Fiber-reinforced Reactive Powder Concrete Research Articles

Influence of Fiber Orientation on the Shear Properties of Steel Fiber-Reinforced Reactive Powder Concrete Beams

Steel fiber-reinforced reactive powder concrete (SFRPC) has good mechanical properties and is thus useful for engineering applications. Generally, the fibers in SFRPC are randomly distributed. To study the effects of the amount, length, and orientation of steel fibers on the shear strength of SFRPC beams, nonreinforced aligned steel fiber-reinforced reactive powder concrete (ASFRPC) beams were prepared using a large-scale electromagnetic field orientation device. Shear tests of specimens with a shear span ratio of 1.5 were performed under two fiber contents (1.0% and 2.0%) and three fiber lengths (20, 30, and 40 mm). The full-field strain during the loading process was obtained via the digital image correlation method, and the effects of fiber quantity and orientation on the shear strength of the beams were analyzed. The ASFRPC beams exhibited higher ductility but lower shear capacity than the SFRPC beams under the same conditions. The shear capacity increased with the quantity of steel fibers. According to the test results, the calculation formulas of the shear-bearing capacities of ASFRPC and SFRPC beams were established.

Durability analysis and damage constitutive modeling of fiber-reinforced reactive powder concrete of drilling shaft in porous water-bearing rock stratum

The drilling activities at the mining sites in western China generally involve an extremely high drilling depth and complex formation environment, and the external load borne by the drilling shaft lining is also very high. Hence, in this study, fiber-reinforced reactive powder concrete (FRRPC) is proposed as the construction material to enhance the durability of deep drilling shaft structures. Firstly, the main physical and mechanical properties of FRRPC are examined by an orthogonal test method. Then, range analysis and comprehensive balance method are used to determine the optimal mix ratio of FRRPC as cement: silica fume: quartz sand: quartz powder: water: water reducer = 1: 0.25: 1.1: 0.40: 0.0237: 0.031. Next, taking C70 concrete commonly used in drilling engineering of deep loose layers in central and eastern China as a control, the permeability resistance and sulfate resistance of drilling shaft FRRPC in porous water-bearing rock stratum are investigated. The results show that compared with the C70 control group, the relative permeability and corrosion resistance coefficient of FRRPC are increased by 87.7% and 9.9%, respectively. Besides, the FRRPC specimen exhibits significantly better impermeability and sulfate resistance than the C70 control group. Finally, a damage constitutive model of FRRPC under sulfate attack is deduced based on the sulfate resistance test. Overall, this study provides useful insights to boost the application of FRRPC in drilling shafts in northwest China.

Performance evaluation of fiber-reinforced reactive powder concrete exposed to high temperature combining nondestructive test

An experimental study has been performed in an attempt to evaluate the performance of fiber-reinforced reactive powder concrete (RPC) after high temperatures using nondestructive methods. In this context, four RPC mixtures containing 2% steel fibers and 0–0.2% polypropylene (PP) fibers were produced. After samples exposure to various temperatures 20 °C, 100 °C, 200 °C, 300 °C, 400 °C, 500 °C, 600 °C, 700 °C and 800 °C, different non-destructive tests (NDTs) including ultrasonic pulse velocity (UPV) and resonance frequency (RF) as well as sound velocity calibration tests were conducted. Besides, specimens damage roughly assessed by physical observation and mass loss. Further on, mechanical performance was evaluated by axial compressive strength, and scanning electron microscopy (SEM) was employed to understand the high temperature deterioration mechanism of RPC specimens. The results indicated that mass loss and NDTs parameters values gradually deteriorated with the increasing temperature. Additionally, the compressive strength raised up to 200 °C. Nevertheless, it dropped dramatically from 200 °C to 700 °C. After that, the strength increased mildly. The weight loss and residual strength as well as NDTs parameters were related to temperature and fiber content. Moreover, quantitative description formulas of mentioned factors were presented. It was also found that 2% steel fiber and 0.15% PP fiber seems to be the optimal fiber combination always performed better in comparison with other fiber contents regarding the residual compressive strength and NDTs parameter values. Furthermore, the regression equations between compressive strength and NDTs values have been provided with all correlation coefficients exceed 0.95. The research demonstrated the potential of the NDTs methods for application of fiber-reinforced RPC exposed to high temperatures.

