Dissertations / Theses on the topic 'Testing samples for compressive strength'

Os ensaios não destrutivos servem como uma importante ferramenta para a análise de estruturas de concreto armado. A utilização de ensaios de velocidade de propagação do pulso ultra-sônico (VPU) permite realizar um acompanhamento das características do material ao longo de sua vida útil. Através da análise dos dados obtidos, pode-se averiguar a uniformidade do concreto, controlar a sua qualidade, acompanhar sua deterioração e, através de comparação com corpos de prova de referência e, até mesmo, estimar a resistência do mesmo. No entanto, as técnicas atuais para análise dos resultados coletados são, em grande parte, baseadas na sensibilidade dos profissionais que as aplicam. Para facilitar o controle e inspeção de estruturas de concreto armado é fundamental desenvolver estratégias para tornar esta análise mais simples e precisa. Este trabalho se baseia na hipótese de que a aplicação de Redes Neurais Artificiais (RNAs) pode gerar modelos de relacionamento úteis e acurados entre as características do concreto, sua compacidade e sua resistência à compressão. O intuito é determinar se com o uso de RNAs é possível estabelecer relações não-lineares que permitam estimar a resistência do concreto a partir do conhecimento de algumas propriedades básicas e da verificação da sua compacidade por meio de ensaios de VPU. Os resultados indicam que as RNAs podem ser usadas para gerar métodos numéricos robustos e flexíveis para estimativa da resistência à compressão a partir de dados de VPU. O estudo evidencia uma considerável melhora nos resultados de estimação da resistência quando se empregam modelos neurais, em comparação a modelos estatísticos tradicionais. Para os dados coletados, provenientes de diversas pesquisas, os modelos tradicionais geram estimativas com coeficientes de determinação que não ultrapassam um valor de R² de 0,40. Já as redes neurais conseguem ajustes com R² da ordem de 0,90. Além de contribuir para uma melhor análise de situações em que haja dúvidas sobre a resistência ou homogeneidade de elementos de concreto, o trabalho demonstra que modelos neurais são uma forma eficiente de ordenar e transferir conhecimento não estruturado. Constatou-se, ainda, que, dada sua capacidade de aprendizagem e de generalização do conhecimento adquirido, as RNAs se constituem em um meio rápido e preciso para modelagem de fenômenos complexos.<br>Nondestructive Testing (NDT) techniques are useful tools for analyzing reinforced concrete (RC) structures. The use of Ultrassonic Pulse Velocity (UPV) measurements enables the monitoring of changes in some critical characteristics of concrete over the service life of a structure. The interpretation of the data collected allows an assessment of concrete uniformity, and can be used to perform quality control, to monitor deterioration and even, by means of comparison against reference samples, to estimate compressive strength. Nonetheless, the current techniques for UPV data analysis are, on a large degree, based on the sensitivity of the professionals who apply these tests. For accurate diagnosis it is necessary to consider the various factors and conditions that can affect the results. To proper control and inspect RC facilities it is essential to develop appropriate strategies to make the task of data interpretation easier and more accurate. This work is based on the notion that using Artificial Neural Networks (ANNs) is a feasible way to generate workable estimation models correlating concrete characteristics, compacity and compressive strength. The goal is to determine if it is possible to establish models based on non-linear relationships that are capable of estimating with good accuracy the concrete strength based on previous knowledge of some basic material characteristics and UPV measurements. The study shows that this goal is achievable and indicates that neural models perform better than traditional statistical models. For the data collected in this work, provided by various researchers, traditional regression models cannot exceed R² = 0.40, while the use of ANNs allows the creation of models that can reach a determination coefficient R² = 0.90. The results make clear that, besides contributing to better the analysis of situations where there is doubts regarding concrete strength or uniformity, neural models are an efficient way to order and transfer unstructured knowledge. It was shown that, given the learning capacity and its ability to generalize acquired information into mathematical patterns, ANNs are a quick and adequate way to model complex phenomena.

