Ultra-high-performance Fiber-reinforced Concrete Research Articles

A multiscale experimental study of CFRP-UHPFRC interfacial bond behaviour: Failure mechanisms and a fibre volume dependent bond-slip law

Carbon fiber reinforced polymer (CFRP) materials are being increasingly used with ultra high performance fiber reinforced concrete (UHPFRC) to construct composite structural members making use of their unique properties. As the interfacial bond behaviour between CFRP and UHPFRC plays a key role in the design of such members, it was investigated in detail by multiscale experiments of single shear pull-off tests of 26 CFRP-UHPFRC bonded joints with different bond lengths and widths of CFRP laminates and 0.5–4% volume fraction (Vsf) of straight high-strength steel fibers (length = 13 mm, diameter = 0.2 mm). 12 CFRP-normal strength concrete (NSC) bonded joints were also tested for comparison. The surface strain evolution and the interfacial debonding process were captured and analysed by the digital image correlation (DIC). The complex microscale failure mechanisms, such as the mortar cracking, the CFRP-UHPFRC interfacial debonding, and the steel fibers’ slipping and pulling out of the mortar, were visualised and analysed by the 3D micro X-ray Computed Tomography (μXCT) scanning. It was found that the debonded layer of mortar under the laminates was much thinner than that in the CFRP-NSC bonded joints, due to the lack of coarse aggregates in UHPFRC. The peak pulling forces for the specimens with Vsf = 0.5%, 1%, 2%, and 4% were 9%, 21%, 28%, and 29% higher than those without steel fibers, respectively. An empirical bond strength model and an interfacial bond-slip model were proposed based on the test results, accounting for Vsf, the material properties, and the laminate to UHPFRC width ratio. Finally, the proposed bond-slip model was applied in finite element modelling to simulate the flexural behaviour of an FRP-UHPFRC composite deck in the literature, with the interfacial debonding failure and the ultimate loads successfully predicted.

Stress wave attenuation in ultra-high performance fibre-reinforced concrete during ballistic impact

Depending on material properties and boundary conditions, various waves propagate within the target, during an impact event. Stress wave attenuation during ballistic impact can be expressed in strain profiles regarding time and distance from the impact point. The design of a ballistic-resistant structure thus depends on the stress wave attenuation. This present study focused on stress wave attenuation under projectile impact in ultra-high performance fibre-reinforced concrete (UHPFRC). 3 mm strain gauges were found suitable for such measurements. Two different types (steel fibres) of UHPFRC (Single fibre (S2): 2 % of 6 mm steel fibre and Hybrid fibre combination (S0.5L1.5): 0.5 % of 6 mm + 1.5 % of 13 mm steel fibres) were used for investigation. During the ballistic impact event, strain profiles at specific distances from the point of impact on both the front and rear surfaces of UHPFRC targets were recorded. The scabbing damage due to tension was captured and analysed in this study through stress wave attenuation. The impact performance of hybrid (Short and Long fibres) S0.5L1.5 UHPFRC combinations was much better than S2 (only short fibres) UHPFRC targets. The hybrid steel fibre UHPFRC also shows higher strain attenuation (than short fibre based UHPFRC) in the range of 10-30 µε/mm. It was concluded that the efficiently designed ballistic-resistant UHPFRC should have higher wave attenuation, implying the concrete has enhanced capacity to absorb and localise energy, thereby mitigating the extent of damage inflicted upon the overall concrete slab.

Investigating the effect of steel micro‐ and macro‐fibers on the bond behavior of steel rebar embedded in ultra‐high performance concrete

