Dissertations / Theses: 'Compressive strength and flexural strength'

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Asia, Winifred. "An in-vitro study of the physical properties of core build-up materials." University of the Western Cape, 2017. http://hdl.handle.net/11394/6307.

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Magister Chirurgiae Dentium - MChD (Prosthodontics) The aim of this study was to evaluate and compare the physical properties of two core build-up materials (ParaCore and CoreXflow) and compare this to conventional composite material (Filtek Supreme Plus and SDR Flow) used as core build-up material.

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Alazemi, Athbi. "Investigate the Effects of Nano Aluminum Oxide on Compressive, Flexural Strength, and Porosity of Concrete." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1544693885397299.

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Zhang, Lihe. "Impact resistance of high strength fiber reinforced concrete." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/705.

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Concrete structures may be subjected to dynamic loading during their service life. Understanding the dynamic properties of concrete structures is becoming critical because of the increased concern about the dynamic loading of both civilian and military structures, and especially, the recent increase in terrorist attacks on structures. Fiber reinforced concrete (FRC) is known to exhibit superior performance in its post-peak energy absorption capacity, (i.e., toughness) under flexural and tensile loading. However, the behavior of fiber reinforced concrete under compressive impact has not previously been investigated. In the present research, the response of fiber reinforced concrete was investigated over the full strain rate regime, from static loading to high strain rate loading, and finally to impact loading. The compressive toughness of FRC under static loading was studied using an existing Japanese standard (JSCE SF-5). Then, a test method for FRC under compressive impact loading was developed, involving the use of a high speed video camera system to measure the deformation of FRC cylinders under compressive impact. The strain rate sensitivity of FRC in both flexure and compression was also fully investigated. FRC was found to have higher strengths under impact loading (both flexural and compressive) than under static loading. The compressive toughness under impact loading increased due to the high peak load and the high strain capacity. FRC under flexural impact loading showed a greater strength improvement than under static flexure. FRC displays a much higher Dynamic Improvement Factor (DIF) under flexural impact than under compressive impact. It gave an overall higher performance under impact than under static loading. It also exhibited a higher strain rate sensitivity than plain concrete in both compression and flexure. Damage analysis, in terms of loss of strain energy, was carried out based on damage mechanics principles. Damage was found to increase with increasing strain rate. A new constitutive model was proposed to account for the relationship between DIF (Comp) and strain rate and the data derived from the model were found to be consistent with the experimental results.

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Alskif, Aiham. "An investigation of the effect of different additives on the compressive and flexural strength of rammed earth." Thesis, The University of Wisconsin - Milwaukee, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10250302.

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The main objective of this research is to study the effect of using different additives on the compressive and flexural strength of rammed earth structures. Different ratios of fly ash, and/or cement were added to the soil to identify their influence on the compressive strength. Recycled fiber materials were used to wrap and reinforce the cement-soil specimens in order to enhance the flexural strength of beams and control the cracks and the mode of failure. The study finds that adding cement to soil has significant effect on the soil strength, and it causes a remarkable increase in the strength while adding fly ash does not increase the compressive strength and it results in elastic modulus reduction. Furthermore, it is concluded that wrapping and reinforcing the specimens by burlap cloth or fiber mesh do not improve the flexural strength due to the weak bond with the cement-soil material. However, when a beam is reinforced by glass fiber exhibited improvement in the flexural strength and it experienced a plastic behavior after the proportional limit and it was able to absorb a large amount of energy without failure.

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Wilson, David Edward. "Structural Properties of ICLT Wall Panels Composed of Beetle Killed Wood." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3230.

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Interlocking Cross Laminated Timber (ICLT) wall panels are a new wood construction product similar to Cross Laminated Timber panels. Besides being an innovative structural system, they also utilize beetle killed timber from many of the forests that have been devastated by the Mountain Pine Beetle. Three tests were performed on three ply ICLT panels measuring 8 feet (2.44m) wide, 8 feet (2.44m) tall and 8.5 inches (21.6cm) thick to determine the racking, flexural and axial strengths of the wall panels. After each test was performed the walls were disassembled and investigated for cause of failure. Using the data from the tests as a benchmark, simple analytical models to predict the design capacities of the walls for racking, flexural, and axial strengths were established. The analytical models for racking strength, flexural strength and axial strength predicted reasonably well the measured strength values. Additional testing is necessary to increase the available database, further validate the analytical models developed, better understand the structural performance of ICLT panels, and establish acceptable design methodology for ICLT wall panels.

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Nilsson, Jonas, and Peter Sargenius. "Effect of microfibrillar cellulose on concrete equivalent mortar fresh and hardened properties." Thesis, KTH, Byggvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-60485.

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A pilot project in 2010, conducted at CBI, showed the capacity for pulp, micro fibrilars from the forest industry to act as Viscosity Modifying Agent (VMA) in concrete. This project was, however, too limited to find answers for optimal use of this kind of material. The forest industry company Stora Enso wants to find out if their pulp can be used in concrete in order to somehow improve its properties. Two micro fibrilar suspensions have been tested. The tested fibrils are in two sizes, the finer material named MFC1 has undergone more homogenization than the course material named MFC2. The fibrils have been evaluated in regard to how the fibrils react with mortars in both its fresh and hardened state. Tests have been conducted on the use of concrete equivalent mortars with a maximum aggregates size of 4 mm. Two water-cement-ratios have been used in the tests, 0.45 and 0.60. Three different fibril dosages have been tested, 1, 2 and 3 kg/m³. The results of these trials of cellulose fibrils has been evaluated in respect of rheology, compressive strength, flexural strength, cracking, shrinkage, water capillary porosity, anti-wash out resistance (underwater concrete) and as a possible surface coverage. The results from the trials, conducted in this report, show that an increased dosage of fibrils leads to an increased plastic viscosity. The fibrils appear to have no effect on the flexural- and compressive strength, and no effect on the shrinkage of the test specimens. According to our results it is not advisable to use the fibrils for the purpose of acting as an agent for anti-washout resistance, or as a surface coverage. The work have been performed at Swedish Cement and Concrete Research Institute, CBI, in Stockholm in the spring of 2011. CBI is an institution whose mission is to create, apply and disseminate knowledge in the concrete and rock area. Ett tidigare pilotprojekt har under 2010 utförts på CBI, och där undersöktes möjligheten för cellulosafibrer från skogsindustrin att fungera som Viscosity Modifying Agent (VMA) i betong. Utrymmet i detta projekt var dock för begränsat för att finna svar för optimal användning av denna typ av material. Nu vill skogsindustriföretaget Stora Enso ta reda på om massa från deras träprodukter kan användas i betong, för att på något sätt förbättra dess egenskaper. Vi har därför provat suspensioner innehållande två olika fraktioner av cellulosafibriller. De testade fibrerna finns i två storlekar, det finare materialet heter MFC1 och har genomgått med homogenisering än det grövre materialer som heter MFC2. Dessa två typer har tillsats i bruk och utvärderats i hur de reagerar i både brukets färska och dess hårdnade tillstånd. Testerna har genomförts på bruk med en maximal ballaststorlek på 4 mm. Två vct-nivåer har använts i försöken, 0,45 och 0,60. Tre olika fibrilldoser har prövats, nämligen 1, 2 och 3 kg/m³ fibriller. Resultaten från dessa försök av cellulosafibriller har utvärderats med avseende på reologi, tryckhållfasthet, böjhållfasthet, sprickbildning, kapillaritet, krympning, anti-urvaskning och som möjlig ytbetäckning. De tester som har genomförts visar att med ökad dos fibriller ökar den plastiska viskositeten. Fibrillerna visade sig inte ha någon effekt på böj- eller tryckhållfasheten, samt ingen effekt på krympning av provkropparna. Testerna visar att fibrillerna inte heller agerar med någon possitiv effekt som anti-urvaskningsmedel, eller som ett täckande ytskikt. Försöken har genomförts vid CBI Betonginstitutet i Stockholm mellan 21 mars och 8 juli år 2011.CBI är en institution vars uppdrag är att skapa, tillämpa och sprida kunskap inom betong och bergområdet.

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Wongkamhaeng, Kan. "Effect of chairside surface treatments on biaxial flexural strength and subsurface damage in monolithic zirconia for dental applications." Thesis, University of Iowa, 2016. http://ir.uiowa.edu/etd/3233.

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Objective: The goal of the present study was to investigate the effect of chairside surface treatments on biaxial flexural strength and subsurface damage of monolithic zirconia ceramics. Methods: Specimens (15x15x1.2 mm3) were prepared by sectioning from commercially available zirconia blanks (BruxZirTM) and sintering according to manufacturer's recommendations. Fully dense specimens were randomly divided into five groups (n=30) and treated as follows; 1) as-sintered (AS) 2) air abraded with 50 μm alumina fine particles (AAF), 3) air abraded with 250 μm coarse alumina particles (AAC), 4) ground (G), and 5) ground and polished (GP) to mimic chairside and dental laboratory treatments. Microstructural changes were thoroughly characterized by optical and scanning electron microscopy, surface profilometry and atomic force microscopy. Crystalline phases and their depth profile were investigated by x-ray diffraction (XRD) and grazing incidence x-ray diffraction (GIXRD). Results were analyzed by Kruskal-Wallis test and Tukey's adjustment for multiple comparisons. A 0.05 level of significance was used. Reliability was evaluated by Weibull analysis. Results: All treatment groups exhibited a significant difference in mean surface roughness (Rq) compared to the as-sintered group (p<0.05). The AAC group showed the highest surface roughness at 1.08 ± 0.17 μm, followed by the G, AAF and AS groups. The GP group exhibited the lowest surface roughness. The group air abraded with fine particles showed the highest mean biaxial flexural strength (1662.62 ± 202.58 MPa), but was not different from the ground and polished group (1567.19 ± 209.76 MPa). The groups air abraded with coarse particles or ground with diamond bur exhibited comparable mean biaxial flexural strength at 1371.37 ±147.62 MPa and 1356.98 ±196.77 MPa, respectively. The as-sintered group had the lowest mean biaxial flexural strength at 1202.29 ±141.92 MPa. The depth of compressive stress layer, measured by GIXRD was approximately 50 μm in the AAF group, followed by the AAC group with ~35 μm, ~10 μm for the ground group and ~5 μm for the ground and polished group. Deep subsurface cracks were observed in the AAC group (~80 μm in depth) and G group (~25 μm in depth), whereas shallower flaws were present in the AAF and GP groups at 10 and 3 μm, respectively. Weibull analysis represented a greater reliability in zirconia specimens treated with air abrasion groups. Conclusions: Surface treatments induced the t-m transformation in 3Y-TZP and associated development of compressive stresses to a depth that varied with the severity of the treatment performed. GIXRD revealed that AAF led to the thickest compressive stress layer, followed by AAC, G and GP. SEM revealed that subsurface damage was most severe with AAC, followed by G, AAF and GP. We propose that the flexural strength results can be explained by the difference between the depth of the compressive stress layer induced by the transformation and the depth of the subsurface flaws.

