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Brittle Matrix Composites 9

Brittle Matrix Composites 9 Book
Author : A M Brandt,J Olek,I H Marshall
Publisher : Elsevier
Release : 2009-11-30
ISBN : 085709307X
Language : En, Es, Fr & De

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Book Description :

The subjects of the symposia are on composite materials with matrices behaving as brittle in normal or special conditions. Brittle matrix composites are applied in various domains (civil engineering, mechanical equipment and machinery, vehicles, etc.) and in the last decades their importance is increasing together with their variety. Papers include: aggregate-binder composites (concretes, fibre concretes, rocks); sintered materials (ceramics); high strength composites with brittle matrices. In principle, the general problems of structures made of composite materials are not included in the papers. Various approaches to the material engineering problems are presented in the papers.

Brittle Matrix Composites 10

Brittle Matrix Composites 10 Book
Author : A M Brandt,M A Glinicki,J Olek,C K Y Leung
Publisher : Elsevier
Release : 2012-11-12
ISBN : 0857099892
Language : En, Es, Fr & De

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Book Description :

The subjects of the symposia are on composite materials behaving as brittle, normal and special conditions of exploitation. Brittle matrix composites are applied in various domains and the series of symposia are closely related to their applications in civil engineering. In the last decades their importance is increasing along with their variety and the use of most advanced methods of testing. Papers include concretes, fibre concretes and ceramics, particularly their composition, microstructure and fracture processes. Various new and advanced engineering problems are presented in the papers.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Agnieszka J Klemm,Paul Baker,Karol Sikora
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 012809012X
Language : En, Es, Fr & De

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Book Description :

Construction industry like any other area of economic and social life undergoes continuous alterations and improvements in order to successfully comply with the requirements of sustainable development. Consumers demand more durable, less labour and service intensive materials at a competitive price. To meet these expectations numerous new composite materials have been developed over the last couple of decades, including cementitious materials modified by superabsorbent polymers (SAP). The paper presents part of the larger research project on the performance of cementitious mortars containing two types of superabsorbent polymers (SAP) as the internal curing agent.SAP A is a copolymer of acrylamide and acrylic acid and SAP B is a polymer based on acrylic acid. Research work presented in this paper involves macro and micro scale characterisation of polymer modified mortars. The microstructural features were studied with application of the Mercury Intrusion Porosimetry and the Scanning Electron Microscopy techniques. Analyses of pore size distribution in mortars of different ages are accompanied by the analyses of strength and autogenous shrinkage development as well as early density changes in immature mortars by the X-ray absorption method. The investigations confirmed the positive effect of SAP A on the reduction of autogenous shrinkage and microcrack propagation. Limited absorption/desorption abilities of SAP B cannot reassure continuous supply of water and hence the performance of SAP B mortars was comparable with the reference samples. The effect of both SAPs on strength development proved to be negligible.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Tomasz Zdeb,Izabela Hager,Jacek Śliwiński
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090227
Language : En, Es, Fr & De

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Book Description :

This paper presents the results from an experimental study on the behaviour of Reactive Powder Concretes (RPC) at high temperature. The exposure to high temperature is related to the potential risk of fire. A previous study has shown that RPC is prone to spalling in such circumstances and for this reason polypropylene fibres were used in RPC concrete to prevent this occurring. The addition of PP fibres reduces the risk of spalling due to an increase in permeability, however it reduces the initial compressive strength of the RPC material by approx. 20 %. The results demonstrate that the strength of concrete along with the modulus of elasticity decrease with increasing temperature. Two experimental concretes were prepared and prismatic specimens, 40x40x80mm in size, were cast from each mixture and tested in compression after being submitted to the high temperature. The relative value of compressive strength course for both types of concrete shows a similar development. The change in modulus of elasticity with temperature was determined from the stress-strain relationship and compared with the dynamic modulus of elasticity determined with the use of a Pundit plus ultrasonic pulse velocity defectoscope.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Piotr Woyciechowski
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090200
Language : En, Es, Fr & De

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Book Description :

