Application Of Ultra-high Performance Concrete Research Articles

Ultra-High-Performance Alkali-Activated Concrete: Effect of Waste Crumb Rubber Aggregate Proportions on Tensile and Flexural Properties

The declining availability of natural sand resources and the significant carbon footprint associated with the extensive use of cement are posing severe limitations on the advancement and application of ultra-high-performance concrete (UHPC). In this study, waste tyre-derived recycled crumb rubber particles (CR) were employed to replace quartz sand, and an alkali-activated cementitious material was used to produce waste tyre-alkali-activated UHPC (T-UHPAC). The influence of different CR replacement ratios (0%, 5%, 20%, 35%, 50%) on the tensile and flexural performance of T-UHPAC was investigated, and a predictive model for the stress–strain response considering the CR replacement ratio was established. An optimization method for improving the tensile and flexural performance of T-UHPAC was proposed. The results indicate that the effect of rough-surfaced CR on the interfacial properties of concrete differs from that of smooth quartz sand. A CR replacement ratio exceeding 35% led to a reduction in both the tensile and flexural strengths of UHPAC, while a replacement ratio at or below 20% resulted in a superior tensile and flexural performance of T-UHPAC. The established predictive model for tensile performance accurately forecasts the stress–strain behaviour of T-UHPAC under varying CR replacement ratios, with the accuracy improving as the CR replacement ratio increases. By utilizing CR to replace quartz sand in proportions not exceeding 20%, the production of low-carbon UHPC with exceptional comprehensive mechanical properties is achievable. Moreover, the development of T-UHPAC through the comprehensive utilization of waste tyres presents a promising and innovative approach for the low-carbon and cost-effective production of UHPC, thereby facilitating the sustainable development of natural resources. This research represents a significant step towards the widespread adoption and application of UHPC and thus holds substantial importance.

A Comprehensive Review of the Advances, Manufacturing, Properties, Innovations, Environmental Impact and Applications of Ultra-High-Performance Concrete (UHPC)

The article presents the progress and applications of ultra-high-performance concrete (UHPC), a revolutionary material in modern construction that offers unparalleled strength, durability, and sustainability. The overview includes the historical development of UHPC, covering its production and design aspects, including composition and design methodology. It describes the mechanical properties and durability of UHPC and highlights recent innovations and research breakthroughs. The potential integration of multifunctional properties such as self-heating, self-sensing, self-luminescence and superhydrophobicity, is explored. In addition, advances in nanotechnology related to UHPC are addressed. Beyond the actual material properties, the article presents an environmental impact assessment and a life-cycle cost analysis, providing an insight into the wider implications of using UHPC. To illustrate the environmental aspects, the determination of CO2 emissions is explained using three numerical examples. Finally, various applications of UHPC are presented, focusing on the construction of buildings and bridges. By synthesizing the above-mentioned aspects, this review paper captures the dynamic landscape of UHPC and serves as a valuable resource for researchers and engineers in the field of construction materials.

Cyclic behavior of UHPC corner beam-column joints under bi-directional bending

Design codes contain special provisions for anchorage lengths of flexural reinforcement and amount of transverse reinforcement in beam-column joints, to safeguard against joint failure and possible structural collapse. However, those stipulations could lead to congested joints with construction problems such as segregation. This study leverages experimental testing of eight corner beam-column joints under constant axial and cyclic bi-directional bending loads. In addition to being one of few on corner joints under a complex and practical loading, the study’s main aim is to evaluate the effectiveness of ultra-high-performance concrete (UHPC) as a joint fill in lieu of normal strength concrete (NSC). Brittle failure, either by pure shear or shear combined with yielding of beam reinforcement occurred in all NSC joints and varied in shape and intensity depending on the column depth-to-beam longitudinal bar diameter (hc ⁄db) ratio and spacing of transverse beam/column reinforcement. Ductile failure characterized by the yielding of beam reinforcement and plastic hinge at the beam-joint interface occurred in all UHPC joints and was independent of the two aforementioned variables. The application of UHPC in the joint region resulted in increasing the joint ultimate strength by 27.6–54.8%, energy dissipation by 24–163%, and stiffness by 20 to 50%, compared to NSC joints. Such results were obtained when no transverse reinforcement is used in the joint, and only half transverse reinforcement is used in the beam/column members, and with hc ⁄db relaxed to 38% of the code recommended ratio, highlighting the advantages of UHPC joints. Predictions of ACI-ASCE 352R code were found to be overly unconservative and in need of future improvement.

