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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Effects of Nano Silica and Basalt Fibers on Fly Ash Based Geopolymer Concrete

Abu Bakar, Asif January 2018 (has links)
Emission of carbon dioxide gas has been a source of major concern for the construction industry. To curb this emission, geopolymer concrete has been deemed as a potential alternative in the recent studies. Previous research also indicates that silica and fibers provide strength benefits to ordinary Portland cement concrete OPC. This study was undertaken to recognize the benefits of adding silica and basalt fibers in Class F fly ash based geopolymer concrete and comparing it with OPC concrete. One OPC and four Geopolymer mixtures were prepared. The results show a tremendous potential of using geopolymer concrete in place of OPC concrete with Nano silica proving to be the most advantageous. Nano silica provided 28% increase in compressive strength, 8% increase in resistivity when compared with normal Fly ash based geopolymer concrete. The SEM analysis of geopolymer concrete indicates that nano silica improved the compactness of concrete providing a dense microstructure.
2

Smyková pevnost vlákny vyztuženého polymerního kompozitu / Shear strength of the fiber-reinforced polymer composite

Jurko, Michal January 2020 (has links)
The diploma thesis deals with the study of Inter-Laminar Shear Strength (ILSS) of polymer composites, based on unsaturated polyester resin with unidirectionally oriented basalt or glass fibers. The basis of the experimental part is the preparation of composite samples with different types of surface treatment of a fibers (a reinforcement) as well as the surface treatment itself. The untreated, the commercially treated fibers and the plasmatreated fibers used as reinforcement in the polymer composites were analysed by a short beam shear test and their ILSS was determined. The effect of various deposition conditions during Plasma-Enhanced Chemical Vapour Deposition (PECVD) on the value of ILSS of the composite with originally unsized glass or basalt fibers was studied. The impact of aging on the interlaminar shear strength of the composites was investigated for commercially treated glass fibers. The Scanning Electron Microscopy (SEM) is also used in the thesis together with the Energy Dispersive Spectroscopy (EDS). Based on all the results a proposal was made to correct and improve the deposition conditions and thus improve the interphase to achieve the required shear properties of polymer composites.
3

Optimalizace hliněných stavebních prvků / The optimalization of clay building components

Melichar, Jindřich January 2012 (has links)
Clay building components are nowadays one of the most used building materials in the world. Except easy availability and processability clay building components have also heat storage function. This master´s thesis will be considering possibilities of improving thermal and mechanic properties of these materils by additing suitable reinforcements.
4

Sustainable Composite Systems for Infrastructure Rehabilitation

De Caso y Basalo, Francisco Jose 15 December 2010 (has links)
The development of composite materials by combining two or more constituents with improved mechanical properties, when compared to either of the constituents alone, has existed since biblical times when straw or horse hair was mixed with clay or mud to produce bricks. During the second half of the twentieth century, modern composites known as fiber reinforced polymers (FRP) - consisting of a reinforcing phase (fibers) embedded into a matrix (polymeric resin or binder) - were developed to meet the performance challenges of space exploration and air travel. With time, externally-bonded FRP applications for strengthening of reinforced concrete (RC) structures gained popularity within the construction industry. To date, the confinement of RC columns using FRP systems is a convenient and well established solution to strengthen, repair and retrofit structural concrete members. This technology has become mainstream due to its cost effectiveness, and relative ease and speed of application with respect to alternative rehabilitation techniques such as steel or concrete jackets. However, significant margins exist to advance externally-bonded composite rehabilitation technologies by addressing economic, technological, and environmental issues posed by the use of organic polymer matrices, some of which are addressed in this dissertation. Articulated in three studies, the dissertation investigates the development of a sustainable, reversible, and compatible fiber reinforced cement-based matrix (FRC) composite system for concrete confinement applications in combination with a novel test method aimed at characterizing composites under hydrostatic pressure. Study 1 develops and characterizes a FRC system from different fiber and inorganic matrix combinations, while evaluating the confinement effectiveness in comparison to a conventional FRP system. The feasibility of making the application reversible was investigated by introducing a bond breaker between the concrete substrate and the composite jacket in a series of confined cylinders. The prototype FRC system produced a substantial increase in strength and deformability with respect to unconfined cylinders. A superior deformability was attained without the use of a bond breaker. The predominant failure mode was loss of compatibility due to fiber-matrix separation, which points to the need of improving fiber impregnation to enable a more efficient use of the constituent materials. Additionally semi-empirical linear and nonlinear models for ultimate compressive strength and deformation in FRC-confined concrete are also investigated. Study 2 compares through a life cycle assessment (LCA) method two retrofitting strategies: a conventional organic-based, with the developed inorganic-based composite system presented in Study 1, applied to concrete cylinders by analyzing three life cycle impact indicators: i) Volatile Organic Compound (VOC) emissions, ii) embodied energy, and, iii) carbon foot print. Overall the cement-based composite provides an environmentally-benign alternative over polymer-based composite strengthening system. Results also provide quantitative information regarding the environmental and health impacts to aid with the decision-making process of design when selecting composite strengthening systems. Study 3 is divided into two parts, Part A presents the development of a novel "Investigation of Circumferential-strain Experimental" (ICE) methodology for characterization of circumferential (hoop) strain of composite laminates, while Part B uses the experimental data reported in Part A to explicitly evaluate the effect of FRP jacket curvature and laminate thickness on strain efficiency. Results showed that the proposed ICE methodology is simple, effective and reliable. Additionally, the ultimate circumferential strain values increased with increasing cylinder diameter, while being consistently lower when compared to similar flat coupon specimens under the same conditions. The ultimate FRP tensile strain was found to be a function of the radius of curvature and laminate thickness, for a given fiber ply density and number. The effect of these findings over current design guidelines for FRP confined concrete was also discussed.
5

