The reuse of crushed aggregates for producing structural concrete is a major concern especially when it comes to its strength and durability. This study evaluated recycled aggregate concrete (RAC) for its strength and durability under simulated environmental degradation in the form of wetting-drying (W-D) cycles. The study consisted of two phases, each involving the determination of the compressive strength and modulus of elasticity using the conventional method and also a nondestructive ultrasonic pulse velocity method (Pundit Lab). Phase 1 involved 7-day curing followed by 30 W-D cycles, while Phase 2 included 28-day cured samples subjected to 15 W-D cycles. It was found that RAC specimens subjected to W-D cycles had minimal degradation in strength, making the use of RAC in construction very promising. Results from Pundit Lab compared reasonably well with conventional test results, showing promise as a nondestructive tool for the evaluation of RAC properties. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Durante muito tempo as estruturas de concreto foram consideradas livres de manutenção, ou seja, estruturas quase eternas a menos que fossem sobrecarregadas ou destruídas intencionalmente ou por acidente. Esse pensamento caiu por terra nas últimas décadas quando várias estruturas de concreto começaram a apresentar problemas degradando-se bem mais rápido que o esperado. O monitoramento estrutural nasceu da necessidade de acessar a condição de segurança de uma estrutura de forma mais rápida, precisa e com o benefício de criar uma base de dados sobre a estrutura monitorada. O monitoramento de edifícios ainda é um assunto pouco abordado nas pesquisas e publicações. O alto custo agregado às pontes, viadutos e outras grandes estruturas atraem o interesse de pesquisadores e fabricantes de equipamentos. O problema escolhido como alvo no monitoramento a ser desenvolvido foi a degradação de blocos de fundações em concreto armado com reação álcali-agregado (RAA) pela dificuldade de acesso em inspeções. Uma simulação da expansão causado por RAA em concreto foi desenvolvida para experimentos com sensores e técnicas de monitoramento de fundações. No experimento foram testadas aplicações de strain gauges na armadura, na superfície através de um long gauge adaptado e LVDTs (linear variable differential transformer) aplicados na superfície. A ancoragem dos long gauges não suportou o esforço, impedindo a correta avaliação do sensor. Os LVDTs têm grande potencial para acompanhar o desenvolvimento de fissuras, mas sofrem depois de alguma expansão, pois se desalinham com a superfície do concreto. Os strain gauges aplicados na armadura mostraram boa relação com a expansão medida e têm grande potencial no monitoramento. O processo de decisão e projeto do monitoramento para os blocos é explicado e definido. Uma proposta de aplicação do conceito de estrutura tolerante a dano aos blocos de fundação com RAA é dada para otimização de planos de manutenção e intervenções. / For a long time, concrete structures were considered \"maintenance-free\", i.e. quasi eternal, unless they were overloaded or destroyed intentionally or by accident. This thought has been reconsidered in recent decades when several concrete structures began to present problems and degraded much faster than expected. Structural monitoring has been originated from the need to access the safety condition of a structure more quickly, accurately and with the benefit of creating a database of the structure monitored. The high cost related to bridges, overpasses and other large structures still attracts the interest of researchers and equipment manufacturers. However, the monitoring of buildings is still a subject rarely addressed in research and publications. The problem chosen to be addressed in this research is the degradation of reinforced concrete foundation blocks by alkali-aggregate reaction (AAR) due to difficult access during inspections and unpredictable development of the problem. A review on the sensors available on the market and on monitoring techniques used in other structures with the problem was undertaken. A simulation of the AAR`s expansion in concrete has been developed for an experiment with sensors and monitoring techniques of foundations. In this experiment, strain gauges were applied on the reinforcing bars and adapted on a long gauge on the surface. LVDTs (linear variable differential transformer) were also applied on the surface. The anchoring of the long gauges did not support the applied tension, preventing a correct evaluation of the sensor. LVDTs have great potential to monitor the development of cracks, but after the concrete suffering some expansion, they get misaligned with the surface. The strain gauges used in the armor showed a good relation with the expansion and have great potential in monitoring. The whole decision and design process for the structural health monitoring (SHM) for AAR attacked foundation blocks is explained and the project is defined. A proposal of a damage-tolerant approach for the block is given for optimization of maintenance and interventions.

