Abstract
In regions with significant temperature variations, such as during winter, concrete structures are exposed to repeated freeze-thaw cycles, which deteriorate their durability. Freeze-thaw damage manifests as internal microcracking and surface scaling, resulting not only in visible deterioration but also in a reduction in structural capacity, ultimately shortening the service life of the structure. Generally, experimental testing is essential to evaluate the freeze-thaw resistance of concrete mixtures; however, such testing requires substantial time and cost investments. Therefore, developing rapid and reliable evaluation methods that minimize the number of experiments is necessary. In this study, a database of freeze-thaw experimental results for various concrete mixtures was constructed based on previous research, and an artificial neural network (ANN)-based evaluation model was developed to assess the resistance and damage characteristics of concrete subjected to freeze-thaw cycles. Additionally, regression-based estimation equations were proposed. Validation of the proposed ANN model showed high prediction accuracy, with mean error rates of approximately 10.4% for resistance and 10.07% for damage characteristics. Furthermore, the regression-based equations showed mean error rates of approximately 10.0% and 17.04%, indicating reasonable accuracy with a simplified modeling approach. Therefore, the ANN-based model and regression equations developed in this study are expected to serve as useful tools for quantitatively evaluating and predicting the freezethaw resistance and damage characteristics of concrete under various mixture conditions.
Key Words
artificial neural network (ANN); concrete; freeze-thaw; freeze-thaw resistance; relative dynamic modulus of elasticity (RDME)
Address
Khaliunaa Darkhanbat: Department of Architectural Engineering, University of Seoul, Seoul, Republic of Korea
Inwook Heo: Urban Safety and Security Research Institute, University of Seoul, Seoul, Republic of Korea
Seung-Ho Choi: Department of Disaster Management and Fire Safety Engineering, University of Seoul, Seoul, Republic of Korea
Jae Hyun Kim: Department of Architectural Engineering, University of Seoul, Seoul, Republic of Korea
Kang Su Kim: Department of Architectural Engineering and the Smart City Interdisciplinary Major Program, University of Seoul, Seoul, Republic of Korea
Abstract
This work investigates the buckling and vibrational behavior of functionally graded concrete beams featuring geometric non-uniformities and controlled porosity. The beams incorporate steel-reinforced, eco-efficient, functionally graded concrete, offering a sustainable alternative to conventional monolithic components. Each beam's external radius varies along its longitudinal axis following linear, convex, or concave profiles, creating intentional geometric non-uniformities that significantly influence structural stability. A theoretical framework combining Hamilton's principle with nonlocal strain gradient theory and first-order shear deformation theory is developed to capture size-dependent phenomena while accounting for simultaneous material hardening and softening. Governing equations are solved via the finite element method, and a physics-informed neural network is trained on these solutions to enable rapid predictions across diverse design parameters. Systematic parametric studies examine the effects of boundary conditions, material grading profiles, geometric configurations, and nonlocal coefficients on critical buckling loads and fundamental natural frequencies. Results demonstrate that deliberate selection of geometry and functional grading can tailor the mechanical response of porous functionally graded concrete elements. This integrated numerical and machine learning framework supports the design of permanent sports infrastructure, including modular climbing wall bases and outdoor fitness equipment supports. In these applications, controlled porosity and variable geometry reduce self-weight while preserving structural integrity under cyclic loading, addressing traditional limitations of concrete in non-portable sports installations.