In this thesis different mechanical properties for shotcrete (sprayed concrete) such as compression strength, bond strength, bending tensile strength, elastic modulus, free and restrained shrinkage as a function of its age was investigated. One of the main issues was to investigate the difference between ordinary cast concrete and shotcrete. Reliable material data for young and hardening shotcrete is scarce which in the past have made such comparisons difficult. Also, less accurate data representative for cast concrete has often been used in numerical modelling and design analyses. The focus of the project has particularly been on the properties bond strength and restrained shrinkage for which two new testing methods has been developed and evaluated. Microstructural studies have also been performed as a complement to the bond strength testing. The bond to rock is one of the most important properties for shotcrete used as rock reinforcement. During the very first time after spraying the physical properties and the bond to the rock depend on the set accelerator and the micro structure that is formed. The investigation of early age bond strength of shotcrete is of great importance both from a production perspective and a safety perspective. The newly developed method was tested and evaluated and proved that it can be used for bond strength testing already from a couple of hours after shotcreting. The bond, or adhesion, depends on several factors such as texture of the rock, the type of accelerator, application technique, etc. In this work the development of the microstructure in the interfacial transition zone (ITZ) and strength of the bond was investigated. The results show that the bond strength is related to the hydration process, i.e. the strength gain of the shotcrete. The early development of the ITZ was here studied using a scanning electron microscope (SEM) making it possible to observe changes over time, before and after proper cement hydration. Restrained shrinkage cracking of shotcrete, especially in the case of shotcrete sprayed on soft drains that are parts of a tunnel lining not continuously bonded to the rock, can be detrimental for the sustainability of an infrastructure tunnel system. Maintenance and repair costs can be high over time. It is shown that the developed test method realistically captures the behaviour of shotcrete drains on hard rock in situ. The method can be used in the evaluation of different technical solutions for avoiding or minimizing shrinkage cracks in shotcreted soft drains. It can also be used to assess the performance of shotcrete fully bonded to a rock surface, with respect to the ability to prevent cracking or to distribute possible shrinkage damage into several fine cracks instead of one wide.<br><p>QC 20140526</p>

The diploma thesis deals with non-destructive testing of concrete as well as with the relationship between determined parameters and the compressive strength of concrete. The thesis is mainly focused on the ultrasonic pulse velocity method and the rebound hammer test. The experimental part of the thesis describes non-destructive tests performed on concrete blocks. The compressive strength was tested on the drill cores taken from the concrete blocks. The aim of this thesis is to find regression models of the relationship between the compressive strength and non-destructive parameters, and the subsequent analysis of the results.