O trabalho tem como objetivo a utilização do método dos elementos finitos para o cálculo da durabilidade de componentes mecânicos. Para isso, foi desenvolvido um estudo de caso que contempla, passo a passo, a metodologia utilizada. Um conjunto knuckle assembly dianteiro de um veículo off-road, fornecido por uma montadora nacional foi utilizado no estudo de caso. A geometria foi discretizada e modelada em software de pré-processamento em elementos finitos, o MSC.Patran®. Em seguida, foi submetida à análise estática no solver MSC.Nastran® para enfim obter-se o cálculo de durabilidade através do solver Fatigue®. Uma extensa revisão teórica foi realizada a fim de que o estudo tivesse embasamento teórico. / The work has as objective the use of the finite elements method for the calculation of the components durability. A case study using the proposal methodology was developed. A front set knuckle assembly of an off-road vehicle, supplied by a national assembly company was used in the case study. Geometry was discretized and shaped in software of pre-processing in finite elements, the MSC.Patran®. After that, it was submitted to the static analysis using the solver MSC.Nastran®, and the durability calculation using the solver Fatigue®. An extensive theoretical revision was carried through so that the study had theoretical basement.

O presente trabalho contempla um estudo experimental de análise do comportamento de concretos projetados por via seca, através de ensaios indicadores dos principais parâmetros de durabilidade, constantes de especificações nacionais e internacionais. A pesquisa envolve a avaliação comparativa entre quatro tipos de cimento especialmente formulados para uso em concreto projetado, em relação a outros dois tipos de cimento tradicionalmente empregados na composição de misturas projetáveis, no que se refere ao atendimento aos requisitos relativos à durabilidade, normalmente especificados para o material. Os concretos projetados, elaborados com consumos de cimento de 300 kg/m³, 350 kg/m³, 400 kg/m³ e 450kg/m³ foram inicialmente caracterizados, no estado fresco, com base em ensaios de consistência e depois produzidas amostras, em condições similares às de obra e estas submetidas aos ensaios balizadores de parâmetros de durabilidade adotados neste estudo, a saber: Absorção por Imersão e Fervura, Índice de Vazios, Massa Específica Real; Absorção de Água por Capilaridade; Migração de Íons Cloreto; Resistividade Elétrica; Penetração de Água sob Pressão e Carbonatação Acelerada. Como alguns dos ensaios supracitados não são destrutivos, foi possível aproveitar corpos-de-prova, que foram depois submetidos a ensaios de resistência à compressão axial e à tração através da compressão diametral, que também contribuíram para caracterização do material. De um modo geral, os resultados foram satisfatórios e atenderam às especificações vigentes. Contudo, os concretos elaborados com cimentos especiais, formulados com granulometria mais fina e adição de metacaulim, apresentaram indicadores de durabilidade consideravelmente superiores aos dos concretos elaborados com cimentos convencionais ou mesmo cimentos especiais formulados com aditivos, inclusive para consumos relativamente baixos. Apesar de não ter sido o foco principal deste trabalho, vale ressaltar os surpreendentes resultados dos ensaios de resistência mecânica, obtidos para os concretos elaborados com cimentos especiais formulados com granulometria mais fina e adição de metacaulim, que atingiram valores de resistência à compressão nunca antes observados, fato que pode tornar o material bastante promissor. / The present work involves an experimental study with dry-mix shotcrete aiming at the behavior analysis, through indicative testing of the main durability parameters of national and international specifications. The research involves the use of four cement types especially formulated for use in shotcrete use in comparison with two other cements that are traditionally used in mix production for shotcrete spraying. The shotcrete mixtures were elaborated with cement consumptions of 300 kg/m³, 350 kg/m³, 400 kg/m³ and 450kg/m³. They were characterized initially, in the fresh state, in terms of stiffness tests, and later, cores were extracted to produce samples, in similar conditions and submitted to ordinary durability tests: Water Absorption, Volume of Voids, Specific Weight; Water Absorption by Capillarity; Chloride Migration; Electric Resistivity; Water Penetration under Pressure and Accelerated Carbonatation. As some of the tests are not destructive, some of the samples was used for compressive and tensile (Brazilian Test) strength determination, what also contributed to additional characterization of the material. In general, the results were very satisfactory and they fit to the specifications requirements. However, the shotcretes elaborated with special cements, formulated with finer gradation and metakaolin addition, presented a much better behavior in terms of durability indicators comparing to the shotcretes produced with conventional cements and cements formulated with accelerators, even when, relatively low consumption of cement was used. Despite not being the main focus of this work, it is worth mentioning the surprising results of the testing of mechanical resistance, obtained for the shotcretes elaborated with special cements formulated with finer gradation and metakaolin addition, which reached resistance values to the compression never observed, making it a promising material.