Experimental Research on Mechanical Properties of Carbon Fiber-Reinforced Reactive Powder Concrete after Exposure to Cryogenic Temperatures.

This study aims to evaluate the mechanical properties of carbon fiber-reinforced reactive powder concrete (CFRPC) after exposure to cryogenic temperature. The mechanical properties of plain RPC and CFRPC with carbon fiber volume contents of 0, 0.5%, 1.0%, and 1.5% were examined after exposure to 20 °C, −5 °C, −15 °C, and −25 °C for 72 h. The effect of fiber contents and exposure temperatures on the cubic and axial compressive strength, splitting tensile strength, elastic modulus, and peak strain were systematically reported and analyzed. The results showed adding carbon fiber to RPC could significantly enhance the strength and slightly improve ductility performance. Additionally, CFRPC with 1.0% fiber content showed the best mechanical properties. The maximum increases in cubic and axial compressive strength and tensile strength were 26.0%, 25.7%, and 21.8%, the elastic modulus was 13.2%, and the peak strain was 13.0% over the plain RPC. Additionally, all mechanical properties continued to degrade with decreasing temperature. After exposure to −25 °C, the cubic, axial compressive strength, and tensile strength of CFRPC degraded to 82.2–84.9%, 80.7–87.5%, and 72.7–73.7% of the normal temperature strength, respectively. In addition, the linear relationship equation between the discount factor of each mechanical property and the temperature was established. Finally, the equation for the stress–strain ascending curve of CFRPC described by a quadratic polynomial was proposed, which fitted well with the experimental results.

Development of reactive powder concrete with recycled tyre steel fiber

Reactive Powder Concrete (RPC) is a part of an ultra-high-strength concrete family. It has a dense matrix due to a very low water-cement ratio, which increases its brittleness. Therefore, RPC is produced with a high volume of fiber reinforcement to attain ductility and fire resistance. Unfortunately, new fibers are expensive and yield a high carbon footprint. The rise in the cost and carbon footprint of fiber-reinforced RPC can be controlled by using Recycled Steel Fibers (RSF) derived from scrap tyres. In this study experimental campaign is conducted to compare the mechanical performance of RPC with new steel fiber (NSF) and RSF. Performance of NSF and RSF is compared at 0%, 1%, 2%, 3% and 4% volume fractions. The studied properties are bond strength, compressive strength (CS), splitting-tensile strength (STS), flexural strength (FS), and ultrasonic pulse velocity (UPV). Testing results showed that 3% RSF improves the CS, STS, and FS of plain-RPC by 9%, 23% and 58%, respectively. RSF-RPC performs around 90% potential of equivalent NSF-RPC in all mechanical properties at the same volume of fiber. RSF has implications for a cheap and eco-friendly substitute for NSF. The optimum dosage of NSF and RSF is 2% considering maximum mechanical strength without a significant increase of the self-load.

Behavior of Fiber and Nonfiber Reactive Powder Concrete in an Aggressive Environment

Abstract Durability studies have been carried out on the performance of reactive powder concrete (RPC) when exposed to a three-month (accelerated) exposure to varying sulfuric acid concentrations. The compressive strength and weight loss of the specimens were the key parameters investigated. Specimens consisted of nonfiber reactive powder concrete (NF-RPC), fiber-reinforced reactive powder concrete (FR-RPC), and a control high-strength concrete (HSC). Concentrations of sulfuric acid (H2SO4) of 1, 3, and 10 % were utilized as the attack solutions in this investigation. RPCs suffered the highest compressive strength and weight loss after 12 weeks when exposed to 1, 3, and 10 % H2SO4 solutions. It is postulated that the high levels of binding constituents within the RPC are extremely reactive with H2SO4. Results from the HSC specimens showed that a reduced cement content and coarse aggregate inclusion reduced the level of sulfuric acid attack. The presence of fibers within the RPC samples appears to provide benefits in relation to decreased weight loss, but this was not observed for higher concentrations of H2SO4. This study has shown that the durability of RPC in environments subject to high concentrations of sulfuric acid is generally not recommended.

