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Titolo/Abstract/Parole chiave

Progetto ed ingegnerizzazione di prodotti industriali estrusi a base cementizia rinforzati con microfibre polimeriche

Bernini, Alessandro (2012) Progetto ed ingegnerizzazione di prodotti industriali estrusi a base cementizia rinforzati con microfibre polimeriche. Tesi di Dottorato , Universita' degli studi di Ferrara.

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    Abstract

    The purpose of research is to study the mechanical behavior and the phases of construction of polymeric micro-fiber reinforced roof tiles. This work can be divided into three distinct parts: the first part covers the types of sloping roofs and as a result of artifacts that can be installed on them, the second part is mainly of a technological nature. In it are briefly listed the manner of realization of concrete products subject of the thesis. The third and last part contains the three years of research conducted in the laboratory and in Vortex Hydra Srl for the study of materials Engineered Cementitious Composites “ECC” in industrial applications resulting in the formulation of simplified constitutive models. The initial chapter first is devoted to the most common types of civil roofing inclined type, since the flat roofing usually intended to be covered with compounds manufactured from different materials. The choice of the base material can vary depending on the architectural choices, the building tradition and also the local availability. Furthermore different roof sub-structure are shown with particular interest for the distinction of the different building materials and different permanent load which they entail. A detailed explanation of different cover elements related to construction technology adopted is shown, together with the permanent weights that they lead and their different civil applications related to climatic conditions. The terminal part of the first chapter is dedicated to the state of the art in the production of covering elements made of fiber reinforced cement-based materials. This section discusses the current technologies used in the production of the roof covering elements of different sizes, and sets out the main reasons why it is considered important to deepen the study of innovative products based on extrusion of cement with the addition of micro-reinforcement of the polymeric type. The state of the art in the production of covering elements, that is reported in the first chapter, shows that currently on the market are not available extrusion technology capable of extruding cementitious polymeric micro-fiber reinforced products. The advantages that would follow are widely discussed, and consist mainly in the high productivity of these systems, and the possibility of reducing the cost of production; which is the key factor to facilitate the market introduction of an innovative lightweight and durable product. For this reason the second chapter is entirely dedicated to the state of the art in the study of ECC which is a class of cement-based high-ductility composite usable for industrial applications; where the costs play a role of great importance. After its introduction ten years ago, the material has been subject to various developments both from of mechanical properties and for its different building applications. The second chapter summarizes the information needed to understand the design and commercial applications of ECC. Great importance is given to the role performed by the micromechanics of the material in the design and optimization of the mixture. Reflections will also be performed on the ductility of the material, the performance characteristics of materials ECC and R / ECC (Reinforced ECC) and important considerations about the mixture cost. The third chapter is devoted to laboratory tests conducted during the years 2009 and 2010, fully documented in two publications. The purpose of the first year of study was to identify the most suitable type of microfibers looking into the composition, the size and quantity in volume fraction. The main objective of the first phase of the research is to assess the best compromise in terms of quantity of fibers, type of reinforcing fibers to achieve industrialized process. Following preliminary tests, additional ones were performed on a wide range of mixture combinations in order to develop a mathematical model useful for the representation of the fracture behavior of elements subjected to decline. The test campaign is completed in the second phase, with further bending tests and compression tests and direct tension test, referring, when possible, with government regulations. The aim of the fourth chapter is to evaluate whether the approach proposed by the CNR DT 204, proposed for steel fiber-reinforced concrete, can be used for extrusion of cementitious polymeric micro-fiber reinforced products. In this section the simplified models proposed in the technical literature are used to simulate the results of the bending test and to find out and to give reliable indications on the behavior of artifacts at the ultimate limit state. The tests described in previous chapters lead to low values of the ratio s / c in order to increase the ultimate strength and get a significant ductility. Can be concluded that to increase both the ductility of the material and the final strength either high quantities of cement or fine aggregates are necessary. The fifth and final chapter deals the aspects mentioned above being taken as the main constituents of the engineering phase. The term engineering is in fact collect in this final chapter all the changes necessary to make the material processable, moving from a laboratory study to a sustainable industrial application aimed at the mass production of manufactured goods.

    Tipologia del documento:Tesi di Dottorato (Tesi di Dottorato)
    Data:30 Marzo 2012
    Relatore:Tralli, Antonio - Tullini, Nerio
    Coordinatore ciclo:Trillo, Stefano
    Istituzione:Universita' degli studi di Ferrara
    Dottorato:XXIV Anno 2009 > SCIENZE DELL'INGEGNERIA
    Struttura:Dipartimento > Ingegneria
    Soggetti:Area 08 - Ingegneria civile e Architettura > ICAR/08 Scienza delle costruzioni
    Parole chiave:ECC, FRC, PVA, microfibre polimeriche
    Depositato il:06 Set 2013 12:44

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