The aim of the paper was to show the important aspect of treating waste additives as the main way to achieve sustainable development in the concrete technology. The author considers the effects of minimizing the use of cement replacing it with waste additives, on the concrete durability. The depth of carbonation is adopted as the possible measure of durability. Results of accelerated and natural tests of carbonation progress for concrete with normal and fluidal fly ash, silica fume and blast furnace slag are shown, influence on carbonation of the additive type, its content in concrete and its role (cement or aggregate substitution) is discussed. The important impact of early water curing on depth of carbonation is stated also.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Tatiana V. Lyashenko,Svetlana A. Kryukovskaya
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 012809026X
Language : En, Es, Fr & De

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Book Description :

Fibre reinforced polymer-cement compositions for self-levelling flooring are studied. The individual and combined effects of dispersible polymer powder with properties of binder and superplasticiser, of various methylcelluloses, and of polypropylene fibre on effective viscosity of the mix and mechanical properties of the hardened mortar are evaluated and analysed. Used for analysis are multifactor experimental-statistical models built on the data obtained for 18 mixes (of the same workability) in the designed experiment and describing the fields of rheological model parameters, of strength, and other criteria in composition coordinates. The models have made it possible to simulate material behaviour in computational experiments, to reveal and evaluate the correlations of the properties for different technological conditions, to find individual and compromise optima.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Conrado de Souza Rodrigues,Mariana Arruda Pereira,Stefan Chaves Figueiredo,Khosrow Ghavami,Piet Stroeven
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090464
Language : En, Es, Fr & De

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Book Description :

More recent investigations on cellulose-cement composites predominantly deal with durability aspects, whereby use is made of accelerated weathering cycles as the main approach to establishing the deterioration mechanisms and the efficiency of treatment methods. As moisture transport is the main mechanism that leads to the deterioration of those composites, accelerated ageing tests are commonly based on wet-drying cycles with a combination of temperature and relative humidity (R.H.) variations. Both variables result in dimensional changes of the samples, leading to interfacial abrasion and the progressive decrease in the composites’ toughness and strength. To investigate the effects of each of these variables, the weathering tests were performed in an environmental chamber considering each variable separately in two ageing cycles. In the first one the composites were submitted to saturation and drying at a constant 25°C, by means of a relative humidity change in the chamber. For the second ageing cycle a temperature variation between 20°C and 60°C at a constant R.H. of 50% was applied. The effects of each ageing cycle on the cellulose-cement composites were assessed on the basis of physical and mechanical parameters, determined after 0, 5, 20 and 50 cycles. Moreover, part of the samples was provided with electrical strain gauges, which rendered possible to determine the composites’ expansion-shrinkage behaviour during the temperature and R.H. variations. As the main treatment approach, the partial replacement of cement (OPC) by rice husk ash (RHA) was investigated. It was found that RHA improved the strength and durability performance of the composites, although the increased porosity resulted from the 30% replacement rate of OPC and carbonate filler by RHA.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Tomasz Ponikiewski,Jacek Gołaszewski
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090278
Language : En, Es, Fr & De

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Book Description :

The paper presents results of tests on self-compacting mixtures with the addition of steel fibres (Steel Fibre Reinforced Self-Compacting Concrete). Four types of steel fibres at 3 levels of the volume ratio are considered. The results include studies on samples belonging to classes of slump flow SF, classes of viscosity T500, and rheological tests. The studies were based on application of two rheometers for rheological properties of concrete mixtures - BT2 Rheometer and Viskomat XL. Additionally, a study of compressive strength fcm,28 and flexural strength f was carried out on concrete SFRSCC. These studies have confirmed the possibility of using steel fibres in concrete SCC while maintaining the assumed technological parameters for concrete mixtures and, above all, their workability.