Coarse synthetic fibers (PP and POM) as a replacement to steel fibers in UHPC: Tensile behavior, environmental and economic assessment

Ultra-high performance concrete (UHPC) has excellent compressive strength and ductility. Nevertheless, the extensive utilization of UHPC has been impeded by factors including the exorbitant cost, substantial carbon emissions, and vulnerability to corrosion associated with steel fibers. This study explores an innovative approach by introducing polypropylene fibers (PPF) and polyoxymethylene fibers (POMF) as replacements for steel fibers (SF) in the preparation of hybrid fiber-reinforced ultra-high-performance concrete (HUHPC), with a total fiber content of 3% vol. The influence and mechanism of different PPF/POMF replacement ratios for SF on the flowability, compressive performance, and tensile behavior of HUHPC were investigated. An axial tensile static constitutive model for HUHPC considering the PPF/POMF replacement ratio was established, and a comprehensive environmental benefit assessment index and economic benefit assessment index considering mechanical performance were proposed. The results showed that using PPF and POMF with low modulus as replacements for high-modulus SF significantly improved the flowability of HUHPC. Notwithstanding there is a decrease in compressive and tensile strength of HUHPC resulting from the utilization of low-modulus and low-strength PPF and POMF as substitutes for SF, it modified the axial tensile stress-strain behavior of conventional UHPC and notably improved its tensile toughness. The established axial constitutive model for HUHPC in this study effectively predicted the tensile stress-strain behavior of HUHPC. Importantly, the comprehensive environmental assessment index reveals that HUHPC offers superior environmental and economic benefits compared to traditional UHPC, leading to substantial cost reductions. The development of HUHPC through fiber hybridization presents a promising strategy for the low-carbon and cost-effective production of UHPC, holding significant implications for the broader adoption and application of UHPC.

Mechanical Properties of Ultra-High Performance Concrete (UHPC) and Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) with Recycled Sand

Use of high-cost raw materials such as quartz sand can limit wider application of ultra-high performance concrete in concrete construction. In this experimental study, recycled sand was used to fabricate ultra-high performance concrete (UHPC) and ultra-high performance fiber-reinforced concrete (UHPFRC). Green UHPC with ordinary Portland cement and industrial by-products such as silica fume, fly ash, as well as recycled sand was first developed through two-step packing density tests to optimize the mix design. UHPFRC was then developed based on the UHPC mix designs and by using 1%, 2%, or 3% 13-mm straight steel fibers (SSF). The compressive strength, elastic modulus, and flexural tensile strength was 128 MPa, 46.9 GPa, and 11.9 MPa, respectively, after 28 days at water-to-binder ratio of 0.17 and with 2% SSFs. All high-performance concretes in this work utilized 100% commercially available recycled sand that was produced by wet processing method. Mechanical characteristics such as strength, elastic modulus, and density, absorption, and voids of the UHPC/UHPFRC were investigated. Development of autogenous shrinkage of UHPC/UHPFRC with recycled sand was monitored for 12 weeks, while mercury intrusion porosimetry test and scanning electron microscopy were performed for microstructural investigation. Finally, the environmental impacts and economical aspects of the green UHPC were evaluated by life cycle assessment (LCA) and cost analysis.

