Top PDF The behaviour of steel fibre reinforced concrete material and its effect on impact resistance of slabs

The behaviour of steel fibre reinforced concrete material and its effect on impact resistance of slabs

The behaviour of steel fibre reinforced concrete material and its effect on impact resistance of slabs

The slabs used were 1800 mm square and 130 mm thick, and were doubly reinforced with equal amounts of steel in the top and bottom mats of reinforcement. Steel fibres with end-hooked were used in this study. The FRC slabs exhibited superior performances under impact loading conditions when compared with no fibrous RC slabs. The addition of end-hooked steel fibres led to reduce crack spacing’s and widths; mitigation of local damage mechanisms, such as mass penetration and concrete scabbing; also increased slab stiffness and capacity. The increased impact resistances, stiffness’s, and displacement capacities of the R/FRC slabs tended to correlate with the steel fibre volume fractions provided. The slabs forming the experimental program were designed such that they would be governed by flexural failure modes under conventional static loading conditions; however, all but one of the slabs were controlled by punching shear failures under impact. Inertial force development, which was shown to result in dynamic loading conditions that differ from those encountered under static testing, is suggested to be the main contributor to the punching shear failure modes observed. Under high-mass, low-velocity impact loading conditions, the behaviours of the slabs were not exclusively governed by local failure mechanisms. Global deformations contributed to the impact responses of all slabs, and the influence of local damage development was found to be of less significance in the R/FRC slabs. As the slabs in this study were ultimately controlled by punching shear failures under impact, limited benefits were attained as a result of increasing the longitudinal reinforcement ratios of the RC slabs.
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Structural Behaviour of Fibre Reinforced Steel Concrete Composite Walls

Structural Behaviour of Fibre Reinforced Steel Concrete Composite Walls

Amongst the different developed concrete materials, steel fiber is the one mostly studied by researchers. Amongst newly discovered fibers the CNF has gained more attention in the world of nanotechnology and it is being studied extensively for the past few years. However, the study on CNF concrete is limited to the material level and is mainly focused on cement mortar paste. A material test on CNF mortar has shown that the addition of such fibers increases the compressive and flexural strength of the mortar. In this study, CNF is considered in the concrete and it was evident that the addition of 0.5% fibers improved the mechanical properties of the concrete. There is a gap in finding the effect of CNF concrete at the structural level, which in this study was analysed using the general purpose Finite Element Programme FEAPpv. The results showed that CNF concrete enhances the cyclic behaviour of the structural members as well as the strength, ductility and energy absorption of the member under load. The performance of SC walls proved to be better when CNF concrete is used compared to steel fiber reinforced concrete.
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Design of Fibre Reinforced Concrete Beams and Slabs

Design of Fibre Reinforced Concrete Beams and Slabs

Concrete has proved to be a versatile material in the construction of structures due to the possibility of moulding it into virtually any shape and geometry. Utilizing this formable nature of the material, concrete architecture has made rapid progress in the recent years. Concrete is a material with varying material behaviour with high strength in compression but poor in tension. This has led to a need for reinforcement in the tensile parts of the structures. Traditionally this has been done using ordinary reinforcing bars. However, the need for designing structures with more complex geometries has led to the development of relatively new reinforcement materials such as steel fibres, which have further raised the potential of designing such geometries. Steel fibres can partly or entirely replace conventional reinforcement owing to the fact that steel fibres also increase the load carrying capacity of structures and improve crack control.
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Finite Element Analysis and Design of Suspended Steel Fibre Reinforced Concrete Slabs

Finite Element Analysis and Design of Suspended Steel Fibre Reinforced Concrete Slabs