AbstractIn recent years, the use of ultra‐high performance concrete (UHPC) has been widely considered in special structures and retrofitting of existing structures. Since most of the relations proposed by the regulations are based on the behavior of concrete with normal strength concrete, it is necessary to conduct more experimental studies to predict the behavior of UHPC. One of these notable behaviors is the bond and cohesion between rebar and UHPC, which plays a critical role in the design and seismic behavior of structures. In the present study, a series of experimental tests of uniaxial compressive strength, splitting (Brazilian) tensile strength, elastic modulus, and pull‐out of ribbed steel bars from ultra‐high performance fiber‐reinforced concrete (UHPFRC) were performed. The tests were done considering the four‐volume fractions of hooked‐end steel macro‐fibers, straight steel micro‐fibers, a hybrid combination of these two fibers, three different diameters of ribbed steel bars, and several embedded lengths. Moreover, direct tensile and compressive stress–strain curves, Young's modulus, bonding properties of rebar with UHPFRC, and fracture mechanisms were considered. The results indicated that applying micro‐fibers may enhance the bond stress between rebar and UHPC better than macro‐fibers. Also applying hybrid fibers resulted in the concurrent enhancement of bond stress and the optimum point slip of UHPC in the stress–slip diagram. This finding maybe attributed to the satisfactory performance of micro‐fibers in reducing the growth speed of micro‐level cracks and the suitable effect of macro‐fibers in decreasing the progression speed of macro‐level cracks. Furthermore, it was revealed that the increase in rebar diameter and embedding length leads to the reduction of maximum bond stress in UHPFRC.

Testing the effect of UHPFRC jacket thickness and steel fiber volume fraction on NSC‐UHPFRC column compressive behavior

AbstractSeveral efficient applications of ultrahigh‐performance fiber‐reinforced concrete (UHPFRC). Among them are UHPFRC jackets utilized for strengthening or permanent formworks of the steel reinforcing normal strength concrete (NSC) columns since UHPFRC jackets could enhance the compressive strength and other properties of the NSC column. However, the efficiency of a UHPFRC jacket simultaneously depends on its thickness and the added steel fiber volume fraction. The paper aims to explore the interaction effect of UHPFRC jacket thickness and steel fiber volume fraction on the behavior of UHPFRC jackets confining the NSC core under compressive load. The circular ultrahigh performance concrete jacket filled inside with the normal strength concrete, named NSC‐UHPFRC column specimen, is tested under loading on the NSC core. UHPFRC jacket thickness of 18‐49 mm with three adding steel fiber volume fractions was conducted for the experimental study. The investigation and analysis of the effect of the UHPFRC jacket and the steel fiber volume fraction on compression behaviors of NSC‐UHPFRC columns proceeded after the compressive strength test results were validated using Richart's model. This comprised a review of various parameters such as specimen failure pattern, stress–strain relationship, and ductile indices. The Weibull distribution was employed to explain the interaction effect on the variation in the experimental results. Finally, an interaction model was proposed and used to discuss the interaction effect of UHPFRC jacket thickness and steel fiber volume fraction and the optimum condition of the compressive strength of the NSC‐UHPFRC columns.

Investigation of key parameters affecting the use of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) as strengthening material

The use of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) for strengthening applications is gaining increasing attention due to its advantageous mechanical and durability characteristics. However, the lack of design guidelines and code recommendations hinders the extensive use of UHPFRC in strengthening applications. The aim of the present study is to offer valuable insights regarding the effect of critical parameters on the performance of UHPFRC as a strengthening material. In this current research, experimental and numerical results have been used to evaluate the effectiveness of UHPFRC layers for the structural upgrade of existing Reinforced Concrete (RC) beams. Critical parameters such as the thickness of the additional layers, the connection at the old-to-new concrete interface, the mechanical performance of UHPFRC, and the amount of additional longitudinal reinforcement have been studied, and recommendations for the effective design of the strengthened elements, considering both performance and cost, are presented. The results of the present study indicate that the addition of steel bars with different diameters in the layer increased the load-carrying capacity by up to 183%. On the contrary, an increase of 5.8% in the load-carrying capacity was achieved when the RC beams had 30 mm layers, and an 18.1% increment was achieved for layers with a higher thickness of 70 mm. The assumption of perfect connection at the interface, which can be achieved with dowels at the interface, resulted in further enhancement of the load carrying capacity, which was found to be equal to 11.8% for the 30 mm layer and 35.3% for the 70 mm layer. An increment of the UHPFRC tensile strength of the strengthening layer from 11.5 MPa to 14 MPa resulted in a further increment of the load-carrying capacity by 8%.

