Fibre Self-compacting Concrete Research Articles

Experimental study on compressive properties of mixed fiber concrete after fire

In recent years, the application of high performance self-compacting concrete with high strength, high durability and high workability has become more and more widespread, and has gradually become the main building material. However, high-performance self-compacting concrete increases brittleness while increasing strength, and at the same time, explosion resistance and fire resistance are significantly reduced. With the development of cities, natural gas and intelligent electrical equipment are becoming more and more popular, but people's awareness of fire safety has not been improved, making the incidence of fire in buildings on the rise. In recent years, the development of hybrid fiber self-compacting concrete (HFRSCC), which combines the high workability of self-compacting concrete (SCC) and the high toughness and high crack-resistant properties of fiber concrete (FRC), giving full play to the fiber's anti-cracking, reinforcing and toughening effect, and after the fire and high temperature effect, the components of the use of hybrid fiber self-compacting concrete to maintain a certain degree of residual load-bearing capacity. The introduction of fibers for reinforcement and toughening, to improve the mechanical properties of concrete materials, blast resistance and fire resistance performance points to a direction.

Regression Anaylsis for the Experimental Study on the Pullout Strength of Steel Fiber Self- Compacting Concrete

This article describes experimental research of the interfacial adhesion of triple blended steel fibre self-compacting concrete (TBSFSCC) and it varies depending on the percentage of steel fibre. In self-compacting concrete, mineral admixtures such as condensed silica fume and flyash are utilised as supplementary cementitious materials (SCMs).the percentage of replacement of cement by condensed silica fume at 10 where as flyash at 20 respectively, to meet the SCC criteria stipulated by ACI. The embedment length of a steel bar with a diameter of 12mm was chosen to be 100mm in all of the standard specimens. Fe-415 steel rod is used in this research. The pull-out test in the universal testing machine is used to evaluate the bond strength of this triple blended Self-Compacting Concrete (TBSCC). Ordinary steel fibres are then added to the concrete volume at various percentages, such as 0.2, 0.4, 0.6, and 0.8. The bond strength, slip, and the method of failure of each rebar were all noted in the test results. The comparison of these results clearly shows that the percentage of steel fibre contributes to the TBSCC bond strength, and conclusions are generated.

Properties of High-Content Micro-Steel Fiber Self-Compacting Concrete Incorporating Fly Ash and Slag Powder Performance Study

The addition or substitution of various gel materials in cement-based composites has been proven to be an effective approach in enhancing the performance of concrete. Current research focuses mainly on enhancing the toughness of concrete, but lacks discussion on the performance of alternative gel materials. Therefore, this study aims to explore the effects of partially substituting cement with fly ash and slag powder as gel materials, while incorporating a high volume fraction of micro-steel fibers (6%), on the workability and mechanical properties of self-compacting concrete. By means of rigorous experimental investigation and meticulous analysis, we comprehensively assessed the workability characteristics of self-compacting concrete, encompassing critical aspects such as filling ability, cohesion, and permeability. Additionally, we conducted an extensive evaluation of the mechanical attributes of self-compacting concrete, encompassing vital parameters, such as compressive strength, axial compressive strength, splitting tensile strength, and flexural strength. Last but not least, through a holistic integration of workability and mechanical properties, we conducted a comprehensive performance evaluation of self-compacting concrete incorporating a synergistic blend of fly ash, slag powder, and micro steel fibers. The experimental results indicate that the composite addition of fly ash and slag powder in self-compacting concrete, while compatible with up to 6% micro-steel fibers, leads to a decrease in concrete workability and an increase in cohesiveness due to the addition of micro-steel fibers. Moreover, fly ash predominantly influences the tensile properties of concrete, while the addition of slag powder significantly affects the compressive and flexural properties of concrete. Additionally, the addition of micro-steel fibers significantly improves the overall mechanical properties of concrete.

The Effect of Polypropylene Fibers on the Behavior of Fiber Self-Compacting Concrete

Fiber self-compacting concrete (FSCC), is a concrete that has been combined with fiber in its mix design. Extensive benefits of self-compacting concrete (SCC) in full fill the mold and achieving full compaction without vibration, with good behavior after concrete cracking, raise the idea of self-compacting concrete production. The fundamental challenge in this area is the unsatisfactory performance of concrete with fibers; In other words, using fibers in concrete will reduce concrete fluidity. Therefore, determining the appropriate percentage of fibers in SCC can be a precursor to extending the use of FSCC. In this study, polypropylene fibers with 0.5, 1, 0.1, and 2% of concrete mix design have been added to the self-compacting concrete mix design. Its impact on the performance of concrete has been evaluated using time and diameter of slump-flow, L-Box, J-ring, and V-funnel flow time tests. Based on the criteria defined by EFNARC standard, it was indicated that the FSCC containing 0.5% polypropylene fibers has an acceptable performance. Additionally, the effect of polypropylene fiber on the mechanical properties of hardened concrete has been studied using compressive strength and tensile tests and shown that changes in FSCC compressive strength and tensile with 0.5% polypropylene fiber are negligible.

