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Fracture Toughness of Fibrous Concrete Incorporated with Treated Recycled Aggregates
No full textThis paper examines the effect of recycled concrete aggregate (RCA) on the behavior of concrete, particularly when combined with different fiber mesh and treatment techniques. Recycled concrete aggregate was treated using two treatment methods. Method 1 used a mix of cement, silica fume, and water, while Method 2 combined cement, silica fume, water, sand, and superplasticizer. Two types of fiber, glass and polypropylene (plastic) fiber mesh, were placed across the expected crack path to study their effect on crack resistance. A total of 24 prisms were cast and tested. Tests measured slump, absorption, unit weight, compressive strength, and fracture toughness. The findings indicate that using recycled concrete aggregate decreases strength and workability compared to normal aggregate. Treated recycled aggregate enhanced the strength, especially in Method 2, which provided compressive strength even higher than normal aggregate. However, fracture toughness decreased due to the sudden formation of cracks. Interestingly, concrete made with untreated recycled concrete aggregate and glass fiber exhibited better crack resistance and fracture toughness. This study compares RCA treated using two different methods and reinforced with two types of fiber mesh, showing that minor changes in the mix design can enhance the behavior of concrete made with RAC
Effect of Incorporating Hematite Powder on Torsional Behavior of High Strength Steel Fiber Reinforced Concrete Members
No full textThis research aims to investigate the effect of hematite powder on the first cracking and ultimate torsional resistance, crack patterns, and angle of twist of high-strength concrete beams strengthened with steel fibers under pure torsion. The study was carried out in two stages. The first stage consisted of six hollow cross-section beams to determine the best ratio and type of steel fiber that provide the highest torsional resistance. The second stage aimed to find the optimal ratio of hematite powder that can improve the torsional resistance of high-strength steel fiber-reinforced concrete without causing implementation problems. This was achieved by testing six hollow cross-section beams with hematite ratios of 0.5%, 1%, 1.5%, 2.5%, 3.5%, and 5% as cement replacements. The results showed that using hematite powder up to 2.5% as a cement replacement, combined with a 1.5% mix of steel fibers (50% end-hooked and 50% corrugated), increased both the first cracking and ultimate torque, along with a relative increase in the angle of twist. Additionally, it delayed crack development, reduced crack width, and increased the number of cracks at failure
Behavior of Deep Beams with Different Proportions of Recycled Plastic Type HDPE Instead of Coarse Aggregate
No full textOne of the most appealing strategies in the ongoing effort to lessen humans' impact on the environment is using waste plastic as coarse particles in concrete. This innovative approach addresses the pressing issue of mounting plastic waste and aims to diminish the adverse effects of traditional building materials, such as natural aggregates, on the environment. Plastic waste as coarse aggregates exemplifies a professional dedication to creating a resilient infrastructure that mitigates environmental harm and contributes to a greener future for future generations. Eight deep beams were cast with sustainable concrete that was made from two mixtures: one in normal strength (C30) and the other in high-strength concrete (HSC) (1% Hyperplast PC200 of cement) that included HDPE plastic, which was taken from fruit boxes that had been crushed and used in 10, 20, and 30 percentage volumetric proportions as a substitute for coarse aggregate. The two still intact have no HDPE replacement and serve as each deep beam's reference deep beam. Shear failure and ductility in the second group were slightly lower than 2% compared to the reference beam for B30. It can be argued that while the replacement has positive environmental impacts, the 23.5% loss in strength is unwanted, while the 2% decline in ductility is acceptable. While maintaining a competent structural flexural behavior, the first group demonstrated an increase in shear failure by the replacement rate (20%, 30%), and the 10% replacement rate dropped by a tiny percentage (1.25%) in comparison to the reference specimen
Seismic Response Analysis of Buckling-Restrained Brace Frames Considering Brace Performance Degradation