Brittle Matrix Composites 7

Brittle Matrix Composites 7 Book
Author : A M Brandt,V C Li,I H Marshall
Publisher : Woodhead Publishing
Release : 2003-10-15
ISBN : 9781855737693
Language : En, Es, Fr & De

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Book Description :

The International Symposium in Brittle Matrix Composites October 13-15, 2003 covers a wide spectrum of topics including cement based composites, ceramic composites and brittle polymer matrix composites. In the papers various topics and issues are considered such as: analytical and numerical studies related to the design of composites, prediction of behaviour and verification of strength and stability, testing methods, manufacturing processes and repair, environmental effects and durability assessment. The present volume of 55 papers proves that there are still many problems in the field of brittle matrix composites deserving theoretical and experimental investigations and that new solutions to these problems are needed for practical application in civil engineering, industrial structures, machinery and other domains.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Waldemar Pichór,Maksymilian Frąc
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090146
Language : En, Es, Fr & De

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Book Description :

The electric resistance and thermoelectric properties of cement composites with addition of expanded graphite were. The expanded graphite was obtained from intercalated graphite by rapid heating in different conditions. The influence of thermal treatment on thermoelectric properties was measured. The cement pastes were prepared in the two different ways, either by mixing together expanded graphite and cement, or by rubbing compounds together in order to obtain smaller particles of graphite (even nanometric size) during mixing. The bulk density and electric and thermoelectric properties of cement pastes with addition of expanded graphite were measured. The results of investigations show that the electric properties of composites are strongly influenced by the conditions of thermal expansion as well as by the technique of preparation.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Agnieszka Ślosarczyk
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090251
Language : En, Es, Fr & De

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Book Description :

Compared to concrete, the compressive strength is not a very important property of cement mortar. It is very important that mortar forms a complete, strong, and durable bond with the building material elements, because it is used as an adhesive and sealant material. The physical and mechanical properties of cement mortar, especially flexural strength, toughness, tensile strength, reduction of plastic as well as drying shrinkage, can be enhanced by the use of randomly dispersed fibres, such as steel, carbon or polymer. In the present research there were investigated cement mortars modified with randomly dispersed polypropylene and steel fibres in different volume fraction used both separately and in a hybrid system. The conducted research proved that the low modulus polypropylene fibres with good flexibility added to cement matrix resulted in good properties of fresh mortar and caused the reduction of early age cracking. The beneficial effects of flexible fibres could be attributed to their high aspect ratio and increased fibre availability at a given volume fraction due to their low density. Because of low stiffness, these fibres are particularly effective in controlling the propagation of micro-cracks. It was found that the hybrid combination of metallic and nonmetallic fibres can offer potential advantages in improving cement matrix properties, such as the ultimate strength and toughness of composites.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Hiroshi Akita,Hideo Koide,Hirozo Mihashi
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090405
Language : En, Es, Fr & De

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Book Description :

In the uniaxial tension test of concrete, inevitably some secondary flexures occur. However the characteristics of the secondary flexures are not well understood among others because of the complexity of performing the uniaxial tension test without the flexures. In this paper the uniaxial tension test in which secondary flexures are minimized, by a specially developed device, are compared to the tests where secondary flexures are left to develop freely. Experimental results and theoretical calculations are shown for the influence of secondary flexures on load-deformation curves, tensile strength and strain energy of the specimen. Plural flexures which grow finally plural cracks were also analyzed concerning to an experimental result. It is concluded that secondary flexures should be minimized, because they produce considerable error to the load-deformation curve and tensile strength. Furthermore, secondary flexures should be controlled continuously during the test because the minimized state is an unstable equilibrium of strain energy in the specimen. And the flexures can only be minimized by using a notched specimen because plural flexures occur in an un-notched specimen.