Valorization of engineered biochar to develop ultra-high-performance fiber-reinforced concrete with low carbon emission

This research introduces an innovative approach to developing carbon-negative Ultra-High-Performance fiber-reinforced Concrete (UHPC) by incorporating substantial quantities of biochar, both as a binder and as an aggregate, replacing up to 25% by weight of Ordinary Portland Cement (OPC) and quartz sand (QS). The study examines the impact of biochar on cement hydration processes, microstructure evolution, and various other performance metrics in the modified UHPC. Samples were formulated with 3% double-hooked steel fibers and biochar quantities ranging from 5 to 25% by weight as substitutes for OPC and QS. The investigation included assessments of changes in rheological properties, strength metrics, long-term shrinkage, resistance to sulfate attacks, freeze-thaw durability, microstructure analysis, and a cost-benefit evaluation. Test results indicated that biochar-incorporated samples exhibited up to a 20% increase in heat evolution by the end of the seventh day and plastic energy at 28 days that rose to 32.14% as compared to control samples in 20% biochar-augmented versions. Shrinkage reduction varied between 58 and 69% at 210 days for samples with 20% biochar. Specifically, the mix containing 20% biochar (G2-M5-BC-20) significantly improved the 90-day compressive and flexural strength by 8.9 and 9.3%, and 30.6 and 36.8%, respectively, while further inclusion of biochar showed no marked enhancement in performance metrics. The G2-M5-BC-20 mix also demonstrated excellent resistance to sulfate attacks and freeze-thaw cycles, exhibiting the least mass loss and highest residual compressive strength. An initial cost-benefit revealed that biochar-enhanced UHPC could offer compelling financial benefits. Given its mechanical behavior, potential for harmful CO2 emissions, and economic viability, the G2-M5-BC-20 mix emerged as the most promising formulation, potentially generating an overall profit of $36 per cubic meter.

Axial compressive behaviour of simulated corrosion-damaged RC columns retrofitted with UHPFRC jackets subjected to dry-wet cycling condition

An experimental investigation was conducted on the axial compressive behaviour of simulated corrosion-damaged reinforced concrete (RC) columns retrofitted with ultra-high performance fiber-reinforced concrete (UHPFRC) jackets. Nine RC columns were casted, retrofitted and tested. The influences of the thickness of UHPFRC jackets and the heated dry-wet cycle accelerated corrosion on the retrofitting effectiveness were explored. The failure modes, axial load versus axial shortening behaviour, initial stiffness, and ductility of the columns were discussed to evaluate their structural performance under axial compression. The results showed that UHPFRC jacket can provide a substantial enhancement in the load-carrying capacities, with benefits amplified by the increased jacket thickness (from 16.51% to 46.41%). Even subjected to the dry-wet cycle accelerated corrosion, these retrofitted columns can maintain a significant portion of their load-carrying capacities (around 97%). By acting as a protective barrier, UHPFRC jackets drastically reduce the corrosion rate of RC columns (from 3.02% to 0.35%), illustrating their capacities to safeguard the structural integrity of the columns against the environmental influence. This finding underlines the potential efficacy of UHPFRC jackets in RC column retrofitting. Finally, a systematic method to calculate the load-carrying capacity is proposed to ascertain the capacity contributions from different parts of column.

Corrosion-induced deterioration and fracture mechanisms in ultra-high-performance fiber-reinforced concretet

Ultra-high-performance fiber-reinforced concrete (UHPFRC) is an excellent material for harsh environments, but corrosion will change its internal microstructure and complicate the fracture evolution, bringing great difficulties in evaluating the long-term service life. Limited attention has been paid to the fracture mechanism of the UHPFRC upon corrosion. In the present study, integrating acoustic emission (AE) and digital image correlation (DIC) techniques are used to assess the micro/macrocracking characteristics of the specimens upon various corrosion degrees. Results show that the 56-day corroded UHPFRC with 2 vol% presents a remarkable decrease rate of 32%, 29% and 30% in the flexural stiffness, flexural strength and compressive strength. During the loading process, compaction of the original defects induced by fiber corrosion is concentrated in the elastic stage, the newborn cracks triggered by loading mainly occur in the strain-hardening stage, and the expansion of cracks mainly lies in the strain-softening stage. Corroded UHPFRC specimens with higher corrosion damage have a greater maximum strain value at the crack. In addition, the failure mode changes from shear crack failure to a brittle failure of tensile crack as corrosion damage increases. The macroscopic destruction of the corroded UHPFRC is a manifestation of internal microdamage evolution in fiber corrosion and matrix deterioration.

