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CONTENTS
Volume 36, Number 3, September 2025
 

Abstract
Fracture energy test, non-destructive investigation, some of the physical and mechanical tests, and microstructural examinations were performed on GRC (glass fiber-reinforced concrete) with different fiber length and weight fractions. Alkaline-resistant glass (AR-GF) fibers with 6, 12, and 19 mm lengths were evaluated to produce GRCs. Weight fractions of 0.7 wt%, 1.3 wt%, and 2.0 wt% AR-GF fibers were used in the GRC mixtures. Fracture tests were performed on Single Edge Notched Beams (SENBs) to investigate fracture energy, crack resistance index (CRI), and flexibility index (FI) of GRCs. Dynamic modulus of elasticity and damping ratios of the GRCs were determined by performing resonant frequency tests on the SENB samples by ASTM C215 standard. In addition, compressive strength, static modulus of elasticity, electrical resistivity, ultrasonic pulse velocity (UPV), Schmidt hammer, and density tests were also performed on the cylindrical samples produced. Field Emission Scanning Electron Microscopy (FE-SEM) and Fourier Transform Infrared (FTIR) analyses were performed to examine the microstructure of the GRC matrix in this study. Test results revealed that the mixtures containing 12 mm long fiber at 2.0 wt% dosage exhibited superior fracture energy by cracking resistance and flexibility index. Dynamic test results showed that the increase in fiber length and ratio increased the damping ratio of GRCs. In sum, with the study, it came out that fiber length had more significant relations with the experimental results once compared to the weight of fiber content.

Key Words
damping ratio; dynamic; fracture mechanics; glass fiber; GRC; resistivity; UPV

Address
Heydar Dehghanpour: Department of Civil Engineering, Faculty of Engineering, Istanbul Aydin University, Kucukcekmece, Istanbul, Türkiye
Serkan Subasi: Department of Civil Engineering, Faculty of Engineering, Duzce University, Duzce, Türkiye
Mehmet Emiroglu: Department of Civil Engineering, Faculty of Engineering, Sakarya University, Serdivan, Sakarya, Türkiye
Muhammed Marasli and Volkan Ozdal: Department of R&D, Fibrobeton Inc., Duzce, Türkiye

Abstract
Due to the shortage of natural sand, manufactured sand concrete (MSC) is widely used owing to its sustainability benefits, but optimizing its mix proportion design remains a challenge. In this paper, the least paste theory is adopted to optimize the cracking resistance of MSC. Artificial neural networks are employed to establish nonlinear relationships between the mix proportion parameters (namely nominal water-cement ratio, equivalent water-cement ratio, fly ash-binder ratio, slag-binder ratio, stone powder-binder ratio, and average paste thickness) and performance indicators (namely slump, 28 d compressive strength, and 28 d chloride ion diffusion coefficient). This study integrates artificial neural networks and the harmony search algorithm to optimize the mix proportion of manufactured sand concrete, enhancing cracking resistance while minimizing cost and carbon footprint. The findings contribute to the advancement of mix proportion design theory and promote the broader application of MSC in engineering projects.

Key Words
artificial neural network; harmony search algorithm; least paste theory; manufactured sand concrete; mix proportion design and optimization

Address
Wanlu Li, Weiwen Luo and Yongning Liang: College of Civil Engineering, Fuzhou University, Fuzhou, Fujian 350108, PR China
Xiangzeng Zheng and Xudong Chen: Pingtan Comprehensive Experimental Area Zheng Xiangzeng Expert Studio, Pingtan, Fujian 350400, PR China
Tao Ji: College of Civil and Transportation Engineering, Hohai University, Nanjing, Jiangsu 210098, PR China

