Fibre-reinforced Self-compacting Concrete Research Articles

Influence of concrete strength, fiber content and aspect ratio in the residual flexural strength of steel fiber reinforced self-compacting concrete

Abstract Steel Fiber Reinforced Self-Compacting Concrete (SFRSCC) is a material that combines the benefits of self-compacting concrete in the fresh state and the greater durability, with the gains of fiber- reinforced concrete in the hardened state, especially the gains in residual flexural strength. Results are presented in this paper of residual flexural strengths on 48 prenotched prisms conducted in accordance with RILEM TC 162 TDF for the Steel Fiber Reinforced Self-Compacting Concretes (SFRSCC). This article presents equations to estimate residual flexural stresses in SFRSCC. For this, SFRSCC prisms of two compressive strength classes, 20 MPa and 40 MPa, were produced with 3 different types of steel fibers with the contents volume of 0.5% and 1.0%. Based on the test results, equations were proposed to determine the residual flexural stresses established through regression analysis, which were, then, further validated with concretes produced in this work and results available in the literature. The equations found, despite showing an indication of the residual flexural strengths that will be achieved, obtained a relatively high error. In order for the equations to be applied in a technical way, further studies for a larger sample need to be carried out, seeking to optimize the equations.

Impact resistance of steel fiber-reinforced self-compacting concrete

Impact resistance of steel fiber-reinforced self-compacting concrete

Fracture properties of self-compacting fiber-reinforced concrete

Self-compacting concrete (SCC) is an innovative concrete that does not necessitate vibration for placing and compaction. Nineteen concrete mixes were investigated including a control mix without fibers as well as eighteen SCC with fibers (SCFRC) mixes. Three types of fibers (polypropylene, glass and steel) were used. Slump flow, L-box, V-funnel as well as column segregation tests were conducted to assess the fresh properties. Whereas, compressive, splitting tensile and flexural strengths were measured to assess the hardened properties of SCFRC. Three point bending tests were performed for the purpose of assessing the fracture properties of SCFRC. Test results showed that the inclusion of fibers to produce SCFRC mixtures remarkably enhanced the fracture properties including fracture energy (Gf) and fracture toughness (K1c). Inclusion of steel fibers with 2% volume fractions showed an improvement with 26.9 times for Gf over the control mix. Whereas, 104% increase in K1c was recorded for the same mix over the mix without fibers. Adding fibers to SCC to produce self-compacting fiber reinforced concrete (SCFRC) will expand its advantages. However, the application fields still need to understand the properties of SCFRC.

WITHDRAWN: The effect of alkali-activated fly ash on the strength properties of FRSCC

In this fast-growing world, urbanization and industrialization are the prime factors which govern the quality of people’s lives. Due to the rapid urbanization, construction industry faces a lot of problems such as non-availability of raw materials, and disposal of waste materials directly into the environment. To save the environment from harmful dumping of debris and turn the same to save exploitation of natural resources a lot of research is being done. In this study cement, a major ingredient of concrete was partially replaced in steel fiber reinforced self-compacting concrete (FRSCC) of M30 grade by normal and activated fly ash from 0% to 30% at an interval of 5%. Activation of fly ash was done by Sodium Hydroxide (NaOH) solution of 10 M. Water to binder ratio and steel fiber addition into the concrete mix were kept constant at0.45 and 1% respectively. Manufactured sand was used as a fine aggregate which would eliminate the problems related to over-exploitation of natural resources. To analyze the behavior of concrete mixes, strength properties like compression, tension, bending and impact strength tests were conducted.

Development of high-early-strength fiber-reinforced self-compacting concrete

High-early-strength fiber-reinforced self-compacting concrete (FRSCC) is a practical material for the precast concrete industry to double its production capacity. This study developed high-early-strength FRSCC mixtures that achieved a compressive and flexural strength of at least 24 MPa and 3.5 MPa, respectively, at 6 h, using commercially available components, typical mixing procedures, and air curing. A mix design process was developed based on the literature and experimental results. The effect of six different fiber reinforcements on the fresh and mechanical properties of concrete was analyzed. The cost limit was set at 523 USD/m3 to make the concrete mix cost-effective.

