Student Number : 0218148W - MSc Dissertation - School of Civil Engineering - Faculty of Engineering and the Built Environment / Self-compacting concrete (SCC) is becoming a popular form of concrete usage in a range of applications throughout the world. This investigation considers the development of the technology and use of SCC. Importantly, the investigation aims to highlight the opportunities for using SCC in South Africa. A mixture design model is proposed and has been found to work well using local materials. The advantage of this model is the simplicity and the adaptability to any aggregate type. This method should be more acceptable to SCC producers who do not have special facilities and testing equipment An overview concerning concrete rheology is included to explain the mechanisms used to describe the flow and deformation of both the concrete and mortar mixtures. Included is a comparison between concrete, mortar and paste rheology. The Tattersall Two Point Tester was used to measure the shear resistance at two shear deformation rates. From the test results it was found that SCC can be made using South African materials and that it is possible to design a mixture with a lower cementitious content. The results from the Tattersall Two Point Tester gave additional information about the flowability of SCC.

Self-compacting concrete (SCC) was first developed in Japan about two decades ago. Since then, it has been offered as a solution to various challenges inherently associated with traditional concrete construction; i.e. quality and speed of construction, impact of unskilled labour force and noise pollution etc. SCC flows into a uniform level under its own weight and fills in all recesses and corners of the formwork even in highly congested reinforcement areas. In recent years the interest in using SCC in structural members has increased manifold; therefore many researchers have started investigating its characteristics. Nevertheless, before this special concrete is widely accepted and globally used in structures, its structural performance under different conditions should be investigated. This research focuses on investigating the behaviour of high strength self-compacting concrete (HSSCC) in reinforced concrete (RC) structures through a systematic approach in order to bridge part of an existing gap in the available literature. The dissertation is comprised of four main stages; namely, mix design development and mechanical properties of HSSCC, bond performance of deformed bars in HSSCC, experimental investigation on interior RC beam-column joints (BCJs) cast with HSSCC under reversed cyclic excitations, and finally finite element (FE) modelling and analysis of interior BCJs. First, a HSSCC mix proportion yielding compressive strength greater than 100 MPa was developed in the laboratory using locally available materials in New Zealand. Two benchmark concrete mixes of conventionally-vibrated high-strength concrete (CVHSC) and normal-strength conventionally vibrated concrete (CVC) were also designed for comparison purposes. Material characteristics (such as compressive, splitting tensile and flexural strengths as well as modulus of elasticity, shrinkage and microstructural properties) of all mixes were evaluated. It was found that, once the lower quality of material in normal strength concrete is offset by achieving a denser mix in high-strength concrete, mechanical properties of HSSCC are equivalent to or higher than those in CVHSC. Given that the performance of RC structures (and in specific BCJs) is highly dependent on bond between reinforcement and concrete, understanding the bond behaviour in HSSCC was an imperative link between the first and third phases of this research. Therefore, the second phase focused on scrutinizing bond properties of deformed bars in HSSCC using monotonic pull-out and innovative cyclic beam tests. Processing of the pull-out results revealed that a shorter development length may be utilized in HSSCC. In addition, the grade (or ductility) of reinforcing steel was found to substantially influence the post-yield bond performance. Important modifications to the bond model used in the CEB-FIP model code and Maekawa’s bond-slip-strain relationship were suggested from the results of this phase. An innovative cyclic beam specimen and test setup were also designed such that a more realistic bond performance could be observed in the laboratory tests compared to that in real RC structures. Deleterious impact of cyclic loading and buckling of reinforcement on bond performance were investigated using this testing protocol. The third phase of this research focused on the design, fabrication and testing of seven full-size BCJs. BCJs are one of the most critical parts in RC frame structures and their response substantially affects the overall behaviour of the structure. In seismically active regions like New Zealand, the criticality of BCJs is exacerbated with the complexities involved in seismic resistance. The already congested intersection of RC beam and column looks more like a solid steel connection after consideration of earthquake requirements, and placement of concrete becomes problematic in such areas. At the same time, in many of the high-rise structures, normal strength concrete does not meet the capacity requirements; this requires the usage of high-strength concrete. Therefore, once the seismic performance of HSSCC is guaranteed, it can possibly be a solution to both the capacity and compaction problems. Variables such as axial load, concrete type, steel grade, casting direction, and joint shear reinforcement were considered variable in the experimental investigations. It was found that HSSCC has similar seismic performance to that of CVHSC and it can also be incorporated in the joint area of CVC for an enhanced performance. Finally, DIANA (a nonlinear FE program) was used to simulate the experimental results obtained in the third phase of this research. All BCJs were successfully modelled using their relevant attributes (such as the mechanical properties of HSSCC, steel stress-strain response, test setup and loading protocol) and nonlinear FE analyses (FEA) were performed on each model. FE results were compared to those obtained in the laboratory which showed a reasonable agreement between the two. The capabilities of the FEA were scrutinized with respect to the hysteresis loops, energy dissipation, joint shear deformations, stress development in the concrete and steel, and drift components. Integrating the results of all stages of this research provided better understanding of the performance of HSSCC both at the material and structural levels. Not only were none of the seismically important features compromised by using HSSCC in BCJs, but also many other associated benefits were added to their performance. Therefore, HSSCC can be confidently implemented in design of RC structures even in seismically active regions of the world.