Abstract
As the demand for sustainable materials grows, geopolymer concrete (GC) has emerged as a low-carbon alternative to Portland cement concrete. However, its long-term compressive strength (CS) remains a limitation. While unconfined GC has been widely studied, limited research exists on carbon fiber reinforced polymer (CFRP)-confined GC. This study evaluates the axial performance of red mud-based geopolymer concrete (RMGC) confined with CFRP. Thirty-six cylindrical RMGC specimens (15 MPa and 30 MPa) were tested under axial loading with one or two CFRP layers. Finite element analysis (FEA), incorporating an enhanced concrete damaged plasticity model, was used to predict structural responses, and a parametric study assessed key confinement effects. Experimental results showed that CFRP confinement significantly improved CS, with increases of 91.77% and 153.85% for 15 MPa RMGC, and 52.28% and 99.33% for 30 MPa RMGC with single and double CFRP layers, respectively. Lower-strength RMGC benefited more in terms of strength, strain capacity, and ductility. The FEA model aligned well with experiments, with discrepancies of 9.1% for CS and 6.6% for strain. A new analytical equation, achieving an R2 of 0.96 and a minimal 4.48% deviation, provided improved predictive accuracy. These findings underscore the potential of CFRP confinement in enhancing RMGC's mechanical properties and offer a reliable analytical tool for FRP-confined GC systems.

Key Words
activated red mud; analytical model; CFRP sheets; finite element analysis (FEA); geopolymer concrete

Address
Zeeshan Ahmad: Department of Civil Engineering, Quaid-e-Azam College of Engineering and Technology (QCET), Sahiwal 57000, Pakistan
Nejib Ghazouani: Mining Research Center, Northern Border University, Arar 73213, Saudi Arabia
Khaled Mohamed Elhadi: 2) Department of Civil Engineering, College of Engineering, King Khalid University, PO Box 394, Abha 61411, Saudi Arabia, 2) Center for Engineering and Technology Innovations, King Khalid University, Abha 61421, Saudi Arabia
Abdelkader Mabrouk: Civil Engineering Department, College of Engineering, Northern Border University, Arar 73222, Saudi Arabia

Abstract
The applications of basalt fiber-reinforced polymer (BFRP) bars in columns have gained attention due to their superior durability and corrosion resistance. However, their structural behavior in composite columns remains inadequately explored. This study experimentally and numerically investigates the performance of various BFRP reinforcement configurations, including plate sections, angle sections, circular tubes, and conventional circular rebars, in square columns. A total of eight examples were tested under axial compression, incorporating different reinforcement types and stirrup spacings (50 mm and 100 mm) to assess their impact on strength, ductility, and failure mechanisms. Experimental results revealed that BFRP tube-confined examples exhibited the highest peak load capacity, reaching up to 1150 kN, a 25% increase compared to steel-reinforced counterparts. The inclusion of stainless-steel stirrups enhanced the confinement effect, improving ductility by approximately 30% over BFRP-reinforced examples without stirrups. Finite element analysis (FEA) using the concrete damaged plasticity (CDP) model demonstrated strong agreement with experimental results, with an average error of less than 5% in peak load predictions. A detailed parametric study highlighted the influence of reinforcement geometry and spacing on load-carrying capacity and failure modes. These findings provide valuable insights for adopting BFRP reinforcement in concrete columns, offering a viable alternative to conventional steel reinforcement for enhanced durability and serviceability in structural applications.

Key Words
axial strain; axial strength; BFRP; concrete columns; finite element analysis (FEA); parametric analysis; theoretical models

Address
Zeeshan Ahmad: Department of Civil Engineering, University of Engineering and Technology, Taxila, 47050, Pakistan
Abdellatif Selmi: 1) Prince Sattam Bin Abdulaziz University, College of Engineering, Department of Civil Engineering, Alkharj, 11942, Saudi Arabia, 2) Ecole Nationale d'Ingénieurs de Tunis (ENIT), Civil Engineering, Laboratory, B.P. 37, Le belvédère 1002, Tunis, Tunisia
Mohamed Hechmi El Ouni: Department of Civil Engineering, College of Engineering, King Khalid University, PO Box 394, Abha 61411, Kingdom of Saudi Arabia
Bilal Ahmed: Department of Structural Engineering, Faculty of Civil Engineering, Doctoral School, Akademicka 2, Silesian University of Technology, 44-100 Gliwice, Poland