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Thamboo, Julian Ajith. "Development of thin layer mortared concrete masonry." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/73815/1/Julian_Thamboo_Thesis.pdf.

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This research was a step forward to developing data sets for thin layer mortared concrete masonry through systematic experimental and numerical studies. Since thin layer mortared concrete masonry is relatively new type of masonry construction, methodical research studies have been undertaken to properly address the gaps in understanding of this masonry system. As part of the ARC Linkage research project, this thesis has been developed to extend the knowledge on thin layer mortared concrete masonry.

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Vinter, Václav. "Latexy modifikované cementové materiály." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216351.

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In this thesis, the development of mechanical properties and structure of latex modified cementious materials during hydration was studied. Latex modified materials are composites of inorganic cement (portland cement) and organic polymer latex. Preparation, processing and fabrication of the polymer cement material based on portland cement was optimized with aim to reach the most compact structure of the product with the finest mechanical characters. The experimental part was pointed to observe influence of the type and amount of polymer latex with focus on mechanical characters and hydration kinetics with given filling as well as without it. In presented work, the possibility of compaction of the material by high-shear mixing within twin-roll mixer (the prototype for production of MDF composite) was verified. The second part of the labor was aimed to analysis of prepared polymer-cementitious material. For determination of influence of batching of added polymer latex on hydration of cement paste the thermal analysis (DTA/TGA) and infrared spectroscopy of composite was done. At last the microscopic observation by optical microscope was carried.

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Robles, Sáenz Randolp Julián, and Medina Juan Carlos Sánchez. "Evaluación de pavimentos rígidos mediante la determinación de correlaciones entre el módulo de rotura a la flexión y la resistencia a la compresión para el Centro Poblado San Cristóbal de Chupán – Huaraz." Bachelor's thesis, Universidad Ricardo Palma, 2015. http://cybertesis.urp.edu.pe/handle/urp/1350.

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La resistencia a flexión y la resistencia a la compresión representan parámetros fundamentales en el correcto desarrollo de los pavimentos rígidos, porque definen la calidad del concreto, principal componente de los pavimentos rígidos, después de cumplir satisfactoriamente su ciclo de fraguado y curado. En nuestro enfoque cuantitativo, el problema principal radica en intentar efectuar ensayos de rotura a la flexión en zonas alejadas, como en el centro poblado San Cristóbal de Chupán, reconociendo que sólo es posible realizarlo en pocos laboratorios a nivel nacional. Por esta razón se determinó, en base a ensayos realizados en laboratorio, un factor de correlación que vincula el Módulo de Rotura a la flexión y la Resistencia a la Compresión, siendo el resultado experimental el factor (k) expresado por la ecuación Mr = (k)*√f’c, que identifica rápidamente resultados del Módulo de Rotura a la flexión, aplicable a proyectos de condiciones similares, ante las altas exigencias del control de calidad en los proyectos de construcción. The flexural strength and the compressive strength are fundamental parameters in the correct development of rigid pavements, because they define the quality of concrete, principal component of rigid pavements, after performing successfully their setting and curing cycle. In our quantitative approach, the principal problem has roots in realizing flexural strength tests in remote rural areas such as San Cristobal de Chupán populated, recognizing could only do it in a few laboratories nationwide. Therefore written, it is determined a correlation factor, based on laboratory tests, what can relating Flexural strength and compressive strength. The experimental result express a factor (k), what is on the equation Mr = (k)*√f'c, which quickly identifies results of Flexural Strength, applicable to projects of similar conditions, to the demands of quality control in construction projects.

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Bandi, Raghava. "Effect of Surface Treatment on the Performance of CARALL, Carbon Fiber Reinforced Aluminum Dissimilar Material Joints." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011869/.

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Fiber-metal laminates (FML) are the advanced materials that are developed to improve the high performance of lightweight structures that are rapidly becoming a superior substitute for metal structures. The reasons behind their emerging usage are the mechanical properties without a compromise in weight other than the traditional metals. The bond remains a concern. This thesis reviews the effect of pre-treatments, say heat, P2 etch and laser treatments on the substrate which modifies the surface composition/roughness to impact the bond strength. The constituents that make up the FMLs in our present study are the Aluminum 2024 alloy as the substrate and the carbon fiber prepregs are the fibers. These composite samples are manufactured in a compression molding process after each pre-treatment and are then subjected to different tests to investigate its properties in tension, compression, flexural and lap shear strength. The results indicate that heat treatment adversely affects properties of the metal and the joint while laser treatments provide the best bond and joint strength.

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Sahin, Serkan. "A Comparative Study Of Aisc-360 And Eurocode 3 Strength Limit States." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610894/index.pdf.

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Nowadays design, fabrication and erection of steel structures can be taken place at different locations as a result of rapid globalization owners may require the use of widely accepted steel design codes. Therefore, engineers are faced with the challenge of being competent with several design specifications for a particular material type. AISC-360 and EC3 are widely accepted steel structure design specifications that utilize limit state principles with some similarities and differences in application. Hereby a study has been undertaken to put together the nominal strength expressions presented in both AISC-360 and EC3 codes in a single document, to identify the similarities and the differences in calculated strengths and to facilitate rapid learning of either of the specifications with prior knowledge of the other. Because of the wide scope of specifications, only fundamental failure modes are considered in this thesis. Resistance equations are directly compared with each other wherever possible. For cases where the treatment of specifications is entirely different, representative members were considered for comparison purposes.

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Dias, Ana Regina Cervantes. "Avaliação da customização por desgaste de pinos pré-fabricados de fibra de vidro." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=4356.

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O objetivo deste estudo foi avaliar pinos pré-fabricados de fibra de vidro (White Post DC/FGM) submetidos à customização por desgaste da porção apical. Experimento 1: 5 pinos n. 4 foram divididos em 5 grupos (G) de acordo com o instrumento de desgaste: GA - sem desgaste, GB- mini torno industrial (Dentsply), GC - ponta diamantada n. 3195F (KG Sorensen), GD - disco de lixa de granulação média (Sof-Lex/3M/ESPE), GE- alicate (Tramontina). Observou-se a micromorfologia dos pinos em microscópio eletrônico de varredura (ZEISS/DSM 960). Experimento 2: 60 pinos de diferentes diâmetros foram divididos em 6 grupos: G0 - pinos n. 0,5, G1 - pinos n. 1, G2 - pinos n. 2, G3 - pinos n. 3, G4 - pinos n.4, G5 - pinos n. 4 com terço apical desgastado com discos de lixa até o equivalente ao terço apical dos pinos n. 2. Os pinos foram submetidos ao teste de flexão de 3 pontos na máquina de ensaios universal (Instron 5500 R), conforme ISO 10477. Experimento 3: 20 caninos humanos permanentes sofreram tratamento endodôntico e remoção das coroas clínicas padronizando 15 mm de remanescente radicular. Os dentes foram incluídos em resina acrílica com simulação do ligamento periodontal, receberam férula de 2 mm e foram divididos em 2 grupos: GI - pinos n. 4 cimentados em condutos preparados com broca equivalente ao pino (FGM), GII - pinos n. 4 customizados no terço apical cimentados em condutos preparados com brocas (FGM) equivalentes aos pinos n. 2 em 10 mm e n. 4 em 5 mm. Os pinos foram cimentados com cimento resinoso (Rely X U100/3M/ESPE), os corpos de prova receberam coroas diretas de resina composta (Enforce Core/Dentsply) padronizadas com coras de policarbonato (TDV) e foram submetidos ao teste de resistência à fratura na Instron a 45da ferramenta cilíndrica, com força de 500 N aplicada a 2 mm da incisal na face palatina/lingual, com velocidade de 0,5 mm/min até falha. O padrão de fratura foi classificado em favorável ou desfavorável. Os resultados foram tratados estatisticamente por teste de análise de variância (ANOVA, p<0,05). Os resultados dos testes de flexão e fratura foram respectivamente: G0 - 58,406,40; G1 - 83,959,43; G2- 103,4219,17; G3 - 160,7817,30; G4 - 170,4711,28; G5 - 106,3521,96; GI - 303,0262,21 e GII - 402,81131,97. O padrão de fratura foi tratado por Mann-Whitney que observou semelhança estatística entre os grupos. Concluiu-se que o desgaste de pinos de fibra de vidro com pontas diamantadas ou discos de lixa produz alterações micromorfológicas aceitáveis. O corte com alicate deve ser evitado. A customização por desgaste da porção apical de pinos de fibra de vidro diminui a resistência à flexão a valores aceitáveis. Dentes restaurados com pinos de fibra de vidro customizados por desgaste possuem resistência à fratura superior a dentes restaurados com pinos intactos. A customização por desgaste facilita a adaptação do pino ao conduto radicular e preserva a estrutura dental. The purpose of this study was to evaluate fibre posts (White Post DC/FGM) submitted to customization of the apical portion. Experiment 1: 5 #4 posts were divided into five groups (G) and submitted to different custom adaptation treatments: GA no surface treatment, GB- industrial shaping tool (Dentsply), GC- #3195 fine diamond bur (KG Sorensen), GD- medium-grain paper discs (Sof-Lex/3M/ESPE), GE pliers (Tramontina). The micromorphology of the posts was observed in a scanning electron microscope (ZEISS/DSM 960). Experiment 2: 60 posts of different diameters were divided into six groups: G0 #0.5 posts, G1 #1 posts, G2 #2 posts, G3 - #3 posts; G4 - #4 posts and G5 #4 posts submitted to custom adaptation of the apical portion with paper discs until the diameter was equivalent to #2 posts. The posts were submitted to a 3 point bending test in a universal testing machine (Instron/5500 R), according to ISO 10477. Experiment 3: 20 freshly extracted permanent healthy human canines with similar size were endodontically treated and the crowns were removed, leaving a remaining root length of 15 mm. The teeth were embedded in acrylic resin with simulation of the periodontal ligament, received a 2 mm ferule and were divided into two groups: G1- 10 #4 posts were cemented into post spaces prepared with #4 drill (FGM) at 10 mm, G2 - 10 #4 customized posts were cemented into root spaces prepared with #2 drill (FGM) at 10 mm and #4 drill (FGM) at 5 mm. The posts were cemented with resin cement (Rely X U100/3M/ESPE), and the teeth received direct crowns of composite resin (Enforce Core/Dentsply), standardized with polycarbonate crowns (TDV). The fracture strength was measured on an Instron, at 45 degrees to the long axis of the tooth, until fracture. The 500 N cylindrical load was applied to the buccal/lingual axis 2 mm below the incisal line, at crosshead speed of 0.5 mm/min. The fracture pattern was observed and classified as favorable or unfavorable. The results were submitted to ANOVA (p<0.05). Flexural strength and resistance to fracture data were, respectively: G0 58.40+6.40; G1 83.95+9.43; G2 103.42+19.17; G3 160.78+17.30; G4- 170.47+11.28; G5 106.35+21.96;GI 303.02+62.21 and GII 402.81+131.97. Fracture patterns were statistically similar according to Mann-Whitney test. It was concluded that customization of fibre posts with diamond burs or paper discs produces acceptable micromorphological changes. The cut of the post with pliers should be avoided. Grounding of the apical portion of fibre posts reduces the flexural strength to acceptable values. Teeth restored with grounded fiber posts have grater fracture strength than teeth restored with intact posts. Grounding of the post facilitates adaptation to root walls and preserves tooth structure.