Ett företag som tillverkar hydrauliska snabbkopplingar har genom regelbundna kvalitetsprover upptäckt att vissa låskulor till snabbkopplingarnas låsmekanism plötsligt fått en bristande kvalité och spricker vid belastning. Låskulorna är gjorda av rostfritt stål och har en viktig funktion i låsmekanismen. Om de spricker vid användning kan det leda till konsekvenser med materiella skador eller personskador. Företaget vill förekomma eventuella kvalitetsproblem och måste därför säkerställa att låskulorna har rätt hållfasthet. Låskulorna köps in från en underleverantör och företaget vill därför utveckla en provmetod som provar låskulornas materialegenskaper när de levereras till fabriken. Arbetet i denna rapport syftar till att hjälpa företaget utveckla en sådan provmetod. Ett första steg är att undersöka orsaken till att låskulorna spricker. Materialanalyser utförs av ett materiallaboratorium för att fastställa vilka faktorer i materialet som orsakar brott i låskulorna. Analyserna visar att låskulorna sannolikt spricker på grund av en ökad sprödhet i materialet. Sprödheten beror på att martensiten i materialet är dåligt anlöpt samt en stor mängd karbider. Med orsaken till sprickorna fastställd undersöks befintliga metoder för materialprovning. En provmetod måste prova materialet i färdigtillverkade låskulor eftersom låskulornas tillverkningsprocess påverkar materialegenskaperna. Många av de standardiserade provmetoderna är dock svåra att tillämpa på låskulorna med anledning av låskulornas geometri och små dimensioner. En form av slagprov och pressprov utförs på låskulorna. Ett av syftena med proven är att undersöka om de är lämpliga att använda som provmetod. Genom proven framträder olika materialegenskaper för olika låskulor. Resultaten är dock inte jämförbara låskulorna emellan och proven anses inte vara lämpliga som provmetod. Även ett utmattningsprov utförs på låskulorna genom en upprepande belastning i en snabbkoppling. Detta prov är inte heller lämpligt att använda som provmetod då provet är mycket tidskrävande samt att det finns vissa osäkerheter kring provresultatet. I detta arbete undersöks även två nyligen framtagna provmetoder för kulor till kullager och möjligheten att tillämpa dessa provmetoder på låskulorna. I undersökningen jämförs de båda provmetoderna med avseende på utförande samt framtagning av provkropp. Även en spänningsanalys av en låskula belastad i en snabbkoppling utförs för att ta reda på i vilket område av låskulan de maximala spänningarna uppstår. Undersökningen ger att enbart en provmetod är intressant för fortsatt arbete.   Den provmetod som föreslås i detta arbete kallas "the notched ball test" (NBT). Provmetoden innebär att en djup och smal skåra bearbetas i en låskula som sedan belastas med en tryckande kraft vinkelrätt mot skåran tills brott uppstår. Den maximala spänningen som verkar vid brottet beräknas med en enkel ekvation och används som mått för låskulans hållfasthet. Provmetoden är lämplig då den går att utföra med befintlig utrustning på företaget, den provar materialet i färdigtillverkade låskulor samt i samma område som de maximala spänningarna i en låskula belastad i en snabbkoppling uppstår. NBT nyttjar även dragspänningar vilket är fördelaktigt när sprödhet ska upptäckas i ett material. För att fastställa hur olika materialegenskaper samt geometrier för provkroppen påverkar provresultaten utförs en djupare analys av provmetoden. Analysen ger även vilka geometrier som bör användas vid utförandet av NBT samt värdet för den konstant som används vid beräkning av brottspänningen. Praktiska prov av NBT utförs inte i detta arbete men rapporten innefattar slutsatser om provmetoden och rekommendationer till företaget hur ett fortsatt arbete med NBT kan utföras.<br>A company that manufactures hydraulic quick-couplings has discovered through regular quality checks that the quality of some of the locking balls for the locking mechanism in the quick couplings suddenly has become insufficient and the locking balls rupture under load. The locking balls are made of stainless steel and if they rupture during usage the consequences can be material damage or even personal injury. The company wants to prevent any quality problems and must therefore ensure that the strength of the locking balls is sufficient. The locking balls are purchased from a subcontractor and the company would therefore like to develop a method for strength testing locking balls delivered to the factory. This thesis aims to help the company in developing such a method.  A first step is to investigate the cause of the locking balls rupture. Material analyses are executed by a material laboratory in order to determine what features in the material that causes the ruptures. The analyses shows that rupture is probably caused by an increased brittleness in the material and the brittleness is a consequence of less tempered martensite and a high amount of carbides. With the cause of rupture determined, existing methods for testing material properties is studied. It is important that strength testing is carried out with test specimens prepared from the actual locking balls. Otherwise the influence of the locking balls manufacturing process on the material properties is not taking into account. Many of the standardized methods for testing material properties, however, are hard to apply to the locking balls due to the geometry and small dimensions of the locking balls. A kind of impact test and compression test is performed. One of the purposes with the tests is to investigate if they are adequate for strength testing the locking balls. The results of the tests, however, are not suitable for comparison. Also, a fatigue test of the locking balls is performed by a repetitive loading of a quick coupling. The fatigue test is, however, time consuming and there are uncertainties in the test results. None of these tests is considered suitable as a strength testing method. In this thesis, two recently developed methods for strength testing ceramic balls and the possibility to apply these methods on the locking balls is studied. The study includes an analysis of the stress distribution in a locking ball under load to determine in which region the highest stresses occur. The study provides that only one of the methods is suitable for the locking balls due to differences in preparing the test specimen and which region of the locking ball that is tested in each method. The strength testing method that is proposed in this thesis is called the notched ball test (NBT). In NBT a long and narrow notch is cut in a locking ball which is then loaded in compression perpendicular to the notch until rupture occurs. The maximum stress acting at the rupture is calculated and used to determine the strength of the locking ball. NBT is suitable because it can be performed with existing equipment at the company, the test specimen is prepared from actual locking balls and the test uses tensile stresses which is an advantage when brittleness is to be detected in a material. An analysis of NBT is performed to determine how material properties and different notch geometries is affecting the test results. The analysis also gives some recommendations for notch geometries that should be used when performing NBT as well as a constant that is used when calculating the maximum stress. Practical experiments of NBT are not carried out in this thesis. Instead, conclusions regarding NBT and recommendations for the company on how they should proceed with NBT are given.

