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CONTENTS
Volume 20, Number 5, November 2025
 

Abstract
Nowadays, the consumption of natural resources is increasing due to the rapidly developing construction sector. In this case, the need to reuse the wastes in any industry arises in order to support the circular economy and sustainability. In this study, in the production of lightweight concrete, natural fiber waste luffa fibers (LF) and chicken feather fibers (CFF) were substituted into the composite at 2.5-5-7.5 and 10% ratios instead of fine aggregate. Density, compressive, flexural, abrasion resistance, ultrasonic sound permeability (UPV), thermal conductivity, freeze-thaw resistance tests and SEM analyses were performed on lightweight concrete samples with and without fibers. The compressive strength of lightweight concretes containing 2.5% LF was higher than the control concrete, while the strength of all samples with CFF substitution was higher than the strength of samples with and without fibers. Both fiber substitutions contributed to the flexural, thermal transmittance and UPV properties of lightweight concrete. In addition, the hydrophobic properties of CFF increased the freeze-thaw resistance of CFF-substituted specimens and the strong hard keratin structure of CFF increased the abrasion resistance. SEM analysis results and experimental results are consistent with each other. Considering all the experimental results, it is seen that 2.5% substitution rate for LF and 7.5% substitution rate for CFF is ideal. Owing to the ductility that fibers add to lightweight concrete, the brittleness of lightweight concrete will be reduced and its bending resistance will be increased, making it suitable for use in monolithic structures. Since lightweight concrete becomes more porous as the fiber substitution increases, the decrease in thermal conductivity and UPV values indicates that the concrete becomes more insulated. Fiber substituted lightweight concrete will reduce the dead load on the building by reducing the unit weight and will contribute to durability properties such as freeze-thaw and abrasion resistance with CFF substitution.

Key Words
chicken feather fiber; durability properties; fine pumice aggregate; lightweight concrete; luffa fiber; mechanical properties; natural fiber aggregate

Address
Department of Construction Technology, Vocational School of Technical Sciences, Sutcu Imam University, Kahramanmaras, Turkey.


Abstract
The present research evaluated the effect of carbon-fiber-reinforced polymer (CFRP) plates in strengthening reinforced concrete (RC) flat slab-column connections under punching shear and seismic loading conditions and proposed an optimal design for CFRP plates in these connections. To this end, comprehensive parametric studies were performed in the ABAQUS finite element software using 33 different models incorporating various values of the 5 main variables, namely loading conditions, number of fiber layers, orientation, thicknesses, and dimensions of the CFRP plate. The numerical model was validated via experimental tests of the laboratory model. In addition, an optimal design model for CFRP plates was developed using the gray wolf optimization (GWO) algorithm. The main objective of the optimization model was to reduce damage in the slab-column connection under loading. The optimal values of the geometric parameters of the CFRP plates retrofitted in the RC slab-column connection were obtained by simultaneous computations performed by MATLAB and ABAQUS software. The results along with the CFRP optimization model developed using GWO can be used in practice to design CFRP plates optimally for reinforcement purposes.

Key Words
CFRP; concrete slab; GWO; optimal design; RC slab-column connection seismic behavior; seismicbehavior

Address
Department of Civil Engineering, Mah.C., Islamic Azad University, Mahabad, Iran.


Abstract
The sustainable utilization of agricultural by-products in concrete production is essential for reducing environmental impact and enhancing material efficiency. Rice Husk Ash (RHA), a by-product of rice milling, serves a dual role in concrete as both a pozzolanic and filler material. This study investigates the influence of RHA on concrete properties, focusing on its pozzolanic activity and filler effect. RHA was incorporated into concrete at 0%, 5%, 10%, 15%, 20%, and 25% of the cement weight without replacing the cement. After thorough mixing, workability was evaluated through a slump test, while compressive strength was assessed after 7 and 28 days of curing. The results revealed that RHA significantly increased water demand to maintain workability and reduced the unit weight of hardened concrete. However, at an optimal dosage of up to 5%, RHA enhanced compressive strength and modulus of elasticity due to its pozzolanic reaction and particle packing effect. Higher replacement levels negatively impacted strength performance, highlighting the need for a balanced approach in mix design. This study underscores the potential of RHA as a sustainable alternative in concrete, reducing agricultural waste while improving material performance. By leveraging its dual functionality, RHA contributes to environmentally friendly construction practices by incorporating it into concrete production.

Key Words
filler effect; pozzolanic activity; rice husk ash; strength; sustainable concrete

Address
Graduate School of Bioresources, Mie University, 1577 Kurimamachiya-cho, Tsu city, Mie, Japan.


