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CONTENTS
Volume 20, Number 6, December 2025
 

Abstract
Carbonation of high volume fly ash (HVFA) cement cementitious materials has been reported to cause corrosion and cracking of reinforcing bars in structures. In addition, although the early strength of the modified high volume fly ash (MHVFA) cement mortars with the addition of nano-silica (NS) and silica fume (SF) is significantly enhanced, its strong pozzolanic reaction consumes a large amount of calcium hydroxide (CH), which may further decrease carbonation resistance. In this paper, the effects of hydrated lime (HL), calcined hydrotalcite (C-HT), magnesium oxide expansive agent (MEA) and polypropylene fibers (PPF) on the carbonation resistance of HVFA cement mortars and MHVFA cement mortars were investigated, the possible ways of carbonation resistance enhancement were explored both chemically and physically. In addition to fluidity and compressive strength, the anti-carbonation effect of the four additives was evaluated using accelerated carbonation test and pH test, and the anti-carbonation behavior was further analyzed by x-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen (N2) adsorption/desorption test. The test results showed that the additives with the best effect in enhancing the mechanical properties and carbonation resistance of (M)HVFA cement mortars were HL for HVFA cement mortars and MEA for MHVFA cement mortars, respectively.

Key Words
carbonation; expansive agent; high volume fly ash; hydrated lime

Address
(1) Heping Yuan, Yang Liu, Bowen Wang:
Department of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, Hunan, China;
(2) Hui Peng:
Key Laboratory for Safety Control of Bridge Engineering, Ministry of Education and Hunan Province, Changsha 410114, Hunan, China.

Abstract
The proliferation of glass waste (GW) necessitates sustainable solutions, with its incorporation into concrete representing a promising approach. This study experimentally examines the dual application of GW-derived materials, glass powder (GP) as a partial cement replacement and glass sand (GS) as a substitute for natural sand, with varying water-to-cement ratios (w/c) of 0.35, 0.40, and 0.44. Glass concrete was prepared by replacing cement and sand with GW at varying levels (0%, 5%, 10%, 15%, 20%, 25%, and 30%). 30 concrete mixes were designed to evaluate the effects of incorporating GW on key performance parameters, including workability, density, compressive, splitting and flexural strengths, and water absorption. The test results demonstrate that slump flow increases with higher w/c ratios, reaching 250 mm in the mix with 30% GP, highlighting the combined effect of w/c ratio and GP in enhancing concrete flowability. Regarding compressive strength, an increase in both GP and w/c ratios led to continuous reduction in concrete strength, whereas the addition of GS resulted in a slight improvement. The most significant strength reduction, decrease to 35% of the original concrete's compressive strength, was observed in the mix containing 30% GP and a 0.44 w/c ratio. This decline is likely due to the smooth surface texture of the glass particles, which weakens the interfacial bond between the glass and the cementitious matrix. The optimal GS replacement and w/c ratios for improving splitting and flexural strengths are 20% and 0.35, respectively. Concrete density is influenced by the particle size of GW; 30% replacement of GP and GS with 0.44 w/c ratio reduced the density by 0.4% and 0.5%, respectively. Furthermore, GP and GS with 0.44 w/c ratio significantly reduce water absorption, by 24.5%, leading to a less permeable concrete. Overall, the combination of 5% GP and 20% GS at a 0.35 w/c ratio provides the best improvement in both internal microstructure and external durability of the concrete, compressive strength increased by 12%, and water absorption decreased by more than 20%. These findings highlight the potential of WG as a sustainable material for improving concrete performance, particularly when accounting for variations in the w/c ratio, offering significant environmental and engineering advantages.

Key Words
glass powder; recycled concrete; mechanical properties; sustainable concrete; w/c

Address
(1) Abdelrahman Shams, Mohamed M. Yousry Elshikh:
Structural Engineering Department, Mansoura University, Mansoura 35516, Egypt;
(2) Abdelrahman Shams:
Civil Engineering Department, Horus University, New Damietta 34517, Egypt;
(3) Mosbeh R. Kaloop, Jong Wan Hu:
Department of Civil and Environmental Engineering, Incheon National University, Incheon, Korea;
(4) Mosbeh R. Kaloop, Jong Wan Hu:
Incheon Disaster Prevention Research Center, Incheon National University, Incheon, Korea;
(5) Mosbeh R. Kaloop:
Public Works Engineering Department, Mansoura University, Mansoura, Egypt;
(6) Ibrahim Abd El-Mohsen:
Civil Engineering Department, Damietta University, New Damietta 34517, Egypt.

Abstract
This study examined the impact of different ratios of slag and polyamide fibers on the load deformation behavior of reinforced geopolymer concrete. To achieve this objective, the performance of geopolymer concrete was assessed by varying the ratios of slag-polyamide fiber and the percentage of replacement. Additionally, the utilization of a combination of ambient and oven curing methods in the reinforcing of geopolymer concrete was also examined. Adjustments were made to the ratio of slag in a number of different proportions, including 5%, 10%, and 15% to achieve this purpose. The ratios of polyamide fibers, on the other hand, were chosen to be 1%, 2%, and 3% respectively. This objective was accomplished by producing a total of twelve different mixing ratio samples. A cross-sectional area of 100 mm by 150 mm and a length of 1000 mm were the dimensions that were utilized in the construction of the examples. This was done to achieve the intended outcome. The study investigated the effect of varying the slag ratio while keeping the polypropylene fiber ratio constant. A 10% increase in the slag ratio resulted in a direct improvement of 26% and 45.5% in the load bearing capabilities of R-C-Bs for Ambient and Oven curing, respectively. In addition, it was observed that increasing the polypropylene fibers ratio by 1% during the ambient and oven curing process led to a significant 31.9% and 31.7% enhancement in the load carrying capacity of R-C-B. At the conclusion of the studies, it was shown that strengthening the reinforcing geopolymer concrete significantly benefited from the concrete being subjected to an oven curing method.