Erstanwendung eines eigenen UHFB‐Systems in situ in Deutschland für die Bushaltestelle Olympia Einkaufszentrum in München

AbstractReporting about the first application of UHPC in situ in Germany. As Switzerland's leading construction provider Implenia has developed an in situ UHPC application in the last 10 years. We report about the general idea of UHPC, the materials behavior, the tasks and solutions as well as possible use cases for infrastructure projects in Germany for this Ultrahigh‐Performance‐Concrete (UHPC)

Experimental study on fatigue behavior of UHPC joint in negative moment region of π-shaped steel–concrete composite beams

To improve the crack resistance of concrete bridge decks in the negative moment region of π-shaped steel–concrete composite beam, a novel ultra-high performance concrete (UHPC) joint was first proposed. Based on an actual bridge, a 1:2 scale model was then designed as the specimen. A fatigue test was conducted to investigate the variation of its structural properties during fatigue loading, and a static test was performed to evaluate its residual bearing capacity. The test results show that the new UHPC joint has good crack resistance under fatigue loading and can meet the engineering requirements. The stiffness of the specimen significantly decreases after 3 million fatigue cycles. However, without significant fatigue damage on the surface of specimen, plenty of stiffness is reserved. It is found that there is no significant slip between the concrete deck and steel girder, and between the UHPC and normal concrete in the static test after fatigue, indicating that the studs inside the π-shaped steel–concrete composite beam are arranged reasonably and the interaction of the overall structure is reliable. Furthermore, the ultimate bearing capacity of the specimen decreased by only 9.4% from its design value after being subjected to 3 million fatigue cycles. It is revealed that the application of UHPC in the composite beam effectively improves its crack resistance, resulting in a smaller reduction in bearing capacity. This paper can provide theoretical foundation for the preparation and application of the π-shaped steel–concrete composite beams with UHPC joints.

Characterization of interface properties for modeling the shear behavior of T-beams strengthened with ultra high-performance concrete

The application of Ultra high-performance concrete (UHPC) lateral layers on normal-strength concrete (NSC) beams substantially improves their shear performance. However, the impact of the NSC-UHPC interface properties on the shear performance has been scarcely studied and may hinder the strengthening efficiency and modify the failure mode. This study has characterized the complete shear and tensile behavior of interface specimens and evaluated the effect of anchors at the interface. Then, the complete curves of the interface allowed calibration of an interface concrete fracture (CF) model that was introduced in finite element (FE) simulations replicating the shear behavior of UHPC-strengthened T-beams tested in the same project. Parametric studies were then made with FE simulations. Results showed the FE simulations with the CF model better capture the stiffness evolution and failure mode of strengthened beams than that with the perfect bond model. The increase of UHPC layer thickness up to 80 mm and anchor spacing at the interface smaller than 300 mm considerably increased the stiffness and shear capacity of the strengthened beams. Existing dead load on beams did not impair UHPC strengthening and a substantial increase in shear capacity can still be achieved in real-size strengthened T-beams.

Spalling resistance and mechanical properties of ultra-high performance concrete reinforced with multi-scale basalt fibers and hybrid fibers under elevated temperature

The weak spalling resistance of ultra-high performance concrete (UHPC) at elevated temperature restricts the further application of UHPC and urgently needs to be improved. Macro basalt fiber (MBF), a kind of minibar produced by basalt fiber reinforced polymers (BFRP), was innovatively used to improve the spalling resistance of UHPC in this study as mono fiber or one of hybrid fibers. The effect of MBFs and hybrid fibers on the spalling resistance and mechanical properties of UHPC under elevated temperature were systematically tested and evaluated. The mechanism was comprehensively revealed by analyzing the permeability, porosity, microstructures of UHPC, and thermal analysis of fibers. According to test results, compared to UHPC with steel fibers, UHPC with MBFs showed better spalling resistance and higher mechanical properties at 400 and 500 °C, as well as the close mechanical properties and higher flowability at normal condition. The reason for higher spalling resistance was that more vapor released from channels formed by resin volatilization which was a part of MBF, thereby decreasing pore pressure. Although the obvious synergistic effects of hybrid micro and macro basalt fibers on the mechanical properties of UHPC were observed at normal condition, the spalling resistance was significantly reduced compared to UHPC with MBFs at elevated temperature. It was because that microcracks were restricted by micro basalt fibers with superb thermal stability, resulting in relatively isolated channels and decrease in vapor release. In brief, this work proposed a novel method to improve the spalling resistance and mechanical properties of UHPC under elevated temperature by using MBFs, the method which slightly reduced the mechanical properties and improved the flowability of UHPC at normal condition compared to the UHPC with steel fibers.