As estruturas de concreto armado existentes em regiões marítimas são fortemente atacadas por agentes agressivos, sendo os cloretos os causadores dos maiores danos quando atingem níveis críticos, afetando de forma significativa a vida útil do concreto. Nos últimos anos a comunidade científica vem realizando pesquisas relativas à penetração de cloretos e suas conseqüências, sendo a maioria desenvolvida em laboratórios. Em ambiente natural, no Brasil, foram realizadas pesquisas nas regiões Nordeste e Sul, mais especificamente no Rio Grande do Sul na cidade de Rio Grande. O litoral Norte do Rio Grande do Sul possui condições climáticas diversas em relação ao litoral Sul, apresentando municípios com significativo incremento na indústria da construção civil, justificando assim o desenvolvimento do estudo nesta região. Esta pesquisa tem por objetivo estudar a influência do tipo de cimento utilizado, do uso de adições de sílica ativa da relação água/aglomerante em relação à penetração de cloretos nas estruturas de concreto em ambiente natural. Foi analisado, também, o distanciamento da estrutura de concreto em relação ao mar e as condições ambientais do local, tais como direção dos ventos predominantes e umidade relativa. Para fundamentar a pesquisa, foram realizados ensaios químicos para determinar o teor de cloretos nas amostras retiradas dos corpos-de-prova colocados em Tramandaí a três distâncias do mar (50, 150 e 800 m) e junto a Lagoa Tramandaí (1800 m em relação ao mar), em Imbé, a diversas profundidades (superficial, 5, 15 e 25 mm). Os resultados indicam que quanto menor a relação água/aglomerante e maior o distanciamento em relação ao mar, menor o teor de cloretos que ingressam nas estruturas de concreto, sendo que a 800 m da orla marítima essa agressividade não é significativa. Concretos com as faces posicionadas a nordeste foram as que apresentaram maior penetração de cloretos. O uso de cimento CP V-ARI com adição de sílica ativa proporciona uma maior concentração superficial de cloretos no concreto, porém, um menor ingresso em seu interior. Nesta pesquisa, nenhum concreto atingiu o teor crítico de cloretos (0,15%) para o ambiente de atmosfera marítima onde foram expostos. / The reinforced concrete structures existing in maritime regions are heavily attacked by aggressive agents, with chlorides those who cause more damage when they reach critical levels, significantly affecting the life of the concrete. In recent years the scientific community is conducting research on the penetration of chlorides and their consequences, mostly developed in laboratories. In the natural environment, in Brazil, were searched in the Northeast and South, more specifically in Rio Grande do Sul in Rio Grande. The northern coast of Rio Grande do Sul has different climatic conditions over the south coast, with municipalities with a significant increase in the construction industry, thereby justifying the development of the study in this region. This research aims to study the influence of cement type, the use of additions of silica fume of the water / binder for the penetration of chlorides in the concrete structures in the natural environment. We also analyzed the distance of the concrete structure from the sea and the environmental conditions of the site, such as direction of prevailing winds and relative humidity. In support of this research, we conducted chemical tests to determine the chloride content in the samples of soils-proof Tramandaí placed in the three distances from the sea (50, 150 and 800 m) and along the lagoon Tramandaí (1800 m above the sea), in Imbé at various depths (surface, 5, 15 and 25 mm). The results indicate that the lower the water / binder and the greater the distance from the sea, the smaller the amount of chlorides entering the concrete structures, and 800 meters from the seafront this aggression is not significant. Concrete with faces positioned northeast showed the highest penetration of chlorides. The use of cement CP V-ARI with the addition of silica fume provides greater surface concentration of chlorides in concrete, however, a lower entry inside. In this study, no case has reached the critical content of chloride (0.15%) to the environment of maritime atmosphere where they were exposed.