Fresh and mechanical performance and freeze-thaw durability of steel fiber-reinforced rubber self-compacting concrete (SRSCC)

The self-compacting concrete (SCC) with the replacement of recycled rubber aggregates is limited for the field application due to high-performance requirements. The steel fiber was introduced to the rubberized SCC (RSCC) to enhance its performance and promote its application. The fresh and mechanical properties and durability performance of steel fiber-reinforced rubber self-compacting concrete (SRSCC) were evaluated. The SRSCC samples were prepared with replaced rubber aggregate based on fine aggregate volume percentages of 10%, 15%, and 25% and a consistent steel fiber ratio of 0.2%. The plain SCC and rubberized SCC samples were also produced for comparison. The fresh performance was evaluated with slump flow, J-ring flow, V-funnel, and U-box tests. The results showed that both filling and passing ability could be affected by the added steel fiber and rubber aggregate. However, the SRSCC could still meet most of the recommended criteria for passing and filling abilities when the rubber content is lower than 25%. Regarding the hardened properties, the compressive strength was reduced in rubber SCC samples with increased rubber contents by comparing with the control SCC samples. Nevertheless, SRSCC samples with 10% rubbers have higher splitting tensile strength than RSCC and plain SCC. Also, the SRSCC specimens showed excellent freeze-thaw resistance after 600 F-T cycles. The relative dynamic modulus of elasticity slightly increased without any dimensional expansion in SRSCC samples. In summary, the proposed SRSCC can meet required flowability, filling and passing abilities along with good mechanical and freeze-thaw performance. This study will provide lab test data for the applications of recycling waste tire aggregates in steel fiber-reinforced SCC.

Effects of concrete flow on the distribution and orientation of fibers and flexural behavior of steel fiber-reinforced self-compacting concrete beams

Several parameters during the fabrication process cause segregation and poor orientation of the fibers in steel fiber-reinforced concrete (SFRC) members. With its high flowability and compactability, self-compacting fiber-reinforced concrete (SCFRC) can be used as an alternative to conventional SFRC, as it exhibits improved orientation and lesser fiber segregation. This study aims to investigate (1) the effects of concrete type (i.e., SCFRC versus SFRC), fiber content, and specimen depth on the fiber distribution and orientation and (2) the structural performance of SCFRC and SFRC beams considering their fiber distribution and orientation using X-ray images. The X-ray images showed that owing to the high-flow properties, the SCFRC beams exhibited a lower fiber segregation and better fiber alignment than the SFRC beams. The bending test results demonstrated that the SCFRC beams exhibited better flexural performance than the SFRC beams owing to the improved distribution and orientation of the fibers. Moreover, a finite element (FE) analysis was performed to evaluate the structural performance of the beams considering the varying fiber distribution properties observed in the X-ray images. The FE method could differentiate the superior structural performance of the SCFRC beam from that of the SFRC beam.

Experimental Investigation on the Effect of Varying Fiber Mix Proportion on the Mechanical and Thermal Performances of Fiber-Reinforced Self-Compacting Concrete under Hydrocarbon Fire Condition

This paper presents the experimental analysis of the effects of simulated hydrocarbon fire exposure on the mechanical properties and the heat transmission in fiber-reinforced self-compacting concrete, FR-SCC. For that purpose, 300-mm thick, and 1200-mm square-shaped slabs were cast. Basalt and polyvinyl alcohol (PVA) fibers were added using the content of 1, 1.5, and 2% in self-compacting concrete. For investigating the heat transmission within 300-mm thick slabs, five external thermocouples were installed at the unexposed face to the fire of the slabs. Similarly, eleven internal thermocouples were installed at an interval of 25 mm throughout the slab thickness. It has been found that fibers have shown better insulation than the controlled concrete; the unexposed to fire surface of FR-SCC showed temperatures lower by ten degree Celcius than the controlled concrete. Compressive strength results showed that fiber addition caused a higher reduction in strength because of softening and stiffness reduction due to high-temperature exposure. After 120 min of fire exposure, basalt fibers caused an average reduction of 30% in the compressive strength, and PVA fibers caused an average reduction of 25%. Whereas, the addition of fibers improved the split cylindrical tensile strength even after exposure to 120 min of fire exposure in comparison with the unreinforced samples.

