The widespread adoption of fiber-reinforced polymer (FRP) bars in concrete structural members underscores their efficacy as a non-corrosive alternative to steel reinforcement. This property substantially enhances structural durability and extends the lifespan of concrete structures. Nonetheless, their compressive performance under high strain rate loading remains underexplored. Understanding the dynamic compressive properties of GFRP bars is particularly important for structures subjected to impact, blast loads, and other high-rate loading scenarios, where the material response can significantly deviate from quasi-static behavior. This study presents experimental findings on the behavior of ribbed GFRP bars subjected to dynamic impact compressive loading. A series of dynamic tests were conducted on GFRP bars of 12 mm diameter using a Split Hopkinson Pressure Bar (SHPB) apparatus. Different strain rates, in the range of 700 to 1900 s−1, were achieved through varying the impact pressure. A high-speed camera was also used to monitor the failure mode and provide a full-field visualization of deformations during impact. This study evaluates the stress-strain relationship, strain rate-time relationship, and failure modes of the tested GFRP bars under various loading rates. The experimental results revealed a reduction of approximately 35

Reinforced concrete (RC) structures are frequently exposed to extreme events such as fire, which can significantly degrade their structural integrity and load-carrying capacity, often necessitating effective rehabilitation strategies. While traditional repair techniques such as steel or concrete jacketing and externally bonded fiber-reinforced polymer (FRP) systems have been widely used, fabric-reinforced cementitious matrix (FRCM) composites have recently emerged as a promising alternative due to their compatibility with concrete substrates and improved thermal resistance. However, the effectiveness of FRCM systems in rehabilitating fire-damaged RC members remains insufficiently explored, especially in columns. This study investigates the potential of polyparaphenylene-benzo-bisthiazole (PBO) FRCM in restoring the axial performance of fire-damaged RC columns. Five columns were tested, including three specimens exposed to a standard ASTM E119 fire for 133 min and two unexposed control specimens. The influence of pre-fire strengthening and insulation systems on the residual axial performance of the columns was evaluated. The results showed that repairing the fire-exposed column without insulation or pre-fire strengthening restored approximately 68% of its original axial capacity. In contrast, the column that was wrapped with PBO-FRCM and protected with insulation prior to fire exposure exhibited significantly improved performance, achieving residual capacities comparable to the unwrapped control column, although still 17% lower than the wrapped control column. These findings highlight the potential of combining strengthening and insulation systems to mitigate fire-induced damage and enhance the post-fire structural performance of RC columns. Analytical predictions were also conducted to estimate the residual axial capacity, providing approximate engineering-level estimates with experimental-to-predicted capacity ratios ranging from 1.13 to 1.30 for control columns and 1.17-1.50 for fire-exposed columns, reflecting the uncertainties associated with residual material properties after fire exposure. Overall, the study demonstrates the feasibility of using PBO-FRCM as an effective rehabilitation technique for fire-damaged RC columns, while providing insights into the role of FRCM and insulation system in preserving structural capacity during fire events.

In recent years, fiber-reinforced polymers (FRP) have been gaining attention as a replacement for steel bars in concrete columns. Like steel reinforcement, FRP contributes to the axial load-carrying capacity. Multiple equations were proposed to understand the load-carrying capacity of FRP-reinforced concrete columns. However, existing design codes limit the use of FRP bars in columns since comprehensive predictive models are lacking. To address this gap, artificial intelligence (AI) and machine learning (ML) methods provide a powerful alternative by capturing nonlinear relationships between key structural parameters and column capacity. The study aims to check the reliability of the most well-known physical models that predict the effect and contribution of FRP bars to the overall capacity of columns at the ultimate limit state. The key parameters included in the data to be considered in this study are the column’s cross-sectional area, the column length, the compressive strength of the concrete, the elastic modulus of GFRP bars, and both longitudinal and transverse GFRP reinforcement ratios. A comprehensive dataset of tested FRP-RC was collected from existing literature to train, validate, and test machine learning models. Ann and Extreme Gradient Boosting ML algorithms are explored to determine the most accurate predictive model. Feature Sensitivity analysis is implemented using Shapley Additive explanations (SHAP) method to understand the machine learning models in the study, with focus on which variables influence the ML models the most or the least. The outcome of this research will contribute to ongoing discussions on using FRP reinforcement in compression members, where existing gaps in design methodologies will be addressed and potentially influencing future structural codes.