Mechanical Properties and Crack Resistance of Basalt Fiber Self-Compacting High Strength Concrete: An Experimental Study.

Pure self-compacting concrete has many disadvantages, such as early shrinkage and cracking. The addition of fibers can effectively improve the properties of resistance to tension and cracking of self-compacting concrete, thereby the effect of improving its strength and toughness can be achieved. Basalt fiber is a "new green industrial material" that has unique advantages, such as high crack resistance and being lightweight compared with other fiber materials. In order to study the mechanical properties and crack resistance of basalt fiber self-compacting high-strength concrete intensively, the self-compacting high-strength concrete of C50 was designed and obtained using the absolute volume method with multiple proportions. Orthogonal experimental methods were used to study the influence of the water binder ratio, fiber volume fraction, fiber length, and fly ash content on the mechanical properties of the basalt fiber self-compacting high-strength concrete. Meanwhile, the efficiency coefficient method was used to determine the best experiment plan (water binder ratio 0.3, fiber volume ratio 0.2%, fiber length 12 mm, fly ash content 30%), and the effect of fiber volume fraction and fiber length on the crack resistance of the self-compacting high-performance concrete was investigated using improved plate confinement experiments. The results show that (1) the water binder ratio had the greatest impact on the compressive strength of basalt fiber self-compacting high-strength concrete, and as the fiber volume fraction increased, the splitting tensile strength and flexural strength both increased; (2) there was an optimal value for the effect of the fiber length on the mechanical properties; (3) with the increase in fiber volume fraction, the total crack area of the fiber self-compacting high-strength concrete significantly decreased. When the fiber length increased, the maximum crack width first decreased and then slowly increased. The best crack resistance effect was achieved when the fiber volume fraction was 0.3% and the fiber length was 12 mm. Therefore, basalt fiber self-compacting high-strength concrete can be widely used in engineering fields, such as national defense construction, transportation, and building structure reinforcement and repair, due to its excellent mechanical and crack resistance properties.

Study on static and dynamic mechanical properties of steel fiber self-compacting concrete after heating in a high-temperature

While supporting impact loads, steel fiber self-compacting concrete (SFRSC) is frequently impacted by temperature loads. Therefore, it is essential to investigate how the SFRSC responds mechanically when impact and high temperature are combined. To ascertain the effects of temperature and impact load on the static and dynamic mechanical characteristics of SFRSC, static and dynamic mechanical tests were performed on SFRSC treated at 25 °C, 100 °C, 200 °C, 400 °C, 600 °C, 800 °C, and 1000 °C using the RMT-150C system and SHPB, respectively. The laws of mechanical response changes were presented from the viewpoints of the stress-strain relationship, compressive strength, DCF, DSF, elastic modulus, XRD phase analysis, and failure morphology. Systematically examined were the effects of temperature on mechanical behavior when impact and high temperature are coupled, including the temperature strengthening effect, temperature weakening effect, critical temperature, and strain rate effect. A damage-type viscoelastic constitutive model taking temperature into account was created by incorporating the temperature effect coefficient K and the damage factor D. According to the results, static and dynamic mechanical characteristics were improved at temperatures of 100 and 200 °C, but they dramatically degraded at 400–1000 °C, and strain rate sensitivity significantly increased with temperature.