Abstract
In this paper, the experimental investigation into the flexural strengthening of reinforced concrete (RC) beam specimens applying a novel side hybrid (SH) technique that encompasses carbon fiber reinforced polymer (CFRP) bars and plates with or without end anchorage systems is presented. This SH strengthening technique was an incorporation of the Side Near Surface Mounted (SNSM) and Side Externally Bonded Reinforcement (S-EBR) approaches. A total of nine rectangular RC beam specimens were manufactured and exposed to flexural assessment. Among them, one specimen was used as the unstrengthened reference specimen, four specimens were strengthened exercising the SH technique using CFRP reinforcements without an end-anchorage system, and the remaining four specimens were strengthened exploiting the SH scheme by engaging CFRP reinforcements with an end-anchorage system. The constraints under investigation comprised the bonding length for CFRP reinforcements and the anchorage system at the ends for strengthening. The experimental outcomes exhibited that the SH technique with CFRP reinforcements extensively boosted the flexural responses of the structural components. Moreover, combining CFRP fabrics as an end-anchorage system along with the SH technique for strengthening reinforcements for RC specimens further intensified the flexural strength of the specimens. Also, the SH strengthening technique remarkably enriched the stiffness and had a substantial proficiency in energy absorption capability improvement of the RC beam specimens. The SH-CFRP technique for strengthening of RC beam specimens with the end-anchorage system exhibited excellent bonding performance, with no debonding observed before reaching full flexural strength, ensuring the ductile failure of the RC beam specimens.

Key Words
ductile failure; energy absorption capacity; flexural improvement; RC Beam; SH technique; stiffness; strengthening

Address
Md. Akter Hosen: Department of Civil and Environmental Engineering, College of Engineering, Dhofar University, PO Box 2509, PC 211, Salalah, Sultanate of Oman
Azlinda Saadon: School of Civil Engineering, College of Engineering, Universiti Teknologi MARA, 40450, Shah Alam, Selangor, Malaysia
Mohd Zamin Jumaat and U. Johnson Alengaram: Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603, Kuala Lumpur, Malaysia
N.H. Ramli Sulong: School of Civil & Environmental Engineering and Group of Sustainable Engineered Construction Materials, Faculty of Engineering, Queensland University of Technology, 2 George St, Brisbane, QLD 4000, Australia
Zhen Li: College of Aerospace and Civil Engineering, Harbin Engineering University, China
Reventheran Ganasan: Department of Transportation Engineering Technology, Faculty of Engineering Technology, Universiti Tun Hussein Onn Malaysia, Campus (Pagoh Branch), 84600, Malaysia

Abstract
Pile foundations are typically utilized when it is required to move substantial super structural loads through brittle subsoil. Along with axial loads, piles are subject to heavy lateral loads and overturning moments. While the lateral loads for onshore structures are typically between 10% and 15% of the vertical loads, they may exceed 30% for coastal and offshore structures. Pile constructions must be properly built to withstand such lateral loads. Recently, numerous studies have focused on outwardly glued fibre-reinforced polymer composites to strengthen concrete structures. This study applies static lateral forces on cast-in-situ reinforced concrete (RC) piles, which have undergone wrapping and strengthening with carbon fibre-reinforced polymer (CFRP). In this study, static lateral forces were applied on cast-in-situ reinforced concrete (RC) piles that underwent CFRP wrapping and strengthening. The experiment demonstrated that CFRP confinement significantly improved the lateral load-bearing capacity of the piles, with unidirectional CFRP-confined piles exhibiting up to 63.35% greater strength than unconfined piles under similar loading conditions. These findings highlight the efficiency of CFRP in reinforcing piles for coastal and offshore applications.