Key Words
ambient curing; flexural behavior; geopolymer concrete; oven curing; polyamide fibers; slag ratio

Address
(1) Ali Īhsan Çelik, Ufuk Tunç, Atahan Gűven:
Department of Construction, Tomarza Mustafa Akincioglu Vocational School, Kayseri University, Kayseri, 38940, Turkey;
(2) Memduh Karalar:
Department of Civil Engineering, Zonguldak Bulent Ecevit University, Zonguldak, Turkey;
(3) Yasin Onuralp Őzkılıç:
Department of Civil Engineering, Faculty of Engineering, Necmettin Erbakan University, Konya 42000, Turkey;
(4) Yasin Onuralp Őzkılıç:
Department of Unique Buildings and Constructions Engineering, Don State Technical University, Gagarin Sq. 1, Rostov-on-Don, 344003, Russia.

Abstract
Cold-formed steel sections face the issues of local buckling due to the smaller thickness and the presence of free edges. Concrete-filled steel tube (CFST) is considered a promising solution for enhancing structural performance and preventing the occurrence of local buckling for steel tubes. In addition to the conventional CFST members, recent research has focused on replacing the infilled concrete with lightweight concrete and recycled aggregate concrete. Incorporating lightweight concrete aims to reduce the overall self-weight of the composite members, whilst recycled aggregate promotes the utilization of waste materials, making CFST members more environmentally friendly. The presence of internal stiffeners further increased the loadbearing capacity and stiffness of the CFST members. This study aims to examine the current research on the flexural behavior of CFST beams, with a specific emphasis on the type of infilled materials and the impact of internal stiffeners. The reviews cover experimental findings, numerical simulations, and analytical methods for the CFST beams. The insights drawn from this review aim to guide the current research gap and future research directions on CFST beams.

Key Words
CFST beam; cold-formed steel; flexural behavior; lightweight aggregate concrete; recycled concrete; stiffeners

Address
(1) Tan Wan Han, A.B.M.A. Kaish, Shahrizan Baharom, Jacob Lim Lok Guan:
Department of Civil and Structural Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia;
(2) Ahmed W. Al Zand:
Department of Design, College of Fine Arts, Alturath University, Baghdad, Iraq.

Abstract
This research explores the use of wheat husk ash and silica fume as partial substitutes for cement in concrete production. The study focuses on enhancing the durability and mechanical properties of concrete, which include compressive strength, tensile strength, and elasticity. The research explores various mix ratios of wheat husk ash and silica fume as partial replacements for cement. The experimental phase involved preparing concrete samples with different proportions of wheat husk ash and silica fume, replacing a portion of the cement content. The results demonstrate the viability of wheat husk ash (WHA) and silica fume (SF) as partial cement substitutes. The study reveals that certain mix ratios of these materials not only maintain the essential properties of conventional concrete but can even enhance them. The study observed that the inclusion of Silica Fume and Wheat Husk ash in concrete not only enhances its mechanical properties but also improves its durability characteristics. The SF10WHA15 mix, in particular, demonstrates the best overall performance, suggesting an optimal balance between the two additives. These results indicate that incorporating WHA and SF in concrete is a viable approach to enhance both the structural and durability properties of concrete, making it a promising solution for sustainable construction practices.

Key Words
durability; mechanical properties; silica fume; sustainable concrete; wheat husk ash

Address
Department of Civil Engineering, Samrat Ashok Technological Institute, Vidisha, 464001, India.


Abstract
In this experimental study, the reinforced concrete degradation subjected to chlorides penetration was investigated by electrochemical and physical-chemical tests at changes in coating depth. A comparative study was carried out on reinforced concrete specimens produced in the laboratory with different coating thicknesses. One of these specimens was kept as a control, while the two others were immersed in an aggressive environment (seawater) for a period of t = 4 years. The aim is to carry out an in-depth study of concrete and reinforcing steel in the test specimens' degradation, by analysing and quantifying the chloride-concrete-reinforcing steel interactions as a function of the thickness of the coating, while interpreting and justifying the phenomena underlying the degradation studied. The results of the tests carried out have provided a quantitative basis and an indepth understanding of the parameters of concrete degradation that cause a decrease in its mechanical strength, as well as the depassivation of steel through corrosion.

Key Words
chlorides; concrete; corrosion; reinforcement; XRD

Address
(1) Nassima Khial, Kamel Ghouilem:
Geomaterials, Environment and Development Laboratory, Mouloud Mammeri University of Tizi-Ouzou, Algeria;
(2) Youcef Bellal:
Research Center in Industrial Technologies CRTI, P.O. Box 64, Cheraga, 16014 Algiers, Algeria;
(3) Rabah Chaid:
Civil Engineering Department, Faculty of Engineering, M'Hamed Bougara University, Boumerdes, Algeria.

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