In this research work, the behaviour of suspended SFRC slabs was studied under concentrated loadings. Available experimental data were used to study the effect of steel fibres on the post- cracking response of concrete. Subsequently, the SFRC constitutive model proposed by Lok and Xiao (1999) was adopted alongside the concrete damaged plasticity model of ABAQUS based on the validation work done. The reliability of the FE numerical model predictions was ensured by calibrating it against existing experimental data. Consequently, additional analyses were carried out examining three main case studies of SFRC slabs namely, single simply supported slabs, 4-panel pile-supported slab (i.e. statically-indeterminate) and 9-panel elevated slab. Parametric studies were carried out covering the full practical range of steel fibre dosages. The results testify that numerically steel fibres can replace rebar in slabs as obtained in the experiment and additional fibres increase the load-carrying capacity, strength and stiffness (thus enhancing response at both the serviceability and ultimate limit states). Ductility was improved by the additional Fibres, and the mode of failure was altered from brittle to ductile.
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Flexural Behaviour of Hybrid Steel Basalt Fibre Reinforced Concrete

Flexural Behaviour of Hybrid Steel Basalt Fibre Reinforced Concrete

numerous micro-cracks. On application of the load, the micro- cracks begin to propagate in the concrete matrix. The addition of randomly spaced discontinuous fibres help in restricting the propagation of the micro-cracks and macro-cracks. Fibres also improve the mechanical properties of plain concrete such as, resistance to impact, resistance to fracture and resistance to dynamic loads [8]. In the modern era, hybridization technology has also been an area of interest to researchers. Hybridization is the process of combining fibers with different characteristics, such as, length, diameter, and aspect ratio, modulus of elasticity, material type and tensile strength, to produce a unique composite that derives benefits from each of the individual fibers [4]. In this study, hybrid fibre reinforced concrete is prepared by combining basalt and steel fibers together according to different volume fraction and aspect ratio. Different experiments were carried out to determine the flexural strength, toughness index and load deflection behaviour of hybrid fibre reinforced beams. For comparison steel fibre reinforced concrete beams and basalt fibre reinforced concrete beams were also casted. All these beams were compared with control beam consisting of no fibres. Key Words: Hybrid fibre reinforced concrete beam, Steel fibre, Basalt fibre.
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Behaviour of steel fibre reinforced concrete beams under high rate loading

Behaviour of steel fibre reinforced concrete beams under high rate loading

It has been established numerically (Cotsovos et al., 2008, Cotsovos, 2010, Saatci and Vecchio, 2009, Kishi et al., 2011) and experimentally (Abbas et al., 2010, May et al., 2006) that the dynamic structural responses of RC members differ to those observed under corresponding static loading once certain thresholds of applied loading rate are surpassed. The observed shift in structural response with increasing loading rates is considered to be associated with (a) structural arrangements (such as geometry, reinforcement and boundary details), (b) the brittle nature and tri- axiality characterising concrete material behaviour, (c) the nature of the problem at hand (i.e. a wave propagation problem within a highly non-linear material) and (d) the development of high strain rates within concrete and steel which is widely considered to affect material behaviour, i.e. strain-rate sensitivity (Cotsovos and Pavlović, 2012). The current work aims to examine the potential benefits of introducing steel fibres to the concrete mix in order to enhance the responses of (the otherwise RC) structural elements under high rate loading due to impact. The work is based on dynamic Non-linear Finite Element Analysis (NLFEA), which was initially validated using existing experimental data to ascertain its accuracy before the subsequent parametric studies were carried out. The work builds on previous NLFEA-based studies on various steel-fibre-reinforced concrete (SFRC) structural configurations subjected to both static monotonic and cyclic loading. The specimens covered a wide practical range from simply-supported beams to more complex structural systems characterised by a certain degree of static indeterminacy, such as continuous columns and beam-column sub-assemblages (Abbas et al., 2016, 2014a,b,c,d). Both previous and current studies utilise a material model for SFRC that is focused
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Steel Fibre Reinforced Concrete Pavements for Roads