No full textTo elucidate the degradation mechanisms of the hysteretic behavior of buckling-restrained braces (BRBs) in hot–humid service environments and their implications for structural seismic performance, this study tested six BRBs of identical specifications under different numbers of hygrothermal cycles (0, 24, 48, 72, 96, and 120), combining alternating high–low temperature hygrothermal exposure with subsequent quasi-static cyclic loading. The evolution of hysteretic performance parameters with cycle count was quantified. Test results indicate that hygrothermal cycling induces corrosion of the steel core and deterioration of the unbonded material, weakening interfacial bond strength and increasing axial friction effects; consequently, the tensile yield load, elastic stiffness, and ultimate tensile capacity decrease. Based on the experimental observations, a modified Bouc–Wen model was employed to simulate BRB hysteretic nonlinearity, and the identified parameter evolution closely reproduced the measured trends. The degradation model was further incorporated into time-history analyses to assess the influence of BRB performance deterioration on structural response for four representative bracing layouts: single-diagonal (symmetric), single-diagonal (asymmetric), chevron (inverted-V), and multi-story X-braced schemes. All layouts significantly reduced seismic responses; among them, the chevron configuration exhibited the lowest sensitivity to degradation, with response amplification after 120 hygrothermal cycles markedly lower than that of the single-diagonal asymmetric scheme. The findings provide an experimental basis and design reference for seismic design and durability assessment of structures in long-term hot–humid service regions
Groundwater Quality and Irrigation Suitability Assessment Using Geochemical and GIS-Based Approaches in Arid Regions
No full textIn arid and semi-arid climates, such as Iraq's Salah Al-Din Governorate, the availability of surface water is much lower than demand, so groundwater becomes a vital resource. Groundwater is one of the basic needs for agricultural irrigation, and therefore this study presents a suitable groundwater suitability assessment for agricultural irrigation based on a comprehensive assessment of groundwater geochemical properties and spatial distribution using the kriging technique within Geographic Information Systems (GIS). Key water quality parameters, including EC, TDS, pH, Cl⁻, Na⁺, K⁺, NO₃⁻, HCO₃⁻, CO₃²⁻, SO₄²⁻, Ca²⁺, and Mg²⁺, were determined in a total of 51 wells across the study area. In addition, two wells located in the Al-Alam District of Salah Al-Din Governorate were remeasured in 2025 to assess changes in water levels. These measurements were compared to the static water levels recorded in 2014 for one well and in 2008 for the other. To determine irrigation suitability, the Water Quality Index, Sodium Adsorption Ratio, Residual Sodium Carbonate, and Total Hardness were calculated and analyzed. Groundwater quality was spatially variable, but several areas exceeded the FAO limits for safe agricultural use at all groundwater depths considered owing to salinity, sodicity, and anthropogenic contamination. Spatial mapping using GIS identified the risk zones and assisted in recommending appropriate management practices for sustainable groundwater development. Such findings emphasize the importance of regular monitoring together with appropriate irrigation management and remediation measures to reduce groundwater degradation and maintain agricultural development in Salah Al-Din Governorate
Statistical (SPSS) Models: Ultimate Uplift Capacity of Horizontal Square Anchor Plate
No full textThis paper examines the relationship between ultimate capacity and vertical displacement for single anchors and line anchor groups (1×2), (1×3), (1×4), and (1×5), in relation to the number of anchors and the embedment depth. Studies addressing statistical analysis in this area are limited; therefore, it was considered appropriate to conduct a statistical investigation to support this field with analytical results and to provide a foundation for future research. The statistical analysis for the single anchor plate indicated that the correlation between ultimate capacity, number of anchors, and embedment depth was strong, with acceptable values of R and R² and a well-fitting mathematical model. In contrast, vertical displacement showed insufficient mathematical representation when analyzed against the number of anchors and embedment depth, as vertical displacement is influenced by additional factors such as loading duration (creep effects), soil unit weight, plate shape and dimensions, internal friction angle, and moisture content, rather than by ultimate capacity alone. When the number of anchor plates in a group exceeds three, the vertical displacement at system failure increases due to the reduced strength of the soil associated with larger anchor groups
Advanced Retrofitting Solutions for RC Slabs: CFRP, ECC, and Steel Plate Comparison
No full textRetrofitting reinforced concrete (RC) slabs is crucial for enhancing their flexural strength, ductility, and durability, particularly in aging or seismically deficient structures. This study aims to evaluate and compare the effectiveness of three retrofitting techniques: steel plate bonding, carbon fiber reinforced polymer (CFRP) sheets, and engineered cementitious composites (ECC) with expanded steel mesh in improving the structural behavior of RC slabs. The research integrates both experimental testing and numerical analysis using ABAQUS finite element modeling to assess load–deflection behavior, failure mechanisms, and strength enhancement. The findings revealed that the use of CFRP sheets and ECC with expanded mesh significantly improved the slabs’ structural performance, increasing ultimate load capacity by up to 58% and ductility by more than 40% compared to the control specimens. Conversely, steel plate retrofitting showed inferior performance due to inadequate interfacial bonding. The numerical results exhibited strong agreement with the experimental data, with an average FEM-to-test ratio of 1.04. The study highlights the superior efficiency of CFRP and ECC techniques in strengthening RC slabs, offering enhanced deformation capacity, energy dissipation, and overall seismic resilience, which contributes to the ongoing development of sustainable and high-performance rehabilitation strategies for concrete structures