Highly porous, eco-friendly nano-silica is essential for sustainable applications. Biomass-derived nanosilica (n-SiO2) provides a sustainable route to enhance cement-based materials (CBMs); however, the role of its intrinsic properties, particularly specific surface area (SSA), remains inadequately understood. This study systematically and uniquely explores how engineered SSA in highly porous n-SiO2 interacts with varying water-to-binder systems to govern low-carbon cementitious performance. Using a Box–Behnken Design (BBD), the cement strength was optimized. The impact of these influencing factors on hydration kinetics, microstructural properties, and the mechanisms underlying the enhanced properties has been explained. The study revealed that lower and medium SSA n-SiO2 (263 and 579 m²/g) significantly enhanced cement strength at low w/b ratios, whereas high SSA performed better in high w/b systems. The 3

This study provides experimental evidence for a carbon fabric-reinforced cementitious matrix (C-FRCM) strengthening solution as an innovative approach to strengthening circular reinforced concrete (RC) columns under both concentric and eccentric loading conditions. Twelve RC columns were tested under different eccentricity-to-depth ratios (e/h) of 0.0-0.3. Experimental results showed that applying a single layer of C-FRCM resulted in minimal or no improvement in the axial load capacity of RC columns. However, the use of two layers of C-FRCM led to incremental load increases across all levels of eccentricity, with strength gains ranging from 12.6 % to 38.6 %. These incremental load increases tended to decrease with higher e/h ratios, indicating reduced confinement effectiveness under greater bending conditions. A new analytical model was developed for strength prediction, accounting for the nonlinearity of the materials and the interaction between the internal steel tie confinement and the external FRCM wrapping confinement. The model's predictions were validated using experimental data from the present study, as well as additional data available in the literature. The model also generated P-M interaction diagrams that reasonably reflected the experimental trends, validating its applicability as a robust tool for structural assessment and strengthening design.

Decarbonizing High-Performance Concrete (HPC) necessitates a paradigm shift from strength-based clinker predominance to performance-based microstructure control in systems with high Supplementary Cementitious Material (SCM) substitution. This review proposes a performance-normalised carbon intensity framework as an analytical lens, where embodied CO₂ could be evaluated relative to compressive strength, chloride diffusion, and service life durability, rather than binder mass alone. Based on a synthesis of recent research, optimised nano-dosages (1–3%) effectively mitigate clinker dilution by accelerating hydration kinetics, promoting secondary C-S-H precipitation, and densifying the Interfacial Transition Zone (ITZ). Quantitative findings indicate compressive strength increases of 15–40% and a 79–87% reduction in chloride permeability (311–900C in optimised mixes versus 1711–4230C in the corresponding controls), confirming that nano-modification acts as a fundamental microstructural regulator. Performance-based systems achieve embodied carbon values of 286–313 kg CO₂-eq/m3, demonstrating that nano-enabled optimization facilitates deep clinker reduction while maintaining structural viability. However, the synthesis reveals a non-monotonic dose-response relationship, emphasizing that dispersion quality and SCM chemistry are critical for long-term microstructural homogeneity. This work concludes that multi-scale design is the optimal pathway for next-generation low-carbon HPC, balancing hydration chemistry, durability, and carbon efficiency.

This study examines the post-fire flexural performance of concrete beams reinforced with GFRP bars and evaluates the influence of lap splice length and intumescent paint protection. Nine beams with continuous reinforcement, 500-mm splices, and 1000-mm splices were tested. Six beams were exposed to ASTM E119 fire for 260 min, which exceeds the standard 2-3-hour fire resistance requirements. After cooling, all specimens were tested under four-point bending. Fire exposure caused severe reductions in flexural capacity, particularly in the 500 mm splice specimens, which failed by bond loss at the splice region. Beams with 1000 mm splices retained substantially higher residual capacity and exhibited failure behavior more closely resembling that of the continuous-bar specimens. Intumescent paint reduced reinforcement temperatures by up to 150-200 degrees C and improved residual strength by 10-15% relative to unprotected counterparts. The results establish that splice detailing remains the governing weakness of GFRP-RC members in fire and that surface protection with intumescent paint, combined with adequate splice length, can maintain measurable residual capacity after extended fire exposure. Although the paint was applied over the full fire-exposed span in this study, targeted application at splice zones represents a practical and economical protection strategy for critical regions in real structure.

