Normal Strength Concrete Research Articles

Heat endurance and impact resistance: Investigating fibrous engineered cementitious composites under impact loads at elevated temperatures

This study presents experimental findings that assess the influence of boundary end conditions on the response of engineered cementitious composites (ECC) reinforced plates under impact loading, both before and after exposure to elevated temperatures. Testing encompassed three sets of small-sized ECC plates alongside three comparable sets of normal-strength concrete (NC) plates. The distinguishing factor among the three groups lies in the end boundary conditions. Specimens were tested under different scenarios, including four-end restriction, two-end restriction, and a clamped case. Within each group, three plate specimens underwent heating to temperatures of 200, 400, and 600 °C, while the fourth plate specimen served as an unheated reference for comparison. In total, 24 specimens were subjected to repeated drop-weight impacts until failure. The study recorded key parameters for each plate, including impact force, central deflection, and acceleration for each impact blow. In addition, the number of blows that caused failure (Nf) was recorded for each plate. The test results revealed that exposure to elevated temperatures led to decreased Nf and impact force for both NC and ECC plates, concurrently with increased deflection. A semi-stabilized region between 200 and 400 °C was identified in the relationships between the Nf and temperature, where Nf records decreased by up to 62 % and 77 % for NC, and 85 % and 91 % for ECC after exposure to 200 and 400 °C, respectively. However, the impact resistance significantly diminished for plates exposed to 600 °C, exhibiting minimal Nf records, reduced impact forces, and high deflections. In the case of unheated plates, the augmentation of the end restriction resulted in an increase in the retained impact force and a decrease in deflection. However, a discernible trend was not observed for heated plates, mainly attributable to the thermal degradation affecting the corners of the restrained edges in some plates.

Effects of CaO-based expansive agent on carbonation resistance of marine concrete

Marine concrete contains a high volume of supplementary cementitious materials, which benefits low-carbon concrete production. However, they may also increase the risk of cracking and accelerate the carbonation due to the pozzolanic reaction. Theoretically, the CaO-based expansive agent (CEA) can inhibit shrinkage cracks and introduce external calcium sources that aid in the carbonation resistance of concrete. A comprehensive understanding of the impact of CEA on the carbonation resistance of marine concrete is currently scarce.In this study, marine concretes with varying dosages of CEA were exposed to 20% CO2 for 28 days. The carbonation depth, carbonation coefficient, air permeability, pore structure characteristics and CO2 buffer capacity of concrete were investigated. When the CEA dosage was less than 6%, the carbonation resistance and air permeability approached the reference groups in normal-strength concrete (NSC) and high-strength concrete (HSC). However, more than 6% CEA significantly decreased the carbonation resistance of concrete, particularly for HSC. For NSC, there was an excellent correlation between the carbonation coefficient and compressive strength, while for HSC, the carbonation coefficient correlated well with porosity. Also, CO2 buffer capacity was essential to assess the carbonation resistance of marine concrete.

Bond and Flexural Behaviour of Locally Available Spent Catalyst Based Normal and High Strength Concrete

Bond and Flexural Behaviour of Locally Available Spent Catalyst Based Normal and High Strength Concrete

Punching shear behavior of ultra-high-performance fiber-reinforced concrete and normal strength concrete composite flat slabs

This paper presents the results of tests on flat slabs with partial application of ultra-high-performance fiber-reinforced concrete (UHPFRC) mixtures to improve the punching shear capacity of slab-column connections. One normal strength concrete (NSC) slab and two UHPFRC slabs were tested as a reference for tests on 12 UHPFRC-NSC composite slabs with full depth UHPFRC in the center area of the NSC slab. The main test parameters were the steel fiber volume (0.8 % and 1.6 % volume fractions) and the dimensions of UHPFRC mixtures. The load-column displacement curves, crack patterns, slab rotations at failure, and failure loads are presented and discussed. The failure loads are compared with estimates obtained following the yield line analysis, design codes, and other theoretical models. Test results showed that the use of UHPFRC mixtures led to an increase in initial stiffness, punching shear strength, and deformation capacity, along with a change in the slab failure mode. The shear capacity of the slab improved proportionally to the increase in the dimension of the UHPFRC. These tests confirmed the effectiveness of the UHPFRC mixtures as an alternative to enhance the punching shear capacity for slab-column connections.