Behaviour of hybrid polypropylene and steel fibre reinforced ultra-high performance concrete beams against single and repeated impact loading

The high cost of steel fibres limited the application of ultra-high performance concrete (UHPC) in practical construction. To balance the performance and cost, hybrid polypropylene and steel fibre reinforced UHPC was proposed. The material properties of UHPC that contained 2 vol% polypropylene fibre and 1 vol% steel fibre were measured by the four-point bending tests and uniaxial compression tests. Three large-sized hybrid fibre reinforced UHPC beam specimens were tested against repeated and single impact loading. The weight of the drop hammer was 641 kg and the impact location was at the mid-span, the impact velocity varied from 3.13 to 4.43 m/s. The UHPC beams showed the flexural response in all the impact scenarios. With the same total impact energy, single impact loading was noted to be less hazardous than the repeated impact loadings. Based on the test results, a concrete numerical model of hybrid fibre reinforced UHPC was developed. The bond-slip relationship between UHPC and steel bars was incorporated into the structural model. Compared to the simulation considering the bond-slip relationship, the simulation with perfect bonding assumption exhibited an overall smaller mid-span displacement, where the maximum and residual displacement were 11.41% and 9.43% smaller, respectively. The numerical drop weight tests were reproduced and validated with experimental data. Finally, the failure mechanism and energy absorption of the test specimen under the repeated impact loading scenario was analysed.

Hydration characteristics, hydration products and microstructure of reactive powder concrete

Reactive Powder Concrete (RPC) is a new type of cementitious materials with a complex hydration mechanism, and active admixtures greatly influence the hydration reaction, formation of hydration products, and evolution of microstructure. In order to comprehensively study the quantitative effects of active admixtures contents, namely silica fume, slag and fly ash, on hydration characteristics, hydration products, and microstructure of RPCs, tests of workability, setting time, electrical conductivity, bound water and mechanical properties were conducted. Furthermore, a series of properties including morphology and micro-structure characteristics of RPCs were analyzed by thermogravimetric (TG) analysis, X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), mercury intrusion porosimetry (MIP), Brunauer-Emmet-Teller (BET), and scanning electron microscope (SEM). The results indicate that the initial hydration reaction rate of RPCs is reduced by partly replacing cement with active admixtures. The pozzolanic effect created by the active admixtures enhances hydration and improves RPC's compressive and flexural strength. RPCs made of cement-silica fume mixture exhibit the best macroscopic properties. The adoption of silica fume promotes the production of C–S–H gel during hydration and exerts pozzolanic and crystal nucleation effects to promote cement hydration. RPCs made of pure cement exhibit 15.3% porosity after 28 days of hydration, with the largest proportion of less harmful pores in the microstructure. The porosity is reduced to 5.2% when cement is partially replaced with silica fume, and the microstructure is dominated by harmless pores. When replacement of silica fume is kept at 25%, using slag powder or fly ash substitute part of cement also reduces the number of less harmful pores. It is beneficial to add slag powder to increase the number of gel pores, whereas fly ash reduces the number of gel pores. The investigation presented in this paper would contribute to the production of low cost and environmentally-friendly RPCs, and accelerate the wider applications of ultra-high performance concrete (UHPC) in engineering structures.