Il problema della mitigazione del rischio sismico degli edifici esistenti è in Italia una questione di primaria importanza, sia a causa dell’elevata vulnerabilità strutturale di gran parte del patrimonio edilizio esistente, sia a causa, nel caso degli edifici storici, del loro valore artistico e culturale. In un’ottica di prevenzione, date le scarse risorse disponibili e data la necessità di intervenire nel minor tempo possibile, risulta fondamentale poter disporre di strumenti affidabili che consentano di evitare inaccurate valutazioni di sicurezza sismica. La presente tesi affronta quindi alcune delle problematiche più importanti presenti nella pratica ingegneristica nella valutazione della sicurezza degli edifici esistenti, con particolare riferimento agli edifici in muratura ed in cemento armato. In particolare, dopo aver brevemente descritto le principali vulnerabilità degli edifici in muratura, viene presentata quindi una analisi critica approfondita della letteratura disponibile del metodo di modellazione a telaio equivalente. Tale metodo risulta essere oggi lo strumento di modellazione più diffuso nella pratica ingegneristica oltre ad essere consigliato da diversi codici normativi nazionali e internazionali. Da tale analisi, sono stati definiti limiti e campi d’applicazione per il suo corretto di utilizzo. In particolare, il telaio equivalente può essere utilizzato come primo approccio di tipo conservativo per lo studio della risposta sismica di edifici caratterizzati da un comportamento scatolare a prevalente risposta nel piano e con una disposizione delle aperture pressoché regolare. Diversamente da quanto accade per gli edifici esistenti in muratura, i metodi di modellazione utilizzati nella valutazione sismica degli edifici in cemento armato risultano piuttosto consolidati anche nella pratica ingegneristica. In questo caso, le maggiori fonti di incertezza presenti nella valutazione sono fornite dalla stima delle caratteristiche meccaniche delle proprietà meccaniche in situ del calcestruzzo gettato in opera. L’alta dispersione dei parametri meccanici spesso presente all’interno degli edifici esistenti in c.a., rende infatti ardua la loro rappresentazione. In questa tesi, viene proposto e applicato a sei casi studio un metodo statistico per la caratterizzazione meccanica del calcestruzzo capace di isolare alcune delle fonti di dispersione. Dall’analisi dei risultati è emerso come tale metodo sia capace di fornire una rappresentazione più accurata della dispersione effettivamente presente e di ridurre la dispersione dei risultati delle prove in situ.<br>The mitigation of the seismic risk of existing buildings is a relevant issue in Italy due both to the high seismic vulnerability of most of the building stock and, in case of historic masonry buildings, to their high artistic and cultural value. From this point of view, due to limited resources available and the need to intervene as quickly as possible, it is essential to have reliable tools in order to avoid inaccurate seismic assessments. This thesis addresses some of the most common problems that are present in the engineering practice related to the structural assessment of existing URM and RC buildings. After having briefly described the main vulnerability of masonry buildings, this work presents a critical analysis of the equivalent frame modelling approach through an in-depth analysis of the literature. This method is today the most widespread modelling tool in the engineering practice, and suggested by national and international standards. From this analysis, the limits and the applicability domain of this method have been defined. As a general result, it has been shown that the equivalent frame model can be used as a conservative approach for the study of the global response of buildings with box-like behavior and quite regular arrangement of openings. Unlike masonry buildings, the modelling methods used in the professional practice for the seismic assessment of existing RC buildings, are well validated. In this case, one of the most important source of uncertainty is probably the evaluation of the in situ mechanical properties of the concrete. Indeed, the high dispersion of the concrete mechanical parameters makes often inaccurate the seismic assessment of these buildings. In this thesis, a statistical method for the mechanical characterization of concrete is proposed and applied to six case studies. As a result, it is showed that the proposed method is capable of providing a more accurate representation of the actually strength distribution and of reducing the dispersion obtained from in situ tests.