Effect of carbon fiber on mechanical properties of reactive powder concrete exposed to elevated temperatures

An ultra-high-performance cement-based composite like reactive powder concrete (RPC) achieves its exceptional engineering properties due to a dense and homogenous microstructure. To improve the ductility and fire-resistance, RPC is often reinforced with a high volume of steel fibers (SF). Due to the issues of high density, low durability, and high conductivity; there is a need to study RPC with lightweight and durable fibers. In this research, the mechanical properties of RPC are studied with a single and hybrid fiber mixture of carbon fiber (CF) and conventional SF. The mechanical properties of plain and fiber-reinforced RPC were examined after exposure to 200oC, 400oC, 600oC, and 800oC temperatures for the 2 h. The results showed that CFRPC mechanically performs up to 85–90% potential of conventional SFRPC. Hybridization of 1.5% SF and 0.5% CF produced synergistic effects on the mechanical properties of RPC at both normal and elevated temperatures. After exposure to 800oC, CFRPC showed about 2, 4, and 5 times higher residual compressive, tensile, and flexural strength than plain RPC, respectively. Compressive strength-per-unit weight of CFRPC was notably higher than SFRPC.

Experimental study on seismic performance of strengthening masonry wall using hybrid fiber-reinforced reactive powder concrete

An experimental study was conducted to investigate the seismic performance of masonry walls strengthened using hybrid fiber-reinforced reactive powder concrete (HyFRRPC) as a coating. The proposed reinforcement technique was employed to improve the overall strength and structural integrity of the confined masonry wall. In order to guarantee the composite action between the masonry substrate and the coating material, material tests were conducted to achieve an optimal mixture for the HyFRRPC. Then, six full-scaled confined masonry specimens strengthened by HyFRRPCs with varied strengthening configurations were tested under in-plane quasi-static horizontal loading. The test and analysis results indicated that the proposed HyFRRPC-strengthening technique can effectively improve the lateral carrying capacity, displacement ductility, and energy dissipation capacity of masonry walls, and provide an optimal reinforcement. Finally, a simplified analytical model was also proposed for practical application.

Research on the self-sensing and mechanical properties of aligned stainless steel fiber-reinforced reactive powder concrete

Stainless steel fibers (SSFs) were added into reactive powder concrete (RPC) to fabricate aligned (improved by L-shaped device) and random directional distributed SSFs conductive RPC. The aspect ratio of SSFs ranged from 30 to 150, while the SSFs amount was 0.2%–1.2% by volume of RPC. Curing ages for RPC ranged from 7 d to 60 d. The conductive performances (electrical resistance and AC impedance spectroscopy), the speed of ultrasonic passing through specimens and the following piezoresistivity were investigated. Moreover, the compressive strength, flexural strength and toughness of specimens cured for 60 d were tested. Finally, high-resolution images of SSFs’ dispersion and orientation were gained. Results showed that the ultrasonic velocity and electrical resistance of SSFs-RPC grew in the form of a quadratic function with the increasing curing ages. The SSFs content of 0.4% was the percolation threshold value of SSFs-RPC. Additionally, RPC with higher aspect ratio and aligned fibers performed better conductivity, piezoresistivity and mechanical performance. The conductive mechanism of SSFs-RPC can be explained through the conduction models of three series connected electrical components. The image analysis showed that SSFs with higher aspect ratio dispersed more uniformly in RPC and the L-shaped device could effectively improve the alignment of fibers.