Investigations on the fatigue loading of thin-walled and resource-efficient UHPFRC segmental bridges

Many reinforced concrete and prestressed concrete bridges are defective or can no longer withstand the increased traffic loads for a sufficiently long time. In the long term, they will have to be replaced by new structures. In previous reinforced concrete and prestressed concrete bridges, fatigue loading (e.g. traffic, wind) is rarely a problem with regard to the concrete, especially since the cyclic traffic loads are relatively low compared to the static dead loads due to a solid construction method. However, for reasons of sustainability and compliance with climate targets, future structures and bridges should be built in a resource-efficient and materials-compatible manner, while at the same time fast and durable. A target-oriented approach to this is segmental bridge construction with keyed dry joints made of ultra-high-performance fiber-reinforced concrete (UHPFRC). In these bridge structures the fatigue loads could become more relevant due to the slenderness of the thin-walled UHPFRC bridges superstructure and fatigue problems could occur. In order to investigate this in more detail, FE investigations on segmental box girder bridges under variation of the concrete strength (NSC, HSC and UHPFRC) were carried out, while optimising the cross-section dimensions. It was shown that due to the performance of UHPFRC and the associated cross-section optimisation, an exponential increase in the ratio of cyclic live loads to static dead loads and thus an exponential increase in fatigue loading occurs at thin-walled and resource-efficient UHPFRC segmental bridges compared to NSC and HSC bridges and that this can become relevant for the design of such bridges.

Experimental Study of Cast in Anchors Embedded in UHPFRC

This paper describes an experimental investigation of the behaviour of anchors precast in Ultra High-Performance Fiber-Reinforced Concrete (UHPFRC) under static loading. Initially, the current state of the art and related experimental studies are briefly mentioned. The next part of the paper is devoted to an experimental program aimed at describing the anchorage in cement composite UHPFRC in more detail. A total of 45 pull-out tests were performed. The tests investigated the effect of the fiber quantity in volume in the UHPFRC matrix (vf), the effective embedment depth of the anchor (hef) and the position of the anchor in the mould during concreting. Finally, the results are documented, the failure mode and the shape of the concrete cone, load-displacement curves and summary tables are presented. The paper concludes with a discussion of the results and further directions for solving the problem.

Seismic performance and flexural strength prediction of high-strength bar reinforced UHPFRC walls under high axial load ratio

A new-type shear wall built with high-strength reinforcement and ultra-high performance fiber reinforced concrete (UHPFRC) is proposed in this paper, aiming to solve the problem of too large cross-section size of bottom shear wall members of high-rise and super high-rise buildings. Four UHPFRC wall specimens built with high-strength reinforcement were tested under cyclic loading to examine the influence of the parameters of fiber volume fractions (0 vs. 1.5% vs. 2.5%) and the spaces of horizontal distribution reinforcing bars (150 mm vs. 300 mm) on the seismic performance. In addition, a calculation method of flexural strength of UHPFRC shear wall is established. The research results show that: the UHPC wall specimen without fibers failed in the axial compression brittle mode, and the UHPFRC wall specimens with fibers failed in flexure-dominated ductile mode. The bridging effect of steel fibers at the cracks kept the integrity of the UHPFRC. The drift ratio capacities of the UHPFRC wall specimens under high axial compression ratio of 0.5 were 3.56%. Increasing the fiber volume fractions can improve the strength, initial stiffness, and cumulative energy consumption of the wall specimens, reduce the damage degree of the UHPFRC at the toes of the wall specimens, and can also reduce the reinforcement ratio of horizontal reinforcement without influence on the seismic performance. The proposed method of flexural strength of UHPFC walls shows reasonable prediction accuracy.

Performance Evaluation of Architectural Modular Member with Ultra-High-Performance Fiber-Reinforced Concrete for Application