Bond Strength and Corrosion Protection Properties of Hot-Dip Galvanized Prestressing Reinforcement in Normal-Strength Concrete

Bond Strength and Corrosion Protection Properties of Hot-Dip Galvanized Prestressing Reinforcement in Normal-Strength Concrete

Design-oriented stress-strain model for short concrete columns wrapped with FRP sheets

Previous studies have presented models aimed at predicting the axial stress-strain behavior of circular concrete columns wrapped with carbon fiber reinforced polymer (CFRP). The majority of these models were developed based on normal strength concrete (NSC) with strengths below 50 MPa. Moreover, several of these models relied on a limited experimental database. In this study, a large collection of experimental data was gathered, including 310 concrete columns confined with CFRP wraps. This database comprised test results for unconfined concrete with a compressive strength ranging from 19.7 to 169.7 MPa, and a height-to-diameter (H/D) ratio of two. From these data, two new expressions were developed to estimate the ultimate compressive strength and the corresponding strain. To model the stress-strain behavior, new relationship was suggested. A comparison between the proposed model and the experimental results revealed good agreement, outperforming several existing models. Additionally, the expressions for ultimate strength and corresponding strain are simple and accurate, making them easy to apply in design. Furthermore, the proposed model demonstrates superior performance compared to other existing models.

Fatigue and Ultimate Strength Evaluation of GFRP-Reinforced, Laterally-Restrained, Full-Depth Precast Deck Panels with Developed UHPFRC-Filled Transverse Closure Strips

A depth precast deck panel (FDDP) is one element of the prefabricated bridge element and systems (PBES) that allows for quick un-shored assembly of the bridge deck on-site as part of the accelerated bridge construction (ABC) technology. This paper investigates the structural response of full-depth precast deck panels (FDDPs) constructed with new construction materials and connection details. FDDP is cast with normal strength concrete (NSC) and reinforced with high modulus (HM) glass fiber reinforced polymer (GFRP) ribbed bars. The panel-to-girder V-shape connections use the shear pockets to accommodate the clustering of the shear connectors. A novel transverse connection between panels has been developed, featuring three distinct female-to-female joint configurations, each with 175-mm projected GFRP bars extending from the FDDP into the closure strip, complemented by a female vertical shear key and filled with cementitious materials. The ultra-high performance fiber reinforced concrete (UHPFRC) was selectively used to joint-fill the 200-mm transverse joint between adjacent precast panels and the shear pockets connecting the panels to the supporting girders to ensure full shear interaction. Two actual-size FDDP specimens for each type of the three developed joints were erected to perform fatigue tests under the footprint of the Canadian Highway Bridge Design Code (CHBDC) truck wheel loading. The FDDP had a 200-mm thickness, 2500-mm width, and 2400-mm length in traffic direction; the rest was over braced steel twin girders. Two types of fatigue test were performed: incremental variable amplitude fatigue (VAF) loading and constant amplitude fatigue (CAF) loading, followed by monotonically loading the slab ultimate-to-collapse. It was observed that fatigue test results showed that the ultimate capacity of the slab under VAF loading or after 4 million cycles of CAF exceeded the factored design wheel load specified in the CHBDC. Also, the punching shear failure mode was dominant in all the tested FDDP specimens.

Behavior of corroded HSC beams repaired by sprayed UHTCC and textile: Experimental study and theoretical analysis

Behaviors of twelve high strength concrete (HSC) beams were studied, including one control specimen, five corroded but non-repaired beams, and six corroded beams repaired by sprayed ultra-high toughness cementitious composites (UHTCC) with or without textile reinforcement. Galvanostatic accelerated corrosion technique was adopted, and three targeted corrosion levels (5 %, 10 %, and 15 %) were selected for each tensile steel bar. Corrosion-induced results, such as voltage change, crack initiation, concrete spalling, corrosion crack length and width, and non-uniform corrosion of steel bars were studied and compared with the results observed in normal strength concrete (NSC) beams. Structural behaviors, including failure modes and load-displacement responses were investigated through four-point bending tests. Results revealed that compared to NSC beams, HSC beams sustained more severe damages under a comparable corrosion level. Spalling was observed at a relatively lower corrosion ratio of 4.43 % and the maximum non-uniform corrosion coefficient, which was defined as the ratio of the maximum corrosion ratio to the average corrosion ratio, was 4.28. Corrosion-induced bonding degradation can alter the failure mode of corroded specimens in bending tests from bending to debonding. For repaired beams, however, the bonding degradation effect was reduced and bending failure was observed for all specimens. The bearing capacity of the beams repaired with sprayed UHTCC cannot be restored with a 12.42 % corrosion ratio, while the beams repaired with sprayed UHTCC/textile can recover their capacity even at a 13.6 % corrosion ratio. Furthermore, an improved theoretical model based on the fiber section analysis and virtual work method was developed to predict structural bending responses. The comparison of the experimental and theoretical results indicated the average corrosion ratio-based method may overestimate the loading capacity, especially for the beams with severe corrosion.