Performance Evaluation of Hybrid Fibre Reinforced High Volume Fly Ash based Self Compacting Concrete

Self-compacting concrete has become increasingly popular lately for usage in crowded concrete-reinforced buildings having challenging casting circumstances. New cement needs to have high fluidity and strong cohesion for these applications. The necessary concrete characteristics can be ensured through the use of fine elements like fly ash. The preliminary findings of a trial to produce and assess SCC created using large amounts of Fly ash is given and discussed. During this investigation, few SCC combinations and a control concrete is examined. The water/cementitious material ratio is ranges from 0.35 while cementitious material amount remained constant (300 kg/m3). Its self-compacting mixes replaced 25%,35%,37.5%,40%, and 50%, of the cement with fly ash. All mixes were put through tests to determine their viscosity and stability as fresh concrete. Additionally, the compressive strength, Flow Ability Test, Flexural strength and Split Tensile Strength of cured concretes were measured. For the purpose of testing the flow characteristics and mechanical properties of Hybrid Propylene Steel Fibre Self-Compacting Concrete (HPSscc), Steel Fibre in combination with Poly Propylene PP Fibre (Hybrid Fibre) are used to regulate SCC at concentrations of 0.25+0.15%, 0.50+0.30%, 0.75+0.45%, 1.0% + 0.60%, and 1.25+0.75%.The ideal quantity of hybrid fibre is established. The 28-day compressive strengths of the SCCs ranged from 35 to 54 MPa. It is important to research the effects of adding steel fibres to control SCC of various types, aspect ratios, and volume fractions. Concrete can benefit from having its tensile strength increased by using synthetic fibres like polypropylene PP. It is important to achieve the ideal quantity of PP fibres to be added for a specific characteristic of the mix's constituents. Hybrid fibre is used in concrete when more than one fibre is included. The performance of concrete can be improved by using the characteristics of one type of fibre with another type of fibre. Also Flow Ability Test carried out immediately after producing concrete earlier and Split Tensile Strength tests are conducted. The outcomes demonstrate that a cost-effective SCC might be successfully constructed by adding significant amounts(35%) of fly ash.

Stress-strain behaviour of unconfined and confined hybrid glass/steel fibre self-compacting concrete

An experimental study was conducted to investigate the effectiveness of transverse reinforcing bars of self-compacting concrete mix (PSCC) and hybrid glass fiber reinforced self-compacting concrete mix (HFRSCC) grade M 40 under monotonically increasing axial compression. was performed for cylinders enclosed in . The behavior of SCC cylinders surrounded by a circular ring and having different volume ratios and clearances was compared under axial compression. In this work, we present a mathematical model developed to predict the stress-strain behavior of SCC and FRSCC under constrained and unconstrained conditions and validate the model using experimental results. To develop SCC, Nan Su blending method based on filling rate 1.12 and 1.14, S/A ratio 0.50 and 0.57 is applied. The steel and glass fiber usage in the hybrid fiber reinforced SCC mixture is assumed to be 1% and 0.05% of the concrete volume respectively. M 40 grade plain self-compacting concrete mixes (PSCC) and hybrid glass/steel fiber reinforced self-compacting concrete mixes (HFRSCC) constrained to different volume ratios, stresses, strains, elastic moduli, plasticity ratios, ductility ratios, and unlimited strength ratios ) has been evaluated experimentally. The following conclusions can be drawn from the stress-strain diagram: 1) Maximum load-bearing capacity and strain at peak stress are higher for his HFRSCC than for PSCC. 2) The presence of steel and fiberglass increases the strength bearing capacity and allows it to withstand greater loads at peak loads. 3) If the containment is in the form of a lateral ring boundary, the effect of fibers is almost negligible. This clearly shows that HFRSCC has a stronger containment effect compared to his PSCC. The strength confinement factor is lower for HFRSCC, suggesting that HFRSCC offers a superior confinement factor compared with his PSCC.

Performance of hybrid glass/steel fibre self-compacting concrete beams under static flexural loading

In this paper, it is proposed to study the static flexural performance of hybrid (glass and steel) fiber reinforced M30 grade self-compacting concrete (SCC) beams made with glass fiber reinforcement polymer (GFRP) re-bars. Nan Su mix design approach is adopted to develop the M30 grade plain SCC (PSCC) mixes. Glass fibre SCC (GFRSCC), steel fibre SCC (GFRSCC) and hybrid fibre SCC (HFRSCC) mixes are prepared using the optimum dosages of glass (0.05%) and steel fibres (1%) by volume fraction. HFRSCC reinforced beams of size 1200 *200*150 mm will be casted with steel and GFRB rebars and tested to study the flexural properties such as ultimate flexural strength, load at first crack, deflection at the center, crack width and crack patterns. For the above fibred beams, load-deflection relations will be established. The HFRSCC beam made with GFRP rebars have the load carrying capacity 37.03% more than HFRSCC beam made with steel rebars. The deflection for the HFRSCC beam made with GFRP rebars is 61.52% more than beam made with steel rebar HFRSCC beam made with GFRP rebars increases the load at first crack, ultimate flexural strength, and deflection at the centre at failure and the crack width for same HFRSCC beam made with steel rebars