Water abrasion and drop-mass impact of mono and hybrid steel fiber-reinforced reactive powder concrete

In addition to strength, the durability of concrete is a major characteristic to measure its quality. Abrasion and accidental impacts are types of loads that negatively influence the strength and durability of concrete. This article aims to compare the water-impact and drop-mass impact resistances of reactive powder concrete (RPC). Three mixtures of RPC were prepared to evaluate their abrasion resistance using the water jet method in addition to their impact resistance using the repeated drop-mass impact test based on the ACI 544-2R repeated impact procedure. All of the three mixtures have same material properties and a fiber content of 2.5% by volume. One of them contains steel fiber with length of 6 mm, the second contains 15 mm steel fiber, and the last one contains a combination of 15 and 6 mm steel fibers. The experimental work results showed that the mixture contains 15 mm steel fibers showed the best abrasion and impact resistances, while the combination of 15 and 6 mm steel fibers showed the lowest impact resistance and the lowest abrasion resistance at the first six hours. The resulted compressive strength values were close, but that of the sample contains 15 mm fibers was the highest.

Steel Corrosion Evaluation of Basalt Fiber RPC Affected by Crack and Steel-Concrete Interface Damage Using Electrochemical Methods.

Basalt fiber (BF) is a new anti-corrosion and environmentally friendly material, which is expected to delay the corrosion process of steel bars and improve the durability of reinforced reactive powder concrete (RPC). The electrochemical method is a nondestructive testing and real-time monitoring technique used to characterize the corrosion behaviors of steel bars embedded in concrete structures. In this paper, the electrochemical technique was employed to evaluate the corrosion of steel bars embedded in basalt fiber modified reactive powder concrete (BFRPC). Besides, crack and steel-concrete interface damage (SCID) were considered as typical factors that affect steel corrosion in concrete. Thus, both reinforced fiber-free RPC and BFRPC specimens with crack and SCID were prepared for evaluating the steel corrosion behaviors by electrochemical methods. The results revealed that both crack and SCID would aggravate the steel corrosion, and the crack was the major factor that affects the corrosion process. Moreover, the excellent compactness of BFRPC and the bridging action of BF could effectively prevent the concrete cracking and steel corrosion process of concrete. Using reinforced BFRPC instead of ordinary concrete in practical projects could greatly extend the service life of steel bars.

Repeated Drop-Weight Impact Tests on RPC Containing Hybrid Fibers

The impact resistance of micro-steel fiber-reinforced and hybrid fiber-reinforced reactive powder concrete is investigated in this study. Six groups of specimens were prepared with 2.5% volumetric contents of different combinations of fibers. For this purpose, micro-steel fibers with 6 and 15 mm length in addition to polypropylene fibers were used. Each group includes 12 identical specimens. The impact tests were conducted using the repeated drop-weight impact test of ACI 544-2R. However, higher drop-height (700 mm) and drop-weight (10 kg) were adopted to accelerate the failure and reduce the effort required to crack the specimens. The test results showed that the use of only 15 mm micro-steel fiber led to much higher impact resistance than other micro-steel fiber combinations. The recorded number of blows for the group with SF15 was 247, while those of SF6 and combined SF6 and SF15 were 127 and 112, respectively. The replacement of 0.5% of micro-steel fiber by 0.5% of PP fiber was found to reduce the impact resistance regardless of the type or combination of the used micro-steel fiber.

Mechanical Properties of Hybrid Steel–Glass Fiber-Reinforced Reactive Powder Concrete After Exposure to Elevated Temperatures

Due to extremely dense microstructure, reactive powder concrete (RPC) shows poor performance at elevated temperatures owing to the development of high pore pressure that causes the deterioration of the material. By using fiber reinforcement, elevated temperature performance of RPC can be improved, as noted by many researchers. To this end, 3% volume fraction of four combinations of steel fiber (SF) and glass fiber (GF) [(3%, 0%), (2%, 1%), (1%, 2%), and (0%, 3%)] was used in RPC to study the change in residual mechanical properties of RPC after exposure to elevated temperatures. Three main mechanical properties, i.e., compressive strength, splitting tensile strength, and flexural strength properties, were studied. Experimental results showed that using 3% volume fraction of fibers (regardless of combination), explosive spalling of RPC was completely prevented. Hybrid fiber RPC with 2%SF–1%GF showed the maximum best mechanical performance at both elevated and normal temperatures. Single 3%SF–RPC performed significantly better than single 3%GF–RPC at both normal and elevated temperatures. A strong correlation existed between the normal temperature strength, residual strength, and exposure temperature.