Experimental and numerical study on flexural performance of ultra-high performance concrete frame beams reinforced with steel-FRP composite bars

This paper presents the bending tests of four ultra-high performance concrete (UHPC) frame beams and one normal strength concrete (NSC) frame beam, all reinforced with steel-FRP composite bars (SFCBs). A comprehensive analysis was carried out, encompassing evaluation of the failure mode, crack propagation, bearing capacity, deformation, strain response, and plastic rotational capacity of the frame beams. Investigating the effects of concrete type, reinforcement type, and beam-end reinforcement ratio on the flexural performance of the frame beams was a key aspect of this study. A three-dimensional finite element (FE) model of the frame beam was established and rigorously verified. The developed model enabled a detailed parametric analysis involving the steel ratio, the yield strength of the inner core steel bar, the elastic modulus of the FRP, and the ultimate tensile strength of the SFCB. The results indicated a consistent failure mode of all frame beams: crushing of concrete at the beam-end, initiating a sequence of plastic hinge occurrence starting at the beam-end and then progressing to mid-span. The substitution of normal strength concrete with UHPC significantly enhanced various aspects of the frame beams, including the flexural capacity, deformation, ductility, ultimate energy dissipation, and plastic rotational capacity, while inhibiting the generation and expansion of cracks. Notably, the plastic rotation angle of SFCB-UHPC frame beams was 4.9 times greater than those of steel-UHPC frame beams, emphasizing the effectiveness of SFCB in enhancing the beam-end plastic rotational capacity. A decrease in the beam-end reinforcement ratio significantly reduced the flexural capacity, ultimate energy dissipation, and beam-end plastic rotational capacity, while improving ductility. Additionally, the study established a formula for calculating the equivalent plastic hinge length, utilizing the relative compressive zone height and effective section height of the beam-end controlling section as variables, which demonstrated good alignment between predicted and experimental results.

Shear behavior of RC beams with openings under impact loads: unveiling the effects of HSC and RECC

Incorporating transverse openings in reinforced concrete (RC) beams reduces their load-bearing capacity and stiffness, making them prone to premature failure. This highlights the need for a more nuanced understanding of their behavior to ensure structural integrity, particularly under impact loads. This research delves into a relatively unexplored area, investigating the impact performance of RC beams containing openings through numerical analysis. By comparing different concrete types, the study seeks to identify optimal materials for such applications. The concrete damage plasticity model, accounting for strain rate effects, will be employed to simulate the material behavior of normal-strength concrete (NSC), high-strength concrete (HSC), and a novel eco-friendly alternative: rubberized engineered cementitious composite (RECC). RECC incorporates recycled tire rubber as a partial substitute for traditional concrete aggregates, offering a sustainable solution while mitigating environmental hazards associated with waste tire incineration. The finite element models are validated with experimental results, accurately predicting ultimate capacities, failure modes, and post-cracking response in RC beams (with/without openings) under static/impact loads. A comprehensive parametric analysis investigates the effects of concrete strength, impact energy, impactor mass, drop height, and opening location, providing valuable insights into how these factors influence the impact behavior under drop-weight testing. The results reveal that openings in RC beams under impact loads significantly reduce strength and stiffness, with detrimental effects observed for dual shear-zone openings. Surprisingly, a small mid-span opening can enhance impact response. HSC beams exhibit lower initial displacements but higher residual values, while RECC improves overall behavior in beams with openings, reducing maximum displacement and promoting energy dissipation for improved post-impact recovery.

A comparative study between ultra-high-performance concrete structures and normal strength concrete structures exposed to fire

The use of ultra-high-performance concrete (UHPC) in civil infrastructure is increasing due to its numerous advantages compared to normal strength concrete (NSC). In this research, thermal analysis of NSC and UHPC beams and columns was developed to understand and compare the fire performance of these structures. A numerical analysis was performed using finite element (FE) modeling with ABAQUS software. Compared to NSC, UHPC structures in some cases have lower fire resistance due to their slender cross-sections and unfavorable thermal properties and mechanical capacity degradation due to temperature effect. The results show that UHPC structures experience significantly higher cross-sectional temperatures when exposed to fire compared to NSC. The results are particularly relevant for high-rise buildings, where fire safety requirements are more stringent and the use of UHPC is attractive, leading to an unprecedented contradiction. Alternative strategies for the application of UHPC, such as the contradictory increases in cross-section or the use of fire protection coatings, must be considered. In some cases, NSC may be more attractive as a structural material than UHPC if structural fire design requirements are taken into account.