As the modular industry expands, the most widely used building materials are primarily concrete, steel, and wood. However, the use of wood and steel is severely limited compared to concrete for reasons such as durability and economy. To overcome these shortcomings, we aimed to apply ultra-high-performance fiber-reinforced concrete (UHPFRC), which has excellent compressive strength and tensile strength, high durability, and minimal reinforcement with steel fibers. In this study, research was conducted on the development of unit box-type architectural modules using UHPFRC with a compressive strength of 120 MPa and a tensile strength of greater than 7 MPa. Various amounts of steel fibers (Vf = 1.0, 1.5, and 2.0%) were evaluated to determine the optimal mixing ratio of UHPFRC, in which both the durability and mechanical performance were assessed. The compressive strength and tensile strength of UHPFRC were found to be 132 MPa and 10.1 MPa, respectively, while its resistance to chloride penetration averaged 14.47 coulombs, indicating superior durability compared to conventional concrete. To reduce the weight of the unit components of the architectural modular system, both normal concrete (NC) components and UHPFRC were applied. The main variables in the flexural tests were the cross-sectional thickness, steel fiber content, and presence of an insulation material, comprising a total of three variables for evaluating the flexural performance. The application of UHPFRC with a compressive strength of 120 MPa, a cross-sectional thickness of 120 mm, and a 10 mm diameter reinforcement provided a similar performance to that of NC components while reducing concrete usage by 60% compared to NC components. Additionally, structural analysis was performed to prototype the unit box-type modular structure using UHPFRC. The modular structural system developed in this study was found to reduce construction costs by 18.7% compared to traditional steel structural systems. Further research is necessary to address issues such as floor slab vibration and noise, connections, and expansion to multistory buildings for commercialization of modular structures using UHPFRC.

Interface Shear Behavior of Ultrahigh-Performance Fiber-Reinforced Concrete Using Digital Image Correlation Technique

Interface Shear Behavior of Ultrahigh-Performance Fiber-Reinforced Concrete Using Digital Image Correlation Technique

Early-age bond behavior of embedded CFRP bars in UHPFRC: Test study and theoretical analysis

The combination of carbon fiber-reinforced polymer (CFRP) bars and ultra-high-performance fiber-reinforced concrete (UHPFRC) has great potential for use in producing structures with exceptional mechanical properties. Nevertheless, a research gap exists regarding the early-age bond behavior of embedded CFRP bars in UHPFRC, which is key to evaluating structural crack resistance. To address this gap, in this study, a series of tests was conducted on 90 pull-out specimens consisting of UHPFRC and CFRP bars. The influences of the concrete age (t), bond length (lb), and cover thickness-to-bar diameter ratio (C/D) on bond behavior were investigated. Each pull-out test generated the acquisition of a complete bond stress–slip curve. The bond interface was analyzed mechanically using the thick-walled cylinder theory and elasticity theory. A bond strength theoretical model that accounted for the surface wear of CFRP bars was proposed. The results of the pull-out test and theoretical analysis indicated that the bond strength tended to grow as t and C/D increased and was negatively correlated with lb. The model predictions agreed well with the test results while exhibiting excellent predictive accuracy compared to existing models. Furthermore, a three-branch bond stress–slip model was established to depict the bond behavior, demonstrating acceptable consistency with test curves.

Exploring strength and ductility responses of beam-column joints using UHPC and UHPFRC employing concrete damaged plasticity

Structures subjected to severe loads, such as earthquakes, often develop cracks at the beam-column joints, underscoring the significance of these regions in design. This study focuses on a comparative analysis of beam-column joints constructed with Ultra-High-Performance Concrete (UHPC) and Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) using the Finite Element Method (FEM) within the Abaqus software, contrasting with Low-Strength Concrete (LSC) and Normal-Strength Concrete (NSC). The results underscore the superiority of UHPFRC in compressive and tensile strength, coupled with enhanced ductility. Furthermore, distinct failure mechanism are observed in the concretes, captured by concrete damaged plasticity (CDP), leading to a deeper understanding of the behavior of these high-strength materials. These findings carry significant implications for enhancing structural safety and performance, particularly in situations involving seismic or other severe loads.

Effect of GFRP bar diameter and concrete cover on bond and development length in UHPFRC

This study investigates the bond strength and development length of glass fiber-reinforced polymer (GFRP) sand-coated bars embedded into ultra-high-performance fiber-reinforced concrete (UHPFRC) with 2% steel fibers. A total of 42 notched beams following the RILEM RC5 standard bond test method were fabricated. The study focused on three GFRP bar sizes (#4, 5 and 8) with diameters (db) of 13.5 mm, 17.3 mm and 27.0 mm, while varying the concrete cover to the center of the bar (C) from 20 mm to 55 mm, which results in C/db ratio ranging from 1.0 to 3.7. Three embedment lengths (Le) for each case were used: 4db, 9db and 14db. The study established a correlation between development length (Ld) and (C/db). All beams, except for four, failed by splitting bond failure as would be expected. ACI440.11–22 code equations significantly overestimated bond strength at low (Le/db) ratios and underestimated it at high (Le/db) ratios as well as overestimated Ld by factors of 2.0 to 3.5. The Michaud et al. (2021) design equation for Ld which is intended for UHPFRC had limitations in that it does not account for C or db. As such, at lower C/db ratios (i.e. at small concrete covers), it underestimated Ld while at higher C/db ratios (i.e. at larger cover), it overestimated Ld. A new general equation for Ld has been developed using the combined database, accounting for all critical parameters.