Self-Compacting Concrete (SCC) is a material which under its own self-weight flows to form and fill any shape, attains full compaction, without external energy input, to create a dense homogenous mass (based on Holton, 2003; The Concrete Society and BRE, 2005; Damtoft et al, 2008). It is, in respect to the history of concrete, a relatively new development, with its first UK application occurring in the late 1990s. Since then a significant amount of research has sought to understand its physical and structural properties, but there is a lack of a knowledge base on its practical application and performance in construction projects. Where it does exist, such research lacks robust and transparent data, particularly relating to the claimed attributes of the material (such as better surface finish, faster construction and lower overall costs). Using a combination of qualitative and quantitative research methods, this research investigates the construction practices employed when pouring SCC and presents new data on its practical applications. Interviews with a range of building contractors, ranging from multinationals to small UK businesses (SMEs), show that current perceptions of SCC limit its use to specific applications because practitioners see SCC as just another type of concrete . A critical examination of these attitudes led to the identification of three distinct scenarios for the use of SCC: 1. Reactive selection: in which a particular attribute of SCC provokes its use to solve a particular problem, often as a last minute substitution for conventional concrete the most common scenario. 2. Strategic change: in which the material is chosen on the basis of a balanced assessment of all its benefits and on the understanding that such benefits can only be attained if the contractor appreciates that there may be implications for the construction process a rarely experienced scenario. 3. Specification: in which there is complete acceptance of SCC as a method, not just as a material; a significant amount of early project involvement with knowledge holders, such as contractors and material suppliers, optimises the construction process. A rigorous work measurement study of live construction projects has made it possible to quantify the as-built costs of SCC for selected UK residential slab and multi-storey flat slab applications and compare this with the equivalent conventional concrete slab construction. On-site use of self-compacting concrete vi The results indicate that SCC can reduce construction times of structural topping layers of residential slabs by up to 73%, and has shown that SCC can also match, if not reduce, total as-built concrete placement costs in multi-storey applications. This new data will enable contractors, designers and specifiers to better understand the practical implications of using SCC for on-site applications, thereby leading to more potential instances of its early and planned specification, hence resulting in more of its full benefits being realised.

This research studies the properties of self-compacting concrete by applying bamboo-charcoal to improve the fresh concrete property, physical property and micro-scale property.Conventionally, the Pozzolanic materials used in the self-compacting concrete are fly ash and slag. They are used to replace part of the cement such that the flowing property and compacting property can reach the requirement of the self-compacting concrete. According to previous research the bamboo-charcoal can absorb part of water, and enhance the early strength of concrete. In this study, we use bamboo-charcoal to replace parts of the fine-aggregate in the mixture of self-compacting concrete. The replacement ratio is designed as 0‰,2‰,3‰,3.5‰,4‰ and 5‰. From the experimental test of fresh concrete property, we can evaluate whether the concrete mix design can achieve the requirements of self-compacting concrete. Test for the compressive strength development, water absorption and rapid chloride penetration test are performed to evaluate the physical property of concrete. In addition, the scanning electronic microscope photos are taken to examine the microstructure of the concrete. In our results, it is found that the best proportion of replacement is 3‰. The requirements of self-compacting concrete can be satisfied, and the development of strength is also good.