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Hanuš, Petr. "Experimentální ověření vlivu typu vláken na chování vláknobetonů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392039.

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This diploma thesis deals with the comparison of different properties of fibre-reinforced concrete according to the type of fibres. The main monitored property is flexural strength, tested on prisms with a cross section of 150x150 mm and a length of 600 mm. Four concretes of natural aggregate and four concrete of lightweight aggregate were prepared for the experiment. There were 2 reference concrete and 6 fibre-reinforced concrete. Three types of fibres were used: steel, polypropylene and glass. More than 2500 kg of concrete was produced. The aim of the thesis is to assess the influence of fibres on the flexural strength and other characteristics of fibre-reinforced concrete.

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Ajaxon, Ingrid. "Can Bone Void Fillers Carry Load? : Behaviour of Calcium Phosphate Cements Under Different Loading Scenarios." Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-316656.

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Calcium phosphate cements (CPCs) are used as bone void fillers and as complements to hardware in fracture fixation. The aim of this thesis was to investigate the possibilities and limitations of the CPCs’ mechanical properties, and find out if these ceramic bone cements can carry application-specific loads, alone or as part of a construct. Recently developed experimental brushite and apatite cements were found to have a significantly higher strength in compression, tension and flexion compared to the commercially available CPCs chronOS™ Inject and Norian® SRS®. By using a high-resolution measurement technique the elastic moduli of the CPCs were determined and found to be at least twice as high compared to earlier measurements, and closer to cortical bone than trabecular bone. Using the same method, Poisson's ratio for pure CPCs was determined for the first time. A non-destructive porosity measurement method for wet brushite cements was developed, and subsequently used to study the porosity increase during in vitro degradation. The compressive strength of the experimental brushite cement was still higher than that of trabecular bone after 25 weeks of degradation, showing that the cement can carry high loads over a time span sufficiently long for a fracture to heal. This thesis also presents the first ever fatigue results for acidic CPCs, and confirms the importance of testing the materials under cyclic loading as the cements may fail at stress levels much lower than the material’s quasi-static compressive strength. A decrease in fatigue life was found for brushite cements containing higher amounts of monetite. Increasing porosity and testing in a physiological buffer solution (PBS), rather than air, also decreased the fatigue life. However, the experimental brushite cement had a high probability of surviving loads found in the spine when tested in PBS, which has previously never been accomplished for acidic CPCs. In conclusion, available brushite cements may be able to carry the load alone in scenarios where the cortical shell is intact, the loading is mainly compressive, and the expected maximum stress is below 10 MPa. Under such circumstances this CPC may be the preferred choice over less biocompatible and non-degradable materials.

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Ganaw, Abdelhamed I. "Rheology of grout for preplaced aggregate concrete : investigation on the effect of different materials on the rheology of Portland cement based grouts and their role in the production of preplaced aggregate concrete." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5766.

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Preplaced aggregate concrete (PAC) is produced by grouting high workability cement based grouts among the voids of compacted coarse aggregate mass. Because of its low shrinkage, PAC has been used for many repair jobs like; tunnel lines, dams and bridge piers. Moreover, it has been used for underwater construction. Grout has a major effect on the properties of produced PAC and well defined grout controls the properties of resulted PAC. The effect of types and amount of powder materials, admixtures, sand and water content on the properties of fresh and hardened grout for the production of PAC have been investigated. Tests on hardened grout and PAC properties have also been carried out to investigate the most important effects. A correlation between hardened properties of grout and PAC has also been analyzed. Grout rheology using four different gradation sands at two different cement-sand and at different w/c ratios ratios has been identified experimentally; no added chemical admixtures or mineral additives had first employed, then superplasticizer (SP) was added at 2% and 1%, and finally a combination of 1% SP and pulverized fuel ash (Pfa) at 20% of the cement weight was employed for all mixes. Grout tests have included two point workability tests by the Viskomat NT, flow time funnel test, Colcrete flow meter test, and water bleeding test. After that, eighteen grout mixes with high workability were produced using three different sands at three w/c ratios and two c/s ratios with 1% SP and Pfa at 20% of the cement weight were designed. Eighteen hardened grout and PAC then produced and their compressive strength and sorptivity were tested. Grout rheology can be defined by the rheology of cement paste employed and the internal distance between sand particles. The effect of sand surface texture on grout rheology is important at very low internal distances. Fresh grout yield stress is the most important property which gives the same degree of sensitivity for all grouts regardless the material type and content used in the mix. There are strong relations between compressive strength of grout and PAC, but less correlation between them in sorptivity test because of the effect high quantity of coarse aggregate of PAC. Sorptivity of PAC is low comparing with different kinds of concrete suggesting its advantage for underwater construction.

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Castro, Denise Tornavoi de. "Efeito da incorporação de vanadato de prata nanoestruturado na atividade antimicrobiana, propriedades mecânicas e morfologia de resinas acrílicas." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/58/58131/tde-04022015-093559/.

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Materiais odontológicos inovadores que apresentem propriedades antimicrobianas são altamente desejáveis na cavidade oral. O objetivo deste estudo foi avaliar a atividade antimicrobiana do vanadato de prata nanoestruturado (β-AgVO3) incorporado em duas resinas acrílicas frente a Candida albicans, Streptococcus mutans, Staphylococcus aureus e Pseudomonas aeruginosa, além de examinar as propriedades mecânicas e o padrão de incorporação do nanomaterial nas resinas. O nanomaterial foi caracterizado por difração de raios X (DRX), espectroscopia no infravermelho por transformada de Fourier (FTIV), análise elementar por energia dispersiva (EDS) e microscopia eletrônica de varredura (MEV). As propriedades antimicrobianas das resinas acrílicas incorporadas com diferentes porcentagens de β-AgVO3 foram investigadas pelo método de redução do XTT, unidades formadoras de colônias (UFC) e microscopia confocal à laser e o comportamento mecânico por meio de ensaios de dureza e rugosidade superficial, resistência à flexão, à compressão e ao impacto. O padrão de incorporação do β-AgVO3 nas resinas foi analisado por microscopia eletrônica de varredura (MEV) e análise elementar por energia dispersiva (EDS). Os dados foram analisados por ANOVA, Tukey e pelo teste Generalized Linear Models (α=0,05). Para ambas as resinas, em relação ao grupo controle, a incorporação de 5% e 10% de β-AgVO3 reduziram significantemente a atividade metabólica de C. albicans e P. aeruginosa (p<0,05), enquanto que para S. mutans houve redução significante apenas com a incorporação de 10% (p<0,05). Não houve diferença na atividade metabólica pelo método do XTT frente a S. aureus (p> 0,05). Para ambas as resinas, observou-se uma redução significativa no número de UFC/mL de C. albicans para o grupo incorporado com 10% de β-AgVO3 e de S. mutans para os grupos com 2,5%, 5% e 10% do nanomaterial (p<0,05). Para S. aureus e P. aeruginosa, houve redução significante com a incorporação de 5% e 10% (p<0,05). A dureza superficial da resina termopolimerizável permaneceu inalterada pela incorporação do nanomaterial (p>0,05) e da autopolimerizável aumentou com 0,5% (p<0,05). Concentrações maiores que 1% promoveram redução na resistência flexural das resinas (p<0,05) enquanto que a rugosidade superficial permaneceu inalterada (p>0,05). A resistência à compressão da resina autopolimerizável permaneceu inalterada (p>0,05) e da termopolimerizável reduziu com a incorporação de 0,5% e 10% (p<0,05). As concentrações de 5% e 10% promoveram redução significante na resistência ao impacto das resinas, em relação ao controle (p<0,05). A caracterização das resinas quanto a dispersão da carga utilizada mostrou a presença de domínios de β-AgVO3 ao longo da matriz polimérica seguindo um padrão circular. Conclui-se que o método proposto foi capaz de promover atividade antimicrobiana às resinas acrílicas frente aos micro-organismos avaliados, sendo a mesma dependente da concentração do nanomaterial. Porém, alterações na dispersão do β-AgVO3 na matriz dos polímeros são necessárias para não sacrificar as propriedades mecânicas e para potencializar o efeito antimicrobiano Innovative dental materials that have antimicrobial properties are highly desirable in the oral cavity. The aim of this study was to evaluate the antimicrobial activity of nanostructured silver vanadate (β-AgVO3) incorporated into two acrylic resins against Candida albicans, Streptococcus mutans, Staphylococcus aureus and Pseudomonas aeruginosa, while examining the mechanical properties and the pattern of nanomaterial incorporation into resins. The nanomaterial was characterized by X-ray diffraction (XRD), infrared spectroscopy Fourier transform (FTIR), elemental analysis by energy dispersive (EDS) and scanning electron microscopy (SEM). The antimicrobial properties of acrylic resins incorporated with different percentages of β-AgVO3 were investigated by the reduction of XTT method, colony forming units (CFU) and confocal laser microscopy and the mechanical behavior through hardness, surface roughness, flexural, compression and impact tests. The pattern of incorporation of β-AgVO3 resins was analyzed by scanning electron microscopy (SEM) and elemental analysis by energy dispersive (EDS). Data were analyzed by ANOVA, Tukey test and the Generalized Linear Models (α = 0.05). For both resins, compared to the control group, the incorporation of 5% and 10% β-AgVO3 caused a significantly reduced in the metabolic activity of C. albicans and P. aeruginosa (p <0.05), while for S. mutans significant reduction was observed only with the incorporation of 10% (p <0.05). There was no difference in metabolic activity by XTT method against S. aureus (p> 0.05). For both resins, there was a significant reduction in the number of CFU / mL for C. albicans incorporated group with 10% β-AgVO3 and S. mutans in groups with 2.5%, 5% and 10% of nanomaterial (p <0.05). For P. aeruginosa and S. aureus, there was a significant decrease with the incorporation of 5% to 10% (p <0.05). The surface hardness of the heat-cured resin was unchanged by the incorporation of the nanomaterial (p <0.05) and increased self-cured with 0.5% (p <0.05). Concentrations above 1% promote the reduction in flexural strength of the resins (p <0.05) while the surface roughness remained unchanged (P> 0.05). The compressive strength of the self-cured resin remained unchanged (P> 0.05) and heat-cured reduced with the incorporation of 0.5% and 10% (p <0.05). Concentrations of 5% and 10% caused a significant reduction in impact strength of resins, compared to control (p <0.05). The characterization of the resins as the dispersion of the filler used showed the presence of β-AgVO3 domains along the polymer matrix following a circular pattern. It was concluded that the proposed method was able to promote antimicrobial activity to acrylic resins against microorganisms evaluated, with the same concentration dependent of the nanomaterial. However, changes in the β-AgVO3 dispersion in the polymer matrix are necessary to do not sacrifice the mechanical properties and to enhance the antimicrobial effect