Experimental study of bond-slip relationships in high-performance self-consolidating concrete with plain steel bars

Self-consolidating concrete is being used more frequently in structures with high density of reinforcement bars or prestressing strands therefore, it is important to carefully consider whether bond stress-slip relations defined for normal strength concrete can be safely applied to high-strength and self-consolidating concrete. This paper aims to investigate the bond behaviour between plain steel bars and high-performance self-consolidating concrete, with a focus on studying the effect of embedment length and concrete compressive strength on bonding performance. The main parameters that were tested are the active bonded length and the compressive strength of the concrete. The value of adhesive bond stress is discussed, as a factor in determining whether the bar slips against the adhering concrete. Based on the results, it can be observed that the maximum bond stress tends to increase with higher concrete compressive strength, while it decreases with longer embedment length of plain steel bar. Conversely, the adhesive bond tends to increase with longer embedment length and higher concrete compressive strength. The experimental investigations indicate that the bond strength increases proportionally to the square root of the compressive strength of concrete, regardless of the concrete compressive strength. Furthermore, a new bond stress-slip model has been analyzed, which takes into account the initial bond strength (adhesive bond) and the lower convex property to predict the post-peak branch. The model has been compared to the test results, and good agreement has been achieved.

Enhanced impact resistance of RC beams using various types of high-performance fiber-reinforced cementitious composites

This study investigates the impact resistance of reinforced concrete (RC) beams using various types of high-performance fiber-reinforced cementitious composites (HPFRCCs). A total of ten large-sized RC beams were fabricated and tested under static and impact loading conditions. Four different types of HPFRCCs with 2% by volume of steel, polyvinyl alcohol (PVA), and polyethylene (PE) fibers were considered. Ultra-high-performance fiber-reinforced concrete (UHPFRC) based on steel fibers demonstrated superior compressive and tensile strengths, while high-performance strain-hardening cementitious composite (HP-SHCC) based on PE fibers exhibited the highest strain and energy absorption capacities. The steel-bar reinforced (R-) UHPFRC and HP-SHCC beams showed superior flexural load capacity compared to reinforced normal strength concrete (R-NSC) beams. The highest ductility of 8.02 was found in the R-HP-SHCC beam, almost 5 times higher than that of the R-NSC beam. By drop hammer impact with a kinetic energy of 30 kJ, the R-UHPFRC beam completely failed due to its higher reaction load and lower structural ductility, while other RC beams made of NSC and HPFRCCs withstood the identical impact load. The R-HP-SHCC beam exhibited the best impact resistance, with a 29.1% lower maximum deflection compared to the R-NSC beam, and the largest residual load capacity after the impact damages. The R-HP-SHCC beam, despite being damaged, showed no reduction in flexural stiffness, yet it demonstrated an impressive 5.4% increase in load capacity compared to the undamaged beam.

Flexural performance of functionally graded UHPFRC-NSC beams

This paper presents an experimental and numerical study on the flexural performance of Functionally Graded Reinforced Concrete (FGRC) beams using Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) with Normal-Strength Concrete (NSC). The experimental results were used to examine the applicability of the codes’ predictions of flexural capacity adopted in ACI 318-2019, EC-2, and ECP-203-2020. The flexural design recommendations of AFGC-2013, JSCE-2008, and KCI-2012 were also examined. The experimental program involved ten simply supported beams with identical cross-sectional dimensions and two different tensile reinforcement ratios (ρl = 1.38 % and 5.68 %). FGRC beams consisting of UHPFRC (with fcu = 174.3 MPa) and NSC (with fcu = 45.8 MPa) were tested under four-point bending. The layer of UHPFRC was positioned either in the utmost compression region or in both the compression and tension regions. The experimental results revealed that the FGRC beams exhibited strength and ductility comparable to those of pure UHPFRC beams but at a significantly reduced cost. When UHPFRC layers constituted 66.7 % of beam thickness, the FGRC beams were capable of carrying 97.4 % of the load sustained by a full UHPFRC beam, while for UHPFRC layers constituted 40 % of beam thickness the FGRC beam carried 77.5 % of that of a full UHPFRC beam. Increasing ρl% from 1.38 % to 5.68 % in the tested specimens led to a considerable enhancement in the flexural capacity. The sectional analysis conducted in accordance with the recommendations of AFGC-2013, JSCE-2008, and KCI-2012 showed precise predictions of the flexural strength in both UHPFRC and FGRC beams, while the flexural strength calculated using the equations adopted in the studied codes gave conservative estimations. The proposed numerical model displayed a high level of agreement with the experimental findings of the studied FGRC beams.