Reinforced concrete (RC) beams experience significant strength degradation when exposed to fire, especially those reinforced with fiber-reinforced polymer (FRP) bars, which are highly vulnerable to thermal damage. This study experimentally investigates the flexural performance of full-scale fire-damaged concrete beams reinforced with glass FRP (GFRP) bars and retrofitted using carbon fiber-reinforced cementitious matrix (C-FRCM) U-wraps. A beam was exposed to fire in accordance with ASTM E119 for a duration of three hours. Following fire exposure, the beam was strengthened with a single layer of C-FRCM U-wrap and tested under four-point bending. A second beam, which was neither exposed to fire nor strengthened with C-FRCM, served as the control specimen. Both test specimens had uniform dimensions of 300 mm in width, 400 mm in depth, and 5000 mm in length. The test results showed that the strengthened fire-exposed beam gained only 40

This study provides direct experimental evidence comparing carbon fiber-reinforced polymer (C-FRP) and carbon fabric-reinforced cementitious matrix (C-FRCM) systems for rehabilitation of short reinforced concrete (RC) columns. Fifteen RC columns were tested under eccentricity-to-depth ratios (e/h) of 0.0-0.3. Corroded columns were pre-damaged through accelerated corrosion, resulting in steel losses of 22% in longitudinal bars and 42% in ties. Corrosion reduced the load capacity by 41% under concentric loading and by an average of 17% under eccentric loading. Both repair systems effectively restored the load capacity of the corroded columns. C-FRP repairs increased the load capacity by 80-167%, while C-FRCM achieved load capacity gains of 49-86%. The lower effectiveness of C-FRCM was ascribed to a premature debonding at the fabric-mortar interface. A new analytical model was developed to predict the load capacity, incorporating material nonlinearities, corrosioninduced degradation, and combined confinement from internal steel ties and external composite wraps. Model predictions were validated using experimental results from this study and additional literature data. The model produced P-M interaction diagrams consistent with experimental trends, confirming its reliability and practical use as a simple, accurate tool for structural evaluation and retrofit design.

Corrosion in steel-reinforced concrete has long been a challenge, leading researchers to explore alternative materials like Glass Fiber-Reinforced Polymer (GFRP) bars. These bars are non-corrosive and non-magnetic, offering higher tensile strength and a better strength-to-weight ratio than traditional steel. As a result, they are increasingly used in bridges, pavements, and parking garages. While design codes like ACI 440.11-22 and CSA S806-12 provide guidance for GFRP reinforcement, they offer limited coverage for deep beams. In addition, there is limited research on how web reinforcement affects the shear performance of GFRP-reinforced deep beams. This study investigates the shear behaviour of high-strength concrete (HSC) deep beams reinforced with GFRP bars using different web reinforcement configurations. The study focuses on a single shear span-to-depth (a/d) ratio, testing four beams made with 70 MPa concrete under four-point bending. Results showed that vertical web reinforcement increased shear capacity by 69%, while horizontal reinforcement improved it by 42% and enhanced initial stiffness. The combined configuration had the highest stiffness but slightly lower strength than the vertical-only beam. These findings highlight the significance of web reinforcement in improving the shear strength, stiffness, and crack control of GFRP-reinforced deep beams.