Lime stabilisation is a ground improvement technique used to improve the engineering properties of cohesive fill materials. During earthworks operations, specialist plant is used to rotovate the clay fill material and intermix lime binder around clay clods. After completion of the lime treatment, the layer is compacted in the usual way. Immediately after mixing, the lime instigate a series of physico-chemical reactions within the clay soil. Where the chemical reactions are favourable and with time after compaction (curing) the material becomes progressively stronger and durable to environmental influences, e.g. inundation by surface or ground water. However, where sulphate is present within the soil, the reactions may change and the ingress of water into the layer can result in the expansive growth of deleterious minerals e.g. ettringite. While sulphate swell issues are relatively rare, when they do occur the degree of expansion can be very high. A high profile sulphate swell failure developed during the construction of the M40, Oxford, UK in 1989. Over the winter period after the lime stabilisation works, a 250mm deep lime treated layer heaved by up to 150mm - destroying the overlying road construction. Since the M40 failure, a substantial amount of effort has been undertaken to better understand the sulphate swell reactions and in this regard the state of scientific knowledge is relatively strong. A fundamental issue for field applications of lime stabilisation is that the vast majority of research has been undertaken on laboratory specimens prepared using methods which do not reflect site practice. Laboratory studies often use oven dried and finely crushed clay, whereas site operations will treat much larger clay clods to result in a more heterogeneous distribution of lime through the compacted soil body. With large clay clods, the chemical reactants must migrate through clods and this may cause the sequence of chemical reactions to change. A further challenge is that laboratory studies are typically undertaken with cure temperatures of 20°C, whereas a typical near surface temperature in the UK is <10°C. This is of particular relevance to sulphate swell failures which are reported to coincide with a reduction in ambient temperature over winter periods. Thus, the direct relevance of laboratory studies to site application was unclear. A series of laboratory experiments using a preparation method which reflects field applications of lime stabilisation was used to investigate the influence of large clay clods on the durability of lime stabilised clay soil. This method was applied to both low and high sulphate clay soils. A fundamental discovery from work on low sulphate clay is that the addition of lime binder to the surface of the clay clods causes a physico-chemical boundary to form. This boundary develops due to the rapid increase to the plastic limit of the clay preventing adjacent clods from joining together during compaction. This causes the engineering properties of each individual clod to develop independent to its neighbours and for each clay clod to be separated by an inter-clod pore space. The strength of each individual clay clod will increase with curing as the added lime dissociates into Ca2+ and OH- and migrates to form C-S-H deep within the clods. Where the material is compacted wet of the optimum water content, this condition improves ion migration and enables development of diffuse cementation deep within clods. The inter-clod porosity remains as a weakness throughout curing especially during specimen soaking, where the pore channels comprise a pathway, accelerating the ingress of soaking water. With low sulphate soil, the soaking water softens the treated material, however, with high TPS soil substantial sulphate swelling may develop. Thus, efforts to minimise this porosity during preparation is important and the use of quicklime with longer mellowing periods can cause the clay clods to develop high strength before compaction. The high strength clods resist compaction and the degree of inter-clod porosity in the compacted mass increases, worsening specimen durability to water ingress. The investigations into high sulphate clays included the development of a Novel Swell Test (NST) to assess volume change. A unique aspect of the NST was that the sulphate swell response of the lime treated material was investigated at site realistic temperatures of 8°C. It was identified that, when compared with standard laboratory test temperatures of 20°C the rate of sulphate swell is substantially higher at the low temperature. The mineralogical testing has permitted the hypothesis that, at 8°C the growth of crystalline ettringite becomes