFRC) to reduce shear reinforcement in reinforced and prestressed concrete members and slabs,or even eliminate it, is supported by several experimental studies. However its practical application remains marginal mainly due to the lack of standard, procedures and rules adapted to its performance. The stationary processes in precast industry offer optimal possibilities for using high performance cementitious materials such as Self Compacting Concrete (SCC) and High Strength Concrete (HSC). For the author, the combination of High Performance Concrete and steel fibres is the following step in the development and the optimization of this industry. The High Performance Fibre Reinforced Concrete (HPFRC) stands between conventional SFRC and Ultra-High Performance Fibre Reinforced Concrete (UHPFRC). The HPFRC exhibiting a good strength/cost ratio is, thus, an alternative of UHPFRC for precast elements. The principal aim of this work was to analyse the shear and punching shear behaviour of HPFRC and UHPFRC structures without transversal reinforcement and to propose recommendations and design models adapted for practitioners. Several experimental studies on structural elements, i.e. beams and slabs, were undertaken for this purpose. Firstly, an original experimental campaign was performed on pre-tensioned members in HPFRC. A total number of six shear-critical beams of a 3.6 m span each, and two full scale beams of a 12 m span each, were tested in order to evaluate the shear and flexural strength. The principal parameter between the specimens was the fibres (...)

It is important to ensure that vulnerable structures (federal and provincial offices, military structures, embassies, etc) are blast resistant to safeguard life and critical infrastructure. In the wake of recent malicious attacks and accidental explosions, it is becoming increasingly important to ensure that columns in structures are properly detailed to provide the ductility and continuity necessary to prevent progressive collapse. Research has shown that steel fibre reinforced concrete (SFRC) can enhance many of the properties of concrete, including improved post-cracking tensile capacity, enhanced shear resistance, and increased ductility. The enhanced properties of SFRC make it an ideal candidate for use in the blast resistant design of structures. There is limited research on the behaviour of SFRC under high strain rates, including impact and blast loading, and some of this data is conflicting, with some researchers showing that the additional ductility normally evident in SFRC is absent or reduced at high strain loading. On the other hand, other data indicates that SFRC can improve toughness and energy-absorption capacity under extreme loading conditions. This thesis presents the results of experimental research involving tests of scaled reinforced concrete columns exposed to shock wave induced impulsive loads using the University of Ottawa Shock Tube. A total of 13 half-scale steel fibre reinforced concrete columns, 8 with normal strength steel fibre reinforced concrete (SFRC) and 5 with an ultra high performance fibre reinforced concrete (UHPFRC), were constructed and tested under simulated blast pressures. The columns were designed according to CSA A23.3 standards for both seismic and non-seismic regions, using various fibre amounts and types. Each column was exposed to similar shock wave loads in order to provide direct comparisons between seismic and non-seismically detailed columns, amount of steel fibres, type of steel fibres, and type of concrete. The dynamic response of the columns tested in the experimental program is predicted by generating dynamic load-deformation resistance functions for SFRC and UHPFRC columns and using single degree of freedom dynamic analysis software, RCBlast. The analytical results are compared to experimental data, and shown to accurately predict the maximum mid-span displacements of the fibre reinforced concrete columns under shock wave loading.