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Sáček, Josef. "Vysokohodnotné betony na bázi druhotných surovin." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216352.

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This work is devoted to study of physical-mechanical properties and structure of high performance concretes (HPC) based on portland cement. The attention is focused on possibility of substitution of economic high-cost components of concrete with utilization of secondary raw materials or cheaper components. Properties of raw materials and their influence on whole quality of concrete were tracked by various methods. Mechanical properties of prepared HPC samples were tested especially (compression and flexural strength) with further microscopic study of structure. Isoperibolic calorimetry and X-ray powder diffraction method were also used for concrete characterisation. These methods allowed to determine the influence of raw materials on prepared HPC and to carry out a certain optimization among price and quality of this material.

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Julon, Zambrano Neiser Aldeir, and Quispe Elvis Smith Marcañaupa. "Mejoramiento de la resistencia a compresión y flexión de concreto sostenible a elevadas temperaturas, con adición de cenizas puzolánicas." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2021. http://hdl.handle.net/10757/657263.

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El presente artículo de estudio analizó la resistencia al fuego del concreto con adición de cenizas de cascara de arroz (CCA) y bagazo de caña de azúcar (CBCA). Se adoptó un método experimental como diseño de investigación, que produjo setenta y dos probetas cilíndricas (72) y cincuenta y cuatro vigas (54), para ensayos a compresión y flexión respectivamente. Se utilizaron cenizas en porcentajes de 5% y 10% y además una combinación binaria de 5% y 5% de ambas cenizas como reemplazo parcial de cemento. Las muestras fueron ensayadas luego de 28 días de curado a temperaturas de 24 °C (ambiente), 300 °C y 500 °C, con una duración de 2h de exposición y luego de 24 horas de enfriamiento al aire libre. Los resultados muestran un aumento de resistencia promedio a la compresión y flexión de hasta un 95% y 25%, respectivamente, luego de ser expuestos a temperaturas elevadas con respecto a las muestras de control. This study article analyzed the fire resistance of concrete with the addition of rice hull ash (CCA) and sugarcane bagasse (CBCA). An experimental method was adopted as the research design, which produced seventy-two cylindrical specimens (72) and fifty-four beams (54), for compression and bending tests respectively. Ashes were used in percentages of 5% and 10% and a binary combination of 5% and 5% of both ashes as a partial replacement for cement. The samples were tested after 28 days of curing at temperatures of 25 ° C (ambient), 300 ° C and 500 ° C, with a duration of 2 hours of exposure and after 24 hours of cooling in the open air. The results show an increase in average resistance to compression and flexion of up to 95% and 25%, respectively, after being exposed to high temperatures compared to the control samples. Trabajo de investigación

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Zanella, Andrigo Kemel. "ANÁLISE DAS PROPRIEDADES MECÂNICAS DE CONCRETOS PARA PAVIMENTAÇÃO EMPREGANDO DIFERENTES PROCESSOS DE CURA." Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/7861.

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To develop a project sizing concrete pavement is necessary to know the mechanical properties and the different treatment processes of material to be used. This study aimed to analyze the mechanical properties such as flexural strenght, compressive strength, indirect tensile strength and static modulus of concrete paving. The three types of concrete were studied: An actual reference (typically used in paving, one with the addition of polypropylene fibers (common practice for floors), and a high strength concrete used to rapidly release the traffic. Different methods of curing were applied: chemical cure with and without the use of wet burlap bags (widely applied in pavements) and curing in a moist chamber (as recommended by standard). This evaluation of the mechanical properties for the concrete studied in different curing methods applied, showed that the microstructure of concrete is significantly interfering with the results, especially in cured concrete to track conditions (chemical cure without and with the placement of burlap sacks). Where factors such as the absorption and reabsorption of water evaporation to cement hydration, cracking the interface folder / aggregate, ambient conditions related to temperature and humidity, are interfering with the tensile strength in bending, compressive strength, indirect tensile strength and particularly in the static modulus and still, from the results obtained in this study and those reported by other authors who studied a high-strength concrete, it is possible to verify that there are particularities still unknown about the behavior of high strength concrete. Para o desenvolvimento de um projeto de dimensionamento de pavimentos de concreto é necessário conhecer as propriedades mecânicas e os diferentes processos de tratamento do material a ser utilizado. Este trabalho teve por objetivo analisar as propriedades mecânicas, tais como, resistência à tração na flexão, resistência à compressão axial, resistência à tração por compressão diametral e módulo de elasticidade estático em concretos para pavimentação. Foram estudados os três tipos de concretos: um concreto referência, (tipicamente empregado em pavimentação, outro com a adição de fibras de polipropileno (prática comum em pavimentos) e um concreto de alta resistência, utilizado para rápida liberação ao tráfego. Diferentes métodos de cura foram aplicados: cura química com e sem a utilização de sacos de aniagem úmidos (largamente aplicados em pavimentos) e cura em câmara úmida (conforme preconizado por norma). A avalição das propriedades mecânicas para os concretos estudados, nos diferentes métodos de cura aplicados, mostrou que a microestrutura dos concretos, está interferindo de forma significativa nos resultados obtidos, principalmente nos concretos curados para condições de pista (cura química sem e com a colocação de sacos de aniagem), onde fatores como a absorção e reabsorção da água de evaporação para hidratação do cimento, a fissuração da interface pasta/agregado, as condições ambientes relacionadas à temperatura e umidade, estejam interferindo na resistência à tração na flexão, resistência à compressão axial, resistência à tração por compressão diametral e principalmente no módulo de elasticidade estático e ainda, a partir dos resultados obtidos na presente pesquisa e daqueles apresentados por outros autores que estudaram um concreto de alta resistência, é possível verificar que existem particularidades ainda desconhecidas sobre o comportamento do concreto de alta resistência.

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Žižlavský, Tomáš. "Vliv použitého kameniva na vlastnosti vápenných malt." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265681.

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The thesis is focused on the comparison of the role of different types of aggregates and the binder-aggregate ratio on the properties of lime mortars. The theoretical part of the thesis deals with the effect of properties of aggregate, a binder-aggregate ratio and a use of calcareous aggregate, especially limestone, on the properties of mortars. It also deals with the utilization of limestone as aggregate in a history of masonry. In the practical part of the thesis there is a comparison of physically-mechanical and microstructural properties of mortars prepared with different type of aggregate (siliceous sand and limestone aggregate), with varying binder-aggregate ratio and also with a partial substitution of the aggregate by limestone fines. It was found that the usage of limestone instead of quartz sand produces the mortar of comparable properties. The partial substitution of the aggregate with limestone fines caused noticeable growth of strength, especially in mortars with higher binder-aggregate ratio.

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MAHMOUD, TAREK IBRAHIM. "Evaluation of the degradation process of cement-based materials exposed to aggressive environment by using ultrasonic techniques and physical characterisation." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/27550.

