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Highly reinforced precast monolithic refractories
Abstract
Steel fibers have been used successfully as reinforcement in castables and other monolithic refractories for about 10 years. Until recently, the maximum amount of fiber that could be practically handled in these materials using conventional mixing and placing procedures was about 2 vol%. A new construction procedure described in this paper provides for the incorporation of up to 16 vol% steel fiber reinforcement. The procedure involves the infiltration of a packed bed of steel fibers with a fine-grained refractory slurry. Property measurements in the laboratory and limited application experience suggest that there are situations where these highly reinforced refractories can provide improved performance on a cost-effective basis. It is hoped that the information presented at this time will stimulate interest and experimentation with these new refractory materials.
... Analytical models are proposed to predict the stress-strain response of SIFCON in both compression and tension as well as its stress-crack opening response in tension. These models depend on a few variables (over) For specimens reinforced with fibers aligned primarily in the loading direction, average tensile strengths were about 2 k/in 2 (14 MPa) with maximum observed strengths of up to 4 k/M 2 (28 MPa). ...
... The shape of the stress-displacement (descending branch) curve of SIFCON is different from that of ordinary fiber-reinforced concrete which shows an exponentially decaying response (1,2). With SIFCON the curve has an inflection point quite similar to the descending branch under compressive loading. ...
... . Specimens made with Mix One and deformed fibers yielded an average elastic modulus of 1.48x103 k/in2 (10,200 MPa). Specimens made with Mix Four and deformed fibers yielded an average elastic modulus of 2.01x10 3 k/in 2 (13,860 MPa); while specimens made with Mix One or Four and hooked fibers yielded an average elastic modulus of only 0.66x103 k/in 2 (4550 MPa). ...
This report presents a comprehensive investigation of the properties of SIFCON composites in both uniaxial compression and uniaxial tension, as well as their stress-displacement response in tension. The importance of the primary reinforcing parameters such as fiber type, fiber orientation, matrix properties, and matrix penetration of the fiber network is highlighted. Test results indicate that very high compressive strengths (up to 20 k/sq. in. or 140 MPa) can be achieved an compressive strains of up to 10% can be expected at about half the strength. Similarly, high tensile strengths (up to 4 k/sq. in. or 28 MPa) with strains of up to 2% accompanied by extensive multiple cracking were also observed. Surface energies and toughness indexes in tension reached about three orders of magnitude above those known for plain concrete. The toughness of SIFCOM in compression computed at 10% strain was up to 50 times that of plain concrete. Analytical models are proposed to predict the stress-strain response of SIFCON in both compression and tension as well as its stress-crack opening response in tension. SIFCON, FIber concrete, Cement composites, Constitutive modeling, Mathematical modeling, Uniaxial compression, Uniaxial tension.
... Fiber was widely used to improve concrete ductility. The ability of steel fibers has been shown particularly, to enhance the resistance of spalling of refractory concrete [6]. It is therefore recognized that steel fibers could help enhance the fire efficiency of SlFCON components by delaying concrete spalling. ...
... From the results of Table 4, it can be observed that the reduction in elastic modulus values at the same fire flame temperatures is more significant than the reduction in compressive strength. Reducing the elastic modulus is due to the breakage of bonds in the cement paste microstructure and the differential movement between the cement paste and the aggregate that occurs when the SIFCON is subjected to high firing temperatures [6]. Table 4. Test values of elastic modulus of SIFCON samples before and after exposure to fire flame Figure 11. ...
SIFCON is a special type of fiber reinforced concrete (FRC) with an unattached fiber matrix that gives the composite matrix important tensile properties and, due to its high fiber content, SIFCON also has distinctive and unique ductility and energy absorption properties. Higher temperature resistance is one of the most important parameters affecting the durability and service life of the material. In this research, the compression strength and elastic modulus of Slurry Infiltrated Fiber Concrete (SIFCON) were tested both before and after exposure to high temperatures. Two fire exposure durations of 2 and 3 hours are examined. In addition to room temperatures, three temperature ranges of 400 ° C, 600 ° C and 900 ° C have been introduced. The results of the experiment showed that the compressive strength and elastic modulus decreased after exposure to high temperatures. The drastically reduction of compressive strength took place with increasing temperature above 600 °C. While, the reduction in elastic modulus values is more significant than the decrease in compressive strength at the same fire flame temperatures. The residual compressive strength and elastic modulus at 900 °C were in the range of (52.1% to 59.6%) and (30.6% to 34.1%) respectively.