Steel Fibre Reinforced Concrete Pavements for Roads

Road transportation is undoubtedly the lifeline of the nation and its development is a essential issue. The traditional bituminous pavements and their wishes for non-stop preservation and rehabilitation operations factors towards the scope for cement concrete pavements. There are numerous blessings of FRCP over CC and bituminous pavements like low upkeep fee, availability of cement is extra in comparison to bitumen. FIBRE REINFORCED CONCRETE PAVEMENTS, which is a latest development in the area of reinforced concrete pavement layout. FRC pavements show to be more efficient than conventional RC pavements. Main function of fibres is to bridge the cracks that increase in concrete and growth the ductility of concrete factors. Improvement on Post-cracking behaviour of concrete and imparts greater resistance to effect masses.
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Flexural Behaviour of Mono Fibre and Hybrid Fibre Reinforced Concrete using Steel and Nylon

Flexural Behaviour of Mono Fibre and Hybrid Fibre Reinforced Concrete using Steel and Nylon

Concrete is a tension-weak building material, which is often crack ridden connected to plastic and hardened states, drying shrinkage, and so on. The cracks generally develop with time and stress to penetrate the concrete, thereby impairing the waterproofing properties and exposing the interior of the concrete to the destructive substances containing moisture, bromine, acid sulphate, etc. The exposure acts to deteriorate the concrete, with the reinforcing steel corrosion. To counteract the cracks, a fighting strategy has come into use, which mixes the concrete with the addition of discrete fibres. Plain cement concrete has some shortcomings like low tensile, limited ductility, little resistance to cracking, high brittleness poor toughness, and so on that restrict its application. The cracking of concrete may be due to economic structural, environmental factors, but most of the cracks are formed due to inherent internal micro cracks and the inherent weakness of the material to resist tensile forces. Drying shrinkage in the concrete may also results in the formation of cracks. To overcome these deficiencies, extra materials are added to improve the performance of concrete.
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Structural behaviour of two-way fibre reinforced composite slabs

Structural behaviour of two-way fibre reinforced composite slabs

Since concrete has a relatively high compression strength and, for most practical purposes, negligible tensile strength it is advantageous to pre-stress concrete before the actual load is applied. In this case, applied loads only reduce the amount of compressive stress without producing tensile stress. Currently, high strength steel tendons are generally used for pre-stressing concrete. Even though concrete cracks can be prevented by the prestress, concrete is porous and water and chemicals may still reach the prestressed tendons, particularly in a caustic environment. Due to their superior durability, FRP prestressing tendons show great potential to replace conventional steel tendons. The first prestressed concrete bridge to be built using glass reinforced prestressing strand was a small footbridge in Dusseldorf, Germany which was completed in 1980. This bridge was essentially designed as a reinforced concrete bridge allowing some of the tendons to be removed for testing. During the past twenty years, a number of concrete structures have been built worldwide utilizing prestressed FRP tendons (Hollaway and Head 2001). However, due to the high material cost of FRP composites compared to steel, the use of FRP reinforcement for concrete structures is currently limited to special applications where the cost disadvantage is out-weighted by other benefits.
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Mechanical Behaviour and Long-Term Performance of Steel Fibre Reinforced Rubberised Concrete

Mechanical Behaviour and Long-Term Performance of Steel Fibre Reinforced Rubberised Concrete

In a recent study, the authors [38] demonstrated that the inclusion of fibres in RuC with high volumes of rubber (e.g. 30% or 60%) promote the development of SFRRuC with enhanced flexibility and ductility characteristics and flexural strengths that comply with the specifications defined in pavement design EN 13877-1 [39]. It has also been identified [40] that the substitution of natural aggregate by rubber particles increases the permeability of SFRRuC (i.e. volume of permeable voids and sorptivity) as rubber content increases. However, this increment is minor and the permeability properties of these concretes lie within the range of highly durable concretes. Furthermore, SFRRuC exhibit very high resistance to chloride permeability when assessed under accelerated wet-dry cycles [40]. The combination of such properties makes SFRRuC mixes ideal candidates for flexible concrete pavements. However, the effect of large volume of rubber on freeze-thaw resistance needs to be addressed. Due to the weak bond between cementitious materials and rubber particles [25, 26], micro-cracks forming in RuCs might propagate locally at a fast rate, making these materials more prone to damage. However, the authors hypothesised that this issue would be greatly mitigated by the inclusion of fibres in RuC as fibres tend to bridge micro-cracks and resist their opening. Hence, this study aims to examine the influence of freeze-thaw on the performance of SFRRuC under accelerated conditions. Performance is assessed through visual inspection of the specimens, mass loss, coefficient of thermal expansion (CTE), changes in relative dynamic modulus of elasticity (RDM), and residual mechanical properties including compressive strength, flexural strength, flexural modulus of elasticity and toughness.
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Behaviour of Steel Fibre Reinforced Concrete Under Flexural Failure