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El hormigón armado compuesto de cemento Portland fue inventado hace algo más de un siglo aproximadamente y se ha convertido en el material más utilizado en la construcción. La durabilidad de este hormigón es una de las consideraciones más importantes a ser tenidas en cuenta en el diseño de nuevas estructuras y en la evaluación estructural de las ya existentes. Cuando un hormigón sujeto a un ambientes o cargas que puede degradarlo, como puede ser su uso en puentes y ambientes marinos o si contiene grandes cantidades de alúmina o áridos reciclados, el conocimiento o predicción de su durabilidad es una aspecto crítico para su comportamiento en servicio. Los ensayos no destructivos se han mostrado como unos de los ensayos preceptivos con una importancia económica y social más relevante desde que se han aplicado para la auscultación de la durabilidad de las estructuras de hormigón pertenecientes a la ingeniería civil, donde estos materiales son ampliamente utilizados. En cualquier caso, el uso de las técnicas no destructivas en estos materiales no está suficientemente implementado, hecho este motivado por las características heterogéneas de su microestructura. De todos los métodos no destructivos aplicables para el hormigón, el uso de pulsos ultrasónicos es de gran interés para la caracterización de la microestructura y las propiedades de materiales heterogéneos. El objetivo del presente trabajo es obtener un procedimiento de evaluación del ciclo de vida del hormigón preparado y puesto en servicio para ambientes marinos. Además, será estudiado y analizado la incorporación de varias metodologías (destructivas y non destructivas) para caracterizar el proceso de degradación de morteros y hormigones expuestos a disolución de sulfato de sodio y a exposición en disolución de nitrato amónico. Con esta finalidad, una integración adecuada de diferentes técnicas será usada para la caracterización de propiedades y el seguimiento del proceso de degradación que afectan al hormigón. Como objetivos adicionales, destaca que fueron estudiadas las relaciones entre los parámetros destructivos y no destructivos, así como la relación entre los distintos parámetros no destructivos entre sí. Muchos de los estudios anteriores que han usado la inspección ultrasónica las cuáles fueron utilizadas para determinar la relación agua/cemento del mortero, de la pasta de cemento y del hormigón, o para monitorizar los cambios estructurales, para diferentes relaciones a/c, en el proceso de curado. En este trabajo de investigación fue analizado el efecto que tiene para diferentes relaciones a/c en los parámetros ultrasónicos durante el proceso de degradación. Para este objetivo, se utilizaron un Cemento Portland tipo II A L 42.5 (LPC), y otro sulforresistente tipo I 42.5R/SR (SRPC) que fueron usados en la fabricación de dos marcos de hormigón, los cuales fueron utilizados como hormigón en servicio (caso real). Para el estudio del efecto de la variación de a/c en los parámetros ultrasónicos durante la degradación se utilizaron muestras de mortero con deferentes relaciones agua cemento 0.525- 0.45- 0.375 and 0.30 a partir de LPC para obtener diferentes niveles de degradación. Para monitorizar el proceso de degradación se utilizó la inspección por pulso/eco (1 y 3.5 MHz) para la obtención del parámetro del área del perfil de atenuaciones (APA) el cual fue estimado por L Vergara et al., 2003 y usado por Fuente et al, 2004. Para seguir el proceso de curado de pasta de cemento y morteros, este parámetro ha demostrado una alta sensibilidad para caracterizar los cambios microestructurales de materiales derivados del cemento a lo largo de su curado. El método de transmisión se ha utilizado para la determinación de las velocidades de ondas longitudinales con la frecuencia de 1MHz y transversales con la frecuencia de 500 kHz. La velocidad ultrasónica también ha demostrado la capacidad para seguir los cambios microestructurales de un modo sencillo porque dicho parámetro está relacionado con la variación de las propiedades mecánicas, y bajo ciertas premisas, con la variación de la porosidad. El análisis con la imagen ultrasónica con 2 MHz fue también usada para la consecución de los mismos objetivos. Como métodos destructivos, los ensayos de resistencia a la compresión y flexión fueron los utilizados para determinar la pérdida de actividad resistente de morteros y hormigones, y la porosidad conectada al agua para analizar los cambios en la matriz porosa por el efecto de la difusión de elementos agresivos que penetran en el material provocando su degradación. La porosimetría de mercurio (MIP) fue usada para observar las variaciones del volumen y tamaño de poro y, por último, la microscopía electrónica de barrido (MEB) que fue utilizada para cuantificar y detectar los cambios en la microestructura por el ataque de elementos agresivos. Los resultados obtenidos muestran que, la degradación producida por exposición a sulfato de sodio, tiene dos etapas, en la primera etapa se forma la etringita que llena los poros pero que no produce microfisuración. En esta etapa se observó una variación en los parámetros obtenidos por ejemplo, incremento de la velocidad de la onda ultrasónica, de las resistencias a compresión y a la flexión o la disminución de la porosidad. Esta variación en los parámetros podría indicar una mejora en las prestaciones mecánicas del material objeto de la investigación, pero en realidad esto no es cierto porque los poros están llenos de etringita, provocando una expansión, que es la causa de la degradación en la segunda etapa. En dicha segunda etapa, se produce una microfisuración generalizada por la expansión de la etringita e incrementando su volumen dentro de los poros. Este hecho produjo un cambio en los parámetros medidos que contrastan con la evolución en la primera etapa, disminución de la velocidad de las ondas ultrasónicas, y de las resistencias mecánicas y consecuentemente un aumento de la porosidad. Por otro lado, la degradación por ataque de nitrato amonio tiene una única etapa debida al proceso de descalificación que comienza desde el principio del proceso de exposición y es lineal durante todo el periodo de exposición. Para ambos casos, la integración de las diversas técnicas se revela como satisfactoria para el seguimiento del proceso de degradación, encontrando buenas correlaciones entre los parámetros no destructivos y los parámetros destructivos de técnicas de análisis físico-químico. Mahmoud, TI. (2013). Evaluation of the degradation process of cement-based materials exposed to aggressive environment by using ultrasonic techniques and physical characterisation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/27550 TESIS

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Cano, Duplex Bryan Alexander, and Mateo Edwin Jean Marco Galarza. "Propuesta de uso de cenizas de cáscara de arroz y fibras de polipropileno en diseños de mezclas de concreto para el control de fisuras en losas macizas entrepiso in-situ en la ciudad de Lima." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/654901.

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La presente investigación fue elaborada con el fin de estudiar la influencia que tiene el agregar cenizas de cascara de arroz (CCA) y fibras de polipropileno (FPP) en la fisuración por contracción plástica del concreto. El estudio de investigación tuvo lugar en la ciudad de Lima, donde nos enfocamos a investigar las propiedades plásticas y mecánicas de un concreto f´c=210 kg/cm2, que se utiliza comúnmente en la fabricación de losas macizas, con reemplazo parcial del cemento por CCA en porcentajes de 5%, 10% y 15% respecto a su peso, y FPP en rendimiento de 900 gr/m3. Las principales propiedades en estado endurecido fueron investigadas, la resistencia a la compresión y la resistencia a la flexión y la propiedad en estado plástico que se desarrolló fue la fisuración debido a la contracción plástica a través del ensayo ASTM C1579. Teniendo en cuenta que no existe un acuerdo relativo al ancho de fisura máxima en un elemento estructural, se decidió utilizar límites entre 0.2 a 0.4 mm, para ambientes normales, sugeridos por el Mg. Ing. Gianfranco Ottazzi. De los resultados obtenidos, la mezcla adicionada con CCA en reemplazo parcial del cemento en 5%, 10% y 15% junto con las FPP en rendimiento de 900 gr/m3, podemos inferir que las CCA reducirán, no de manera significativa, las propiedades de la resistencia de un concreto f´c= 210 kg/cm2, sin embargo, reducen el promedio de apariciones de fisuras producidas en las losas macizas debido la contracción plástica del mismo. The present investigation was elaborated with the purpose of studying the influence of the addition of rice husk ash (RHA) and polypropylene fibers (PPF) on the plastic shrinkage cracking of concrete. The research study took place in the city of Lima, where we focused on investigating the plastic and mechanical properties of a concrete f´c = 210 kg / cm2, which is commonly used in the manufacture of solid slabs, with partial replacement of the cement by RHA in percentages of 5%, 10% and 15% respect to its weight and PPF in yield of 900 g / m3. The main properties in the hardened state were investigated, the compressive strength and flexural strength and the property in the plastic state that developed was cracking due to plastic shrinkage through the ASTM C1579 test. Taking into account that there is no agreement regarding the maximum width in a structural element, it was decided to use limits between 0.2 to 0.4 mm, for normal environments, suggested by Mg. Eng. Gianfranco Ottazzi. According to the results obtained, the mixture added with RHA in replacement of cement in percentages of 5%, 10% and 15% together with PPF in yield of 900 gr / m3, we can infer that the RHA will reduce, not significantly, the strength properties of a concrete f´c = 210 kg / cm2, however, reduce the average occurrence of cracks produced in solid slabs due to the plastic shrinkage of the same. Tesis

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Reutter, Oliver. "Assessment of masonary flexural bond strength." Thesis, Kingston University, 2007. http://eprints.kingston.ac.uk/20328/.

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This thesis presents the results of an experimental assessment of masonry flexural bond strength. Since there is insufficient experimental data on key performance requirements for bond between units and mortar, investigations into the development of bond and flexural strength across a range of masonry units for both traditional and new mortar types, reflecting the recent changes in European standards, were conducted. In order to demonstrate the performance of bond between unit and mortar, the latter ranging from weak to strong, a practical bond wrench testing rig was developed for use with couplets and stack bonded prisms. This involved carrying out investigations into existing designs and revaluations using up to date modelling techniques. The result is a new bond wrench applicable for use in laboratories and on site.

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Shani, Mehul A. "Compressive strength of eccentrically loaded steel angles." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0013/MQ52481.pdf.

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Heva, Yasintha Bandula. "Behaviour and design of cold-formed steel compression members at elevated termperatures." Queensland University of Technology, 2009. http://eprints.qut.edu.au/29310/.