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Civil Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology / Self-compacting concrete (SCC) is a flowable self-consolidating concrete which can fill formwork without any external vibration. A self-compacting concrete mix requires the addition of superplasticiser (SP), which allows it to become more workable without the addition of excessive water to the mixture. The effect of different CEM I 52.5N cements produced by one company at different factories on self-compacting concrete was investigated. The properties of SCC are highly sensitive to changes in material properties, water content and addition of admixtures. For self-compacting concrete to be more accepted in South Africa, the effect that locally sourced materials have on SCC, partially replaced with extenders, needs to be investigated. The European guidelines for SCC (2005) determined the standard, through an extensive study, for the design and testing of self-compacting concrete. Using these guidelines, the properties of self-compacting concrete with the usage of local materials were investigated. The effect on SCC mixes was studied by using four cements; two types of SPs – partially replaced with two types of fly ash; and one type of slag. Mix design and tests were done according to the European Specification and Guidelines for Self-Compacting Concrete (2005). Using locally sourced materials (different cements, sand, coarse aggregate, fly ashes and slag), mixes were optimised with different SPs. Optimisation was achieved when self-compacting criteria, as found in the European guidelines, were adhered to, and the binders in these required mixes were then partially replaced with fly ash and slag at different concentrations. Tests done were the slump flow, V-funnel, L-box, sieve segregation resistance as well as the compressive strength tests. The results obtained were then compared with the properties prescribed by the European guidelines. The cements reacted differently when adding the SPs, and partially replacing fly ash and slag. According to the tests, replacing cement with extenders – in order to get a sufficient SCC – seemed to depend on the chemical and physical properties of each cement type, including the soluble alkali in the mixture, C3A, C3S and the surface area. The range, in which the concentration of these chemical and physical cement compounds should vary – in order to produce an acceptable SCC partially replaced by extenders – was determined and suggested to the cement producer. The main conclusion of this project is that cement properties vary sufficiently from factory to factory so as to influence the performance of an SCC mix. The problem becomes even bigger when such cements are extended with fly ash or slag, and when different SPs are used. When designing a stable SCC mix, these factors should be taken into account.

Orientadores: Rosa Cristina Cecche Lintz, Luísa Andréia Gachet Barbosa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-28T13:32:52Z (GMT). No. of bitstreams: 1 Verzegnassi_Emerson_M.pdf: 3873734 bytes, checksum: 73682762affd1136f183e9120a07a536 (MD5) Previous issue date: 2015 / Resumo: Com a descoberta de aditivos químicos e adições minerais muitos tipos diferentes de concreto surgiram ao longo das últimas décadas. Porém o peso próprio do concreto convencional é considerado a sua maior desvantagem. Com isso abre-se campo para um material que apesar de ser conhecido pelos romanos, era pouco utilizado, o concreto com agregados leves. Muitas pesquisas surgem e em aproximadamente duas décadas aparece o concreto autoadensável e mais recentemente o concreto leve autoadensável. Este trabalho propõe o estudo deste material ainda pouco explorado o concreto leve autoadensável. Para isso são produzidos concretos com argila expandida em duas granulometrias diferentes: uma graúda em substituição total ao agregado graúdo de massa normal e uma miúda em substituição parcial ao agregado miúdo. São elaboradas três famílias de traços de concreto com consumos diferentes de cimento, 320, 360 e 440 kg/m³ de concreto, e realizados ensaios no estado fresco (anel J, funil V e caixa L) e endurecido (resistências à compressão e à tração, determinação do módulo de elasticidade, absorção e densidade). Os concretos leves foram classificados como auto adensáveis e apresentaram bons resultados quanto ao fator de eficiência e resistência sendo possível estabelecer equações de correlação para seu módulo de elasticidade. Para os ensaios de densidade observaram-se concretos leves com massas mínimas de até 1550 kg/m³ e resistências à compressão superiores aos valores estipulados pela norma NBR NM 35 para as densidades apresentadas em todas as misturas / Abstract: With the discovery of admixtures and mineral additions many different types of concrete emerged over the last decades. But the own weight of conventional concrete is considered their biggest disadvantage. With this opens up the field for a material that despite being known to the Romans, it was little used, the concrete with lightweight aggregates. Much research and come in about two decades appears the self compacting concrete and more recently the lightweight concrete self compacting. This work proposes the study of this material still little explored concrete lightweight self compacting. For this are produced concrete with expanded clay in two different particle sizes: one coarse in total replacement of coarse aggregate of normal mass and a fine partially substituting fine aggregate. Are designed three families of concrete mixtures with different cement consumption, 320, 360 and 440 kg / m³ of concrete, and the tests carried out in the fresh state (ring J, V funnel and L box) and hardened (resistance to compression and traction , determining the modulus of elasticity, absorption, and density). The concretes were classified as self compacting and showed good results as to efficiency and resistance factor being possible to establish a correlation equations for its modulus of elasticity. For the density tests were observed concretes with minimum masses of up to 1550 kg / m³ and compressive strengths greater than those stipulated by NBR NM 35 standard for the densities presented in all mixtures / Mestrado / Tecnologia e Inovação / Mestre em Tecnologia