Shear performance and failure process of perfobond connector in steel-UHPC composite structures

Nowadays, the application of Ultra-High Performance Concrete (UHPC) provides innovative concepts for structural designs of composite structures. Perfobond connectors (PBLs) with excellent shear capacity and fatigue performance may fully use the superiority of UHPC and thus are increasingly adopted in various novel steel-UHPC composite structures. However, the shear behavior and failure modes of PBLs embedded in UHPC slabs still need to be clarified. Therefore, this paper aims to evaluate the shear performance and further propose an equation for the shear capacity of UHPC PBLs. Firstly, six standard push-out tests taking the hole diameter, hole height, and whether perforated rebar was used as the parameters were performed. Subsequently, a detailed finite element (FE) model for the push-out test was established and validated by the test results, which took the fracture of perforated rebars into account by introducing the LW fracture criterion. Further, a parametric study was carried out to clarify the effects of dowel area, rebar sectional area, and hole shape. The results showed that benefiting from the high rigidity of UHPC, the PBLs with perforated rebars presented a slip-hardening behavior and excellent ductility. The slip corresponding to the rebar fracture grew with the rebar and hole diameter. Besides, the shear stiffness markedly rose with the hole diameter and height, while the effect of perforated rebars on shear stiffness was relatively small. Finally, the shear capacity equations for long-hole PBLs embedded in UHPC were proposed. The calculated results matched well with the 80 numerical and 21 collected experimental results.

Ultra-High-Performance Concrete (UHPC) - Applications Worldwide: A State-of-the-Art Review

Research is in progress on the applications of ultra-high performance concrete (UHPC) as a new additive material in construction technology. Over the last twenty years’ significant improvements have been achieved in mechanical properties of UHPC, such as its strength, workability, and ductility, with further improvements made in self-placing properties, higher density, and durability compared with normal concrete. One of the biggest advantages offered by ultra-high performance concrete over normal concrete is the possibility to minimize the cross-sectional dimensions of the structural elements. UHPC can be used to provide significant long-span members, whilst also showing less variation, creep, and drying shrinkage compared to conventional concrete. After many years of development and research into UHPC’s properties, it is being used in commercial applications to meet the rising demand for quality constructions. Many projects in the world started using UHPC for different construction objectives such as long spans, columns, jacketing, rain-screen cladding systems, panel systems, façades, etc. Furthermore, there are not enough sources in the literature describing mixture design, preparation, and curing. This research gives an overview of the uses of UHPC in structural and architectural applications.

Investigation of Lateral Stability of UHPC Beams Supported by Bearing Pads Considering the Nonlinear Lift-Off Effect

Ultrahigh-performance concrete (UHPC) is an advanced cement-based material with a compressive strength greater than 150 MPa. The application of UHPC on prestressed girders allows the design of very long spans with thin sections. However, the increased slenderness, low lateral flexural stiffness, flexible supports, and beam imperfections make lateral instability critical. Therefore, this paper presents an analytical prediction of precast beams’ behaviors considering the nonlinear contact interaction with the bearing pads. The nonlinear geometric theory for the slender element is coupled with the nonlinear contact mechanism developed between the beam and pad through the energy approach. The proposed solutions are compared with the equations available in the literature that consider the linear stiffness contact interaction. Changes in the limit load of up to 84% were a result of the lift-off effect (contact interaction). From the results, the UHPC is highly sensitive to lateral instability, giving a maximum load/dead weight ratio of up to 1.08 where the common technical recommendation is greater than four.

A Review in Technologies, Definitions, Properties and Applications of Ultra High-Performance Concrete (UHPC)

Concrete technology has changed dramatically during the last decades, where the high-strength concrete concept has gone from 30 MPa to well over 100 MPa. In this paper, a review study has been conducted on ultra high-performance concrete (UHPC), however, researchers have a lot of definitions for this term, but all of them agreed that (UHPC) which refers to cement-based materials exhibiting superior properties, including compressive strength higher than 150 MPa with high ductility, and excellent durability. This paper reviews the theoretical principles of UHPC, definitions, raw materials, mixture design methods, successful mixture components with the required properties, challenges, and some of the successful applications of UHPC, focusing on bridge applications. The paper concluded by summarizing the benefits of using UHPC, the future of this superior concrete, current challenges and some recommendations for wider use.