Behaviour of Steel Fibre Reinforced Concrete Under Flexural Failure

The amount of fibers added to the concrete mix is expressed as a percentage of total volume of the composite (concrete and fibers), termed volume fraction (Vf). Vf typically ranges from 0.1 to 3%. Aspect ratio (l/d) is calculated by dividing fiber length (l) by its diameter (d). Fibers with a non-circular cross section use an equivalent diameter for the calculation of aspect ratio. If the modulus of elasticity of the fiber is higher than the matrix (concrete or mortar binder), they help to carry the load by increasing the tensile strength of the material. Increase in the aspect ratio of the fiber usually segments the flexural strength and the toughness of the matrix. However, fibers which are too long tend to ―ball‖ in the mix and create workability problems. Some recent research indicated that using fibers in concrete has limited effect on the impact resistance of the materials. This finding is very important since traditionally, people think that the ductility increases when concrete is reinforced with fibers. The results also indicated out that the use of micro fibers offers better impact resistance compared with the longer fibers.
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Numerical Simulation of Missile Impact on Reinforced Concrete Slabs: Effect of Concrete Pre-stressing

Numerical Simulation of Missile Impact on Reinforced Concrete Slabs: Effect of Concrete Pre-stressing

Non-linear dynamic behavior of reinforced concrete slabs was analyzed using commercial Finite Element (FE) code LS-DYNA. Explicit version was selected for the entire modelling. FE predictions based on Winfrith MAT084 concrete material model without strain-rate were compared with tests results. Concrete erosion criteria as well as other ”non-physical” parameters of FE model were selected identical to earlier authors work on modelling concrete slab without pre-stressing. The behaviour of Dywidag bars was also examined. FE predictions obtained are in good agreement with tests, showing similar trend for concrete damage patterns at both front and back sides of the slab. Subsequently, it was concluded that FE model developed earlier for slabs without pre-stressing could be successfully used for pre-stressed concrete structures as well.
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Behaviour of Steel Fibre Reinforced Concrete under Flexural Failure

Behaviour of Steel Fibre Reinforced Concrete under Flexural Failure

Rana.A,(2013) also mentioned in his studies that the steel fiber used in concrete to control cracking due to both of drying shrinkage and plastic shrinkage. Then the fibers also reduce the permeability of concrete and thus reduce bleeding of water. Among types of fibers such as glass, natural and synthetic polymer, the focus given on steel fiber because it is used in this research. The reason using the steel fiber because it can improve the durability of concrete and increase the impact resistance of concrete. Then, the steel fiber having a various types with different properties.
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Fatigue behaviour of steel fibre reinforced concrete – a Review

Fatigue behaviour of steel fibre reinforced concrete – a Review

---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Now a day there are so many fibres are available in the civil engineering sector. Generally their behaviour is considered satisfactory if they withstand two million cycle of repetitive loading without distress or failure at the required mean stress level. The addition of fibre in the concrete mix improves the monotonic flexural strength, flexural fatigue strength, impact strength, shock resistance, ductility, and flexural toughness in concrete, besides delaying and arresting crack proportion. Fatigue is described by a parameter, which essentially represents the number of cycles the material can withstand under a given pattern of repetitive loading, before falling. This paper presents to study the behaviour of reinforced concrete beam cast at different types of steel fibre in the concrete matrix and subjected to fatigue loading.
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Impact resistance of pre-damaged ultra-high performance fibre reinforced concrete (UHPFRC) slabs