Regression Analysis for the Bond Strength of Steel Fibre Self-compacting Concrete Based on the Experimental Studies

This article describes experimental research of the interfacial adhesion of triple blended steel fibred self-compacting concrete (TBSFSCC) and it varies depending on the percentage of steel fiber. In self-compacting concrete, mineral admixtures such as condensed silica fume and fly ash are utilized as supplementary cementitious materials (SCMs). Condensed silica fume can replace 10 percent of the cement and fly ash can replace 20 percent of the cement to fulfill ACI's SCC guidelines. The embedment length of a steel bar with a diameter of 12mm was chosen to be 100mm in all the standard specimens. Fe-415 steel rod is used in this research. The pull-out test in the universal testing machine is used to evaluate the bond strength of this triple blended Self-Compacting Concrete (TBSCC). Ordinary steel fibers are then added to the concrete volume at various percentages, such as 0.2, 0.4, 0.6, and 0.8. The bond strength, slip, and the method of failure of each rebar were all noted in the test results. The comparison of these results clearly shows that the percentage of steel fiber contributes to the TBSCC bond strength, and conclusions are generated.

Investigation the properties of sustainable ultra-high-performance basalt fibre self-compacting concrete incorporating nano agricultural waste under normal and elevated temperatures

Producing sustainable concrete using waste materials has a noticeable impact on the environment. From another aspect, understanding the effect of high temperature on concrete can help in reduce the environmental fire impact and lower rehabilitation costs. This study presents a systematic experimental investigation to produce sustainable ultra-high-performance basalt fibre self-compacting concrete (UHPBF-SCC) using agricultural waste materials including nano sugar cane bagasse, nano cotton stalk ash and nano rice straw ash as cement replacement. The three dosages of nanoparticles are mechanically produced after heat treatment at 700°C. The performance of the three dosages of nanoparticles (partially replacing 1–5% of cement) was investigated in the presence of basalt fibre. This study also examines the effect of elevated temperatures of 300°C and 600°C on the behaviour of UHPBF-SCC. The physical properties, including passing ability, flowability and segregation resistance, were studied. Compressive strength, strength loss at elevated temperature, mass loss, ultrasonic pulse velocity, splitting, and flexure strength were also investigated. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX) analysis were conducted to show the microstructure of the mixes. Mechanical characteristics are significantly increased in the presence of nanoparticles, more than 18% in compressive, 32% in tensile strength and 28% in flexure strength compared with the reference mix. SEM analysis showed compacted sections with high bonded matrix and high ITZ at normal conditions, but microcrack propagation appeared at 300°C and 600°C due to ettringite decomposition and evaporation of capillary and adsorbed water. EDX analysis showed high Ca/Si with the addition of nanomaterials.

Creep Strain Behaviour of Triple-Blended Steel Fiber Self-Compacting Concrete

The objective of the research article is to present the experimental results on the creep strain behaviour of steel fiber Self-Compacting Concrete (SFSCC). In respect of binder content, aggregate size, fine-to-coarse aggregate ratio, water-to-cement ratio, and chemical admixtures, Self-Compacting Concrete (SCC) differentiates from conventional cement concrete. Steel fibers are also inserted into SCC at a predetermined percentage to reinforce it. Steel fibers have been shown to contribute to improved strength characteristics, a dense mass of concrete with little or no voids, reduced pores in concrete, a higher Young’s modulus, and fewer deflections and strains in concrete. Hence, an investigation was conducted on the creep variation of SFSCC over a longer duration. The test approach follows ASTM C512’s standard test method for concrete creep in compression. The test specimens (SFSCC) are standard cylinders that have been cast and cured for 28 days before being tested. Three SFSCC cylinders with 0.80% steel fiber were tested at the same time. The load is applied to just the cylinders in the loading frame and kept constant, producing constant stress. The strains that occur only due to creep, excluding the initial elastic strain, are digitally recorded. As a logarithmic function, the creep strain-time connection was established. The conclusions are observed based on the findings of the experiments and compared with normal cement concrete (NCC).