The Processing and Mechanical Properties of High Temperature High Performance Composites Mechanism Based Constitutive Laws and Design

The Processing and Mechanical Properties of High Temperature  High Performance Composites  Mechanism Based Constitutive Laws and Design Book
Author : Anonim
Publisher : Unknown
Release : 1994
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

This document discusses the following: (1) Materials selection and innovation in design; (2) Elasto-plastic analysis of interface layers for fiber- reinforced metal-matrix composites; (3) Modeling of anisotropic behavior of weakly bonded fiber reinforced MMCs; (4) On the tensile properties of a fiber reinforced titanium matrix composite; (5) Control of strength anisotropy of metal matrix fiber composites; (6) inelastic strains due to matrix cracking in unidirectional fiber-reinforced composites; (7) Location and ultimate tensile strength of fiber-reinforced ceramic-matrix composites; (8) Matrix cracking and debonding of ceramic-matrix composites; (9) Matrix cracking of cross-ply ceramic composites; (10) Transverse cracking in fiber-reinforced brittle matrix, cross- ply laminates; (11) The mechanisms of deformation and failure in carbon matrix composites subject to tensile and shear loading; (12) Uncoupled and coupled approaches to predict crack-initiation in fiber-reinforced ceramic-matrix composites; (13) Stress corrosion cracking in a unidirectional ceramic-matrix composite; (14) Effects of gauge length on the tensile strength of SiC fibers; (15) Tunneling cracks in constrained layers; (16) The effect of interfacial properties on the flow strength of discontinuous reinforced metal matrix composites; (17) On dislocation storage and the mechanical response of fine scale microstructures; and (18) Effect of microstructural parameters on the yield strength of Al-4%Mg/Al2O3p composites.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Zbigniew Ranachowski,Daria Jóźwiak - Niedźwiedzka,Mariusz Dąbrowski,Jolanta Wołowicz,Maciej Sobczak,Tomasz Dębowski,Michał A. Glinicki
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090294
Language : En, Es, Fr & De

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Book Description :

In the paper a new method of determination of cement paste microhardeness is presented. It includes the procedure of systematic indentation with a Vickers tip and a statistical processing of population of obtained results. The tested specimens were cast with different kinds of blended cements, containing high calcium fly ash (HCFA) as one of major components. Differences in values of microhardeness obtained for six series of tested specimens mixes are discussed and compared with compressive strength of investigated materials.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Nghi L.B. Le,Piet Stroeven
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090391
Language : En, Es, Fr & De

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Book Description :

Portland cement (PC) production contributes by about 6% to global emissions of C02. Reduction of the PC content in the binder exerts therefore a direct positive effect on such emissions. Partial replacement of the Portland cement by pozzolanic mineral admixtures has been proven a possible option. The green character is even reinforced by making use of incinerated vegetable waste, such as rice husk ash (RHA). Moreover, as a result of the gap-grading effect on particle packing density with RHA as the fine component, high strength concrete can be achieved with RHA-blended cement. This has been published earlier, so the paper only briefly covers these aspects. Characteristics of the capillary pores developed in the hydrating binder have direct impact on the transport-based durability properties. However, assessment of such pore characteristics of the RHA-blended cement constitutes a complicated problem, especially in experimental approaches. This paper, therefore, presents a new economic approach to conduct such investigation on the realistically produced cementitious materials in virtual reality. The fresh packed state of the paste’s particles is simulated by a discrete element modeling (DEM) system, HADES. The hydration of a (blended) cement is simulated by a so-called ‘extended integrated particle kinetics model’ (XIPKM). Pore characteristics, such as topology, location distribution, degree of percolation and fraction of main channels in the pore network, are explored by a new modern approach named ‘double random multi-tree structuring’ (DraMuTS). The size distribution of throats that significantly limit the transport in the pore network system is derived from star volume measurements. Four examples of plain PC and of RHA-blended PC with two w/b ratios are presented. The expected positive effects on transport-based durability issues due to RHA-blending are discussed.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Christopher K. Y. Leung,Dongwei Hou
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090189
Language : En, Es, Fr & De

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Book Description :