Propuesta de mejora de la carpeta asfáltica por medio de fibras de basalto y lignina, para el control de deformaciones permanentes en carreteras sometidas a carga vehicular pesada y altas temperaturas / Proposal to improve the asphalt layer by means of basalt and lignin fibers, for the control of permanent deformations on roads subjected to heavy vehicular load and high temperatures

Farfan Gonzales, Fabrizio Jesus, Huaquía Díaz, José Luis 30 August 2021 (has links)
La deformación permanente es una de las principales responsables del deterioro temprano de la capa asfáltica de carreteras. Este tipo de fenómeno, se ve impulsado en el país debido a la carga vehicular pesada y la variedad climática, en particular, las altas temperaturas. Se sabe que el comportamiento de la mezcla asfáltica, depende directamente de los materiales que la constituyen. Y ante condiciones desafiantes, estos materiales son insuficientes. En ese sentido, la presente investigación busca mejorar las propiedades de una mezcla asfáltica convencional mediante la adición de fibras de basalto y lignina, de tal manera que sea menos propensa a sufrir deformaciones permanentes. Para la parte experimental, se contó con agregados procedentes de la cantera Conchán, en Lima. Mediante la metodología de Marshall, se diseñaron dos mezclas asfálticas. La primera mezcla fue elaborada sin aditivos y en base a expedientes técnicos de la zona. La segunda mezcla se elaboró con los mismos componentes y con adición de 0.3% fibras de basalto y 0.3% de fibras de lignina. Las muestras fueron sometidas a ensayos de estabilidad y flujo, índice de rigidez, vacíos de agregado mineral y resistencia a la compresión. Los resultados de la investigación mostraron que al incorporar fibras de basalto y fibras de lignina se aumentan la estabilidad de la mezcla en 7%, el índice de rigidez de Marshall en 6%, el porcentaje de vacíos de agregado mineral en 2% y la resistencia a compresión en 4%. De lo anterior de infiere que la mezcla asfáltica propuesta tiene una mayor capacidad para distribuir la carga, mayor resistencia a la deformación por fluencia, mayor capacidad de expansión para contrarrestar las altas temperatura y, en consecuencia, mayor resistencia a las deformaciones permanentes. / Permanent deformation is one of the main causes of the early deterioration of the asphalt layer of roads. This type of phenomenon is driven in the country due to the heavy vehicle load and the climatic variety, in particular, the high temperatures. It is known that the behavior of the asphalt mixture depends directly on the materials that make it up. And in challenging conditions, these materials are insufficient. In this sense, the present research seeks to improve the properties of a conventional asphalt mixture by adding basalt and lignin fibers, in such a way that it is less prone to permanent deformation. For the experimental part, it was used aggregates from the Conchán quarry, in Lima. Using Marshall's methodology, two asphalt mixes were designed. The first mixture was made without additives and based on technical files in the area. The second mixture was made with the same components and with the addition of 0.3% basalt fibers and 0.3% lignin fibers. The samples were subjected to stability and flow tests, stiffness index, mineral aggregate voids and compressive strength. The results of the investigation showed that when incorporating basalt fibers and lignin fibers the stability of the mixture is obtained in 7%, the Marshall stiffness index in 6%, the percentage of voids of mineral aggregate in 2% and the resistance a compression in 4%. From the foregoing, it can be inferred that the proposed asphalt mix has a greater capacity to distribute the load, greater resistance to creep deformation, greater expansion capacity to counteract high temperatures and, consequently, greater resistance to permanent deformations. / Tesis
6