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Cold-formed steel members have been widely used in residential, industrial and commercial buildings as primary load bearing structural elements and non-load bearing structural elements (partitions) due to their advantages such as higher strength to weight ratio over the other structural materials such as hot-rolled steel, timber and concrete. Cold-formed steel members are often made from thin steel sheets and hence they are more susceptible to various buckling modes. Generally short columns are susceptible to local or distortional buckling while long columns to flexural or flexural-torsional buckling. Fire safety design of building structures is an essential requirement as fire events can cause loss of property and lives. Therefore it is essential to understand the fire performance of light gauge cold-formed steel structures under fire conditions. The buckling behaviour of cold-formed steel compression members under fire conditions is not well investigated yet and hence there is a lack of knowledge on the fire performance of cold-formed steel compression members. Current cold-formed steel design standards do not provide adequate design guidelines for the fire design of cold-formed steel compression members. Therefore a research project based on extensive experimental and numerical studies was undertaken at the Queensland University of Technology to investigate the buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. As the first phase of this research, a detailed review was undertaken on the mechanical properties of light gauge cold-formed steels at elevated temperatures and the most reliable predictive models for mechanical properties and stress-strain models based on detailed experimental investigations were identified. Their accuracy was verified experimentally by carrying out a series of tensile coupon tests at ambient and elevated temperatures. As the second phase of this research, local buckling behaviour was investigated based on the experimental and numerical investigations at ambient and elevated temperatures. First a series of 91 local buckling tests was carried out at ambient and elevated temperatures on lipped and unlipped channels made of G250-0.95, G550-0.95, G250-1.95 and G450-1.90 cold-formed steels. Suitable finite element models were then developed to simulate the experimental conditions. These models were converted to ideal finite element models to undertake detailed parametric study. Finally all the ultimate load capacity results for local buckling were compared with the available design methods based on AS/NZS 4600, BS 5950 Part 5, Eurocode 3 Part 1.2 and the direct strength method (DSM), and suitable recommendations were made for the fire design of cold-formed steel compression members subject to local buckling. As the third phase of this research, flexural-torsional buckling behaviour was investigated experimentally and numerically. Two series of 39 flexural-torsional buckling tests were undertaken at ambient and elevated temperatures. The first series consisted 2800 mm long columns of G550-0.95, G250-1.95 and G450-1.90 cold-formed steel lipped channel columns while the second series contained 1800 mm long lipped channel columns of the same steel thickness and strength grades. All the experimental tests were simulated using a suitable finite element model, and the same model was used in a detailed parametric study following validation. Based on the comparison of results from the experimental and parametric studies with the available design methods, suitable design recommendations were made. This thesis presents a detailed description of the experimental and numerical studies undertaken on the mechanical properties and the local and flexural-torsional bucking behaviour of cold-formed steel compression member at ambient and elevated temperatures. It also describes the currently available ambient temperature design methods and their accuracy when used for fire design with appropriately reduced mechanical properties at elevated temperatures. Available fire design methods are also included and their accuracy in predicting the ultimate load capacity at elevated temperatures was investigated. This research has shown that the current ambient temperature design methods are capable of predicting the local and flexural-torsional buckling capacities of cold-formed steel compression members at elevated temperatures with the use of reduced mechanical properties. However, the elevated temperature design method in Eurocode 3 Part 1.2 is overly conservative and hence unsuitable, particularly in the case of flexural-torsional buckling at elevated temperatures.

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Heva, Yasintha Bandula. "Behaviour and design of cold-formed steel compression members at elevated temperatures." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/29310/1/Yasintha_Heva_Thesis.pdf.

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Cold-formed steel members have been widely used in residential, industrial and commercial buildings as primary load bearing structural elements and non-load bearing structural elements (partitions) due to their advantages such as higher strength to weight ratio over the other structural materials such as hot-rolled steel, timber and concrete. Cold-formed steel members are often made from thin steel sheets and hence they are more susceptible to various buckling modes. Generally short columns are susceptible to local or distortional buckling while long columns to flexural or flexural-torsional buckling. Fire safety design of building structures is an essential requirement as fire events can cause loss of property and lives. Therefore it is essential to understand the fire performance of light gauge cold-formed steel structures under fire conditions. The buckling behaviour of cold-formed steel compression members under fire conditions is not well investigated yet and hence there is a lack of knowledge on the fire performance of cold-formed steel compression members. Current cold-formed steel design standards do not provide adequate design guidelines for the fire design of cold-formed steel compression members. Therefore a research project based on extensive experimental and numerical studies was undertaken at the Queensland University of Technology to investigate the buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. As the first phase of this research, a detailed review was undertaken on the mechanical properties of light gauge cold-formed steels at elevated temperatures and the most reliable predictive models for mechanical properties and stress-strain models based on detailed experimental investigations were identified. Their accuracy was verified experimentally by carrying out a series of tensile coupon tests at ambient and elevated temperatures. As the second phase of this research, local buckling behaviour was investigated based on the experimental and numerical investigations at ambient and elevated temperatures. First a series of 91 local buckling tests was carried out at ambient and elevated temperatures on lipped and unlipped channels made of G250-0.95, G550-0.95, G250-1.95 and G450-1.90 cold-formed steels. Suitable finite element models were then developed to simulate the experimental conditions. These models were converted to ideal finite element models to undertake detailed parametric study. Finally all the ultimate load capacity results for local buckling were compared with the available design methods based on AS/NZS 4600, BS 5950 Part 5, Eurocode 3 Part 1.2 and the direct strength method (DSM), and suitable recommendations were made for the fire design of cold-formed steel compression members subject to local buckling. As the third phase of this research, flexural-torsional buckling behaviour was investigated experimentally and numerically. Two series of 39 flexural-torsional buckling tests were undertaken at ambient and elevated temperatures. The first series consisted 2800 mm long columns of G550-0.95, G250-1.95 and G450-1.90 cold-formed steel lipped channel columns while the second series contained 1800 mm long lipped channel columns of the same steel thickness and strength grades. All the experimental tests were simulated using a suitable finite element model, and the same model was used in a detailed parametric study following validation. Based on the comparison of results from the experimental and parametric studies with the available design methods, suitable design recommendations were made. This thesis presents a detailed description of the experimental and numerical studies undertaken on the mechanical properties and the local and flexural-torsional bucking behaviour of cold-formed steel compression member at ambient and elevated temperatures. It also describes the currently available ambient temperature design methods and their accuracy when used for fire design with appropriately reduced mechanical properties at elevated temperatures. Available fire design methods are also included and their accuracy in predicting the ultimate load capacity at elevated temperatures was investigated. This research has shown that the current ambient temperature design methods are capable of predicting the local and flexural-torsional buckling capacities of cold-formed steel compression members at elevated temperatures with the use of reduced mechanical properties. However, the elevated temperature design method in Eurocode 3 Part 1.2 is overly conservative and hence unsuitable, particularly in the case of flexural-torsional buckling at elevated temperatures.

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Mulligan, Ann Marie. "Attainable Compressive Strength of Pervious Concrete Paving Systems." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2630.

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The pervious concrete system and its corresponding strength are as important as its permeability characteristics. The strength of the system not only relies on the compressive strength of the pervious concrete but also on the strength of the soil beneath it for support. Previous studies indicate that pervious concrete has lower compressive strength capabilities than conventional concrete and will only support light traffic loadings. This thesis investigated prior studies on the compressive strength on pervious concrete as it relates to water-cement ratio, aggregate-cement ratio, aggregate size, and compaction and compare those results with results obtained in laboratory experiments conducted on samples of pervious concrete cylinders created for this purpose. The loadings and types of vehicles these systems can withstand will also be examined as well as the design of appropriate thickness levels for the pavement. Since voids are supposed to reduce the strength of concrete 1% for every 5% voids(Klieger, 2003), the goal is to find a balance between water, aggregate, and cement in order to increase strength and permeability, two characteristics which tend to counteract one another. In this study, also determined are appropriate traffic loads and volumes so that the pervious concrete is able to maintain its structural integrity. The end result of this research will be a recommendation as to the water-cement ratio, the aggregate-cement ratio, aggregate size, and compaction necessary to maximize compressive strength without having detrimental effects on the permeability of the pervious concrete system. This research confirms that pervious concrete does in fact provide a lower compressive strength than that of conventional concrete; compressive strengths in acceptable mixtures only reached 1700 psi. Extremely high permeability rates were achieved in most all mixtures regardless of the compressive strength. Analysis of traffic loadings reinforce the fact that pervious concrete cannot be subjected to large numbers of heavy vehicle loadings over time although pervious concrete would be able to sustain low volumes of heavy loads if designed properly. Calculations of pavement thickness levels indicate these levels are dependent on the compressive strength of the concrete, the quality of the subgrade beneath the pavement, as well as vehicle volumes and loadings. M.S.C.E. Department of Civil and Environmental Engineering Engineering and Computer Science Civil Engineering

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Wen, Edward A. "Compressive strength prediction for composite unmanned aerial vehicles." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=959.

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Thesis (M.S.)--West Virginia University, 1999. Title from document title page. Document formatted into pages; contains ix, 117 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 83-84).

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Choi, Wonchang. "Flexural Behavior of Prestressed Girder with High Strength Concrete." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-10302006-114609/.

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The advantages of using high strength concrete (HSC) have led to an increase in the typical span and a reduction of the weight of prestressed girders used for bridges. However, growing demands to utilize HSC require a reassessment of current provisions of the design codes. The objective of one of the research projects, recently initiated and sponsored by the National Cooperative Highway Research Program (NCHRP), NCHRP Project 12-64, conducted at North Carolina State University is to extend the use of the current AASHTO LRFD design specifications to include compressive strength up to 18,000 psi (124 MPa) for reinforced and prestressed concrete members in flexure and compression. This thesis deals with one part of this project. Nine full-size AASHTO girders are examined to investigate the behavior of using different concrete compressive strength and subjected to the flexural loadings. The experimental program includes three different configurations of prestressed girders with and without a deck slab to investigate the behavior for the following cases: 1) the compression zone consists of normal strength concrete (NSC) only; 2) the compression zone consists of HSC only; and 3) the compression zone consists of a combination of two different strengths of concrete. An analytical model is developed to determine the ultimate flexural resistance for prestressed girders with and without normal compressive strength concrete. The research also includes investigation of the transfer length and the prestress losses of HSC prestressed girders. Based on materials testing and extensive data collected from the literature, a new equation is proposed to calculate the elastic modulus for normal and high strength concrete.

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Jackson, Rahsean LaNaul. "Vibration and Flexural Strength Characteristics of Composite Castellated Beams." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/31242.

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With the development of lightweight concrete and design optimizations, floor vibration problems are becoming a serious serviceability problem. The castellated beam is a prime example and was the focus of this study. The vibration and flexural strength performance were verified in this paper. The vibration characteristics of castellated beams were examined using experimental and analytical test methods. The effective moment of inertia is essential to accurately predict the frequency and deflection of a floor system due to human occupancy. Since castellated beams have non-prismatic cross-sections, their effective moment of inertia is an uncertainty and was verified in this study. This paper confirmed the accuracy of the AISC Design Guide procedures used in for prismatic beam, when applied to castellated beams. The flexural strength of various composite castellated beam were studied. Three full-scale specimens were tested to failure to evaluate their yield and maximum applied load. Each specimensâ moment strength was verified based on span, beam properties, concrete slab, and amount of shear connection. Master of Science

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Peng, Jun, and 彭军. "Strain gradient effects on flexural strength and ductility design of normal-strength RC beams and columns." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48329630.

