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CONTENTS
Volume 21, Number 2, February 2026
 

Abstract
The extensive global exploitation of mineral resources has resulted in significant accumulation of tailings sand, creating substantial environmental and land-use challenges. Currently, the utilization of tailings sand as concrete materials has emerged as a promising solution to this issue. Take the example of iron, gold and molybdenum tailings sands, which are the main sources of solid waste in Shaanxi, China. This paper comprehensively examines the basic physical and chemical properties of iron, gold, and molybdenum tailings sand and discusses their effects on the workability, mechanical behavior, and durability of concrete. Meanwhile, the effects of them on concrete hydration and microstructure are analyzed in a microscopic overview. The scope of their applications is discussed, and relevant recommendations are made for their shortcomings. The aim is to provide new ideas for the utilization of tailings sand solid waste and construction sand substitutes.

Key Words
concrete; fineness; hydration; microstructure; sustainability; tailings

Address
Yuhao Jiao, Jianping Tan, Wei Li, Puxin Yang, Wenyuan Ren: College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, China
Chen Chen: Xi'an Engineering Investigation & Design Research Institute of China National Nonferrous Metals Industry Co. Ltd., Shaanxi 710001, China

Abstract
This study investigates the influence of compaction mechanisms and corresponding cement paste thickness on the properties of porous concrete. Using Proctor and Marshall hammers, cylindrical specimens were compacted in both 3-layer and 5-layer configurations with 25 blows per layer. Two aggregate size ranges, 4.75-8.0 mm and 8.0-12.5 mm, were utilized. Experimental evaluations using the both compaction methods demonstrated their effectiveness in producing a uniform mix, as evidenced by consistent measurements of compressive strength, density, porosity, and permeability. While compaction energy influences void structure, cement content has a more significant effect on compressive strength, indicating that optimizing cement content is key to achieving desired strength. MATLAB image analysis showed effective cement paste thickness (d50) ranged from 0.485 mm (Marshall 5-layer) to 0.605 mm (Proctor 3-layer), with over 50% of values below 0.6 mm and a peak at 0.1 mm. Cement paste thickness is primarily controlled by cement content rather than compaction energy and shows a positive correlation with compressive strength. Overall, increasing cement paste thickness enhances strength. Furthermore, a two-factor ANOVA was performed to statistically evaluate the effects of aggregate size and compaction method, confirming that compaction method significantly influences compressive strength, while both factors significantly affect permeability. These results highlight the importance of managing compaction technique, cement paste distribution and aggregate size to balance mechanical performance and permeability in porous concrete design.

Key Words
cement paste thickness; compaction mechanisms; compressive strength; image analysis; permeability; porosity; porous concrete

Address
Thaman Bahadur Khadka, Gokarna Bahadur Motra, Bharat Mandal, Kshitij C. Shrestha: Department of Civil Engineering, Pulchowk Campus, Tribhuwan University, Lalitpur, Nepal

Abstract
As one of the most important structural materials in the construction industry, concrete has long used Ordinary Portland Cement (OPC) as the main cementing material. However, the preparation process of cement has great problems of carbon emission and energy consumption, and a large amount of solid waste is attached, Cause serious environmental pollution. Obviously, the preparation of concrete with OPC no longer meets the requirements of "sustainable development". Therefore, the development of a new green material that can not only have the strength of cement but also can save energy and environmental protection is the current urgent need. In this paper, Mixed Coal gangue Geopolymer Concrete (MCGC) is prepared with coal gangue, fly ash and slag as raw materials. On this basis, steel fibers with different properties are selected. An experimental study on the mechanical properties of Steel Fiber reinforced Mixed Coal gangue Geopolymer Concrete (SFMCGC) was carried out, and the microstructure was analyzed by means of SEM and microhardness testing. To explore the toughening mechanism of SFMCGC, in this paper, it is found that the mechanical properties of MCGC are greatly improved by the three types of steel fibers. Through microscopic test analysis, it is found that the vertical and horizontal distribution of fibers plays a "bridge" effect, blocking the generation of micro cracks and the development of long cracks, and ensuring the integrity of the specimen. However, if the fiber content is too high, bubbles will be introduced to different degrees, which will affect the porosity and density of the specimen.

Key Words
geopolymer concrete; mechanical properties; microstructure; steel fiber; toughening mechanism

Address
Yuting Deng: School of Architectural Engineering, Sichuan University of Arts and Science, Dazhou 635000, China
Rui Xie: School of Intelligent Manufacturing, Sichuan University of Arts and Science, Dazhou 635000, China
Ge Tang: Library, Sichuan University of Arts and Science, Dazhou 635000, China
Hongbin Peng: School of Architectural Engineering, Sichuan University of Arts and Science, Dazhou 635000, China