The effect of surface treatment and environmental actions on the adhesive connection between GFRP laminate surface and fresh FRC

An experimental study on the performance of adhesive connection between Glass Fibre Reinforced Polymer (GFRP) plates and Steel Fibre reinforced self-compacting Concrete (FRC) was conducted. Fresh FRC was poured out onto the surface of GFPR plates, to create 40 square specimens (300 by 300 by 45 [mm]). Pull-off tests were performed to evaluate the tensile strength of the adhesive connection when different types of adhesives (four) and surface treatments (three) are used. Furthermore, the effect of five different environmental conditions on the tensile strength of the adhesive connection was also evaluated. After analysing the results and performing a variance analysis (ANOVA), it has been shown that the pull-off behaviour is highly influenced by the type of adhesive and by the environmental action. In spite of that, the dominant failure mode was cohesive failure in the FRC substrate, therefore good bond conditions between both materials were achieved.

Fracture properties and impact resistance of self-compacting fiber reinforced concrete (SCFRC)

This study was aimed at investigating the impact strength and fracture properties of self-compacting concrete reinforced with basalt fiber (BF), glass fiber (GF) and polypropylene fiber (PPF). In the study, BF, GF and PPF, each at a time, were added to the concrete in volume fractions of 0.15%, 0.20%, 0.25% and 0.30% for the purpose of determining their impact on the properties of fresh and hardened self-compacting fiber reinforced concrete (SCFRC). Experimental research consisted of a series of tests performed on cube, disk and notched prismatic samples. On fresh SCFRC, slump-flow, V-funnel and L-box tests were performed. Additionally, properties such as compressive and flexural strength, impact resistance, toughness and fracture energy were examined on the hardened samples. Results showed that addition of BF, GF and PPF all increased the flexural strength, impact resistance and fracture energy, whereas the no obvious change in compressive strength was observed. In contrast to the expectations, PPF mixtures exhibited higher impact resistance and fracture energy values than did the BF and GF ones.

Effect of fibers types on fresh properties and flexural toughness of self-compacting concrete

This research aimed to experimentally examine the workability and mechanical properties of self-compacting concrete (SCC) with silica fume (SF) and different types of fibers. Five types of fibers, namely, hook-end steel (H), mild steel (M), carved-steel (S), basalt rock (R), and polypropylene (P) fibers, were used to produce fiber-reinforced SCC (SCRFCx). Each fiber type was added to the concrete at a rate of 0.25% of the concrete volume, and a silica fume replacement rate of 30% of the cement mass was applied. The workability of fresh concrete samples was assessed using slump flow, slump flow T50, L-box, V-funnel, V-funnel T5, bleeding, and segregation tests. In addition, the overall strength of hardened concrete was investigated by using compressive, indirect tensile, and flexural strength tests. Results showed that fiber addition generally reduces the fresh concrete. The slump flow diameter was 670 mm of SCC; moreover, slump flows decreased to 630, 640, 640, 610, and 650 mm when H, M, S, P, and R fibers were respectively added to the concrete. The respective compressive strengths were of 34.5, 33.9, 32.1, 36.9, 35.8, and 33.3 MPa when add the fibers of type H, M, S, P, and R, at test age 28 d, respectively.

Experimental, statistical and simulation analysis on impact of micro steel – Fibres in reinforced SCC containing admixtures

Self-compacting concrete is one of the special concretes that flow in its own weight, which is used in the densely reinforced concrete structures. This concrete requires higher binder content. Higher cement content leads to uneconomical design, higher heat of hydration, higher shrinkage, etc. These factors can be counteracted by addition of mineral admixtures. Hence, Fly ash (30%) and micro silica fume (10%) are mineral admixtures replaced with cement. Concrete is having a poor flexural properties; this can be enhanced by using fibrous materials. Addition of steel fibres improves the strain softening property of composite system. Hence hooked ended micro steel fibres are used in this study. In order, to study the fresh and mechanical properties of SCC, totally eight mix (M1 to M8) designs are developed using Nan Su proposed method of mix design, with varying steel fibres (0.0%, 0.25%, 0.50% and 0.75%) and varying binder content. To evaluate the impact of steel fibres in reinforced concrete; four mixes (C-1 to C-4) of prism dimension 0.1 m × 0.15 m × 1 m were cast with optimized steel fibres and mineral admixtures content and tested using standard UTM. The key properties such as deflection, strain softening and effect of orienting the steel fibres along the direction of flow of concrete were studied. Later the experimental work was virtually modeled and analyzed using ABAQUS. In rheological study, the mix containing mineral admixtures showed better fresh concrete properties. Addition of fibres reduced the flowing ability of SCC. There is no significant change in compression strength due to addition of steel fibres. Flexural strength increased by 63% by addition of 0.75% of steel fibres. The SEM analysis helped to study the hydration process and morphological behaviors in concrete structures. The statistical analysis were carried out and regression equations have been developed for the better understanding in the field of micro steel fibre-reinforced self-compacting concrete containing admixtures. Stress-Strain behavior of mix C3 and C4 is more linear compared to C1 and C2, due to presence of micro steel fibres, which is arrested the development of micro-cracks. C4 shows better strength compared to C3, showing steel fibres are aligned align the direction of flow of concrete in between the reinforced structures. The analyzed theoretical model, developed used ABAQUS showed similar displacement results.