HSC-RSW with laterally installed XADAS dampers: Seismic performance

This study investigates the seismic behavior of high-strength concrete (HSC) rocking shear walls (RSW) equipped with X-shape Adding Damping and Stiffness (XADAS) dampers installed perpendicular to the wall via brackets. Unlike previous studies where dampers are integrated along the wall length, this research leverages the advantages of HSC to minimize sectional dimensions while employing laterally installed XADAS dampers to enhance the cyclic response, yielding flag-shaped hysteresis curves. The alignment angle of the XADAS dampers is also considered a crucial variable in assessing the overall seismic performance of the proposed HSC-RSW system. A novel constructional approach using brackets to install lateral XADAS dampers is implemented. Post-tensioning (PT) forces are applied as consistent axial strains in cables, achieved through predefined cable support displacements. A macro-FEM model is developed to validate the chosen experimental reference test and is subsequently used for further parametric studies. The parametric studies indicate that increasing concrete compressive strength (CCS) enhances the self-centering capability by reducing RSW strains and facilitating rocking. Additionally, incorporating XADAS dampers into the system improves energy dissipation, with a zero-degree alignment angle identified as optimal. Notably, the modeled HSC-RSW systems exhibit limited drift capacity (less than 2 %) compared to normal strength concrete (NSC)-RSW systems, where wall toes are conventionally prone to crushing.

Pengaruh Penambahan Serat Ampas Tebu Sebagai Tulangan Micro pada Beton

Based on this research, concrete has high compressive strength but low flexural strength. There-fore, the addition of sugarcane bagasse fibers is carried out as an additive to overcome the low flexural strength issue in concrete. This study aims to determine the effect of adding sugarcane bagasse fibers on the characteristics of concrete, including compressive and flexural strength. Fiber-reinforced concrete is a composite material consisting of regular concrete and other mate-rials, such as natural or artificial fibers. The method used in this research is an experimental method, adding 1% of sugarcane bagasse fibers by weight of cement to the normal concrete with a target strength of F'c 19.3 MPa and fiber length of 5 cm. The samples used in this research are concrete cylinders and beams tested using a Universal Testing Machine. The research results show that the optimum compressive strength of normal concrete is 20.36 MPa at 28 days of age. Meanwhile, for fiber-reinforced concrete BSTC and BSTH, the compressive strengths are 17.83 MPa and 16.49 MPa, respectively, indicating a decrease compared to the normal concrete. This decrease is attributed to the addition of sugarcane bagasse fibers, which are lightweight addi-tives and not solid aggregates, resulting in some voids in the sugarcane bagasse fibers. The re-sults of the flexural strength testing show that the optimum flexural strength of BSTC is 4.44 MPa, and for BSTH, it is 4.09 MPa, while the normal concrete (BN) only achieves 3.61 MPa. This is due to the increased bonding effect in concrete caused by the addition of fibers, which helps to resist the occurrence of cracks during flexural testing

Comparative study on the compressive performance of NSC and HSC with preload under 24-hour high temperatures

This study explores the compressive performance of normal strength concrete (NSC) and high strength concrete (HSC) with preload under 24-hours sustained high temperature (SHT). A unique test setup was designed to accomplish the compressive tests of concrete under high temperatures. The effects of temperature, concrete strength and preloading are given attention. Besides, microscopic tests were carried out to reveal the variation mechanism of concrete performance. The results show that the degradation of the compressive strength of concrete under SHT is significantly more severe than under short-term high temperatures. At the same temperature and initial load level, HSC shows greater strength degradation than NSC. Pre-loaded concrete generates considerable creep under SHT, and its effect on the peak strain of concrete cannot be ignored. The peak strain of NSC and HSC is most significantly affected by the initial load level and temperature, respectively. At temperatures not higher than 350 °C, the deterioration of the compressive performance of concrete is mainly attributed to the dehydration decomposition of calcium silicate hydrate and the cracking of interface transition zone. Preloading can inhibit these reactions and improve the compressive performance of concrete under SHT. Further, a general model for the compressive stress-strain relationship of concrete under SHT considering concrete strength and preloading was developed, which can be used for the design and analysis of concrete structures serving at high-temperature environments.