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The stress-strain characteristics of concrete developed in flexure is very important for flexural strength design of reinforced concrete (RC) members. In current RC design codes, the stress-strain curve of concrete developed in flexure is obtained by scaling down the uni-axial stress-strain curve to account for the strain gradient effect. Therefore, the maximum concrete stress that can be developed under flexure is smaller than its uni-axial strength, and the use of which always underestimates the flexural strength of RC beams and columns even though the safety factors for materials are taken as unity. Furthermore, the value of strength underestimation was different for RC beams and columns, which indicates that the extent of strain gradient will affect the maximum concrete stress and stress-strain curve developed under flexure. To investigate the maximum concrete stress, 29 column specimens were fabricated and tested in this study. They were divided into 9 groups, each of which was poured from the same batch of concrete and contained specimens with identical cross-section properties. In each group, one specimen was tested under concentric load while the rest was/were subjected to eccentric or horizontal load. To study the strain gradient effects, the ratio of the maximum concrete compressive stress developed in the eccentrically/horizontally loaded specimens to the maximum uni-axial compressive stress developed in the counterpart concentrically loaded specimens, denoted by k3, is determined based on axial force and moment equilibriums. Subsequently, the concrete stress block parameters and the equivalent rectangular concrete stress block parameters are determined. It is found that the ratios of the maximum and equivalent concrete stress to uni-axial cylinder strength, denoted respectively by k3 and , depend significantly on strain gradient, while that of the depth of stress block to neutral axis depth, denoted by , remains relatively constant with strain gradient. Design equations are proposed to relate and  with strain gradient for strength calculation, whose applicability is verified by comparing the strengths of RC beams and columns tested by various researchers with their theoretical strengths predicted by the proposed parameters and those evaluated based on provisions of RC codes. Based on the test results, the stress-strain curve of normal-strength concrete (NSC) developed under strain gradient is derived using least-square method by minimising the errors between the theoretical axial load and moment and the respective measured values. Two formulas are developed to derive the flexural stress-strain curve, whose applicability is verified by comparing the predicted strength with those measured by other researchers. Lastly, the application of the proposed stress-block parameters and stress-strain curve of NSC will be illustrated by developing some charts for flexural strength design of NSC beams and columns. The application will further be extended to develop strength-ductility charts for NSC beams and columns, which enable simultaneous design of strength and ductility. By adopting the proposed design charts, the flexural strength design, as well as that of the plastic hinge forming mechanism during extreme events, will be more accurate. The resulting design will be safer, more environmentally friendly and cost effective. published_or_final_version Civil Engineering Doctoral Doctor of Philosophy

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Lam, Weng Kin. "Prediction of 28-day compressive strength of Macau cement." Thesis, University of Macau, 2003. http://umaclib3.umac.mo/record=b1445095.

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Ulker, Elcin. "Comparison Of Compressive Strength Test Procedures For Blended Cements." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612506/index.pdf.

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The aim of this thesis is to twofold, in order to demonstrate the variabilities that can be faced within the compressive strength of blended cements, one blended cement namely CEM IV / B (P-V) 32.5N is selected and the 28-day compressive strength is obtained by 16 different laboratories following TS EN 196-1 standard. Later, to show the variabilities that could be faced by different standards, three different cement types were selected and their compressive strengths are determined following two procedures first with TS EN 196-1, later with similar procedure described in ASTM. The strength of cement is determined by TS EN 196-1 in Turkey that is the same for all types of cements. However, American cement producers use different standards for testing the strength of Portland cement and blended cements. The main difference is the amount of water utilized in producing the cement mortar. It was observed that for Portland and Portland composite cements there is not any significant difference in between the compressive strength results of cement mortars prepared by both methods. However, for pozzolanic cements, there is much deviance in the compressive strength results of cement mortars prepared by TS EN 196-1.

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Ip, Felix. "Compressive strength and modulus of elasticity of masonry prisms." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0019/MQ48451.pdf.

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Guy, Teresa A. (Teresa Ann). "Compressive residual strength of graphite/epoxy laminates after impact." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/43188.

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Vincent, Edward Creed. "Compressive Creep of a Lightweight, High Strength Concrete Mixture." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/30962.

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Concrete undergoes volumetric changes throughout its service life. These changes are a result of applied loads and shrinkage. Applied loads result in an instantaneous recoverable elastic deformation and a slow, time dependent, inelastic deformation called creep. Creep without moisture loss is referred to as basic creep and with moisture loss is referred to as drying creep. Shrinkage is the combination of autogeneous, drying, and carbonation shrinkage. The combination of creep, shrinkage, and elastic deformation is referred to as total strain. The prestressed concrete beams in the Chickahominy River Bridge have been fabricated with a lightweight, high strength concrete mixture (LTHSC). Laboratory test specimens have been cast using the concrete materials and mixture proportions used in the fabrication of the bridge beams. Two standard cure and two match cure batches have been loaded for 329 and 251 days, respectively. Prestress losses are generally calculated with the total strain predicted by the American Concrete Institute Committee 209 recommendations, ACI 209, or the European design code, CEB Model Code 90. Two additional models that have been proposed are the B3 model by Bazant and Baweja, and the GL2000 model proposed by Gardner and Lockman. The four models are analyzed to determine the most precise model for the LTHSC mixture. Only ACI 209 considered lightweight aggregates during model development. GL2000 considers aggregate stiffness in the model. ACI 209 was the best predictor of total strain and individual time dependent deformations for the accelerated cure specimens. CEB Mode Code 90 was the best predictor of total strain for the standard cure specimens. The best overall predictor of time dependent deformations was the GL2000 model for the standard cure specimens. Master of Science

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Ip, Felix (Mong Kau Felix) Carleton University Dissertation Engineering Civil and Environmental. "Compressive strength and modulus of elasticity of masonry prisms." Ottawa, 1999.

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Violette, Melanie Glenn. "Time-dependent compressive strength of unidirectional viscoelastic composite materials /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.

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Yosefani, Anas. "Flexural Strength, Ductility, and Serviceability of Beams that Contain High-Strength Steel Reinforcement and High-Grade Concrete." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4402.

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Utilizing the higher capacity steel in design can provide additional advantages to the concrete construction industry including a reduction of congestion, improved concrete placement, reduction in the required reinforcement and cross sections which would lead to savings in materials, shipping, and placement costs. Using high-strength reinforcement is expected to impact the design provisions of ACI 318 code and other related codes. The Applied Technology Council (ATC-115) report "Roadmap for the Use of High-Strength Reinforcement in Reinforced Concrete Design" has identified key design issues that are affected by the use of high-strength reinforcement. Also, ACI ITG-6, "Design Guide for the Use of ASTM A1035 Grade 100 Steel Bars for Structural Concrete" and NCHRP Report 679, "Design of Concrete Structures Using High-Strength Steel Reinforcement" have made progress towards identifying how code provisions in ACI 318 and AASHTO could be changed to incorporate high-strength reinforcement. The current research aims to provide a closer investigation of the behavior of beams reinforced with high-strength steel bars (including ASTM A615 Grade 100 and ASTM A1035 Grades 100 and 120) and high-strength concrete up to 12000 psi. Focus of the research is on key design issues including: ductility, stiffness, deflection, and cracking. The research includes an extensive review of current literature, an analytical study and conforming experimental tests, and is directed to provide a number of recommendations and design guidelines for design of beams reinforced with high-strength concrete and high-strength steel. Topics investigated include: strain limits (tension-controlled and compression-controlled, and minimum strain in steel); possible change for strength reduction factor equation for transition zone (Φ); evaluation of the minimum reinforcement ratio (þmin); recommendations regarding limiting the maximum stress for the high-strength reinforcement; and prediction of deflection and crack width at service load levels. Moreover, this research includes long-term deflection test of a beam made with high grade concrete and high-strength steel under sustained load for twelve months to evaluate the creep deflection and to insure the appropriateness of the current ACI 318 time-dependent factor, λ, which does not consider the yield strength of reinforcement and the concrete grade.

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Heying, Jamie John Gratton David G. "Flexural strength of interim fixed prosthesis materials after simulated function." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/377.

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Hettiarachchi, M. T. P. "The theoretical prediction of the flexural strength of structural plywood." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/11768.

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Heying, Jamie John. "Flexural strength of interim fixed prosthesis materials after simulated function." Thesis, University of Iowa, 2009. https://ir.uiowa.edu/etd/377.

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Statement of Problem There are limited studies evaluating the effect of a cyclic load on interim fixed prosthetic materials and its effect on flexural strength. Purpose of Study 1) To verify the flexural strength of previously studied interim fixed prosthetic materials. 2) To establish the flexural strength of new, advanced generation and untested interim fixed prosthetic materials. 3) To determine the effect of cyclic load on the flexural strength of interim fixed prosthetic materials. Materials and Methods Bar-type specimens of Caulk Temporary Bridge Resin, VitaVM CC, Protemp 3 Garant and Radica were fabricated according to International Standards Organization 4049 and American National Standards Institute/American Dental Association specification 27. After being stored in distilled water for 10 days, specimens were divided into Noncycled and Cycled Groups. The Noncycled Group specimens were fractured under a 3-point loading in a Bose Electroforce 3300 testing instrument at a crosshead speed of 0.75 mm/min. Cycled Groups specimens underwent a 6-12 Newton 3 Hertz cyclic load for 20,000 cycles in a Bose Electroforce 3300 testing instrument. Immediately following completion of the cycles, the specimens were fractured under a 3-point loading. Maximal loads to fracture in Newtons were recorded and mean flexural strengths were calculated (n = 20 per group). Comparisons were made with analysis of variance and Tukey's Multiple Comparison Test. Results Noncycled (NC) and Cycled (C) groups order of mean flexural strengths (MPa) from lowest to highest mean were as follows: Caulk (Noncycled - 53.83; C - 60.02), Vita VM CC (NC - 65.96; C - 66.83), Protemp 3 Garant (NC - 75.85; C - 77.18), and Radica (NC - 106.1; C - 115.96). In the Noncycled and Cycled groups, Radica was statistically superior when compared to all materials and Protemp 3 Garant was statistically superior to Caulk Temporary Bridge Resin. There was no statistically significant difference between the material's flexural strengths before and after cycles. Conclusion Within the limitations of this study, 20,000 cyclic loads of 6-12 Newtons at 3 Hertz did not have a significant effect on the flexural strength of interim fixed prosthetic materials. Radica demonstrated significantly superior flexural strength over other materials tested.

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Magnani, Marco. "Effect of fibre damage on compressive strength of CFRP laminates." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22322/.