Thermal Properties of Hybrid Fiber-Reinforced Reactive Powder Concrete at High Temperature

AbstractIn order to study the thermal properties of reactive powder concrete (RPC) at high temperatures, the thermal conductivity, thermal diffusivity, specific heat capacity, and linear expansion ...

Mechanical properties of steel, glass, and hybrid fiber reinforced reactive powder concrete

This study examines the properties of fiber-reinforced reactive powder concrete (FR-RPC). Steel fibers, glass fibers, and steel-glass hybrid fibers were used to prepare the FR-RPC. The non-fibrous reactive powder concrete (NF-RPC) was prepared as a reference mix. The proportion of fibers by volume for all FR-RPC mixes was 1.5%. Steel fibers of 13 mm length and 0.2 mm diameter were used to prepare the steel fiber-reinforced RPC (SFR-RPC). Glass fibers of 13 mm length and 1.3 mm diameter were used to prepare the glass fiber-reinforced RPC (GFR-RPC). The hybrid fiber-reinforced RPC (HFR-RPC) was prepared by mixing 0.9% steel fibers and 0.6% glass fibers. Compressive strength, axial load-axial deformation behavior, modulus of elasticity, indirect tensile strength, and shear strength of the RPC mixes were investigated. The results showed that SFR-RPC achieved higher compressive strength, indirect tensile strength and shear strength than NF-RPC, GFR-RPC, and HFR-RPC. Although the compressive strengths of GFR-RPC and HFR-RPC were slightly lower than the compressive strength of NF-RPC, the shear strengths of GFR-RPC and HFR-RPC were higher than that of NF-RPC.

Experimental investigation of mode I fracture features of steel fiber-reinforced reactive powder concrete using semi-circular bend test

Semi-circular bend tests were performed on reactive powder concrete (RPC) to investigate the mode I fracture characteristics. A total of 12 RPC specimens including non-fibrous RPC and steel fiber-reinforced RPC (SFR-RPC) with 1%, 2% and 4% volumetric fractions of steel fiber were tested. The characteristics of acoustic emission, fracture parameters and failure patterns were systematically investigated. The test results show that with the incorporation of steel fibers, the SFR-RPC specimens own an increasing enhancement of ductility, carrying capacity and AE activities with the increase of the steel fiber content. The crack initiation deflection, initiation toughness and initiation energy of the specimens vary as exponential functions of the steel fiber content, while the fracture toughness and fracture energy follow linear functions against the steel fiber content. The produced fracture surface shows a decrease in the smoothness with the increase of the steel fiber content.

Effect of specimen size on dynamic compressive properties of fiber-reinforced reactive powder concrete at high strain rates

This study presents an experimental study of similar reactive powder concrete (RPC) cylinders with different sizes subjected to axial impact loading. Dynamic compressive experiments were conducted on two dimensional RPC specimens using split Hopkinson pressure bar device. 54 hybrid fiber-reinforced RPC samples with 2% steel fiber and 0.2% polypropylene (PP) fibers contents by volume were characterized at strain rates from 107 to 356 s−1. Results from this and previous studies are analyzed to comprehensively investigate the effect of RPC specimen size on dynamic compressive performance. A series of quantitative analyses examining the relationship between dynamic properties and specimen size, strain rate, and steel fiber were conducted. Dynamic increase factor (DIF) of RPC compressive strength for specimens with larger diameters was consistently greater than RPC specimens with smaller diameters when the length to diameter ratio (l/d) was constant. RPC specimen size exhibited no visible effect on the critical strain DIF. Critical strain DIF increased with increasing strain rate and decreasing steel fiber addition. Critical damage variables of RPC specimens of greater size were higher than that of smaller sizes. Under identical strain rates, RPC specimen size had no visible effect on the DIF of Young's modulus or energy absorption.