Fresh properties of mortars are important factors in altering the performance of self compacting concrete (SCC). Measurement of the rheological properties of the fine mortar part of concrete is generally used in the mix design of SCC. It can be stated that SCC rheology can be optimized if the fine mortar part of concrete is designed properly. However, measurement of the rheological properties is often impractical due to the need for complex equipment. Therefore, more practical methods of assessing mortar workability are often preferred. In this study, four mineral admixtures, three superplasticizers (SP) and two viscosity modifying admixtures (VMA) were used to prepare self compacting mortar (SCM). The mineral admixtures included fly-ash, brick powder, limestone powder, and kaolinite. Two of the SPs were polycarboxylate based and another one was melamine formaldehyde based. One of the viscosity modifying admixtures was based on an aqueous dispersion of microscopic silica and the other one was based on high molecular weight hydroxylated polymer. Within the scope of the experimental program, 43 mixes of SCM were prepared from different materials with keeping the amount of mixing water constant. Workability of the fresh mortar were determined using V - funnel and slump flow tests. The setting time of the mortars, were also determined. The hardened properties that were determined included the ultrasonic pulse velocity (UPV) and the strength which was determined at 7, 28, and 56 days. It was concluded that among the mineral admixtures used, only fly-ash and limestone powder increased the workability of the mixes. The two polycarboxylate based SPs yield approximately the same workability and the melamine formaldehyde based SP was not as effective as the other two.

Evolution of concrete is continuously taking place to meet the ever-growing demands of the construction industry. Self compacting concrete (SCC) has emerged as a result of this demand to overcome the scarcity of labour. SCC is widely replacing normal vibrated concrete (NVC) these days owing to its advantages such as homogeneity of the mix, filling ability even in heavily congested reinforcement, smooth finish, reduction in construction time etc. The ingredients used for SCC is the same as that of the NVC. But the proportioning of ingredients to achieve self compactability alters the microstructure of SCC which in turn affects the mechanical and fracture properties. Moreover, the mineral admixtures such as fly ash and silica fume when used for improving the workability of SCC help in the development of the microstructural skeleton. In this study, three SCC mixes SCC1- made with only cement, SCC2 - with fly ash in addition to cement and SCC3 - with fly ash and silica fume in addition to cement for achieving normal, medium and high strength SCC respectively are cast. The microstructural changes in SCC with and without mineral admixtures over a period of time are studied using different techniques such as scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The modification of mechanical properties at microstructural level brings difference in the behavior at macro level. Hence in this study, the mechanical properties at microstructural are obtained by using microindentation test and are scaled up to the macro level to predict the influence of micromechanical properties on macro response. The fracture properties of SCC is considered to be the interest of this study and is carried out with the help of advanced techniques such as acoustic emission (AE) and digital image correlation (DIC). From the various studies carried out, it is inferred that the mixes with mineral admixtures behave in a more brittle manner when compared to mix having no mineral admixture. It is also observed that class ‘F’ fly ash hydrates at a slow pace and the strength gain is observed after 28 days and even beyond 90 days. Hence, it is concluded that it is appropriate to consider the strength at 90 days instead of 28 days for a SCC mix with class ‘F’ fly ash. Silica fume on the other hand is observed to result in a more rapid gain in strength and this can partially offset the delay in strength gain due to fly ash.

L'industrie du béton est une source importante d'émissions de gaz CO2 lors de la production de ciment. Une des solutions proposées à l'industrie de la construction est de remplacer le ciment par des matières premières secondaires moins polluantes (ex : filler calcaire, fumée de silice), qui peuvent également améliorer les caractéristiques rhéologiques du liant et accroître la durabilité du béton.Le but principal de cette thèse est donc de : (1) standardiser la formulation de béton issue des différents travaux de recherche publiés tout en assurant une bonne compréhension de ses propriétés rhéologiques; (2) adapter ces principes aux conditions de réalisation (prise en compte des caractéristiques des matériaux locaux utilisés); et (3) vérifier dans le laboratoire ou sur le terrain la viscosité plastique et le seuil d’écoulement des bétons.Outre les moyens expérimentaux classiques nous avons utilisé, dans notre étude, un autre moyen de caractérisation rhéologique : c’est l’écoulement de béton dans un V-Funnel couplé à un canal horizontal en plexiglas. Dans un premier temps nous cherchons à comprendre la corrélation entre la viscosité et les paramètres rhéologiques de béton en se basant sur des modèles proposés dans la littérature. À partir de là, nous cherchons à présenter le modèle qui décrit le comportement de béton. Pour ce faire, nous proposons une corrélation théorique entre la viscosité plastique du béton frais et le temps d’écoulement dans le V-Funnel, puis nous comparons cette solution théorique avec des mesures expérimentales rapportées dans la littérature. / The concrete industry is an important source of carbon dioxide gas emissions during cement production. One of the proposed solutions to the construction industry is to replace the cement by less polluting secondary raw materials (e.g. limestone filler, silica fume), which can also improve the rheological properties of binder and increase the concrete durability.Thus, the development of self-compacting concrete can be seen as an attempt to reduce the environmental impact of the construction. Similarly, the structure optimization also aims at reducing the quantity (in volume) of concrete and is reflected in the use of high performance concrete and ultra performance fiber-reinforced concrete (HPC and UPFRC).The most widely adopted approach to quantify these rheological properties is to experimentally measured the shear stress versus strain rate using a concrete rheometer.In addition to traditional experimental tests such as the V-funnel, spread, sieve stability and L box, in our study we used another test of rheological characterization: it is the flow of concrete in a V-Funnel and then in a horizontal channel Plexiglas.The main purpose of this thesis is to: (1) standardize the concrete formulation outcome of various research works published while ensuring a good understanding of its rheological properties, (2) adapt these principles to the realization conditions (taking into account characteristics of local materials used), and (3) check, in the laboratory or in the field, the plastic viscosity and the flow threshold of concrete.