Vliv anorganických vláken na fyzikálně mechanické vlastnosti cihlářského střepu / The effect of fibres addition on the properties of brick body

Novotný, David January 2017 (has links)
This diploma thesis will discuss possibilities of using inorganic fibers to improve the mechanical properties of the resulting physical body bricks. Assessment of the effect of fiber length, fiber thickness is in the order of micrometers. In this work we were used fibers which are commercially produced for the purpose of reinforcement, but also waste fibers, which mainly serves as an insulator.
7

Propuesta de diseño de concreto permeable reforzado con fibras de basalto (18mm, l7 µm) para mejorar su desempeño aplicado en pavimentos urbanos

Challco Estrada, Bianca Francesca, Tuesta Gonzales Zúñiga ,Lea Rebeca 27 January 2021 (has links)
El crecimiento acelerado de las urbes y el uso de materiales impermeables han impactado negativamente en el ciclo hidrológico. Las fuertes precipitaciones durante la época de lluvias generan el colapso de redes de alcantarillado en ciudades con la infraestructura inadecuada. Dicha escorrentía acelera el deterioro de los pavimentos, además de la incomodidad y peligro debido al hidroplaneo que impacta en los peatones. El concreto permeable es un material adecuado para mitigar estos problemas debido a su propiedad de discurrir el agua entre sus poros, además de ser ecológico y sostenible. Ya que su resistencia es menor a la del concreto convencional, su uso es limitado en pavimentos rígidos, por ello la incorporación de fibras le proporcionaría un mejor desempeño mecánico. Mediante un análisis cualitativo de diversos factores, se determinó que las fibras de basalto optimizarían el comportamiento del concreto permeable para su aplicación en pavimentos urbanos. Además, se tomó en consideración que el suelo del área de estudio es de grava y la infiltración requerida es de 192.22mm/h. El diseño de mezcla de referencia corresponde a similares características con el área de estudio y finalmente las cantidades requeridas en el diseño de esta investigación son 443.12 kg/m3 de cemento, 130.43 l/m3 de agua, 135.16 kg/m3 de agregado fino, 1312.04 kg/m3 de agregado grueso, 3.99 kg/m3 de aditivo superplastificante; añadido a fibras de basalto en porcentajes de 0%, 0.1%, 0.2% y 0.3% respecto del diseño de mezcla. / The accelerated growth of cities and the use of waterproof materials have negatively impacted the hydrological cycle. Heavy rainfall during the rainy season leads to the collapse of sewerage networks in cities with inadequate infrastructure. Such runoff accelerates the deterioration of pavements, in addition to the discomfort and danger due to hydroplaning that impacts pedestrians. Pervious concrete is a suitable material to mitigate these problems due to its property of running water through its pores, in addition to being ecological and sustainable. Since its resistance is less than that of conventional concrete, its use is limited in rigid pavements, therefore the incorporation of fibers would provide better mechanical performance. Through a qualitative analysis of various factors, it was determined that basalt fibers would optimize the behavior of pervious concrete for application in urban pavements. In addition, it was taken into consideration that the soil of the study area is gravel and the required infiltration is 192.22 mm/h. The reference mix design corresponds to similar characteristics with the study area and finally the quantities required in the design of this research are 443.12 kg/m3 of cement, 130.43 l / m3 of water, 135.16 kg/m3 of fine aggregate, 1312.04 kg/m3 of coarse aggregate, 3.99 kg/m3 of superplasticizer additive; added to basalt fibers in percentages of 0%, 0.1%, 0.2% and 0.3% with respect to the mix design. / Trabajo de investigación
8

Studium vlastností cementových kompozitů s rozptýlenou výztuží z anorganických vláken / Study of properties of cementitious composites with fiber reinforcement from inorganic fibers

Gottwaldová, Aneta January 2019 (has links)
Diploma thesis deals with study of properties of cementious composites with fiber reinforcement from glass and basalt inorganic fibers. Diploma thesis includes a theoretical and experimental part. The theoretical part deals with information about glass and basalt fibers, their durability and usage. In the experimental part we monitored properfies of cement composites with basalt and glass fibers. Fibers were exposed to an aggressive environment. The properties of composites with reference fibers were compared with composites with fibers affacted by the aggressive environment. The properties of composites were examined after 28 and 90 days. We monitored compresive strenght, bending tensile strenght, tensile strenght, surface layer strenght and SEM.

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