... Fibers are widely used to increase the ductility of concrete. It has been demonstrated that steel fibers improve the resistance of refractory concrete to spalling [8]. By delaying concrete spalling, it is understood that steel fibers might improve the fire effectiveness of SlFCON elements. ...
In this research, an experimental and numerical investigation was conducted to study the flexural behavior of modified slurry-infiltrated fiber concrete slurry-infiltrated fibrous concrete (SIFCON) one-way plates after being subjected to a high temperature. The first part is an experimental work to ensure that the model developed is adequate, while the second part is a 3D finite element modeling of the SIFCON plates with the program ABAQUS using a sequentially coupled thermal displacement analysis. The experimental program included testing eight modified SIFCON plates containing waste powder rubber as a partial substitute for natural sand (0%, 5%, 10%, and 15%). All adopted specimens had identical dimensions (1,000 mm length, 300 mm width, and 50 mm thickness). Four specimens were exposed to fire for 2 hr at a constant temperature of 600°C, after which they were rapidly cooled by spraying them with water. Test results showed that increasing the powder rubber content of burned and unburned modified SIFCON specimens decreased the failure load and increased the specimens’ ductility factor, as well as the ultimate and service deflections. During the test, the failure of SIFCON was observed to be gradual, and the plates remained in contact even after the ultimate load was attained, whereas the failure of the reference mix (without wasted rubber) was observed to be more rapid than that of other SIFCON mixtures. For the flexural test, it gives desirable strength and good fire resistance. This study provides guidance for the study of SIFCON with waste rubber. Overall, the percentage of error between the experimental and numerical results for the load capacity and midspan displacement was about 5.05% and 8.65%, respectively.
... An answer to the problem of the low ductility of the cementitious matrices obtained with these various techniques, was found with the incorporation of steel fibers. Thus the Slurry Infiltrated Fiber Concrete (SIFCON) technique [6] involves filling the formwork with bulk fibers, and injecting a fluid mortar slurry. SIFCON, although an interesting material, has had only limited industrial applications because of the difficulties in placing it. ...
High performance concretes with compressive strengths of 100 to 120 MPa have been developed and are being increasingly used for the construction of structural elements. More recently, Reactive Powder Concretes (RPCs) have been developed which have enhanced homogeneity (by the elimination of coarse aggregates and the replacement of natural sand with very fine quartz sand), enhanced microstructure (by the use of a high dosage of silica fume and post-set heat-treating), and enhanced ductility (by the incorporation of small specially developed steel fibers. In order to determine guidelines for the production of RPCs the effects of the following parameters on fresh and/or hardened properties have been determined: (a) superplasticizers obtained from different suppliers, (b) water-binder ratio, (c) quartz sand grading, (d) silica fume content, (e) ternary blends, i.e. pulverised fly ash or ground granulated blast furnace slag in combination with silica fume, and (f) volume and type of fibers. Tests on the mechanical properties indicate that RPC has enhanced tensile strength and ductility, i.e. flexural strengths are likely to be between 30 and 60 MPa and fracture energies above 10000Jm -2 . Initial results from simple impact load tests, without instrumentation, on 1000mm square x 100mm thick unreinforced slab supported on all sides, were very encouraging; the concrete at the top powdered under repeated impacts but there was no indication of tensile cracking. A cone of concrete sheared off from the underside of the slab after about 70 impacts when the thickness of the slab had been reduced considerably by the powdering on the top surface. Key words: High performance fiber reinforced cementitious composites (HPFRCC), reactive powder concrete (RPC), pulverised fly ash (pfa), silica fume, compressive and flexural strength, impact load.