O concreto autoadensável (CAA) é um concreto especial com a capacidade de fluir e preencher completamente todos os espaços das fôrmas pela ação de seu peso próprio, sem que haja ocorrência de bloqueio e segregação da mistura. Contudo, para alcançar essas características, normalmente esse concreto é dosado com um maior teor de materiais finos e/ou com aditivo modificador de viscosidade. Os agregados provenientes de Resíduos de Construção e Demolição (RCD) já estão sendo utilizados na produção de concretos, porém o uso dos materiais finos de agregados reciclados não é recomendado para a produção de concretos convencionais. Entretanto, acredita-se que em CAA esses materiais finos podem ser uma oportunidade interessante, tanto para a questão da reutilização desses resíduos, conseguindo uma destinação nobre para esses materiais com baixa demanda no mercado, como na manutenção das propriedades deste concreto, sendo os principais agentes do controle de segregação. Desta forma, o presente trabalho consistiu em estudar a influência da utilização de finos de RCD (concretos, argamassas e tijolos cerâmicos), separadamente, em substituição parcial ao agregado miúdo natural, nas principais propriedades do concreto autoadensável no estado fresco (fluidez, habilidade passante e resistência à segregação) e no estado endurecido (resistência à compressão e módulo de elasticidade), bem como avaliar seu desempenho quanto à durabilidade (absorção de água e penetração de íons cloretos). Os resultados demostraram perda de fluidez e boa coesão nos concretos autoadensáveis que empregaram agregados reciclados. No entanto, ainda conferem boas características de autoadensabilidade, atendendo as condições normativas para uso em estruturas correntes de engenharia. No que tange às propriedades mecânicas, foi observado aumento de resistência à compressão e decréscimo do módulo de resistência para concretos com finos de RCD. No quesito de durabilidade, os concretos com agregados reciclados apresentaram valores mais elevados para absorção de água por capilaridade e penetração de íons cloretos em comparação aos concretos de referência. / Self-compacting concrete (SCC) is a special concrete with the ability to flow into and completely fill all spaces within the formworks only by the action of their own weight, without blocking and segregation of the mixture. However, to achieve these characteristics, normally this concrete needs to be mixed with more content of fine materials and/or viscosity modifiers additives. The aggregates from Construction and Demolition Wastes (CDW) are used for concrete production, but the use of fine recycled aggregate is not recommended for the production of conventional concrete. Although, it is believed that in SCC these fine aggregates can be an interesting opportunity for the reuse of these wastes, achieving a noble destination for these materials with low demand in the market, as for the maintenance of the properties of this concrete, being the main agents of segregation control. So, the present research consisted in studying the influence of the use of CDW fines aggregates (concretes, mortars and ceramic bricks, separately) to replace the natural sand in the main properties of the self-compacting concrete in the fresh state (flowability, passing ability and segregation resistance) and in the hardened state (compressive strength and modulus of elasticity), as well as to evaluate its performance in terms of durability (water absorption and chloride penetration). The study results showed loss of flowability and increased cohesion in the self-compacting concretes that used recycled aggregates. However, they still confer good characteristics for self-compacting concrete, taking into account the normative conditions for using current engineering structures. With respect to the mechanical properties, it was observed an increase of compressive strength and decrease of the modulus of elasticity for concrete with CDW fines aggregates. In terms of durability, concretes with recycled aggregates presented higher values for capillarity water absorption and penetration of chloride ions compared to the references concretes.