Formulation and study of metal fiber-reinforced reactive powder concrete

PurposeReactive powder concretes (RPCs) are new concretes characterized by a particle diameter not exceeding 600 µm and very high compressive and tensile strengths. This paper aims to the development and study of the physico-mechanical, elastic properties and durability of an ultra-high performance concrete from materials existing on the Algerian market.Design/methodology/approachThree mineral additions such as granulated slag, quartz powder and silica fume are incorporated into the cement with 15, 23 and 25 per cent, respectively, in addition to use two different values of steel fiber volume fraction (2 and 2.5 per cent). The results show that the incorporation of 2.5 per cent metal fibers in the formulation of the RPC gives a high compressive strengths of 143.5 MPa at 60 days. The relationship between the relative value and the longitudinal elasto-instantaneous deformations of the RPC to a linear characteristic throughout the relative stress ranges. Also, the modulus of elasticity developed for a fiber-reinforced reactive concrete is greater than that of the unbound fiber.FindingsResults from the current study concluded that the presence of the mineral additions improves the durability of the concretes compared with that not adjuvanted by mineral additions.Originality/valueIt can be possible to manufacture fiber-reinforced reactive powder concretes (RPCFs) with compressive strength exceeding 140 MPa, with an adequate plasticity, despite the simplicity of means and materials and the incorporation of different percentage of metal fiber on the mechanical strength of concretes and its influence on behavior with respect to aggressive environment were achieved.

Experimental study on dynamic compressive properties of fiber-reinforced reactive powder concrete at high strain rates

Dynamic compression tests were performed on reactive powder concrete (RPC) using split Hopkinson pressure bar (SHPB) apparatus. A total of 102 RPC samples including plain RPC (PRPC), steel fiber-reinforced RPC (SFRPC) with 2% and 5% volumetric fractions of steel fiber, and hybrid fiber reinforced RPC (SPFRPC) with 0.2% polypropylene (PP) fiber and 2% steel fiber were characterized at high strain rate of 72–317 s–1. The characteristics of wave transmission, dynamic compressive strength, compressive deformation, energy absorption ability, and dynamic increase factor (DIF) of RPC under high strain rate impact were systematically investigated. Results revealed that the dynamic compressive strength of PRPC was more sensitive than that of SFRPC. With the addition of 0.2% PP fiber, the dynamic compressive strength of SFRPC exhibited a slight decrease. The critical strain increased with increasing strain rate. In all cases of RPC, the critical damage variable decreased with increasing fiber content subjected to same strain rate impact. The energy absorption of RPC increased with increasing content of steel fiber, which was found to be higher than normal strength concrete and high strength concrete. It was observed that application of CEB formula to calculate DIF of RPC was not safe. Thus, an empirical formula for DIF of RPC was proposed based on test data of this study and existing literature results.

Effects of steel fiber and strain rate on the dynamic compressive stress-strain relationship in reactive powder concrete

Three types of steel fiber-reinforced reactive powder concrete (SFRPC) with steel fiber contents of 0%, 2%, and 5% by volume are tested under dynamic compression by using a 40-mm-diameter split Hopkinson pressure bar (SHPB) apparatus. Data from SHPB experiments are employed to analyze the influence of critical parameters on the dynamic compressive stress-strain relationship of SFRPC at high strain rates. Test results show that steel fiber has a significant effect on the stress-strain relationship and energy absorption of RPC. Peak strain and peak stress increase with the increasing steel fiber content at the identical strain rates. A dynamic compressive damage-softening model for SFRPC at high strain rates is put forward on the basis of the Weibull distribution of SFRPC strength. A theoretical formula for Ed was established in order to ascertain Ed for the proposed constitutive model. The ratio of Ed to static elastic modulus Es increases with increasing strain rate and decreasing steel fiber content. The proposed constitutive model captures the dynamic compressive stress-strain relationship of SFRPC, and theoretical results are in agreement with measured data.