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This paper presents a comprehensive finite element analysis (FEA) of pre-stressed Ultra High-Performance Concrete (UHPC) girders, showcasing intricate structural behaviors under various loading conditions. Utilizing advanced finite element modeling techniques, the study accurately simulates the flexural response of UHPC girders, integrating experimental results from large-scale laboratory tests conducted by researchers at the Turner-Fairbank Highway Research Center. This paper shows the effectiveness of simulating pre-stressing forces via initial equivalent temperature load with relatively accurate stress and strain predictions. The paper also delves into the moment–deflection relationships at critical stages, such as first concrete crack appearance, yielding, and strain localization, to capture the non-linear behavior of UHPC girders under pre-stressed conditions. Additionally, crack propagations were characterized by investigating the damage in tension (DAMAGET) plots. In summary, the results of the finite element model agree well with the experimental observations. Moreover, this study not only demonstrates the effectiveness of FEA in accurately simulating the complex structural behaviors of UHPC girders but also highlights its broader applicability to the design and analysis of other girder types, offering valuable insights compared to ordinary concrete beams. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive finite element analysis (FEA) of pre-stressed Ultra High-Performance Concrete (UHPC) girders, showcasing intricate structural behaviors under various loading conditions. Utilizing advanced finite element modeling techniques, the study accurately simulates the flexural response of UHPC girders, integrating experimental results from large-scale laboratory tests conducted by researchers at the Turner-Fairbank Highway Research Center. This paper shows the effectiveness of simulating pre-stressing forces via initial equivalent temperature load with relatively accurate stress and strain predictions. The paper also delves into the moment–deflection relationships at critical stages, such as first concrete crack appearance, yielding, and strain localization, to capture the non-linear behavior of UHPC girders under pre-stressed conditions. Additionally, crack propagations were characterized by investigating the damage in tension (DAMAGET) plots. In summary, the results of the finite element model agree well with the experimental observations. Moreover, this study not only demonstrates the effectiveness of FEA in accurately simulating the complex structural behaviors of UHPC girders but also highlights its broader applicability to the design and analysis of other girder types, offering valuable insights compared to ordinary concrete beams.

In recent years, attest to the growing prominence of sustainable buildings and the integration of advanced materials like nanomaterials in construction practices. Among these advancements, the strategic application of multi-walled carbon nanotubes (MWCNTs) alongside dispersion techniques such as surfactant agents, functionalization, and ultrasonication is pioneering. These techniques are instrumental in elevating the mechanical strength and durability of cement paste and mortar. The approach involves gradually introducing nanomaterials to create a cementitious composite, allowing for a systematic analysis of their effects on each type and determination of the optimal dosage. The influence of MWCNT with various dosage combination on rheological, mechanical and microstructural properties of ultra high-performance concrete (UHPC) were investigated in this study. According to test results, the UHPC MWCNT 0.06 % mix can be considered as the best UHPC mix due to discussed specifications. The outcomes of the research demonstrate that the optimal dosage of MWCNT enhances various mechanical properties of UHPC significantly. At 28 days of curing, the addition of MWCNT resulted in improvements of 32.97 % in compressive strength, 49.72 % in split tensile strength, 40.41 % in flexural strength, and 9.09 % in dynamic modulus. The observed enhancements in mechanical properties can be attributed to the pore-filling, bridging, and densification effects of MWCNT within the calcium-silicate-hydrate structure of UHPC. Moreover, the incorporation of MWCNT facilitates the development of a more sustainable and environmentally friendly UHPC, thereby supporting sustainable construction practices.

In Accelerated Bridge Construction (ABC), Ultra-High Performance Concrete (UHPC) is often used for connecting precast concrete bridge components, including deck portions of the Deck Bulb-T girders. An alternative low-cost non-proprietary UHPC has been proposed for use in place of the proprietary UHPC for connecting the precast components. The pullout behavior of steel reinforcing bars in closure pour with typical range for embedment lengths is studied for both proprietary and non-proprietary UHPC materials. [ABSTRACT FROM AUTHOR]

In Accelerated Bridge Construction (ABC), Ultra-High Performance Concrete (UHPC) is often used for connecting precast concrete bridge components, including deck portions of the Deck Bulb-T girders. An alternative low-cost non-proprietary UHPC has been proposed for use in place of the proprietary UHPC for connecting the precast components. The pullout behavior of steel reinforcing bars in closure pour with typical range for embedment lengths is studied for both proprietary and non-proprietary UHPC materials.