... An answer to the problem of the low ductility of the cementitious matrices obtained with these various techniques was sought with the incorporation of steel fibres. Thus the Slurry Infiltrated Fibre Concrete (SIFCON) technique (Lankard and Lease, 1982) involves filling the formwork with bulk fibres, and injecting a fluid mortar slurry. SIFCON, although an interesting material, has had only limited industrial applications because of the difficulties in placing it. ...
The research work focused on the determination of guidelines for the production of an UHPFRCC, and the experimental investigation of the quality and the behaviour of this material in a highly demanding application, such as the impact resistance of structures. Specifically, the aim of this study is to present the results of an extended work on the development of an UHPFRCC and the experimental determination of the mechanical properties of the produced material. Furthermore, the paper will present preliminary experimental results on the impact resistance of Reinforced Concrete and UHPFRCC slab specimens. 2 EXISTING KNOWLEDGE Concretes with compressive strengths of 100–120 Mpa have been developed and are being used for the construction of structural elements (Gjorv 1992, Vinches et al. 1993). Concretes with com-pressive strengths of 250–300 Mpa can also be produced using different techniques such as those applied for the development of the Densified Small Particle Systems (DSP) (Bache, 1981) and Macro Defect Free (MDF) (Alford et al. 1982, Birchall et al. 1983) materials. An answer to the problem of the low ductility of the cementitious matrices obtained with these various techniques was sought with the incorporation of steel fibres. Thus the Slurry Infiltrated Fibre Concrete (SIFCON) tech-nique (Lankard and Lease, 1982) involves filling the formwork with bulk fibres, and injecting a fluid mortar slurry. SIFCON, although an interesting material, has had only limited industrial applica-tions because of the difficulties in placing it. None-theless, the above techniques have provided a basis for the development of a number of similar or derivative materials in different parts of the world. One such group of materials is the Ultra High Per-formance Fibre Reinforced Cementitious Compos-ites (UHPFRCCs) which have been developed in an attempt to improve the mechanical performance
... 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.
... ECC has a tensile strain capacity of up to 6% and exhibits pseudo-strain hardening behavior, while other fiber reinforced composites (FRCs) require much larger amount of fibers for comparable mechanical properties. Unlike some high performance FRCs, (SIFCON (slurry infiltrated 5 -20% of steel fibers 4,5 ), SIMCON (slurry infiltrated 6% steel fiber mat 6 ; slurry infiltrated steel wool 7 ), and CRC matrix (using 5 -10% fine steel fibers 8 )), which generally adopt very high fiber contents, ECC utilizes only a limited amount of fibers. In general, only 2% or less by volume of discontinuous fibers are used in ECC. ...
A self-compacting engineered cementitious composite (ECC) was developed by optimizing the micromechanical parameters, which control composite properties in the hardened state, and the processing parameters, which control the rheological properties in the fresh state. In the development concept of self-compacting ECC, micromechanics is adopted to properly select the matrix, fiber, and interface properties to exhibit strain hardening and multiple cracking behavior in the composites. With the selected ingredient materials, the self-compactability of ECC is then realized by the controlled rheological properties of fresh matrix and the uniform dispersion of fibers. The controlled rheological properties of fresh matrix, including deformability, flow rate, and selfcompactability is a result of adopting an optimal combination of a superplasticizer and a viscosity agent. According to the measurements of slump flow and the self-placing test result, the ECC developed in this study is proven to be self-compacting. Flexural tests demonstrate that the mechanical performance of self-compacting ECC is insensitive to the externally applied consolidation during placing. This result confirms the effectiveness of the self-compactability in maintaining the quality of the structural elements.
In this research, an experimental investigation was conducted on eight modified slurry-infiltrated fiber concrete (SIFCON) one-way plates to examine the performance of SIFCON-containing waste powder rubber as a partial substitute for natural sand (0, 5, 10, and 15%) under two point loads applied at the third portions of the plate after being subjected to a high temperature. The incorporation of rubber particles is primarily motivated by environmental concerns and the desire to reduce the danger of spalling after exposure to elevated temperatures. All adopted specimens had identical dimensions (1000 mm length, 300 mm width, and 50 mm thickness). Four specimens were exposed to fire for two hours at a constant temperature of 600°C, after which they were rapidly cooled by spraying them with water. The flexure behavior of the simply supported plates was evaluated by applying two point loads to the middle third of the plate (a test of four point load). The results revealed that the residual ultimate load of the burned plates with powder rubber replacement percentages of 0, 5, 10, and 15% was 83.3%, 61.08%, 61.03%, and 58.73%, respectively.