Rheological Properties and Strength of Polypropylene Fiber-Reinforced Self-compacting Lightweight Concrete Produced with Ground Limestone

In this study, self-compacting lightweight concrete (SCLC) was prepared using crushed limestone dust, and the effects of different types of polypropylene fibers and chemical admixtures on the rheological properties of SCLC were investigated. The workability of SCLC was assessed by conducting slump flow, J-Ring, and V-funnel tests, and the compressive strength of the cubic specimens was measured at the ages of 2, 7, and 28 days. Overall, specimens containing fibers displayed lower workability than the control mix; however, a simple adjustment of the dosages of the superplasticizer and viscosity-modifying admixture remedied this problem. The results reveal that the maximum fiber content is 4 kg/m3 for microfibers and 6 kg/m3 for macrofibers. Producing SCLC containing 33% limestone powder by weight as cementitious material satisfied self-compacting concrete requirements and exhibited compressive strength greater than 55 MPa at the age of 28 days.

Mixture Design Study of Fiber‐Reinforced Self‐Compacting Concrete for Prefabricated Street Light Post Structures

In recent years, there has been an increasing demand to produce strong precast street light posts that are aesthetically pleasing. This study presents experimental results of a considerable number of mixture designs for fabricating precast street light posts where fiber‐reinforced self‐compacting concrete (FRSCC) was employed. The performance of many FRSCC mixtures was evaluated in terms of their structural properties and aesthetic characteristics. A trial‐and‐error procedure was performed for a series of FRSCC mixtures where silica fume, fly ash, and fibers were used. Slump flow and air content tests were conducted to determine the fresh FRSCC properties, and specimens were cast to evaluate their aesthetic. Three‐day and seven‐day compression tests were performed to examine the FRSCC hardened properties. The amount of cement in all batches was kept constant, whereas the distributions of fine and coarse aggregates, water, and other admixtures were adjusted. The largest slump flow of 73.7 cm (29 in) was recorded, and the maximum three‐day compressive strength was 43 MPa (6209 psi). Further refinement of the mixtures, which displayed the best strength and aesthetic attributes, was performed. Test results of the selected FRSCC mixtures indicated an excellent slump flow, air content, and compression values while achieving advantageous aesthetic qualities. Seven‐day compressive strength of 39 MPa (5686 psi) with the air content of 4.8 percent and the slump flow of 66 cm (26 in) was recorded. The study results and the developed FRSCC mixes can be used for mass production of precast concrete street light posts in precast plants.

Prediction of the Fresh Performance of Steel Fiber Reinforced Self-Compacting Concrete Using Quadratic SVM and Weighted KNN Models

Steel fiber reinforced self-compacting concrete (SFRSCC) is a special type of concrete that is widely researched in literature due to its superior properties. As it is difficult to provide its high workability qualities, SFRSCC is thought to be in need of an economic and quick design process. In this study, it is aimed to predict the fresh properties of SFRSCC mixtures following with the standards at the preliminary design stage. With this aim, two different classification methods were applied successfully to a comprehensive dataset collected from international publications. The models used to classify the fresh performance of SFRSCC were Weighted K-Nearest Neighbors (W-KNN) and Quadratic Support Vector Machine (Q-SVM). Consequently, acceptable success rates were obtained from the models. For the prediction of slump-flow, the accuracy values were 0.76 and 0.84 for the W-KNN and Q-SVM models, respectively. For the V-funnel time, the accuracy values were 0.90 and 0.92 for the W-KNN and Q-SVM models, respectively. Owing to the recommended methods, it is expected to reduce the number of trial mixtures in the preliminary design stage of SFRSCC.

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

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

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.