Ultra-high-performance concrete (UHPC) is a kind of high-tech cementitious material with superb mechanical and durability properties compared to other types of concrete. However, due to the high content of cement and silica fume used, the cost and environmental impact of UHPC is considerably higher than conventional concrete. For this reason, several efforts around the world have been made to develop UHPC with greener and less expensive local pozzolans. This study aimed to design and produce UHPC using local fly ash available in Colombia. A numerical optimization, based on Design of Experiments (DoE) and multi-objective criteria, was performed to obtain a mixture with the proper flow and highest compressive strength, while simultaneously having the minimum content of cement. The results showed that, despite the low quality of local fly ashes in Colombia, compressive strength values of 150 MPa without any heat treatment can be achieved. [ABSTRACT FROM AUTHOR]

A super lightweight deck can enhance load rating and functionality of a bridge, especially those identified as structurally deficient. This study was aimed to develop and experimentally validate a novel bridge deck as an ultra-lightweight low-profile waffle slab of ultra-high-performance concrete (UHPC) with either carbon fiber reinforced polymer (CFRP) or high strength steel (HSS) reinforcement. The proposed system lends itself to accelerated bridge construction, rapid deck replacement in bridges with load restrictions, and bridge widening applications without the need to replace girders. Performance and failure modes of the proposed deck were initially assessed through extensive lab experiments and finite element analysis, which together confirmed that the proposed deck panel meets the AASHTO LRFD requirements. The proposed deck system is not susceptible to punching shear of its thin slab and fails in a rather ductile manner. To evaluate its long-term performance, the system was further tested under the dynamic impact of wheel load at the Accelerated Pavement Testing (APT) facility of the Florida Department of Transportation using a Heavy Vehicle Simulator (HVS). [ABSTRACT FROM AUTHOR]

In this paper iron tailing sand (TS) are used as aggerate to develop ultra high-performance concrete (UHPC). The mix proportion of UHPC is designed and TS were added by 25%, 50%, 75% and 100% (wt.%, i.e., weight percentage) to replace natural river sand. Firstly, the influence of TS on the slurry behavior was carried out. The experimental result indicates that with the continuously increasing content of TS, the workability of slurry decreases, while the air content increases. Considering the workability, the optimal replacing dosage of TS should be less than 50%. Then, tests for the hardened specimens were taken. The compressive behavior and micro-porosity deteriorate with increasing content of TS, and the compressive strength had a positive linear relationship with the workability, which indicated that the decline the compressive behavior is mainly due to the loss of flowability. Finally, autogenous shrinkages of UHPC with different TS dosage were also tested. At the same time, the micro-structure of specimens was discussed, which was deteriorate with the increasing dosage of TS. Therefore, comprehensively considering the compressive behavior, micro-structure and shrinkage behavior, as much as 50% of the aggregate could be replaced by TS when developing UHPC.

This numerical study investigates the structural performance of railway sleepers made of ultra high-performance concrete (UHPC). First, numerical concrete sleepers are developed, and the tensile stress-strain relationship obtained from the direct tension test on the UHPC coupons is used for the tensile constitutive model after applying a fiber orientation reduction factor. The numerical sleeper models are validated with the experimental data in terms of the force and crack-width relationship. Second, using the developed models, a parametric study is performed to investigate the performance of the UHPC sleepers while considering various design/mechanical/geometrical parameters: steel fiber contents, size of the cross-section, and diameter and strength of prestressing (PS) tendons. The simulation results indicate that the size of the cross-section has the most impacts on the performance, while the effect of yielding strengths of PS tendons is minimal among all the parameters. Engineers need to pay attention to efficiency and an economical factor when using a larger cross-section, since sleepers with larger cross-sections can be an over-designed sleeper. This study suggests an economical design factor for engineers to evaluate what combination of parameters would be economical designs.

Although ultra high-performance concrete (UHPC) has great performance in strength and durability, it has a disadvantage in the environmental aspect; it contains a large amount of cement that is responsible for a high amount of CO2 emissions from UHPC. Supplementary cementitious materials (SCMs), industrial by-products or naturally occurring materials can help relieve the environmental burden by reducing the amount of cement in UHPC. This paper reviews the effect of SCMs on the properties of UHPC in the aspects of material properties and environmental impacts. It was found that various kinds of SCMs have been used in UHPC in the literature and they can be classified as slag, fly ash, limestone powder, metakaolin, and others. The effects of each SCM are discussed mainly on the early age compressive strength, the late age compressive strength, the workability, and the shrinkage of UHPC. It can be concluded that various forms of SCMs were successfully applied to UHPC possessing the material requirement of UHPC such as compressive strength. Finally, the analysis on the environmental impact of the UHPC mix designs with the SCMs is provided using embodied CO2 generated during the material production.