Influence of Polypropylene Fiber on Mechanical and Shrinkage Behavior of Porcelain Based Geopolymer
No full textThis study examines the effects of polypropylene (PP) fiber content and initial curing temperature on shrinkages, mechanical properties, and microstructural characteristics of porcelain-based geopolymers. Geopolymer mixes were prepared with PP fiber dosages of 0.5%, 1.0%, 1.5%, and 2.0% by weight and initially cured at 60 °C, 75 °C, 90 °C, and 105 °C. Autogenous and drying shrinkage were monitored at 24 h, 72 h and 3, 7, 14, 21, 28, 60, 90, and 120 days, while compressive and splitting tensile strengths were tested at 3, 7, 14, 21, and 28 days. The results demonstrated that the incorporation of PP fiber not only shortened the setting time but also significantly reduced both autogenous and drying shrinkage of the geopolymer mortar. The most favorable performance was observed in specimens containing 2.0% PP fiber cured at 105 °C, which exhibited the lowest shrinkage values. Autogenous shrinkage was 439 μɛ at 24 h and 392 μɛ at 120 days, while drying shrinkage was 544 μɛ at 24 h and 194 μɛ at 120 days. Increasing fiber content decreased porosity, producing a more compact, homogeneous matrix and improving mechanical performance of concrete specimens, particularly splitting tensile strength; the optimal dosage was 2%, yielding 28‑day compressive strength of 41.03 N/mm² and splitting tensile strength of 7.65 N/mm²
Complex Geodetic Monitoring of the Massive Sports Structures by Terrestrial Laser Scanning
No full textThe paper describes the rigorous approach to studying and analyzing the results of geodetic monitoring of massive sports structures. The monitoring results for two ski jumps in Almaty, Republic of Kazakhstan, are considered a case study. The suggested approach is based on the combined use of geodetic measurements and their comparative analysis with the structural analysis results of the structure using the finite element method. The structural analysis was carried out for various loads and their combinations, e.g., dead weight, snow load, wind load, etc. The article's aim is twofold. The first is to develop an appropriate algorithm and technology to accomplish geodetic monitoring, including the assignment of allowable monitoring accuracy. This goal was achieved by the results of structural analysis that helped to determine the allowable displacements and zones of maximum stress. These values defined the necessary observation accuracy and the places for the deformation targets' installation. Thus, the appropriate monitoring network around the complex of ski jumps was created. Geodetic monitoring was carried out using terrestrial laser scanning. Four observation epochs were conducted from autumn 2020 until summer 2022. The second aim is to analyze the monitoring results to determine the actual structure displacements and make conclusions concerning the allowance of these displacements for further structure exploitation. The monitoring results were studied using the structural analysis and B-spline displacement simulation. The results demonstrated no significant displacements of the ski jump ramps. The displacements for landing hills reached 60 mm, which is the allowable value. Doi: 10.28991/CEJ-2025-011-03-05 Full Text: PD
Urban-Rural Differences in Electric Vehicle Adoption Intentions: Integrated TAM, TPB, UTAUT with Environmental Identity
No full textObjectives: This study examines urban-rural differences in electric vehicle (EV) adoption intentions to inform geographically targeted policy implementation for Thailand's goal of 30% EV production by 2030. Methods/Analysis: We integrated the Technology Acceptance Model, Theory of Planned Behavior, and Unified Theory of Acceptance and Use of Technology with environmental identity and trialability constructs. Data from 3,595 respondents (2,311 urban, 1,284 rural) across Thailand were analyzed using structural equation modeling and measurement invariance testing. Findings: Results revealed distinct adoption mechanisms between geographical contexts. Urban areas demonstrated stronger effects in system-related perceptions, with perceived ease of use more strongly influencing perceived usefulness (β=0.631 vs. 0.587) and perceived usefulness having a greater impact on behavioral intention (β=0.445 vs. 0.353). Rural areas showed stronger influences of individual characteristics and social factors, with personal innovativeness more strongly affecting attitudes (β=0.216 vs. 0.157) and environmental identity showing greater impact on perceived ease of use (β=0.350 vs. 0.291). Novelty/Improvement: This research uniquely combines established technological adoption theories with geographical context analysis, providing evidence-based recommendations for differentiated EV promotion strategies that address the specific challenges of urban and rural environments in developing countries. Doi: 10.28991/CEJ-2025-011-05-010 Full Text: PD