Assessing the Seismic Performance of Exterior Precast Concrete Joints with Ultra-High-Performance Fiber-Reinforced Concrete

This study was conducted to evaluate the seismic performance of an exterior precast concrete (PC) beam–column joint with ultra-high-performance fiber-reinforced concrete (UHPFRC). Currently, 45 MPa non-shrinkage mortar is used as grouting for the connection between PC beams and columns. In this study, PC joint specimens were designed using 45 MPa non-shrinkage mortar and 120 MPa UHPFRC as a grouting agent for connecting PC members. The shear reinforcement effect of UHPFRC was confirmed to reduce shear cracks in the joint core; this trend was similar in the specimens with reduced shear rebars. The maximum moment of the test specimen with the corbel was slightly increased, but there was no significant difference, and the failure pattern also showed similar results to the specimen without the corbel. In the test specimen to which the U-shaped beam was applied, the attachment surface of ultra-high-performance concrete and normal concrete were separated, and a large decrease in strength was observed. Considering workability, U-shaped beam do not seem to have any major merits in general, such as increased strength and difficulty in manufacturing, and it was judged that it was effective to separate the PC beams from the column face through corbels. Shear reinforcement through UHPFRC is effective in relieving congestion by reducing shear reinforcement bars at the joint, and it is judged that it can be used as PC joint grouting due to its excellent fluidity.

Detecting Multiple Damages in UHPFRC Beams through Modal Curvature Analysis

Curvature-based damage detection has been previously applied to identify damage in concrete structures, but little attention has been given to the capacity of this method to identify distributed damage in multiple damage zones. This study aims to apply for the first time an enhanced existing method based on modal curvature analysis combined with wavelet transform curvature (WTC) to identify zones and highlight the damage zones of a beam made of ultra-high-performance fiber-reinforced concrete (UHPFRC), a construction material that is emerging worldwide for its outstanding performance and durability. First, three beams with a 2 m span of UHPFRC material were cast, and damaged zones were created by sawing. A reference beam without cracks was also cast. The free vibration responses were measured by 12 accelerometers and calculated by operational modal analysis. Moreover, for the sake of comparison, a finite element model (FEM) was also applied to two identical beams to generate numerical acceleration without noise. Second, the modal curvature was calculated for different modes for both experimental and FEM-simulated acceleration after applying cubic spline interpolation. Finally, two damage identification methods were considered: (i) the damage index (DI), based on averaging the quadratic difference of the local curvature with respect to the reference beam, and (ii) the WTC method, applied to the quadratic difference of the local curvature with respect the reference beam. The results indicate that the developed coupled modal curvature WTC method can better identify the damaged zones of UHPFRC beams.

The Effect of Cross Sectional Properties of Concrete Column on the Repair Material: A Review

The utilization of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) as a material for repairing concrete structures holds immense promise and potential. UHPFRC usage in concrete has been a significant rise in the interest surrounding the enhancement and renovation of concrete structures, particularly focusing on columns. UHPFRC has showcased remarkable bonding potency with concrete, along with an impressive capacity to renew the load-bearing capability of compromised reinforced concrete columns. However, the limited application of UHPRFC as a repair material for concrete columns is primarily attributable to a lack of comprehension regarding the influence of shape and size effects, particularly as they pertain to square and rectangular columns. In this paper, the factors behind the impact of cross-sectional properties on the effectiveness of UHPFRC as a repair material is presented. Therefore, it can be adopted by researchers to explore the UHPFRC potential in structural rehabilitation applications especially for concrete columns. It is believed that the relationship between the cross-sectional area, aspect ratio, and corner radius ratio of the column and repair material is a vital parameter affecting the performance of repaired columns.

Temperature-Dependent Bond–Slip Behavior of CFRP Bars Embedded in Ultrahigh-Performance Fiber-Reinforced Concrete

Temperature-Dependent Bond–Slip Behavior of CFRP Bars Embedded in Ultrahigh-Performance Fiber-Reinforced Concrete