Key Words
CFRP; epoxy; FRP confining; lateral loading; pile strengthening

Address
G. L. Abishek: Department of Civil Engineering, Mar Ephraem College of Engineering and Technology, Elavuvilai, Marthandam, Tamil Nadu, India
R. Murugesan: Department of Civil Engineering, Nandha Engineering College, Erode, Tamil Nadu, India
M. Murugan: Department of Civil Engineering, Government College of Engineering, Tirunelveli, Tamil Nadu, India

Abstract
The presence of lap-splices raises concerns about reinforcement bar slippage in the connection region, which often leads to wall failure and reduces seismic performance. Moreover, high-strength reinforcement bars, known for their high resistance at low strains, are commonly used to reduce strain demand in reinforced concrete shear walls. Therefore, the combined effect of high-strength reinforcement and lap-splices significantly influences the seismic performance of shear walls. In this study, after validating the developed numerical model against reference wall tests, a total of 24 shear wall models with high-strength longitudinal reinforcement were simulated and analyzed. The models vary in longitudinal bar diameter, transverse reinforcement ratio, lap splice length, and rebar debonding. The results indicate that the presence of lap-splices in longitudinal reinforcement leads to slippage in the bond region, reducing wall ductility. Furthermore, the findings demonstrate that debonding techniques can mitigate the negative effects of bar slippage, enhance wall ductility, and improve energy dissipation.

Key Words
bond slip; concrete shear wall; confining ties; high-strength steel; lap-splice; seismic behavior

Address
Erfan Abbasvand Jahedi, Hadi Azizian and Seyed Jamil Ghaderi: Department of Civil Engineering, Mah.C., Islamic Azad University, Mahabad, Iran
Erfan Shafei: Faculty of Civil Engineering, Urmia University of Technology, Urmia, Iran

Abstract
High temperatures can reduce the flexural strength of reinforced concrete beams. This study uses microbially induced calcium carbonate precipitation (MICP) technology to enhance the flexural strength of thermally damaged lightweight aggregate concrete (LWAC) beams. Two experimental groups (A and B) were prepared with lightweight aggregates (LWAs) that were immersed in nutrient and bacterial solutions, while a control group (C) used LWAs without immersion. The specimens repaired themselves differently after exposure to 500 oC. Groups A and C used the same self-healing method, requiring 28 days of daily water spraying to maintain moisture. Group B employed a cyclic curing method, alternating nutrient solution spraying and air drying over the same period. After 28 days, the relative maximum flexural load ratios for groups A, B, and C were 1.094, 1.134, and 1.056, respectively. Groups A and B showed increases of 3.6% and 7.4% compared to Group C, demonstrating the cyclic curing method's greater effectiveness.

Key Words
beam; biomineralization; flexural strength; lightweight aggregate concrete; self-healing

Address
Chao-Wei Tang: 1) Department of Civil Engineering and Geomatics, Cheng Shiu University, No. 840, Chengching Road, Niaosong District, Kaohsiung 83347, Taiwan (R.O.C.), 2) Center for Environmental Toxin and Emerging-Contaminant Research, Cheng Shiu University, No. 840, Chengching Road, Niaosong District, Kaohsiung 83347, Taiwan (R.O.C.), 3) Super Micro Mass Research and Technology Center, Cheng Shiu University, No. 840, Chengching Road, Niaosong District, Kaohsiung 83347, Taiwan (R.O.C.)
Chung-Hao Wu: Department of Civil Engineering, National Kaohsiung University of Science and Technology, No. 415, Jiangong Road, Sanmin District, Kaohsiung City 807618, Taiwan (R.O.C.)
Shu-Ken Lin, How-Ji Chen and Bing-You Wu: Department of Civil Engineering, National Chung Hsing University, 145 Xingda Road, South District, Taichung City 40227, Taiwan (R.O.C.)

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