slower and the ettringite precursor, which has a high affinity to imbibe water, remains in this state for much longer. Thus, laboratory swell tests at 20°C may substantially underestimate the degree of swell that may develop in the field. As a pressing need, it is recommended that the industry adapt sulphate swell test methods to appraise the degree of swell at field realistic temperatures i.e. < 10°C. The work also identifies that the primary defence against sulphate swell is to condition the fill so that the risk of post compaction water ingress, via inter-clod porosity, is minimised. The use of GGBS and water addition during extended mellowing periods also reduces the degree of sulphate swell in natural clay soils. This work concludes that working methods for lime stabilisation of medium high plasticity soils of a potentially high sulphate content, should be adapted to encourage diffuse cementation and minimise the degree of (post compaction) inter-clod porosity. Practically this involves the use of hydrated lime and the addition of mixing water throughout extended mellowing periods. Fundamentally, the study recommends that where construction programmes allow, the long term durability of a fill material should be the priority over immediate strength.

The purpose of this study was to investigate three different programs designed to increase verbal and physical sharing and to determine the generalizability and durability of the behaviors that were trained. Eight groups of four preschool children, balanced for sex, were observed for 16 minutes daily during a free play period in their preschool classroom. After eight days of baseline, 24 children received one of three types of training for eight sessions. Eight children were taught to verbally share, eight to physically share, and eight to both verbally and physically share. All of these children received a treatment package composed of instructions, modeling, behavioral rehearsal, prompting, and praise. After the training phase, these children were returned to the baseline condition for eight days. The remaining eight children served as a no treatment control. Each day immediately following free play the children were observed for 12 minutes while working on a different task (art) in a different classroom, with a different experimenter, observers, and materials. Four weeks after training ended all the children were observed for an additional five days during both the free play and art activities. Children trained to verbally share showed an increase in verbal sharing which diminished when treatment was withdrawn and failed to generalize to another setting (art). There was, however, a concomitant increase in physical sharing during both activities that was maintained even during the follow-up. Similarly, children taught to share verbally and physically demonstrated the same effects of treatment as those receiving only training in verbal sharing. The magnitude of these effects, however, was slightly greater for those children who were taught both types of sharing. Training in only physical sharing produced larger increases in physical sharing in both settings than the other two approaches but these effects were lost when treatment was terminated. Verbal sharing among these children was unaffected by the treatment. Finally, for those children who did not receive any training, no systematic increases in either verbal or physical sharing were observed. Therefore, the high level of physical sharing during the follow-up for those children who were only taught to verbally share and for those who were instructed to verbally and physically share was not due to the change in the natural course of sharing over time but rather due to the treatments. Training children to verbally share, physically share, or both had no effect on the rate with which they refused to share. The present findings suggest that to facilitate sharing among preschool children, at a minimum they must be taught to share verbally. Training children to share only physically is not recommended because it was not durable and did not generalize. Training both verbal and physical sharing produced results with a magnitude slightly greater than teaching just verbal sharing but in the absence of a cost-benefit analysis, the additional training is questionable. Without special programming some of the effects generalized to another setting and were maintained about four weeks after the termination of the treatment. There was response generalization of verbal to physical sharing but not vice versa. Hypotheses concerning why generalization occurred without specific programming, future areas of research, and ethical considerations are discussed.