New generation of fiber self-compacting concrete based on pyrophyllite

The aim of this work is to develop new-generation ultra-high-performance fiber self-compacting concretes (SCCs) by introducing pyrophyllite rock powder as a cement substitute and assess its effects on the fresh and hardened properties. Three series of concretes were developed. The first series of reference fiber SCCs without pyrophyllite contained 1% adherent steel fibers or 1% slippery polymeric polypropylene fibers or a mixture of 0.5% steel and 0.5% polypropylene fibers. The second and the third series contained fibers and 10 or 20% pyrophyllite. The results showed that incorporation of pyrophyllite generates good fluidity, satisfactory stability without any risk of segregation and an ability to flow in a confined environment without risk of blocking of the fiber SCC. Moreover, the ultrasonic velocity, elastic dynamic modulus and rebound hammer number increase with increasing pyrophyllite rate. Also, a gain in compressive and flexural strengths was obtained at 28 days and the fiber SCCs were judged to be of good quality. The best formulation is the one containing steel fibers and 10% pyrophyllite. This additive has shown its potential to be used as a substitute for cement and its beneficial effect in protecting the environment.

Shear capacity of precast half-joint beams with steel fibre reinforced self-compacting concrete

A complex geometry of precast reinforced concrete half-joint beams has resulted from the high shear force at the recessed ends of such beams. Immense levels of reinforcements are provided close to the re-entrant corner of these beams to prevent the propagation of diagonal cracks and sudden failure. However, this condition leads to reinforcement congestion and affects the bond between concrete and reinforcing steel due to improper concrete filling around the congested bars. Hence, the use of steel fibre self-compacting concrete (SFRSCC) was found to combine the advantages of eliminating the vibration works, and reduction of secondary reinforcement. An experimental study was conducted to examine the ability of 1.0% by volume of steel fibre to partially replace the traditional reinforcements on two types of half-joint beams (short recess (SR) and deep recess (DR) beams). Other factors taken into account is the variance in shear span values and nib height, as well as the ratio of shear-span-to-depth, av/d. Observations showed that the replacement of 1.0% by volume of steel fibre volume fraction is possible only when substituting at least 50% of the vertical or horizontal reinforcement in SR beams. Meanwhile, the replacement over diagonal reinforcement is seemed to be not enough and the replacement is only promising in substituting part of stirrups in DR beams. The variance in the shear-span-to-depth av/d ratio affects the shear failure mode of the beam half-joints. Two semi-empirical equations for predicting the shear strength of precast SCC and SFSCC beam-half joints are developed based on the analysis of failure modes. The first equation, which relies on the crushing of the concrete strut, was found to suit the SR beams, while the equation for DR beams suits the theoretical of reinforcement yielding. The two equations give a good correlation with the experimental results.

Effect of high temperature on the mechanical properties of basalt fibre self-compacting concrete as an overlay material

Basalt fibres are modern inorganic concrete fibres, fabricated by melting the basalt rock. These fibres exhibited remarkable resistance to elevated temperatures in comparison with other manufactured fibres. Thus, when the impact of fire is the main consideration, basalt fibres are favoured in the construction of concrete buildings. In this study, the effects of basalt fibres on the workability of fresh self-compacting concrete (SCC) were measured using slump flow, J-ring flow, V-funnel flow and L-box height ratio. The properties of hardened concrete such as compressive strength, splitting strength, modulus of elasticity, flexural strength, and Poisson’s ratio were examined at temperatures between 25 °C and 500 °C. Also, the bond strength between the basalt fibre SCC as an overlay material and a normal concrete substrate was analysed at elevated temperatures. The interfacial surface between the concrete parts of the hybrid samples was roughened in different ways to determine the best roughening mode, which induced high slant shear strength of concrete under fire. The experimental results revealed that increasing the temperature up to 500 °C reduced the tensile and compressive strengths of SCC by over 20%. The optimum slant shear strength of hybrid concrete under fire was achieved by roughening the interfacial surface through the sandblasting method.

Research of Shear Experiment of Interface between New Steel Fiber Self-compacting Concrete and Old Ordinary Concrete

In prefabricated concrete structure, the shear performance of interfaces between prefabricated parts and cast-in-place parts needs improvement. Steel fiber self-compacting concrete is a desirable kind of concrete to solve this problem. This paper introduced Z-shape specimens with interfaces between new steel fiber self-compacting concrete part and old ordinary concrete part as direct shear experiment objects. Factors including steel fibers volume ratio and inserting rebars were also studied. The results show that the shear strengths of interfaces increase with the increases of steel fibers volume ratio, and inserting rebars can improve shear strengths and change failure form from brittle failure to ductile failure.