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This work investigates the effects of fibre damage on compressive strength of CFRP laminates under compressive loading. To characterise the influence of fibre failure, parameters such as the length and depth of the damaged region are considered. 3D Finite Element models are created to reproduce the artificially damaged laminates and gain an initial understanding of how fibre damage may affect the specimens. Secondly, coupons are manufactured and tested in compression following ASTM D 7137. DIC equipment is employed to better visualise the behaviour of the loaded components and gain insight on the effects of the different damage configurations. The results show that although fibre damage reduces the compressive strength of the tested components, the configuration of such damage has little influence. Interestingly, damage configuration seems to play a pivotal role on the development of delamination and kinks at final failure.

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Taylor, Susan Elizabeth. "Compressive membrane action in high strength concrete bridge deck slabs." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314163.

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Fraser, Douglas (Douglas H. ). "Triptycene side unit effects on compressive yield strength in polycarbonates." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35071.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. Includes bibliographical references (leaf 25). Polycarbonates have long been studied for their excellent mechanical toughness. Adding side units to polycarbonate could increase physical properties of the polymer. The role of triptycene in polycarbonate was studied by adding a low concentration of triptycene-containing polymer chains, and using compression testing. The triptycene polycarbonate was a blend created from two separate products. Differential Scanning Calorimetry was used to determine if the samples had phase separated. Thermal degradation of the samples was checked for using Thermogravimetric Analysis. Results indicated that triptycene-containing polycarbonates had higher compressive yield strengths than non-triptycene polycarbonates. The polymers were stronger due to the interlocking mechanism and the steric hindrance of the triptycene units. The design of strengthening polymers by adding triptycene units could prove useful to improve high performing polymers, or to give low molecular weight polymers more stability. by Douglas Fraser. S.B.

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Gogol, Volker R. "The compressive strength of fly ash concrete and its mineralogy." Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/8457.

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Includes bibliographical references. The use of fly ash as a cement extender in portland cement concrete is well established. Strict requirements are set for the fly ash on its physical properties and chemical composition to ensme its successful application as a partial replacement material for cement. An investigation was undertaken into the effectiveness and properties of a high carbon clinker ash when used as a cement extender at a 30 direct mass to mass substitution for portland cement. The clinker ash came from the Van Eck power station in Windhoek, Namibia and was milled to pass a 63micron sieve. For comparison fly ashes from the Escom power stations of Lethabo, Duvha and Matla were used. Both concrete and pure paste specimens were prepared for the evaluations.

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Bettadahalli, Channakeshava Anil. "Non-Local Modeling of the Compressive Strength of Composite Structures." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0018.

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La rupture en compression des composites à fibers de carbone longues est due à des mécanismes complexes. La connaissance de ces mécanismes est importante pour la conception des structures composites car la résistance à la compression et la rigidité des stratifiés sont supposées inférieures à leur résistance à la traction. De plus, la rupture en compression est un mécanisme de ruine non locale qui dépend de la structure du composite (épaisseur de la couche, gradient de charge), ce qui en fait une particularité. Ce mécanisme a été décrit et modélisé dans la littérature avec des outils numériques appropriés et des expériences qui ont pris en compte cet effet. Il existe de nombreux articles dans la littérature intégrant le phénomène de microflambage pour capter l’instabilité locale. Mais uniquement quelques chercheurs ont modélisé le mécanisme à l'échelle structurelle dite mesoscopique. Par exemple, Drapier et collaborateurs ont proposé un modèle homogénéisé en 2D, qui prend en compte les défauts d'alignement initial des fibers, la plasticité de la matrice et les paramètres structurels. Le modèle permet de prédire les modes de microflambage élastique et de prévoir la défaillance en compression. Mais le modèle est construit pour des stratifiés unidirectionnels 2D et suppose que le microflambage est périodique dans la direction des fibers, un seul gradient dans la direction de l'épaisseur est pris en compte et l'influence du désalignement n'est pas complètement appréhendée.Par conséquent, pour étendre les développements de ces travaux, de nouveaux modèles d'éléments finis non locaux sont développés dans cette thèse : l'un avec des éléments de structures proposés de base par ABAQUS®, appelé modèle BNL (Beam Non-Local) et l'autre avec le sous-programme UEL (User Element) d'ABAQUS®, appelé modèle HOMNL (Homogenized Non-Local Model), mis en oeuvre sous la forme d’un élément utilisateur (NL U32), qui peut être utilisé dans le but de prédire la résistance à la compression des plis stratifiés unidirectionnels mais également pour les composites tissés (2D voire 3D). Les effets de non linéarités géométriques et matériels sont bien évidemment pris en compte dans cette modélisation. Avec le modèle BNL, il est possible d’appréhender le mécanisme en 2D et 3D dans des stratifiés de composites unidirectionnels. Les résultats de la bibliographie ont été confirmés et de nouveaux résultats ont été générés, comme par exemple, le mode élastique en 3D ou le mécanisme de microflambage en flexion dans un stratifié. La largeur et l'angle de la bande de pliage sont déterminés automatiquement par ce modèle. Dans un cadre plus général, la validation de l'élément NL U32 a été effectuée par rapport aux éléments classiques ABAQUS® pour les cas linéaires et non linéaires (géométrie et matériau). Les propriétés classiques (élastiques et plastiques) et non locales des matériaux (élastiques) sont identifiées par comparaison avec les réponses d'un élément de volume représentatif (RVE) de microstructures totalement hétérogènes. Certains résultats de résistances ont été validés avec la bibliographie. L'élément utilisateur non local développé (NL U32) est en 2D dans cette thèse mais il peut être étendu très facilement à un cas en 3D, ce qui reste une des perspectives futures.Dans ce travail, ABAQUS® v2017, DAKOTA v6.10.0, PARAVIEW v5.8.0 sont les logiciels utilisés et FORTRAN, Python sont les langages de programmation The compressive failure of long carbon fiber composites is due to complex mechanisms. The knowledge of these mechanisms is important for the design of composite structures because the compressive strength and stiffness of laminates are assumed less than their tensile strength. Further, compressive failure is a mechanism of non-local ruin that depends on the composite structure (layer thickness, load gradient) which makes it a peculiarity. The mechanism has been described and modelled in the literature with suitable numerical tools and experiments that accounted for this effect. There are many articles in the literature regarding the modelling of composites compressive behavior, particularly the microbuckling phenomenon / local instability. But only a few researchers modelled the mechanism at the structural/mesoscopic scale. For example, Drapier et al., [D3] proposed a 2D homogenized model, which takes into account fiber initial alignment defects, matrix plasticity and structural parameters. The model is successful in predicting the elastic microbuckling modes and to predict the failure. But the model is built for 2D unidirectional laminates and assumes microbuckling is periodic in the fiber direction, just one gradient in the thickness direction is taken into account and the influence of the misalignment is not completely described [D4]. Therefore, to extend the developments of these works ([D1],[D3],[G1],[G4]), new non-local finite element models are developed: one with using ABAQUS® in-built structural elements, named Beam Non-Local (BNL) model and the other with User Element (UEL) subroutine of ABAQUS®, named Homogenized Non-Local Model (HOMNL), implemented in the user element (NL U32), which can be applied with the aim to predict the compressive strength of unidirectional plies/laminates and also for woven composites (2D and 3D). Both the non-linear geometrical and material effects are taken into account in this model. With the BNL model, it is possible to capture the mechanism in 2D and 3D space for laminates of unidirectional composites. Results of the bibliography have been confirmed and new results are presented, for example, the elastic mode in 3D or the mechanism under bending. The width and angle of the kink band are determined by this model. In the framework of more general, the validation of the NL U32 element has been performed with respect to ABAQUS® classical elements for both linear and non-linear (geometry and material) cases. The classical (elastic and plastic) and non-local material properties (elastic) are identified by comparison to the responses of a Representative Volume Element (RVE) of full heterogenous microstructures. Some results have been validated with the bibliography. The developed non-local user element (NL U32) is 2D in this thesis and it can be extended easily to a 3D case, which remains one of the future perspectives.In this work, ABAQUS® v2017, DAKOTA v6.10.0, PARAVIEW v5.8.0 are the softwares used and FORTRAN, Python are the programming languages used

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Kumar, Satish. "Study of flexural and compressive strength of glass fiber reinforced graphite composite." Thesis, 2013. http://ethesis.nitrkl.ac.in/5176/1/109CR0666.pdf.

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The attempt of this work is to development of glass fiber reinforced graphite composite by the addition of binder solid pitch. Different physical properties such as bulk density, apparent porosity, flexural strength and compressive strength are assessed with respect to different binder content and glass fiber reinforcement. Binder content is increasing with increment of fiber reinforcement, which ultimately increasing the porosity or decreasing the bulk density. Highest flexural strength 128 kg/cm2 is obtained under optimum 0.5 wt. % fibers and 20 wt. % binder content. Optimum content of glass fiber follows crack wake bridging mechanism and enhancement of flexural strength. Highest compressive strength 118 Kg/cm2 is observed in presence of 0.5 wt% fibers and 25 wt% binder pitch. More fiber content jumbled up during mixing and develops non-uniform matrix which reduces the mechanical properties enormously at even green stage.

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Dara, Sepehr. "Guidelines for preliminary design of beams in eccentrically braced frames." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-05-1495.

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Seismic-resistant steel eccentrically braced frames (EBFs) are designed so that that yielding during earthquake loading is restricted primarily to the ductile links. To achieve this behavior, all members other than the link are designed to be stronger than the link, i.e. to develop the capacity of the link. However, satisfying these capacity design requirements for the beam segment outside of the link can be difficult in the overall design process of an EBF. In some cases, it may be necessary to make significant changes to the configuration of the EBF in order to satisfy beam design requirements. If this discovery is made late in the design process, such changes can be costly. The overall goal of this research was to develop guidelines for preliminary design of EBFs that will result in configurations where the beam is likely to satisfy capacity design requirements. Simplified approximate equations were developed to predict the axial force and moment in the beam segment outside of the link when link ultimate strength is developed. These equations, although approximate, provided significant insight into variables that affect capacity design of the beam. These equations were then used to conduct an extensive series of parametric studies on a wide variety of EBF configurations. The results of these studies show that the most important variables affecting beam design are 1) the nondimensional link length, 2) the ratio of web area to total area for the wide flange section used for the beam and link, 3) the angle between the brace and the beam, and 4) the flexural stiffness of the brace relative to the beam. Recommendations are provided for selection of values for these variables in preliminary design. text

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Dissertations / Theses on the topic 'Compressive strength and flexural strength'

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