Steel corrosion is a major problem with concrete structures. For concrete structures exposed to chlorides, once a critical chloride concentration is reached at the steel surface, corrosion starts to occur. For a given cover thickness, the corrosion initiation time depends on the chloride diffusivity. For different kinds of concrete, the diffusivity Do at the un-cracked state has been measured. However, in reinforced concrete design, concrete members are allowed to crack in tension. Once cracking occurs, chloride can also diffuse through the crack at a faster rate governed by the crack diffusivity Dcr. Recent experiments have shown that Dcr is a function of the crack width. In the present study, finite element analysis is performed to study the effect of cracking on corrosion initiation in concrete with different values of Do. For various crack width and cover thickness, the time for critical chloride concentration to be reached at steel intersected by the crack is determined. Based on the simulation results, we will derive the empirical equation for an effective diffusion coefficient (Deff) which can be employed directly in the solution of the one-dimensional diffusion equation to calculate the corrosion initiation time. The study will provide a convenient but accurate approach for predicting corrosion initiation under real world situations where cracks are present in a concrete structure.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Hans W. Reinhardt,null Oliver Mielich
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090103
Language : En, Es, Fr & De

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Book Description :

The paper reports on an experimental investigation of concrete with three slow reacting aggregates (greywacke, quartz-porphyrite, crushed gravel). The specimens were stored in a fog room at 40°C for 560 days. The compressive strength, the tensile strength, the static modulus of elasticity, and the dynamic modulus of elasticity were measured at certain intervals. The results show how these mechanical properties are affected by the alkali-silica reaction (ASR). It turned out that the dynamic modulus of elasticity cannot be used for the prediction of deterioration due to ASR. However, when the compressive and tensile strengths and the static modulus of elasticity have been determined a re-evaluation of an ASR affected structure can be performed.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Joseph J. Biernacki,Narendar R. Mogula,Jordan K. Dunne,Rajavardhan R. Nagolu
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090170
Language : En, Es, Fr & De

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Book Description :

Samples of a typical Class-F fly ash were sintered in various oxygen partial pressure atmospheres including argon, 21% O2 in argon, air and 50% O2 in argon. A three-mechanism sintering model was proposed along with physiochemical kinetic transformations that cause the mechanism of sintering to naturally change as time and temperature progress. When used to interpret the experimental data, it was found that even trace amounts of carbon can alter the sintering kinetics, although atmosphere does not affect sintering rates as long as carbon is volatilized prior to the onset of sintering. Both a two and three mechanism model provide a good fit; however, a three mechanism model with thermal expansion was found to provide a more natural fit to the data. A global multi-dataset optimization strategy was used. In addition, the sintered products were examined by X-ray diffraction (XRD) to identify the crystalline phases present in the fly ash samples. The main crystalline phases present in fly ash are mullite and quartz, although, different crystalline structures and amounts were observed in the sintered samples.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Kim Van Tittelboom,Manuel Dierick,Nele De Belie
Publisher : Elsevier Inc. Chapters
Release : 2012-11-12
ISBN : 0128090367
Language : En, Es, Fr & De

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Book Description :

Concrete is one of the most widely used construction materials due to its excellent mechanical properties and relatively low cost. However, concrete is prone to crack formation. These cracks do not impair the structural integrity, but they endanger the durability of the structure as aggressive liquids and gasses may enter via these cracks and cause degradation. Therefore, crack repair is needed but these repair works increase the cost of concrete structures by 50 % as they are labour intensive and because the structure becomes in disuse during repair. Accordingly, in this research it was investigated whether cementitious materials can be modified so that cracks heal themselves. Therefore, healing agents were encapsulated by brittle capsules and embedded inside the cementitious matrix in the zones where cracks were expected. When the matrix starts cracking, the capsules break and release their content, leading to crack repair. Water absorption measurements were performed to evaluate the healing efficiency. The amount of absorbed water was determined by gravimetrical measurements and visualized by X-ray radiography. When samples with untreated cracks were placed with their cracked surface in a water reservoir, it was noticed from the radiographs that water penetrated very fast into the cracks. For samples with self-healing properties no water entered into the cracks. Moreover, even in the zone alongside the crack no water entry was noticed. Therefore, it can be concluded that self-healing of concrete cracks can be used to prevent the ingress of liquids and to prevent subsequent damage to the matrix.

Brittle Matrix Composites

Brittle Matrix Composites Book
Author : Anonim
Publisher : Unknown
Release : 1994
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

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