In high-energy ball milling, nanoparticle formation is governed by collision energetics and impact frequency, which collectively control particle refinement, structural disorder, and surface reactivity. The synthesis is primarily influenced by milling speed, ball size distribution, milling duration, ball-to-powder ratio, and the intrinsic properties of the feed material. Despite their critical role, the combined effects of these milling parameters on the physicochemical properties of biomass-derived nanoparticles remain poorly understood, primarily due to insufficient experimental probes. Therefore, this study systematically examines the interactive effects of milling speed (400–800 rpm), powder-to-ball mass ratio (1:8, 1:10, and 1:12), and small-to-large ball mass fraction (20%, 60%, and 100%) on the properties of synthesized engineered nanoparticles from biomass waste. The functional performance of the resulting nanoparticles as cement nano-additives or partial clinker substitutes was further evaluated under different dispersant conditions. The study revealed that optimized milling conditions yield ultra-fine nanoparticles (5–20 nm) with partially amorphized SiO2 networks. Statistical analysis found that milling speed exerted the dominant influence on nanoparticle quality, followed by powder-to-ball ratio and ball size distribution (p < 0.05). When incorporated at low dosages (1–1.5 wt.%), the engineered nanoparticles enabled 10–15% clinker replacement while achieving early-age compressive strength gains of up to 30%. These results demonstrate that biomass-derived nanoparticles can deliver superior performance at substantially lower dosages. This offers a "more cement replacement for less material" pathway that supports clinker reduction, CO₂ mitigation, and the development of high-performance, sustainable cement systems.

This study examines the use of external fire protection systems, cementitious spray-applied fire-resistive material (SFRM) and intumescent paint (IP), to improve the fire performance of full-scale GFRP-reinforced concrete (RC) beams. Three 5-m beams were tested under a sustained load equal to 28 % of their room-temperature flexural strength and exposed to the ASTM E119 standard fire. The SFRM coating delayed heat transfer to the reinforcement, keeping GFRP bar temperatures below 150 degrees C for three hours and limiting midspan deflection to less than 20 mm. The IP coating remained effective for about 60-90 min before the char layer lost integrity, after which bar temperatures exceeded 400 degrees C and larger deflections developed. Cold zones at the beam ends preserved bond strength over lengths of 275-350 mm, which allowed the GFRP bars to maintain tension transfer despite bond loss in exposed regions. The results confirm that SFRM can achieve two- to three-hour fire ratings in GFRP-RC beams even without cold zones, while IP provides shorter-duration protection suitable for limited exposures. External fire protection on concrete members is a new concept intended not to increase the cost of GFRP-RC construction but to enhance fire safety in specific members where the concrete cover or cold-zone length alone does not provide the required resistance. This study demonstrates the feasibility of local external protection for GFRP-RC members and establishes a basis for future design guidance.

This paper explores shear behavior of high-strength concrete (HSC) deep beam reinforced with Glass Fiber Reinforced Polymer (GFRP) bars and with square web openings, as part of the development of construction materials that are environmentally-friendly. Three full-size beam samples were made and tested at four-point bending to determine the effect of varying opening size (75 × 75, 125 × 125 and 175 × 175 mm) on shear capacity, load-deflection behavior, strain distribution and failure modes. Digital Image Correlation (DIC) presented detailed information on strain development, crack shape and reinforcement performance. The findings showed that shear capacity and ductility reduced drastically with the increase in opening size. The beam that had the least opening (75 mm) had the highest load capacity (714.7 kN), the most ideal strain distribution and had the best ductility. Openings with larger sizes (125 and 175 mm) had lower load capacities, concentrated strain around openings, were under rapid crack formation and failed by brittle fractures. The results highlight the need to reduce the opening dimensions and introduce appropriate reinforcement description to ensure structural performance in GFRP-reinforced HSC deep beams. The work offers important insights that will be critical towards designing concrete beams that are sustainable, durable, and structurally efficient in environments that require concrete in construction.

This work predicts the temperature ranges for dynamic strain aging (DSA) activation in C45 steel at various strain rates through constitutive modeling and finite element (FE) simulations. DSA is often defined by a sudden increase in a metal’s strength when subjected to specific combinations of strain rates and temperatures due to the interaction of the diffused solute atoms with dislocations, and there is currently no effective constitutive model in the literature that can explain DSA physically. The current study offers a modification to the Voyiadjis–Abed (VA) model, which is used to predict DSA activation in C45 steel, in order to address this limitation. The modified constitutive model considers the diffusion kinetics and concentration of solute atom along the dislocation cores. The developed model was able to capture the activation of DSA in C45 steel at strain rates of 0.0015/s-0.15/s and temperature ranges of 500 K-750 K, which was found to be caused by carbon solute atoms. Additionally, FE simulations were carried out in ABAQUS through subroutine coded as VUMAT to validate the modified VA model’s prediction abilities. The results obtained compare effectively with the available experimental data. By integrating physical and microstructural features, the modified constitutive VA model can effectively capture the increase in flow stress due to the activation of DSA. This enables further investigation and progress in understanding the behavior of metals under specified temperature and strain rate conditions.