Slurry infiltrated fibrous concrete (SIFCON) and compact reinforced concrete (CRC) are relatively new high-performance and advanced materials which can be considered as special types of steel fibre reinforced concrete (SFRC). Laboratory and field experiments have shown that SIFCON and CRC are innovative construction materials possessing both high strength as well as large ductility. In view of their high tensile strength, ductility, and superior impact and abrasion resistance, the composites have excellent potential for structural applications where accidental or abnormal loads (such as impact, blast etc.) are encountered during service.
A closed form solution is presented for the moment-curvature response of cement-based composites with homogeneously distributed reinforcement. The derivation is based on parametric representation of uniaxial material constitutive response using piece-wise linear and quadratic segments. Effects of tensile and compressive constitutive relations on moment-curvature response were studied and it was observed that the tensile stiffness from the first cracking to the ultimate tensile strength and the ultimate tensile strain were the most important parameters. The moment- curvature relation was combined with crack localization rules to simulate the flexural load-deformation response of a beam under four-point loading conditions. Model simulations indicate that the direct use of uniaxial tension stress-strain response underpredicts the flexural results. This is attributed to the differences in the effective volume of the material subjected to critical stress. By applying a single scaling factor to material models, the model simulations can match the experimental data.
Metal Fiber Reinforcement of Refractories has been investigated at the Combustion Engineering, Inc., Metallurgical and Materials
Laboratory (MML). Castables are used for protection in areas of steam generating units where erosion is severe and in the
inside linings of coal conversion reactors. Improved reinforcement of fine aggregate castables was achieved by development
of the bonding technology of metal fibers to themselves and to substrate alloys. Advances were made in the application of
brazing technology that demonstrated significant improvements in the retention of refractories on substrate surfaces. This
paper highlights developments of metal fiber reinforcement of refractories and describes the development and testing of the
new brazed metal fiber structures supporting refractory coatings.
The strength and ductility of slurry infiltrated mat concrete (SIMCON) tension members were investigated both experimentally and analytically to construct a mechanical model for simulating tensile force–displacement relationships. In addition to standard strength testing, special tests were conducted on tension specimens with preset cracks to determine the interaction between steel fibers and the cement matrix near an opening crack. These tests were conducted on two sets of preset-crack specimens: (i) with symmetrically inclined fibers and (ii) with aligned fibers having variable debonded lengths on each side of the crack. Using measured bridging forces of inclined fibers, an efficiency factor of plane random fibers, compared to aligned fibers, was determined to be approximately 0.58. It was found that the ductility of SIMCON mainly stems from plastic deformation of steel fibers rather than fiber pull-out. SIMCON tensile response was characterized by elastic, nonlinear hardening and softening regimes. The hardening response was notch insensitive without multiple crack formation. In the elastic regime, only minute stiffness reduction was observed. The nonlinear hardening regime was characterized by internal damage growth without visible crack formation and ended with the appearance of a co-linear set of partial cracks. The softening regime was described by a localized failure of fibers with variable failure strains at the co-linear cracks. Based upon the experimental observation that a co-linear set of partial cracks form at the ultimate composite stress, upper and lower bounds of the SIMCON stress–strain relation in the hardening regimes were obtained.
Development of an ultra-high strength ductile concrete designated RPC (Reactive Powder Concrete), was made possible by the application of a certain number of basic principles relating to the composition, mixing and post-set heat curing of the concrete.RPC 200, which can be used under job site conditions similar to those for conventional high performance concretes, can be used in the construction of prestressed structures incorporating no passive reinforcement. RPC800 is suitable for precasting, and can achieve compressive strength values exceeding 600MPa. A value of 810MPa has been obtained with a mixture incorporating steel aggregate.
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