The fibre shear supplement of precast beam-half joints using steel fibre self-compacting concrete

The end region of the dapped-end beam experienced multiaxial stress actions, which requires high amounts of reinforcement and this resulted to the closely space reinforcement. Therefore, hooked-end steel fibres were mixed into all beam specimens to partly replace the secondary shear and bursting reinforcement to reduce the congestion issue. A series of experiments were performed on shallow recess (SR) and deep recess (DR) half joint beams to examine the partial reduction of reinforcement with 1% replacement of steel fibre. All SR and DR beams were then tested under shear load to study the effectiveness of steel fibres over traditional reinforcement in resisting loads, with two different shear span-to-depth ratios, which are 1.4 and 2.1. The experimental shear strength fibre supplement results for the SR and DR beam specimens were compared with theoretical predictions using the analytical and RILEM methods. The incorporation of 1% of steel fibre in the concrete matrix has the ability to replace 50% of horizontal and vertical reinforcement in SR and DR beams. In general, it is found that both the analytical and RILEM methods give a close approximation for the experimental DR beam specimen values, but slightly overestimated the fibre shear supplement of SR beam specimens by 13.4%. The results support the ability of steel fibres to resist tensile stress through its fibre-bridging action.

Properties of steel fiber self-compacting concrete incorporating quarry dust fine powder

Self-compacting concrete (SCC) has great potentials as it offers several environmental, economic and technical benefits. Moreover, the use of fibers extends its possibilities since fibers arrest cracks and retard their propagation. Incorporation of Quarry Dust (QD) in SCC help to reduce environmental hazards during the production of QD. This study evaluated the fresh and hardened properties of steel fiber self-compacting concrete (SFSCC) incorporating QD. The optimum fiber and QD contents with no adverse effects on fresh and hardened properties were determined. A comparative study on behavior of SCC and SFSCC mixtures in terms of workability, compressive strength, compressive strength development ratio, tensile, flexural and energy absorption capacity was carried out. Test results showed that compressive strength increased with increase in QD contents at fixed fiber content by mass of Portland cement (PC) and then decreased. Strength development ratio (C28/C7) for SCC was 1.13, while it was 1.06, 1.08, 1.10 and 1.01 after reinforcing with 0.10, 0.20 and 0.30 contents of fiber. The compressive, tensile, flexural and energy absorption capacity or Toughness of SFSCC increased with the inclusion of the aforementioned contents of steel fiber up to 0.20 % volume of total binder at constant QD content and then decreased when compared with control SCC values. From these results, optimum value for the variables studied was obtained from mix QD20 + 0.2fr. Hence, steel fiber and QD could be successfully used in SCC production not minding the slight draw back on workability of SCC caused by inclusion of steel fiber, but with a modified dosage of super-plasticizer (SP), fresh and hardened properties, in accordance with specifications in relevant code(s) can be achieved.

Physical-mechanical properties of steel fibre-reinforced self-compacting concrete containing natural perlite addition

The aim of this work is to highlight the effect of the Algerian natural perlite used as fillers addition on the workability and physical-mechanical properties of metallic fibre self-compacting concrete (SCC). Effect of the perlite is compared to that of silica fume fillers to replace limestone fillers. One control concrete without fibres containing limestone fillers, two concretes with silica fume or perlite fillers and six SCCs were elaborated with limestone, perlite and silica fume fillers separately containing 1% vol. of steel long wavy or short hooked fibres. Several tests were conducted for evaluating the workability properties in the fresh state, the density, mechanical strengths and elastic modulus in the hardened state. The results show the beneficial effect of the use of perlite as fillers. Workability properties decrease slightly but an increase of mechanical strengths and elastic modulus is much more marked with the use of the steel hooked fibres.

Steel fibre self-compacting concrete under biaxial loading

This study involves the investigation of the effects of steel fibre content volume on the biaxial stress behaviour of steel fibre self-compacting concrete (SFSCC) at different stress ratios. This study covers compression-compression, compression-tension, and tension-tension stress regions. The results are discussed in terms of the uniaxial and biaxial strength, stress-strain relationship, and failure mode of SFSCC specimens. In terms of strength, 1.0% fibre volume fractions showed the highest increment in biaxial compression and compression-tension, which were 55% and 84%, respectively, when compared to plain concrete. This improvement was due to the integration of steel fibre. In contrast with compression strength, biaxial tension strength decreased in comparison to uniaxial tensile strength. Additionally, based on the octahedral stress space, the failure criteria of concrete for each region were proposed in a quadratic polynomial equation, and the parameters were derived from a regression analysis.