Abstract
In construction, anchors for concrete are essential devices that connect structural and non-structural components to concrete structures. However, in many numerical analyses, anchor connections are interpreted with fixed or restrained boundary conditions, and anchors are separately evaluated for tension and shear loads according to ACI 318 standards. Numerous studies evaluating anchor performance have been conducted since the 1970s, leading to formalization and standardization based on various research findings to date. However, research on the loaddisplacement relationship of anchors is still insufficient, especially regarding the development of numerical models for anchor systems based on this relationship. Additionally, recent studies indicate significant degradation in anchor performance under repetitive freeze-thaw exposure conditions for post-installed anchors, whereas performance evaluations under such conditions have not been conducted for cast-in-place anchors. Therefore, this study conducted to: 1) analyze the load-displacement relationship of anchors subjected to combined tensile and shear loads, 2) analyze changes in concrete strength and anchor performance due to freeze-thaw exposure, and 3) propose and compare a numerical model for anchors that simulates the load-displacement relationship based on anchor test results. As result of this study, confirmed that concrete compressive strength varies with freeze-thaw cycles, leading to decreased performance of cast-in-place anchors. Furthermore, the proposed numerical model for anchors confirmed significant alignment with experimental results in terms of peak load and deformation energy within specific displacement ranges.

Key Words
cast-in-place anchor; combined load; freeze and thaw; head bolt; numerical model

Address
Yeongseok Jeong: KALIS Institute of Technology, Korea Authority of Land & Infrastructure Safety, Jinju 52856, South Korea
Suchart Limkatanyu: Department of Civil Engineering, Prince of Songkla University, Songkla, Thailand
Jinsup Kim: Department of Civil Engineering, Gyeongsang National University, Jinju 52828, South Korea
Minho Kwon: Department of Civil Engineering, Gyeongsang National University, Jinju 52828, South Korea

Abstract
This investigation focuses on the connection between reinforced concrete beams' mechanical and corrosion-resistant qualities and the application of nanoparticles. By adding different combinations of nanomaterials to the cement mix, such as nano-magnesium oxide (NMO) and nano-metakaolin (NM), the effects of these materials on both fresh and cured concrete are examined. To assess the compressive and flexural strength, tests were conducted at intervals of 7, 14, and 28 days for cubes, prisms, and beams. The goal is to determine how concrete's mechanical qualities are affected by varying percentages of cement substitution with nanomaterials. When 3% nano-magnesium oxide is added to the concrete, the characteristics are similar to those of regular concrete. Furthermore, the study examines how resistant reinforced concrete beams containing nanoparticles are to corrosion. To ascertain the beams' resistance to corrosion, tests including resistivity, half-cell potential, and fast chloride permeability are used. Certain combinations of nanoparticles are expected to improve the concrete's mechanical qualities and, consequently, its corrosion resistance. The research's conclusions might improve the robustness and lifetime of reinforced concrete buildings in several uses.

Key Words
cement concrete; corrosion resistance; mechanical properties; nano-magnesium oxide; nanometakaolin

Address
Vinodhini Chidambaram, Viswanathan Rajeshkumar: Department of Civil Engineering, KPR Institute of Engineering and Technology, Coimbatore, 641047, India

Abstract
This study investigates the long-term durability of ultra-high-performance concrete (UHC altered with metakaolin (MK) and kieselguhr earth (KE). These materials were used as sustainable alternatives to silica fume and fly ash. Four UHC pastes were developed and tested. Durability performance was evaluated through freeze-thaw resistance, chloride ion permeability, sulfate attack, and drying shrinkage under different curing regimes. All UHC pastes showed excellent freeze-thaw resistance. No mass loss and 100% relative dynamic modulus were recorded after 300 cycles. The control paste exhibited a 23% reduction in modulus of rupture after freeze-thaw exposure. In contrast, the MK and MK-KE pastes showed reductions of only 3.68% and 3.6%, respectively. Chloride permeability was significantly reduced with MK and KE incorporation. Complete replacement of fly ash with MK reduced the total charge passed by 52.9% and increased surface resistivity by 423%. The KE paste showed a 35.2% reduction in charge passed. Sulfate resistance was excellent for all pastes. Length expansion remained below 0.01% at six months, far lower than the ASTM C1012 limit of 0.10%. The MK paste showed the lowest expansion of only 0.001%. Drying shrinkage depended strongly on curing conditions. Under air-dry curing, shrinkage ranged from 748 ue to 1002 ue. The MK paste showed the lowest shrinkage, while the KE paste showed the highest. Under moist curing, shrinkage was significantly reduced. The KE paste recorded the lowest value of 215

Key Words
chloride permeability; drying shrinkage; durability; kieselguhr earth; metakaolin; ultra-highperformance concrete

Address
Umara Nasir: Department of Civil Engineering, University of Engineering and Technology, Taxila, 47050, Pakistan
Nejib Ghazouani: Mining Research Center, Northern Border University, 73213 Arar, Saudi Arabia
Khaled Mohamed Elhadi: Civil Engineering Department, College of Engineering, King Khalid University, Saudi Arabia; Center for Engineering and Technology Innovations, King Khalid University, Abha 61421, Saudi Arabia

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