Fiber reinforced cementitious matrix (FRCM) systems have recently emerged as a promising method for strengthening concrete columns, offering notable gains in strength and ductility due to their mechanical performance and compatibility with concrete substrates. This paper presents a comprehensive review of the behavior of concrete compression elements confined with FRCM systems, based on data from 66 experimental studies – 36 on plain concrete (PC) and 30 on reinforced concrete (RC) columns – covering over 1036 PC and 294 RC tests.Specimens were categorized by slenderness, loading conditions, cross-sectional shape, concrete type, FRCM configuration, and reinforcement ratio. The analysis highlights the improved capacity and ductility of FRCM-confined columns under various conditions, including seismic and fire exposure. Among the fabrics studied, polyphenylene benzobisoxazole (PBO) fabric showed superior bonding and performance, while FRCM systems incorporating modified high-strength matrices delivered outstanding strength and deformation capacity. Key parameters such as concrete compressive strength, number of FRCM layers, cross-sectional geometry, and mortar properties were found to significantly influence confinement effectiveness. Columns with higher concrete strength or noncircular sections exhibited reduced benefits, while smaller or lower-strength columns demonstrated greater improvements. In addition, the review critically examines existing design methods and predictive equations for FRCM-confined columns. Finally, directions for future research are outlined, emphasizing key parameters that require further investigation to enhance the reliability and efficiency of FRCM systems in structural strengthening applications.

Basalt-fibre-reinforced polymer (BFRP) has gained attention as a potential replacement for steel reinforcement in reinforced concrete (RC) structures. However, limited and inconsistent experimental data exist on short concrete columns reinforced with BFRP. This study investigates the axial performance of RC columns reinforced with BFRP, glass fibre-reinforced polymer (GFRP), and steel, considering variations in tie materials and spacing. A total of 20 short columns (1000 mm height, 180 x 180 mm cross-section) were tested under pure compression to focus on material behavior rather than global buckling. Key variables included the type of longitudinal bars (BFRP, GFRP, steel), transverse reinforcement material (BFRP or steel ties), tie spacing (180, 120, and 60 mm), and bar diameter (16 mm and 20 mm). Results showed that both steel and BFRP ties provided comparable axial capacity and confinement in FRP-RC columns. However, steel ties led to 9.1% higher axial capacity and 13.8% greater confinement in steel RC columns. Reducing tie spacing from 180 mm to 60 mm increased axial capacity by up to 10.8% for steel ties and 8.2% for BFRP ties in FRP columns. Smaller tie spacing also enhanced deformability by up to 252% in FRP-RC columns and ductility by 15.6% in steel-RC columns.

Fiber-reinforced polymer (FRP) reinforcement has gained significant attention in research and structural applications due to its desirable mechanical properties and durability. Advances have been made in understanding FRP’s resistance to elevated temperatures; however, uncertainties persist due to inconsistencies in the available experimental data. This study presents an experimental investigation into the effects of various parameters on the performance of reinforced concrete (RC) prismatic beams exposed to elevated temperatures. Key parameters included reinforcement type (steel, Glass FRP (GFRP), and Basalt FRP (BFRP), bar diameter (16 mm and 20 mm), surface texture (ribbed and sand-coated), and concrete cover (40 mm and 60 mm). The prismatic beams were subjected to target temperatures of 200, 400, and 700 °C, followed by testing in a four-point loading setup. The experimental results revealed that BFRP-reinforced prismatic beams exhibited a 17 % higher residual load-carrying capacity and 32.3 % greater toughness at 200 °C and 400 °C, but a 22 % lower capacity and 26.9 % reduction in toughness at 700 °C compared to their GFRP-reinforced counterparts. Additionally, prismatic beams reinforced with sand-coated GFRP bars showed up to a 27 % improvement in load-carrying capacity compared to those with ribbed GFRP bars, and a larger concrete cover contributed to better overall flexural performance of the prismatic beams under elevated temperatures.