Abstract
Composite beams can achieve high material and spatial efficiency in high-rise structures by integrating equipment, such as ventilation or supply lines, through cut-out apertures in the steel web. These apertures result in a redistribution of internal forces, generating further localized requirements for the design of steel, concrete, and shear connections. Composite beams with a single flange and composite dowels provide considerable advantages in ceiling construction. To evaluate the vertical shear performance of steel-concrete composite beams with web openings under static load, five composite beams were tested, and one controlled composite beam was subjected to a concentrated load. The empirical data included vertical load, deflection, slide, and cross-sectional strain, and monotonic static loading was applied. The findings indicate a significant decrease in the composite beam's stiffness and load-bearing capability upon opening holes in the web. Furthermore, the longitudinal strain in the entire region of the hole no longer follows the assumption of a flat, planar geometry. Increasing the thickness may increase the bearing capacity, while raising the reinforcing ratio could improve the deformation capability. When the reinforcing ratio of the concrete wing above the opening is between 51.26% and 55.54% of the cross-section, it holds most of the shear force. Moreover, when web openings are present, the concrete wing significantly enhances the composite beam's vertical shear-bearing capacity. This study presents experimental evidence supporting the use of composite beams that include web openings.

Key Words
composite beam web opening; concrete; concrete fracture; plane section assumption; shear bearing capacity; universal testing machine

Address
(1) Muhammad Akbar, Saqib Zubair:
School of Naval Architecture & Ocean Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China;
(2) Muhammad Usman Arshid:
Department of Civil Engineering, University of Engineering and Technology, Taxila, Pakistan;
(3) Bilal Ahmed:
Department of Structural Engineering, Faculty of Civil Engineering, Doctoral School, Akademicka 2, Silesian University of Technology, 44-100 Gliwice, Poland;
(4) Talal O. Alshammari, Ahmed M. Yosri:
Department of Civil Engineering, College of Engineering, Jouf University, Sakaka, 72341, Saudi Arabia;
(5) Gehan Ahmed:
Department of Interior Design, College of Engineering, Jouf University, Sakaka, 72341, Saudi Arabia;
(6) Yasser Zaghloul:
Department of Civil Engineering, Higher Institute of Engineering, Elshourouk Academy, Egypt.

Abstract
This research investigates thermal stress and deformation behavior in a vertically compressed shear-flexible microplate designed for aerobic fitness applications using a nonlocal continuum framework and virtual displacement principles. The developed analytical framework serves as a functional model for optimizing exercise equipment design. Three-dimensional material relationships are established through fundamental elasticity principles, incorporating thermally induced deformations caused by vertical thermal gradients. Following resolution of the governing equations via a series expansion method, comprehensive parameter evaluations assess how temperature variations and microscale effects influence structural responses. Computational outcomes illustrate correlations between thermal loading profiles, material length parameters, and mechanical performance metrics. Practical implications of this model relate to enhancing biomechanical efficiency in athletic training apparatus through tailored microstructural adaptations.

Key Words
analytical results; deformable models; micro scale; small scale dependent behavior

Address
(1) Zhida Huang, Dongming Zhu:
School of Sports and Health, Nanchang Institute of Science and Technology, Nanchang 330100, Jiangxi, China;
(2) Nianhua Tang:
School of Ecology and Environment, Yuzhang Normal University, Nanchang 330100, Jiangxi, China;
(3) Mostafa Habibi:
Department of Biomaterials, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Sciences, Chennai, 600077, India;
(4) Mostafa Habibi:
Department of Mechanical Engineering, Faculty of Engineering, Haliç University, Istanbul, Turkey;
(5) Nejib Ghazouani:
Mining Research Center, Northern Border University, Arar 73222, Arar, Saudi Arabia;
(6) Hao Wang:
Research and Development Center, Production Engineering Group, Kuala Lumpur, Malaysia.

Abstract
Today, with the development of the construction industry and the use of concrete as one of the most widely used building materials in the structural industry, it is expected that sufficient research will be conducted on all dimensions and angles of concrete. Since one of the main weaknesses of concrete is its low tensile strength and brittle behavior, steps must be taken to reduce its negative effects, and one of the solutions is the use of additives. In this research, the effect of Korta fibers and recycled rubber granules on the tensile, flexural, compressive and ductility behavior of concrete has been investigated in an Experimental. For the research, 45 Experimental samples were made with 5 different mixing designs (0.5 and 1% Korta fibers, 5 and 10% granules). According to the output results, it was observed that in the study of compressive and tensile strength, the mixing design with 5% granules and 1% Korta fibers (CG5F1) resulted in a 12.7% increase in compressive strength and a 16% increase in tensile strength compared to the control concrete. In the study of flexural strength and ductility, the mixing design with 5% granules and 0.5% Korta fibers (CG5F0.5) resulted in a 10.47% increase in flexural strength compared to the control concrete. As a result, it is observed that the use of rubber granules reduces the strength parameters of concrete and Korta fibers increases the strength and ductility parameters. Therefore, if compressive, tensile, and bending strength are of particular importance in a structural design, it is recommended to avoid rubber granules and switch to using Korta fibers.

Key Words
compressive strength; concrete strength; flexural strength; Korta fibers; recycled rubber granules

Address
Department of Civil Engineering, Sha. C., Islamic Azad University, Shahrood, Iran.


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