Experimental and numerical study of shear-lag effect on low-ribbed steel-UHPC composite structure

Due to its excellent mechanical properties, the application of Ultra-High Performance Concrete (UHPC) in the field of civil engineering is rapidly increasing. Recently, a UHPC-based composite structure referred to as a low-ribbed slab steel-UHPC composite beam (SUHPC-LRSCS) is developed, which can reduce the structural self-weight significantly without compromising the mechanical performance of the structure. Because the shear-lag effect (non-uniform stress distribution) tends to cause localized damage to the structure, it is critical to consider this effect on the relatively new composite structure. In this paper, it numerically demonstrates that the shear-lag effect on this low-ribbed composite structure is greater than that of the composite beam with a traditional rectangular cross-section. To avoid the inaccuracy analysis in the structural design, this paper proposes a theoretical calculation approach for considering the shear-lag effect on that based on the bar simulation method. The effectiveness of the proposed method is verified by both the lab experiment and FE models. The proposed method presents high accuracy results showing a potential application in the engineering field. In addition, for the proposed method, the effects on both the determination of the bars quantity and separation ways for calculating the bar equivalent area are investigated. Finally, a suggested upper limit of the shear-lag coefficient for simply supported SUHPC-LRSCS is given for reference.

Interfacial properties between ultra-high performance concrete (UHPC) and steel: From static performance to fatigue behavior

Interfacial properties between UHPC and steel play a vital role in the application of UHPC as overlay in flexural members in bridges, and the shortcomings aroused by welded shear connectors could be eliminated by utilization of steel-UHPC interfaces without mechanical connectors. However, few researchers concerned about the influences of bending conditions and fatigue loading. This paper investigates properties of steel-UHPC interfaces, considering the affecting factors of interface treatments, boundary conditions, and loading patterns. In phase Ⅰ, the static interfacial properties under tension, shear, and bending were investigated by pull-off tests, push-out tests, and bending tests, respectively. In phase Ⅱ, fatigue bending tests were conducted to study the fatigue interfacial properties. The results indicate that the bond connection between the UHPC and the smooth plate was weak. Certain surface roughness is beneficial to the bond strength, and the degree of influence varies with the boundary and loading conditions. For the interface between UHPC and sandblasted steel plate, the nominal bond strength reached 4.84 MPa under bending with superior fatigue performance. Though the nominal bond strength of the steel-UHPC interface with an epoxy layer could reach 4.24 MPa under bending, the fatigue performance is very poor that the interface would slide and fail after about ten to twenty thousand loading cycles.

Shear behavior of large studs and novel bolted connectors in steel-UHPC composite beams

With the gradual application of ultra-high performance concrete (UHPC), steel-UHPC composite bridges produce higher interfacial shear, which require larger diameter studs to avoid the group-stud effect of abundant small studs and accelerate the construction. Considering welding problems of larger studs, bolted connectors could be an alternative and benefit the replacement of composite bridges. The traditional bolted connector expressed early slip on the steel-UHPC interface due to the bolt-to-hole clearance, which reduced the composite action. To decrease the clearance, three novel bolted connectors involving a hinged bolt, a threaded-hole bolt, and a taper-sleeve bolt were proposed and tested along with large studs and traditional bolted connectors. The diameter of shear connectors ranged from 24 mm to 40 mm. Three failure modes were observed, in which the failure of the studs was significantly influenced by the welding quality. The shear capacities of the novel and traditional bolts with the same diameter were similar and unrelated to the bolt-to-hole clearance. The novel bolted connectors did not exhibit an early slip in load-slip curve and their stiffness was maximum 4.1 times that of the traditional bolt. The shear capacity and stiffness of shear connectors increased with their diameter. Six equations for predicting shear capacity and five equations for the shear stiffness of shear connectors were evaluated, the ductility of the studs and bolts were also assessed. The hinged bolt was evaluated to have a better comprehensive shear performance than other bolted connectors.