Concrete cylinder piles produced by a centrifugally cast, vibrated, roller compacted process have shown promising corrosion durability in marine environments. Three bridges in the Florida Panhandle with approximately 40 years of service in aggressive marine service were examined. A newly constructed marine bridge utilizing concrete cylinder piles was also examined to verify corrosion performance of piles manufactured with modern building materials and construction compared to piles built several decades ago. Survey of the marine bridges showed minimal corrosion distress despite low design concrete cover to steel hoop reinforcements (20-40 mm). Typical concrete distress included minor rust staining but not necessarily indicating corrosion of reinforcement steel. Thin longitudinal cracks were frequently observed but were likely caused by mechanical damage from pile driving rather than stemming from corrosion distress. Chloride ion diffusivity was low, in the order of 1x10-13 m2/s. Other measured parameters such as concrete resistivity, porosity, and water absorption indicate low permeability. Chloride analysis of cracked and uncracked concrete cores from the older bridges in this study did not show pronounced preferential chloride penetration. Chloride analysis from the contemporary marine bridge did show some preferential transport of chloride ions at shallow depths through cracks with further evidence of lower electrical resistivity indicating enhanced electrolyte transport. The pore water pH of concrete samples from the contemporary bridge was high despite the presence of pozzolanic materials suggesting that normal chloride threshold values may be valid.

In marine environments and where de-icing salts are applied, the degradation of reinforced concrete structures due to chloride induced corrosion of the reinforcement is a major problem. The expansive nature of the corrosion process results in cracking of the concrete and eventually spalling. In order to select suitable remedial measures it is necessary to make an assessment of the residual strength and the residual life. In order to investigate the effect of corrosion on bond strength of the reinforcement, specimens comprising square prismatic sections containing steel reinforcement in the four corners have been subjected to a wet-dry cycle and corrosion has been accelerated by polarising the bars. The research has studied the change of bond strength with level of corrosion for 12 mm and 16 mm bars with concrete cover of 1 and 3 times the bar size. The bond strength is assessed by means of pull out tests and the corresponding extent of corrosion has been assessed in terms of the mass loss. Observations and measurements of the form of the corrosion (pit dimensions and loss of bar diameter) are also presented. The relationship between bond strength and surface crack width has been investigated. Results show that the surface crack width may be a good indicator of residual bond strength. In addition, the influence on bond strength of concrete compressive strength, reinforcement cover, bar position and bar size on the change of bond strength has been explored. It should be noted that all conclusions drawn in this project are based on tests on specimens without shear reinforcement (unconfined) and that accelerated corrosion (by impressed current) has been adopted. Consequently, care should be exercised in applying these results directly to structures in the field. Additional research is needed to assess the influence of impressed current on crack patterns and the effect of shear reinforcement.

A large portion of an airport property is occupied by runways and taxiways, which must be kept in excellent condition to ensure the safety of the airplanes, and the people on board. Any free objects on the airfield can cause damage to aircraft and are a possible danger to both the airplanes and the passengers. However, deterioration of the concrete airfield can be a major hazard and the presence of de-icing and anti-icing fluids may accelerate degradation. The focus of this project was the evaluation and assessment of aircraft de-icing and anti-icing fluids on the deterioration of airfield concrete. These fluids are used to remove and prevent snow and ice formation on aircraft by lowering the freezing temperature of water. The primary component in both fluids is ethylene glycol, while additives, which are proprietary and unknown, are mixed in to control various properties. Very little research has been done regarding the effect of the de-icer and anti-icers on the concrete deterioration. The aim of this study was to gain a better understanding of its influence on the deterioration of airfield concrete through a series of mechanical and electro-chemical tests, as well as microscopic and elemental analysis. Based on the comparative experiments and analyses performed using water, ethylene glycol, de-icer, and anti-icer, it appears that de-icing fluids do not prematurely cause concrete deterioration. In addition, experimental procedures in this study utilized the de-icing fluids as a concentrate, which are unrealistic conditions on an airfield, where dilution occurs from the addition of water and the presence of snow and ice. There was precipitate formation in all cases of cement paste exposure to de-icing fluid, however, which indicates that reactions are occurring and should be investigated further to determine the long term effects on concrete. With respect to the scope of this study, it was determined that the use of de-icers and anti-icers cause no significant detrimental effects on concrete mechanical properties and durability.