Address
Lingjun Wu: Yongzhou Vocational Technical College, Yongzhou 425100, Hunan, China
Lei Huang: College of Humanities and Social Development, Minxi Vocational and Technical College, Longyan 364000, Fujian, China
Mostafa Habibi: Department of Mechanical Engineering, Faculty of Engineering, Haliç University, Istanbul, Turkey;
Department of Biomaterials, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Sciences, Chennai, India
Tayebeh Mahmoudi: Hoonam Sanat Farnak, Engineering and Technology Knowledge-based Enterprise Company, Ilam, Iran
Abstract
Developing eco-friendly lightweight aggregate materials is crucial globally, especially in Saudi Arabia, due to poor limestone quality, high water tables, and challenging soil conditions. This necessitates alternative lightweight aggregates for lightweight concrete (LWAC). This research developed LWACs by replacing 70-100% of conventional limestone (LS) with local scoria rock (SR) or by substituting 10-30% of LS with artificial polystyrene (AP), creating SR-based and AP-based LWACs. A total of seven concrete mixes were prepared, including a control mix, with cement contents ranging from 411 to 567 kg/m3 and water contents from 164 to 227 kg/m3. Their performance was compared with a control normal-weight aggregate concrete (NWAC) with 100%LS. First, aggregate physical properties were evaluated. Then, mix proportions were developed, and fresh, mechanical, and durability characteristics of the concrete were investigated. AP exhibited the lowest bulk density and specific gravity, followed by SR, then LS. LWACs generally showed lower compressive strength and pulse velocity, with higher chloride permeability and sorptivity than NWAC. LWAC density reduced by 8.2-13.6% with SR and 3.5-10.9% with AP. Twenty-eight-day compressive strengths were 70.3-92.2% (SR-LWAC) and 43.8-54.7% (APLWAC) of NWAC's strength.Thismechanical reduction is attributed to SR's porous nature and AP's lower density, potentially causing cracks. These eco-friendly LWACs show potential for infrastructural applications requiring mediumto lowstructural strength andmoderate durability.
Key Words
artificial polystyrene; durability; lightweight aggregate concrete; limestone aggregate; physicomechanical properties; scoria rock
Address
A.B.M. Saiful Islam: Department of Civil and Construction Engineering, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 31451, Saudi Arabia
Abdulsalam M. Alkhalaf: Department of Civil and Construction Engineering, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 31451, Saudi Arabia
Muhammad Nasir: ReSET Group, Clean Energy Research Platform, Physical Sciences and Engineering (PSE) Division, King Abdullah University of Science and Technology, Thuwal, Makkah 23955, Saudi Arabia
Walid A. Al-Kutti: Department of Civil and Construction Engineering, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 31451, Saudi Arabia
Khalid Saqer Alotaibi: Department of Civil and Construction Engineering, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 31451, Saudi Arabia
Abstract
The incorporation of fibers into ultra-high performance concrete (UHPC) significantly modifies its mechanical behavior. This research quantifies these effects by systematically testing five individual fiber types—
straight steel (SF), hooked-end steel (HF), polypropylene (PP), polyvinyl alcohol (PVA), and basalt (BF)—alongside a multi-scale hybrid fiber (HYF) combination at 1% and 2% volume fractions. Regarding compressive strength, all fiber reinforcements provided measurable enhancements compared to the unreinforced control matrix (124.24 MPa). The SF system proved most effective, delivering a maximum strength increase of 24.97% (reaching 159.84 MPa) at a 2% volume fraction. Notably, the HYF system—comprising a synergistic blend of SF, HF, PP, and PVA—achieved a 20.86% strength gain, performing comparably to the optimal mono-steel fiber mixes while offering enhanced micro- and macro-crack control. A key finding was the universal transformation of the failure mechanism; the inclusion of any fiber type mitigated the inherent brittleness of UHPC, shifting the failure mode from explosive fragmentation to a controlled, ductile response. In contrast to compressive strength and ductility, statistical analysis (ANOVA, p>0.05) revealed that the elastic modulus remained insensitive to both fiber type and content, indicating that matrix properties predominantly govern the stiffness of this composite. This study confirms that strategic fiber hybridization is paramount for optimizing UHPC ductility and compressive strength without materially altering its elastic stiffness, providing a robust baseline for future structural applications.
