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FIBER REINFORCED CEMENT-BASED COMPOSITES.
Abstract
There is considerable worldwide interest in the use of steel, glass, polypropylene, carbon and alumina fibers as reinforcement for conventional, moldable construction materials. Fibrous reinforcement significantly improves many of the engineering properties of these materials. Preparation and properties of the composites are discussed along with potential applications for these new materials. Current research is being directed at optimizing mixing procedures and at improving the bond between the fiber and the matrix so that the tensile strength properties of the fibers can be more effectively used. As an example of the latter, work on polymer impregnated, fiber reinforced mortars has shown that remarkable flexural strengths (a 6-fold increase relative to the fiber reinforced mortar without polymer) can be achieved when good bonds are developed. Polymer impregnation of asbestos cement has also been investigated recently.
... In fact, several types of metal fibre reinforced ceramic composite (MFC) have been developed. These include systems based on low alloy steel fibres in cement [12][13][14][15][16][17] and stainless steel fibres in an alumino-silicate matrix [18]. Many such composites have been manufactured by the infiltration of a ceramic slurry into the spaces between a network of fibres, leading to material with a fibre content of between about 5 and 20 vol.%. ...
A model is presented for prediction of the fracture energy of ceramic–matrix composites containing dispersed metallic fibres. It is assumed that the work of fracture comes entirely from pull-out and/or plastic deformation of fibres bridging the crack plane. Comparisons are presented between these predictions and experimental measurements made on a commercially-available composite material of this type, containing stainless steel (304) fibres in a matrix predominantly comprising alumina and alumino-silicate phases. Good agreement is observed, and it’s noted that there is scope for the fracture energy levels to be high (∼20 kJ m−2). Higher toughness levels are both predicted and observed for coarser fibres, up to a practical limit for the fibre diameter of the order of 0.5 mm. Other deductions are also made concerning strategies for optimisation of the toughness of this type of material.
Durable construction materials are in demand worldwide, for the development of sustainable and low-cost Infrastructure. A lot of research on the advancement of new materials and technology have been carried out for the past few decades. The development of cheap and durable materials from renewable resources contributes to sustainable development. Sisal fibres can be considered as a suitable reinforcing material in concrete due to its low cost, high strength to weight ratio, and recyclability. The advantage of Sisal fibre reinforced concrete composite over other conventional materials seems largely from their higher specific strength, stiffness, and fatigue characteristics, which enable structural design to be more versatile. Another key benefit of Sisal composites are their better environmental compatibility and bio degradability over other conventional materials which makes it eco-friendly and promises to contribute to sustainable construction. In this work, an emphasis is made on durability characteristics of Sisal fibre reinforced concrete composites and an attempt is made to prove Sisal fibre reinforced concrete composites are cost effective.
In recent years, various metal fibre reinforced ceramic systems have been investigated with the object to overcome low tensile strength and thermal shock resistance of conventional ceramic materials. In this paper fibre characterization, strengthening mechanism, properties and successful applications of steel fibre reinforced refractories have been reviewed. In the author's plant, a preliminary effort has been made to incorporate SS 304 type steel fibre in a chrome-based plastic refractory. Trials conducted with this material for reheating furnace applications have been found encouraging.
The paper reviews the theory and practice of particle packing. Work on the packing of solid particles mainly consisted of (a) theoretical calculation of voidage due to different modes of packing of rigid unisized spherical particles, (b) theoretical calculation of voidage for multicomponent particulate system, (c) experimental compaction of unisized spherical as well as irregular particles of different sizes, (d) experimental compaction of multi-component system to obtain denser beds and (e) correlation of variables, such as methods of compaction, shape, size and size distribution of particles as well as the size of the container, etc. The paper also highlights the practical applications of packing of particles.
The impact of different shape fibers on the cracking restriction and bearing capacities, and mechanical behaviors of ultra-high performance hybrid-fibers reinforced concrete were experimentally investigated. The compressive strength, flexural strength, fracture energy, and bend ductility of the Ultra-high performance hybrid-fiber reinforced concrete were investigated with cube specimens and beam specimens. The results shown that, when the fiber volume ratio was 2%, compressive strength and flexural strength of long ultra-fine steel fiber reinforced concrete was the highest. Compared with plain concrete, it is increased by 31.4% and 75.7% respectively. The length of fiber has positive effect on flexural strength and ductility. The largest fracture energy and bending toughness index was obtained with hybrid-fibers, where the volume ratio of long ultra-fine fiber was 1.5%, and the ratio of long end-hooked fiber was 0.5%. The hybrid-fibers here have generated positive intermixing effect.
Thin cement mortar plates reinforced by perforated thin steel sheets have been tested in four-point flexure loading. Six kinds of sheet reinforcement and to additional ones (for control) were used. Perforated sheets of the Daugavpils Factory of Machinery Chains differed by their thickness (0.6–1.8 mm), shape (round, rectangular, oval, “dumbbell”), and mark of steel (St. 08, 50, 70). Dimensions of plantes were 100×20×2 cm. Cements-sand mortar with a 1∶2 ratio of cement PZ35 and river sand of 3 mm grains was used as a matrix. Control specimens of similar dimensions and matrix were reinforced by wire cages and meshes (ferrocement). The testing was performed using an UMM-5 testing machine. Maximum deflection (at the midspan), tension, and shear strains were recorded. The expeimental data are presented in tables and graphs. The testing results showed that the elasticity modulus of material was in good agreement with the “admixture rule;” an onset of cracking for all types (excluding one) practically did not differ from reference samples; the mode of fracture in typical cases included an adhesion failure and significant shear strains. In one case the limit of the tension strength of the reinforcement was achieved.
By using short pitch-based carbon fibers (0.5% by weight of cement, 0.28 vol.% of cement mortar, or 4.5 Kg fibers/m3 cement mortar), together with a water reducing agent and an accelerating admixture, the compressive, tensile and flexural strengths of the carbon fiber reinforced cement mortar were found to increase by about 18–31%, 113–164% and 89–112%, respectively, compared to the corresponding plain cement values. The ductility was also much improved. In addition, the electrical resistivity decreased to 0.1% of the plain cement value. The optimum fiber length was 3.0 – 5.1 mm. By arranging unidirectional continuous carbon fibers (0.25% by weight of cement or 0.13 vol.% of cement mortar) near one side of a cement specimen, together with the use of a water reducing agent and an accelerating admixture, the flexural strength of the specimen increased by 170% compared to the plain cement value.
The possibility of employment of acrylic fibres as reinforcing material in cement paste, mortars and concretes has been studied by the authors of the present paper according to two features characterizing this kind of composite: 1.(a) Reinforcing capacity of poliacylonitrile fibres2.(b) Resistance to chemical attack of the aforementioned fibresThe present paper is the first part of a study projected on the long run; accordingly, in the future more data could be furnished in order to study more closely some specific aspects that can complement these first results. Thus for instance, in pastes of Portland cement, it has been proved that the presence of this type of fibre improves their impact resistance upto around 30–40 times whereas flexural resistances for 1 1·5% wt of addition of fibres have an increase, with respect to those obtained for pure paste, of around 50% in some cases. Simultaneously, it has been proved that the chemical resistance or attackability of acrylic fibres in high alkaline media is quite good.
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