This diploma thesis is focused on methodology for sorting of solid fired bricks for reconstruction of historical buildings. The theorethical part of this thesis includes description of production technology of solid fired bricks and diagnostic methods. In practical part there are these methods aplied on the solid fired bricks, which are intended for reconstruction of the bridge in Sedlec. There are monitored changes in structure of solid fired bricks caused by repeated freezing and defrosting. This changes are monitored by resonant frequency method and ultasonic pulse method.

This thesis deals with building survey of bridge register number 43-011 located near Česká. The part of thesis is literary reaserch dealing with system of management and cotrol of road bridges, precast bridge contructions made with DS-C type girgers and about general diagnostical methods. The practical section contains of in situ diagnostical survey and bridge inspection, laboratory evaluation and comparision, load bearing capacity calculation and suggestion of potencional technical precautions.

High-strength concrete (HSC) belongs in the recent years to frequently used types of concrete. It allows realization of static challenging structures and also shows due to its dense structure greater durability especially against aggressive media. Currently HSC construction realization abroad is not exceptional. It’s using in the Czech Republic is still limited. When realized, then in a small scale in civil engineering works. The realization of high-strength concrete structures is closely related with the concrete construction quality verification. Good efficiency of the quality control methods can provide non-destructive testing methods (NDT), especially when investigating strength of concrete built in structure. A lack on relevant data for non-destructive testing of HSC in technical and normative rules is to be considered as a significant deficiency. Evident for HSC generally is the lack in literature on deeper analysis of the factors affecting their non-destructive testing, as well a meaningful methodology or practically usable calibration relationships. HSC differs from ordinary concrete not only by used components, but also by more compact structure with different strength – elastic characteristics. Considering these differences, HSC strength prediction can not be performed by using calibration relationships developed for ordinary concrete. Moreover, the question is to what extent the current knowledge of the NDT results influencing factors can be considered as valid. The paper presents findings on the effects of the key factors affecting the measurement results of Schmidt hardness method and ultrasonic pulse method, including recommendations for the practical application of these methods. The problematic of static vs. dynamic modulus of elasticity was also solved. Calibration equations for predicting the compressive strength of HSC from the non-destructive testing parameter were elaborated, showing high cohesion among variables and practically usability.

碩士<br>國立中央大學<br>土木工程學系<br>85<br>ABSTRACT The purpose of this study is using proficiency testing to evaluate testing level of Taiwan Construction Engineering Laboratory. The research will concentrate on the test for compressive strength of cylindrical concrete specimens which is the most popular testing item for construction material laboratory. The Quality Assurance Center on civil engineering materials of National Central University ( know as QAC) will be responsible to this research. The expecting results can help to draw up the operating manual for the standard of compressive strength of concrete. QAC will produce the high homogeneity of cylindrical concrete specimens which will be cured twenty- seven days, then send to each participating laboratory to proceed test for compressive strength of cylindrical concrete specimens for twenty-eight days. The result of test will be proceed the statistical analysis and evaluate the proficiency of participating laboratories with the methods of ASTM C802 rule、 Z-scores and ANOVA .key words︰proficiency, cylindrical concrete specimen

碩士<br>國立臺灣科技大學<br>建築系<br>104<br>Recently the world has been facing the global warming issue regarding the increasing number and quantity of CO2. The architecture or the construction ‘realm’ also gave impact through its building material usage. The researchers had been researching for some material which could be used for the green option, then bamboo is one of the solutions upon this problem. Due to its physical characteristic, bamboo is known as the combustible material which is similar to wood or the other carbon-based material. The observation due to its fire safety is needed to carry out for the sufficient bamboo characteristic information under fire condition and fire safety regulation. Fire behavior investigations that have been conducted before mostly upon the glue laminated bamboo (glulam) and some prefabricated bamboos. Currently in Indonesia, most of the architecture is using the raw and un-engineered bamboo. In this research, the specimens that used were the raw bamboo material without being fire-proofed by any chemical compound. A nine-trunk of bamboos were joined into one single big column which taken place as the main structural of the building. One bamboo will be located in the center and surrounded by the other eight-bamboos to make the sacrifice layer as the protection. So that if the fire comes, they may be got burnt before the center. Those un-engineered bamboos were burnt under temperature 700 °C within 5, 10, and 15 minutes burning. For the further investigation, the compression test will be conducted thoroughly to investigate the mechanical properties of bamboo after got burnt. Beside the structural damage observation, several mechanical properties includes the ignition rate, flame spread, the charring rate, the compression stress at the high temperature and water saturation will be investigated more to study the bamboo behavior intensively.