Address
Long P. Nguyen: Vietnam Aviation Academy, Ho Chi Minh City, Vietnam
Quang C. Nguyen: Ho Chi Minh City University of Transport, Ho Chi Minh City, Vietnam
An H. Le: NTT Hi-Tech Institute, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam
Abstract
This study investigates the structural performance and sustainability of alkali-treated abaca fiber reinforced polymer (AbFRP) laminates as a low-carbon alternative to glass FRP (GFRP) for shear strengthening of reinforced concrete (RC) beams. Six RC beams (150x300x2300 mm, a/d=2.6) were tested under four-point bending: two controls, two GFRP-strengthened, and two AbFRP-strengthened in fullU-wrap configuration. AbFRP laminates achieved tensile strength of 83.85 MPa and elastic modulus of 5027.1 MPa, with coefficients of variation below 8%. Both systems enhanced structural performance: ultimate load increased by 34.2% (GFRP) and 35.7% (AbFRP), with failure mode shifting from brittle shear to ductile flexure. Ductility index improved from 1.3 to 3.4 (GFRP) and 2.8 (AbFRP). Unlike GFRP, AbFRP exhibited pseudo-ductile strain hardening through progressive fiber rupture and fiber-matrix interfacial heterogeneity, producing a higher ultimate FRP strain (6384 ue vs. 950 ue) and enhanced energy dissipation. Theoretical validation against ACI 440.2R-17 confirmed that the bond-controlled strain limit (efrp=0.004) yields conservative predictions, while using the measured rupture strain (efu=0.017) overestimated shear capacity by 204%, confirming bond-controlled effective strain governs design. Cradle-to-gate assessment showed AbFRP reduced embodied energy by 63-85%, CO2 emissions by 88%, and material cost by 71% relative to GFRP. These findings establish AbFRP as a structurally reliable, code-compatible, and environmentally efficient alternative for RC shear strengthening.
Address
Fakhruddin: Department of Civil Engineering, Faculty of Engineering, Universitas Hasanuddin, Makassar, 92171, Indonesia; Research Center for Structural Strength Technology, National Research and Innovation Agency, Indonesia
Rudy Djamaluddin: Department of Civil Engineering, Faculty of Engineering, Universitas Hasanuddin, Makassar, 92171, Indonesia
Rita Irmawaty: Department of Civil Engineering, Faculty of Engineering, Universitas Hasanuddin, Makassar, 92171, Indonesia
Luna Nurdianti Ngeljaratan: Research Center for Structural Strength Technology, National Research and Innovation Agency, Indonesia
Pornpen Limpaninlachat: Department of Civil and Environmental Engineering, Faculty of Engineering, Mahidol University, Bangkok, Thailand
Abstract
The sustainable utilization of industrial by-products in concrete is gaining prominence due to the depletion of natural resources and environmental concerns. This study investigates the use of treated steel slag as a partial replacement of natural coarse aggregate in M25 grade concrete, focusing on mechanical properties, durability performance, microstructural characteristics, and empirical modeling. Concrete mixes with 0-50% steel slag replacement were evaluated for compressive, split tensile, and flexural strengths at 7, 14, and 28 days, while durability assessments included water absorption, rapid chloride penetration, and resistance to sulfate, acid, and alkaline exposure. Microstructural analyses using XRD, FTIR, SEM, and EDAX revealed that slag treatment stabilizes free CaO/MgO, enhances C-S-H gel formation, and improves aggregate-paste bonding. Results indicate that 30% steel slag replacement yields optimum performance, with maximum compressive (28.25 MPa), tensile (2.98 MPa), and flexural strength (3.73 MPa), coupled with enhanced durability due to matrix densification and reduced porosity. A quadratic regression model effectively predicted compressive strength, confirming the experimentally determined optimum. Overall, the study establishes that treated steel slag is a viable, sustainable coarse aggregate substitute, improving both the mechanical and durability performances of structural concrete while promoting circular economy principles in construction.
Address
Kaviya Saravanan, Viswanathan Rajeshkumar: Department of Civil Engineering, KPR Institute of Engineering and Technology, Coimbatore, 641047, India