This paper investigated experimentally the shear performance of ultra-high-performance concrete (UHPC) deep beams reinforced longitudinally with glass fiber reinforced polymer (GFRP) bars without web reinforcements. Ten beams were cast, in which seven were longitudinally reinforced with GFRP bars, while the remaining three were reinforced with steel bars for comparison. All beams had similar lengths and widths of 2000 mm and 150 mm, respectively, while the depths varied. The test parameters included the effective depth (d), shear span-to- depth ratio (a/d), number of longitudinal bars, and longitudinal reinforcement ratio (rho). All the GFRP reinforced beams had higher shear capacities and lower post cracking stiffness than their steel counterparts. The experimental results show that varying the test parameters have a significant impact on the shear capacity of the beams. For instance, decreasing the a/d ratio for the GFRP reinforced beams from 1.8 to 1.5 and from 1.8 to 1.1 increased the load carrying capacity by 33 % and 95 %, respectively. The experimental results for the shear capacity were compared against the predictions obtained using the strut and tie method as per the ACI-318-19 and CSA-S806-12 codes. The failure load predictions by the ACI and CSA code showed the same trends as those shown in the experimental results. Moreover, both codes were conservative in predicting the shear capacities.

Concrete is widely used in construction due to its remarkable compressive strength and durability. However, its performance can deteriorate when exposed to harsh environmental conditions, such as acidic or alkaline surroundings. There has been considerable interest in incorporating both basalt and steel fibers (B&SFs) to enhance the resilience of concrete in such challenging settings. This study presents a comprehensive examination of the influence of B&SFs on the strength and microstructure of concrete, utilizing desert sand as a fine aggregate and subjecting it to exposure to acidic and alkaline environments. Employing a systematic experimental approach, this research assesses concrete samples with varying B&SFs proportions. The study encompasses density and compressive strength tests, complemented by microstructural analyses using scanning electron microscopy (SEM) and X-ray diffraction (XRD), to analyze the performance of the concrete under diverse environmental conditions. Initial findings indicate that including B&SFs results in a substantial improvement in concrete strength. The role of basalt fibers (BFs) in enhancing the concrete's resistance to acidic environments by mitigating deleterious effects on microstructural integrity is particularly noteworthy. Notably, when exposed to acidic conditions, concrete mixtures containing 0.5% BFs demonstrated the least strength loss. When B&SFs are synergized, their positive effects are amplified, yielding concrete with exceptional resistance to alkaline environments. Microstructural analysis reveals that incorporating fibers refines and strengthens the interconnected matrix of cementitious products, thereby enhancing cohesion and overall strength. Furthermore, this study underscores that desert sand can be a viable alternative to traditional fine aggregates without compromising concrete resistance if it is appropriately reinforced with fibers. In conclusion, this research sheds light on the promising role of B&SFs in augmenting the strength and microstructure of concrete containing desert sand.

Using Polyvinyl alcohol (PVA) fiber and micro silica sand has adverse effects on the economic and sustainable advantages of Engineered Geopolymer Composites (EGCs). This study suggests replacing PVA fiber with polypropylene fiber (PP) in producing sustainable reinforced slag-based-engineered geopolymer composites (SEGC) subjected to thermal cycling and repeated loads. PP and PVA fibers, with a 2% content as a volume fraction were selected to reinforce the EGCs. The study examined mass loss, microstructural characterization, static (monotonic) and cyclic loading measurements, tensile properties, and flexural properties. The results obtained indicate a substantial reduction in the strength of lightweight SEGC under thermal cycling. The density of LW-EGC and ECC composite ranged between 1758 for ECC and 1870 kg/m3 for PVA-EGC, while the statistic stress ranged between 37.35 for PVA-ECC and 63.78 for PVA-EGC. However, the flexural strength under static and cyclic loading of LW-ECC (LW-ECC) samples showed substantial improvement due to the increased reaction rate of fly ash particles under high temperatures. Microstructure analysis revealed that SEGC samples suffered more severe damage than ECC specimens when subjected to various cooling and heating cycles. These micro-cracks contributed to defects in the residual mechanical behavior of lightweight SEGC specimens.