No<br>This paper presents a series of test results of elliptical concrete filled steel tubular (CFST) beams and columns to explore their performance under bending and compression. A total of twenty-six specimens were tested, including eight beams under pure bending and eighteen columns under the combination of bending and compression. The main parameters were the shear span to depth ratio for beams, the slenderness ratio and the load eccentricity for columns. The test results showed that the CFST beams and columns with elliptical sections behaved in ductile manners and were similar to the CFST members with circular sections. Finally, simplified models for predicting the bending strength, the initial and serviceability-level section bending stiffness of the elliptical CFST beams, as well as the axial and eccentric compressive strength of the composite columns were discussed.

The box corer is a relatively new tool used in the geotechnical community for collection of soft seabed sediments. Miniature full flow and model pipeline probes were developed as tools to characterize and obtain soil parameters of soft seabed sediments collected in the box core for design of offshore pipelines and analysis of shallow debris flows. Probes specifically developed for this study include the miniature t-bar, ball, motorized vane (MV), and toroid. The t-bar, ball, and MV were developed to measure intact and remolded undrained shear strengths (su and sur). The t-bar and ball can obtain continuous strength profiles and measure sur at discrete depths in the box corer while the MV measures su and s ur at discrete depths. The toroid is a form of model pipeline testing which was developed to investigate pipe-soil interaction during axial pipeline movement. Vertical loading and displacement rates can be selected for the toroid to mimic axial pipeline displacement for a variety of pipe weights. A load frame for both miniature penetrometer and toroid testing was developed for testing directly on box core samples offshore. This research presents results from offshore and laboratory testing of the box core and recommended testing procedures for full flow and toroid probes on box core samples.

Робота містить всі передбаченні завданням і нормативними документами структурні елементи. Розроблено проект стенду для випробування великогабаритних будівельних матеріалів. Виконано огляд випробувальних стендів інших проектних рішень. Проаналізовано їхні недоліки та запропоновано варіанти вирішення в дані конструкції. Підібрано спеціальне електронне та механічне обладнання під попередньо закладені характеристики. Зроблені розрахунки навантажень силових установок та каркасних з’єднань. Досліджено фактори негативного впливу та створено інструкції з охорони праці<br>The work contains all the structural elements provided by the task and regulations. A project of a stand for testing large construction materials has been developed. A review of test benches of other design solutions was performed. Their shortcomings are analyzed and solutions to these designs are proposed. Special electronic and mechanical equipment is selected for the pre-set characteristics. Load calculations of testing machines and frame connections are made. Factors of negative influence are investigated and instructions on labor protection are created<br>Вступ Розділ 1. Архітектурно-будівельний 1.1 Приклади великогабаритних конструкцій 1.2 Конструкційні рішення для випробування залізобетонних виробів 1.3 Загальна характеристика сучасних випробувальних комплексів 1.4 Випробувальні стенди для проведення випробувань на міцність при стиску та розтягу Розділ 2. Розрахунково-конструктивний 2.1 Основні вимоги до проведення механічних випробувань 2.2 Вимоги до стендів для великогабаритних будівельних матеріалів та конструкцій 2.2.1 Пристрої вимірювання 2.2.2 Визначення прогинів, лінійних деформацій механічними засобами 2.2.3 Електроні засоби для визначення прогинів, деформацій. Конструктивні схеми засобів 2.3 Конструктивні схеми випробувального стенду Розділ 3. Науково дослідний 3.1 Види з’єднань металевих конструкцій 3.2 Класифікація зварних швів 3.3 Класифікація видів зварок 3.4 Болтові з’єднання 3.5 Робота та розрахунок болтів, що працюють на розтяг 3.6 Робота та розрахунок болтів на дію зсувних сил 3.7 Робота і розрахунок з’єднань на високоміцних болтах 3.8 Розрахунок з’єднань на болтах під дією різних силових факторів Розділ 4. Охорона праці 4.1 Оціночна характеристика 4.2 Аналіз травматизмів 4.3 Профілактика травматизму і професійних захворювань 4.4 Гігієнічна оцінка умов праці 4.5 Загальні вимоги до технічного обладнання та процесів 4.6 Виробнича санітарія 4.6.1 Освітлення 4.6.2 Вентиляція та опалення 4.7 Пожежна безпека 4.8 Інструктажі з техніки безпеки 4.8.1 Інструкція з пожежної безпеки 4.8.2 Інструкція з охорони праці при роботі з випробувальним стендом Бібліографія