Impact resistance of pre-damaged ultra-high performance fibre reinforced concrete (UHPFRC) slabs

Zhang et al. [74] presented an experimental study to evaluate the damage and failure mode of full scale blast shelter hybrid-fibre engineered cementitious composite (ECC) panel under repeated concentric low velocity projectile impact test. The results were compared to the FRC (1% fibre volume) and commercially available reinforced concrete RC blast shelter. The hybrid ECC material was prepared using reinforcing bars, 0.5% steel and 1.5% polyethylene fibre and the concrete grade was maintained at 40 MPa for all specimens. They reported that the ECC panels exhibited smaller indentation depth and crater size compared to FRC and RC. Furthermore, the ECC panels also showed higher residual strength and impact resistance under multiple impacts where the ECC panels suffered less damage per impact as indicated in the trend line of the peak impact force in Figure 2.14 [74]. The authors viewed that the dramatic drop in the gradient shown by the FRC100 and RC100 panels was the result of the greater internal damage leading to earlier reduction in the stiffness for every impact number. In a study on the residual strength of a carbon composite under repeated impact, Wyrick and Adams [75] also expressed the same view and explained that the previously damaged material in the specimen cushioned the impactor during the next impact. However, it is worth mentioning that the magnitude of the peak force is also governed by the amount of impact energy absorbed by the specimen. Obviously, lower impact energy will result in lower peak force.
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Investigation on Impact Resistance of Steel Fibre Reinforced Concrete

Investigation on Impact Resistance of Steel Fibre Reinforced Concrete

Concrete is the most widely used construction material in this world. Generally concrete has low ductility and impact resistance on bridge decks, Aircrafts etc., hence steel fibres are added with concrete mix. Due to an increasing use of FRC (fibre-reinforced concrete) in construction like bridge decks and military industries against impact loads, these concretes are important role in human life. Adding fibres to concrete increases its ductility, tensile strength, flexural strength and resistance against dynamic and impact loads. The aspect ratio (L/d) and volume fraction (Vf) are important fibres parameters in FRC. When cracks are initiated in FRC, the fibres bear the applied loads, when the load increases the fibres tend to transmit the excess stresses to the matrix. If these stresses exceed the fibre-matrix bond strength, which in turn is influenced by fibre properties the fracture process may lead to fibres pullout or rarely rupture of the fibres. Thus, fibre reinforced concretes are more ductile than other concretes.
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Experimental Study of Fibre Reinforced Concrete using GGBS and Steel Fibre

Experimental Study of Fibre Reinforced Concrete using GGBS and Steel Fibre

The Ordinary Portland Cement (OPC) is one of the main ingredients used for the production of concrete and has no alternative in the civil construction industry. Unfortunately, production of cement involves emission of large amounts of carbon-dioxide gas into the atmosphere, a major contributor for green house effect and the global warming, hence it is inevitable either to search for another material or partly replace it by some other material. The search for any such material, which can be used as an alternative or as a supplementary for cement should lead to global sustainable development and lowest possible environmental impact.
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Punching shear of concrete flat slabs reinforced with fibre reinforced polymer bars

Punching shear of concrete flat slabs reinforced with fibre reinforced polymer bars

(FRP bars have a density ranging from 1/6 to 1/4 that of steel (ACI Committee 440 2015)), decreasing the cost of handling and transportation and high specific strength (tensile strength of FRP approximately two to three times of that of steel). In addition, FRP has good corrosion resistance, improved thermal insulation and low thermal expansion. However, the behaviour of FRP bars varies from that of steel in some aspects. For example, FRP bars don’t show ductile behaviour in RC structures, FRP bars have perfectly linear-elastic behaviour until failure without a yielding point. Moreover, FRP bars have a relatively lower modulus of elasticity compared with that of steel (FRP modulus of elasticity is about 1/4 or 1/3 that of steel). Furthermore, FRP bars have different bond characteristics to steel bars, for example, sand-coated GFRP bars have adhesion and friction bond which homogeneously distribute the bond stresses along the embedded length of the bar, whereas, the deformed steel bars have a mechanical bond through bearing on the deformation parts of the steel bars. Therefore, GFRP bar- reinforced concrete structures exhibit lower average crack spacings than those of steel bar-reinforced concrete structures.
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Behaviour of fibre reinforced concrete slabs under impact loads