Most of the bridges and viaducts in the Netherlands were built in the sixties and seventies of the last century, and an increasing number of them will have to be replaced due to technical or functional reasons. The Netherlands is not an exception, many industrialized countries will face a similar replacement task in the near future. With the increased traffic intensities and the importance of mobility, the design and construction strategies for new bridges have to be different from that in the past. New methods need to ensure that traffic hindrance due to construction works and (future) maintenance activities are minimized. At the Delft University of Technology, a SMART bridge concept is being developed for fast and hindrance-free infrastructural replacement. The optimal advantage is achieved by utilizing innovative but proven technologies, and by bringing academic research into practice. A combination of recent innovations in construction technology, such as advanced cementitious materials (ACM), structural health monitoring (SHM) techniques, advanced design methods (ADM), and accelerated bridge construction (ABC) is being used. These innovations represent a step towards the next generation of infrastructure where fast construction, intelligent bridge design, sustainability, zero-energy, no/low maintenance, and aesthetics are key features.

In this paper iron tailing sand (TS) are used as aggerate to develop ultra high-performance concrete (UHPC). The mix proportion of UHPC is designed and TS were added by 25%, 50%, 75% and 100% (wt.%, i.e., weight percentage) to replace natural river sand. Firstly, the influence of TS on the slurry behavior was carried out. The experimental result indicates that with the continuously increasing content of TS, the workability of slurry decreases, while the air content increases. Considering the workability, the optimal replacing dosage of TS should be less than 50%. Then, tests for the hardened specimens were taken. The compressive behavior and micro-porosity deteriorate with increasing content of TS, and the compressive strength had a positive linear relationship with the workability, which indicated that the decline the compressive behavior is mainly due to the loss of flowability. Finally, autogenous shrinkages of UHPC with different TS dosage were also tested. At the same time, the micro-structure of specimens was discussed, which was deteriorate with the increasing dosage of TS. Therefore, comprehensively considering the compressive behavior, micro-structure and shrinkage behavior, as much as 50% of the aggregate could be replaced by TS when developing UHPC. [ABSTRACT FROM AUTHOR]

This numerical study investigates the structural performance of railway sleepers made of ultra high-performance concrete (UHPC). First, numerical concrete sleepers are developed, and the tensile stress-strain relationship obtained from the direct tension test on the UHPC coupons is used for the tensile constitutive model after applying a fiber orientation reduction factor. The numerical sleeper models are validated with the experimental data in terms of the force and crack-width relationship. Second, using the developed models, a parametric study is performed to investigate the performance of the UHPC sleepers while considering various design/mechanical/geometrical parameters: steel fiber contents, size of the cross-section, and diameter and strength of prestressing (PS) tendons. The simulation results indicate that the size of the cross-section has the most impacts on the performance, while the effect of yielding strengths of PS tendons is minimal among all the parameters. Engineers need to pay attention to efficiency and an economical factor when using a larger cross-section, since sleepers with larger cross-sections can be an over-designed sleeper. This study suggests an economical design factor for engineers to evaluate what combination of parameters would be economical designs. [ABSTRACT FROM AUTHOR]

Although ultra high-performance concrete (UHPC) has great performance in strength and durability, it has a disadvantage in the environmental aspect; it contains a large amount of cement that is responsible for a high amount of CO2 emissions from UHPC. Supplementary cementitious materials (SCMs), industrial by-products or naturally occurring materials can help relieve the environmental burden by reducing the amount of cement in UHPC. This paper reviews the effect of SCMs on the properties of UHPC in the aspects of material properties and environmental impacts. It was found that various kinds of SCMs have been used in UHPC in the literature and they can be classified as slag, fly ash, limestone powder, metakaolin, and others. The effects of each SCM are discussed mainly on the early age compressive strength, the late age compressive strength, the workability, and the shrinkage of UHPC. It can be concluded that various forms of SCMs were successfully applied to UHPC possessing the material requirement of UHPC such as compressive strength. Finally, the analysis on the environmental impact of the UHPC mix designs with the SCMs is provided using embodied CO2 generated during the material production. [ABSTRACT FROM AUTHOR]

Most of the bridges and viaducts in the Netherlands were built in the sixties and seventies of the last century, and an increasing number of them will have to be replaced due to technical or functional reasons. The Netherlands is not an exception, many industrialized countries will face a similar replacement task in the near future. With the increased traffic intensities and the importance of mobility, the design and construction strategies for new bridges have to be different from that in the past. New methods need to ensure that traffic hindrance due to construction works and (future) maintenance activities are minimized. At the Delft University of Technology, a SMART bridge concept is being developed for fast and hindrance-free infrastructural replacement. The optimal advantage is achieved by utilizing innovative but proven technologies, and by bringing academic research into practice. A combination of recent innovations in construction technology, such as advanced cementitious materials (ACM), structural health monitoring (SHM) techniques, advanced design methods (ADM), and accelerated bridge construction (ABC) is being used. These innovations represent a step towards the next generation of infrastructure where fast construction, intelligent bridge design, sustainability, zero-energy, no/low maintenance, and aesthetics are key features. [ABSTRACT FROM AUTHOR]