Repeated drop-weight impact tests on self-compacting concrete reinforced with micro-steel fiber

Steel fiber has become a proven material that can significantly alter the behavior of different types of concrete mixtures from brittle to more ductile ones. Rich literature is currently available on the mechanical properties of steel fiber-reinforced self-compacting concrete. However, the investigation of the impact resistance of this material to drop weight is still required to enrich the knowledge about its behavior under different loading conditions. An experimental work was conducted in this research to evaluate the performance of steel fiber-reinforced self-compacting concrete under repeated impact loading using the repeated blows test recommended by ACI 544-2R. The tests investigated the effect of drop weight and drop height in addition to fiber content. Straight micro-steel fibers were incorporated in three volumetric contents of 0.5, 0.75 and 1.0% and were compared with a similar plain mixture. The test equipment was adjusted to conduct repeated impact loading from different drop-heights and using different drop-weights. The adopted drop-heights were 450, 575 and 700 mm, while the adopted drop-weights were 4.5, 6.0 and 7.5 kg. The combination of the adopted drop-heights and weights composes four loading cases in addition to the standard loading case with a drop-weight and drop-height of 4.5 kg and 450 mm. The inclusion of micro steel fiber was found to significantly increase the impact resistance of self-compacting concrete with percentage developments ranging from 150 to 860% compared to plain samples. The specimens tested under 4.5 kg and 450 mm drop weight and height exhibited the highest percentage improvement in impact resistance among the five loading cases. The results also showed that the impact ductility of fibrous specimens was up to 24% higher than that of plain specimens.

Mechanical properties and postcracking behavior of self‐compacting fiber reinforced concrete

AbstractFiber reinforced concrete is widely used due to its high ductility, energy absorbing capacity, and tensile strength. In this study, the effects of fibers on fresh concrete properties and mechanical properties of self‐compacting fiber reinforced concrete (SFRC) were investigated. Basalt fiber (BF), glass fiber (GF), and polypropylene fiber (PPF) were added to the concrete mixtures at the ratios of 0.15, 0.20, 0.25, and 0.30% by volume. The impacts of the content and type of fiber on the fresh SFRC properties (slump–flow diameter, V‐funnel flow time, and blocking rate) and mechanical properties such as compressive strength, flexural strength, splitting tensile strength, and toughness index were analyzed. In addition, the microstructure among cement paste and fibers were investigated using scanning electron microscope images. The results show that the adding of fiber to the mixtures significantly improved the flexural and tensile strength, whereas no significant change in compressive strength was observed. In addition, toughness, which is an important parameter for SFRC, was also determined according to ASTM C 1609. None of the BF and GF specimens reached the intended deflection of L/150 (L is the span). A rapid decrease in load was observed after peak load in both fiber types and the samples showed a brittle fracture. On the contrary, the PPF series showed markedly different postcracking behavior than the BF and GF. Compared with the plain concrete, TL/150 of SFRC with BF, GF, and PPF increase by 29–54%, 17–36%, 133–172%, respectively.

Does the Carbon Fibre Coating Reinforcement Have an Influence on the Bearing Capacity of High-Performance Self-Compacting Fibre-Reinforced Concrete?

This study investigated the impact of the location of a carbon fibre coated reinforcement ring (CFCRr) inside the structure of high-performance self-compacting fibre-reinforced concrete (HPSCFRC). Nowadays, cement matrix is considered as an alternative binder when reinforcing concrete structures with composite materials. Due to the plastic behavior of composite structures at relatively low temperatures when carbon fibres are reinforced with epoxy resin, the author attempted to locate carbon fibres inside a concrete structure. Thanks to this, the reinforcement will be less vulnerable to high temperatures (during a fire) and more compatible with concrete. The fibres act as a perimeter reinforcement that is compatible with the concrete mixture. The position of the CFCRr in the structure of concrete has an influence on the load capacity, stiffness and stress-strain behavior of concrete elements. The research was conducted on circular shape short concrete columns and tested under axial compression. The results demonstrated that by including CFCRr inside a concrete specimen, the maximum compressive strength decreases with an increase in the number of composite rings and a greater distance from the vertical axis of symmetry to the edge of the element. It has been proven in these studies that carbon fibres do not have good adhesive properties between CFCRr and a concrete mixture. As a result of this phenomenon, a shear surface is created, which leads to crack propagation along the CFCRr. Therefore, the presented idea of an internal CFCRr should not be used when designing new concrete structures.