Behaviour of fibre reinforced concrete slabs under impact loads

crete structures and composite materials in infrastructure, increases the demand of design of high strength and durable reinforced concrete structure subjected to static and impact loads. The structural design deals with various types of loads such as earthquake load, and impact occurs from various reasons such as vehicle collision, rock fall, military exercise, missile attacks etc. Construction industry is heading towards a new era with (HPC). High performance concrete overcomes the limitations of conventional concrete. The use of HPC is not only limited to infrastructural projects but also in high rise structures, nuclear reactor, defense structure etc. Now-a-days fibers are the most used materials to improve the ductile property of concrete. The properties of carbon fibers, such as high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance and romising fiber materials to be used in the Fiber Reinforced concrete (FRC). Use of polypropylene fibers reduces cracks during plastic and hardened state particularly when it is use in structural elements such as beam, column, slabs etc. which quality of concrete constructions. Hence, addition of carbon fibers and polypropylene fiber to HPC increases toughness, energy absorption capacity of High Performance Fiber Reinforced The present experimental investigation has been focused to develop a comprehensive understanding of test slab specimen under impact loading. HPC of M60 grade of concrete integrated with carbon fibers and polypropylene fibers. Series of twelve slab test specimens 0mm) with varying thickness of 60, 50 and 40 mm with and without carbon fibres (0.5% by volume),polypropylene fibres (900 gm/m 3 ), and combination of both. Impact tests on the slab test specimens were carried out on a low velocity repeated impact ne using instrumented drop weight hammer of 10.2 kg attached with Load Cell and was designed, fabricated and installed at Civil Engineering Department, UVCE, Bangalore University, 56. Accelerometer, LVDT’s was used to record the Time-histories and Load, Deflection, and Acceleration. The experimental result shows a significant increase in the energy absorption, peak loads same number of impact blows for the carbon and polypropylene fibre reinforced concrete test
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A Practical Investigation on the Behaviour of Steel Fibre Reinforced Concrete

A Practical Investigation on the Behaviour of Steel Fibre Reinforced Concrete

Cement concrete is the most extensively used construction material in the world. The reason for its extensive use is that it provides good workability and can be moulded to any shape. Ordinary cement concrete possesses a very low tensile strength, limited ductility and little resistance to cracking. Internal micro cracks lead to brittle failure of concrete. In this modern age, civil engineering constructions have their own structural and durability requirements. Every structure has its own intended purpose and hence to meet this purpose, modification in traditional cement concrete has become mandatory. It has been found that different type of fibers added in specific percentage to concrete improves the mechanical properties, durability and serviceability of the structure. It is now established that one of the important properties of Steel Fiber Reinforced Concrete (SFRC) is its superior resistance to cracking and crack propagation. In this paper effect of fibers on the strength of concrete for M20 and M40 grade have been studied by varying the percentage of fibers in concrete. Fiber content were varied by 0.50%, 1% and 1.5% by volume of cement. Cubes of size 150mmX150mmX150mm to check the compressive strength and beams of size 500mmX100mmX100mm for checking flexural strength were casted. All the specimens were cured for the period of 7, 28 and 56 days before crushing. The results of fiber reinforced concrete for 3days, 7days and 28days curing with varied percentage of fiber were studied and it has been found that there is significant strength improvement in steel fiber reinforced concrete. The optimum fiber content while studying the compressive strength, flexural strength cube is found to be 1%. Also, it has been observed that with the increase in fiber content up to the optimum value increases the strength of concrete. Slump cone test was adopted to measure the workability of concrete. The Slump cone test results revealed that workability gets reduced with the increase in fiber content.
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