Recent trends in ultra-high performance concrete (UHPC): Current status, challenges, and future prospects

• UHPC is promptly developing as a leading concrete material for construction industries. • UHPC has exceptional properties, making it a potential functional solution for a sustainable construction. • This article scientifically reviews the carbon capturing, challenges, limitations, and applications of UHPC. • The findings of this review likely to help specialists in establishing the design guidelines for sustainable UHPC. • Further efforts are required to standardize testing characterization for the materials used in UHPC. Ultra-high performance concrete (UHPC) combines advanced fibrous and cementitious material technologies to achieve high strength and exceptional durability. The material tends to have microscopic pores that prevent harmful substances such as water, gas, and chlorides from entering. UHPC can also achieve compressive strengths above 200 MPa and tensile strengths above 20 MPa. It also shows significant tensile strain hardening and softening behavior. Owing to all these characteristics, UHPC has excellent performance, making it a potentially attractive solution for improving the sustainability of construction components. Despite UHPC’s outstanding mechanical properties, superior toughness and ductility, and extraordinary durability, various challenges prevent its widespread use. At the same time, several challenges are currently being faced in the applications of UHPC, which include i) design aspects such as material properties; ii) production technology for large-volume and/or long-span elements with low workability, high spalling, and high shrinkage strains; and iii) unknown durability characteristics after the appearance of long-term concrete cracking. With a lack of industry experience, UHPC specialists face additional challenges in spreading hands-on practice to concrete industry professionals so that the latter can be well versed in applying this sophisticated concrete technology. For these reasons, a comprehensive literature study on recent development trends of UHPC should be conducted to determine its current status and prospects. This article scientifically reviews the current status, carbon capturing capabilities, sustainability aspects, challenges and limitations, and potential applications of UHPC. This state-of-the-art review is aimed at helping scientific researchers, designers, and practitioners widen the use of UHPCs in advanced infrastructure applications. This review will help specialists to develop the design guidelines to enable the widespread application of sustainable UHPC. In doing so, design engineers will be provided with an assurance to fully exploit the high strength and other special properties of UHPC and develop models that can efficaciously estimate the ultimate bearing capacity of UHPC sections under various loading conditions.

Enhancement of local concrete compression performance by incorporating ultra-high performance concrete (UHPC) tube

PurposeThe application of ultra-high performance concrete (UHPC) in anchorage zones can significantly improve the local compression performance of structures. However, the high cost and complex preparation of UHPC make UHPC difficult to be widely used in practice. This study proposes a method to strengthen the local compression zone of structures built by normal strength concrete (NSC) by incorporating UHPC cores.Design/methodology/approachIn this study, a Finite Element Model (FEM) of local compression specimens was established by ABAQUS, and the accuracy of FEM was verified by comparing the FEM calculation results with experimental results. The verified FEM was adapted to the research on the influences of affecting factors on local compression performance of structures, including NSC strength, UHPC strength, spiral steel bar strength, and UHPC core diameter.FindingsThe results show that the peak load of the strengthened specimen SC1-U + N increases by 210.2% compared to that of the SC1-NSC. Furthermore, compared to SC1, the strengthened specimen SC1-U + N can save 64.7% amount of UHPC while the peak load decreases by only 34.4%. The peak load of the strengthened specimens increases with the axial compressive strength and the diameter of UHPC cores increasing, crack load increases with increasing the compressive strength of NSC, the spiral steel bar with high strength can prevent the sharp drop of load-deflection curve and the residual bearing capacity increases accordingly. All findings indicate that increasing the diameter of UHPC cores can improve the overall performance of the specimens. Under loading, all specimens fail by following a similar pattern. The effectiveness of this new strengthen method is also verified by FEM analytical calculations.Originality/valueBased on the experimental study, this study extrapolates the influence of different parameters on the local bearing capacity of the strengthened specimens by finite element simulation. This method not only ensures the accuracy of bearing capacity assessment, but also does not require many samples, which ensures the economy of the reinforcement process. The research results provide a reference for the reinforcement design of anchorage zone.