The aim of this study was to assess the strength, durability properties and corrosion resistance of concrete samples using supplementary cementitious blended materials. In this investigation, three supplementary concrete materials (SCMs) were used together with ordinary Portland Cement (OPC) to form cementitious blends at different proportions. The supplementary materials are silica fume (SF), ground granulated blast furnace slag (GGBS) and fly ash (FA). Sixteen (16) different proportions of the cementitious blends were produced. Tests carried out on concrete samples include slump test, compressive strength, oxygen permeability, sorptivity, porosity, chloride conductivity test, resistance to chloride and sulphate attack. The electrode potentials of tested samples were also observed using electrochemical measurements. Concrete specimens prepared with 10%, 20%, 30%, 40%, up to 60% of blended cements replacement levels were evaluated for their compressive strength at, 7, 14, 28, 90 and 120 days while the specimens were evaluated for durability tests at 28, and 90 days respectively. The results were compared with ordinary Portland cement concrete without blended cement. Voltage, and temperature measurements were also carried out to understand the quality of concrete. The corrosion performance of steel in reinforced concrete was studied and evaluated by electrochemical half-cell potential technique in both sodium chloride, and magnesium sulphate solutions respectively. The reinforced concrete specimens with centrally embedded 12mm steel bar were exposed to chloride and sulphate solutions with the 0.5 M NaCl and MgSO4 concentrations respectively. An impressed voltage technique was carried out to evaluate the corrosion resistance of the combination of quaternary cementitious blended cement, so as to get the combination with optimum performance. Improvement of strength, durability, and corrosion resistance properties of blended concrete samples are observed at different optimum percentages for binary, ternary and quaternary samples. The effect of cementitious blends is recognized in limiting the corrosion potential of the tested SCM concrete samples. Generally, the cementitious blends with limited quantity of SF to 10% have the potential to produce satisfactory concrete. These should however be used for low cost construction, where high quality concrete is not required.<br>Civil and Chemical Engineering<br>M. Tech. (Chemical Engineering)

Yes<br>The peripheral nervous system has a limited innate capacity for self-repair following injury, and surgical intervention is often required. For injuries greater than a few millimeters autografting is standard practice although it is associated with donor site morbidity and is limited in its availability. Because of this, nerve guidance conduits (NGCs) can be viewed as an advantageous alternative, but currently have limited efficacy for short and large injury gaps in comparison to autograft. Current commercially available NGC designs rely on existing regulatory approved materials and traditional production methods, limiting improvement of their design. The aim of this study was to establish a novel method for NGC manufacture using a custom built laser-based microstereolithography (muSL) setup that incorporated a 405 nm laser source to produce 3D constructs with approximately 50 mum resolution from a photocurable poly(ethylene glycol) resin. These were evaluated by SEM, in vitro neuronal, Schwann and dorsal root ganglion culture and in vivo using a thy-1-YFP-H mouse common fibular nerve injury model. NGCs with dimensions of 1 mm internal diameter x 5 mm length with a wall thickness of 250 mum were fabricated and capable of supporting re-innervation across a 3 mm injury gap after 21 days, with results close to that of an autograft control. The study provides a technology platform for the rapid microfabrication of biocompatible materials, a novel method for in vivo evaluation, and a benchmark for future development in more advanced NGC designs, biodegradable and larger device sizes, and longer-term implantation studies.