Analysis-oriented stress–strain models for ultra-high-performance concrete confined with fiber-reinforced polymer

The use of fiber-reinforced polymer (FRP) jackets or tubes as confining devices can significantly improve the compressive performance of ultra-high-performance concrete (UHPC). For FRP-confined UHPC, an analysis-oriented stress–strain model is essential for a comprehensive understanding of its compressive behavior and the development of design models. Although several analysis-oriented stress–strain models have been developed for FRP-confined normal-strength concrete (NSC), such models for FRP-confined UHPC are still lacking. In this study, an experiment is conducted to investigate the failure mechanism of UHPC confined with FRP under concentric compression, and the stress–strain behavior of the FRP-confined UHPC is analyzed using the stress–strain models of actively-confined UHPC. Results showed that the stress-path-independency assumption, which has been proven to apply to FRP-confined NSC, was inapplicable to FRP-confined UHPC. By modifying the confining pressure to consider the influence of stress-path dependency, an analysis-oriented model was proposed. The proposed model was verified using a collected test database. The results show that the proposed model accurately predicted the stress–strain behavior of FRP-confined UHPC.

Prediction of axial compressive stresses in ultra-high-performance concrete blocks using non-destructive ultrasonic techniques

The application of ultra-high-performance concrete (UHPC) in civil engineering structures is growing rapidly. On the other hand, previous non-destructive testing (NDT) techniques mainly focused on determining the relationship between the acoustic characteristics and elastic modulus, Poisson's ratio, cracking resistance, and strength. This study presents an experimental approach utilizing ultrasonic techniques to predict the axial compressive stresses in UHPC structures. Both cubic and prismatic UHPC blocks were designed and tested under different compressive axial loading conditions, and their ultrasonic acoustic characteristics were evaluated in detail. Normal strength concrete (NSC) blocks were also included in the investigation for comparison purposes. A detailed account of the tests results is provided, including the relationships between the compressive stresses in UHPC blocks and the typical time- and frequency-domain acoustic parameters. Based on the experimental results, an analytical working stress evaluation method for UHPC components using the ultrasonic acoustic parameters is proposed. It is shown that there is close correlation and high prediction stability between the compressive stress in UHPC blocks and the ultrasonic velocity, which is suggested as the main acoustic parameter for stress detection. The correlation between the acoustic amplitude parameters and concrete compressive stress is also shown to be significant, yet is associated with relatively low prediction stability. Moreover, in comparison with conventional NSC blocks, greater correlation and regularity ratios are observed between the typical acoustic parameters and the axial compressive stress in UHPC specimens. Overall, the analytical models proposed in this study are shown to be in close agreement with the experimental results, and can be used, in conjunction with the ultrasonic NDT techniques, to provide a reliable prediction of the level of compressive stresses in UHPC members.

Interpretable machine learning models for predicting the bond strength between UHPC and normal-strength concrete

Ultra-high-performance concrete (UHPC) boasts superior mechanical properties and durability, rendering it a viable material to repair and reinforce pre-existing concrete structures. The complexity of the bond behavior between UHPC and normal-strength concrete (NC) presents a challenge to make precise predictions of the interfacial bond strength. This study employed four machine learning algorithms, namely artificial neural network, random forest, adaptive boosting, and categorical gradient boosting, to predict the interfacial bond strength of UHPC-NC. A database of 95 samples of slant shear tests was collected from existing literature. The input variables for modeling include joint angle, compressive strength of NC and UHPC, surface treatment, interfacial moisture, curing age, and curing method. The impact of each feature on the slant shear bond strength was assessed using SHapley Additive exPlanations and Partial Dependence Plots. Results show that the categorical gradient boosting model performed the best on the testing set, achieving an R2 of 0.948, RMSE of 1.408, and MAE of 1.028. The accuracy of all four machine learning models surpassed that of two empirical models (AASHTO LRFD 2014 and Eurocode 2). The top three features influencing the interfacial bond strength were identified as the surface treatment, joint angle, and compressive strength of NC, while the impact of the curing method and the interfacial moisture were comparatively limited. The proposed machine learning model exhibits potential as a valuable tool for assisting structural retrofitting and rehabilitation with UHPC.