Browsing by Author "Althaqafi, Essam"

Now showing 1 - 9 of 9

Citation - WoS: 1
Citation - Scopus: 1
Bending Performance of Reinforced Concrete Beams With Partial Waste Glass Aggregate Replacement Assessed by Experimental, Theoretical and Digital Image Correlation Analyses
(Nature Portfolio, 2025) Ozkilic, Yasin Onuralp; Basaran, Bogachan; Aksoylu, Ceyhun; Karalar, Memduh; Zeybek, Ozer; Althaqafi, Essam; Umiye, Osman Ahmed
This study examines the usage of waste glass aggregate (WGA) for the consumption of sustainable reinforced concrete regarding the replacement of fine aggregate (FA) and coarse aggregate (CA). For this purpose, a series of tests consisting of a total of 12 beams were carried out to explore the bending performance. The quantity of the longitudinal reinforcement section area and WGA percentage were selected as the prime variables. For this purpose, the aggregate was swapped with WGA with weight percentages of 10% and 20% for the FA and 10% and 20% for coarse aggregate. The test outcomes revealed that the crack and bending properties of the reinforced concrete beams (RCBs) were greatly affected by the section area of tension reinforcement and the percentage of the WGA. The WGA percentage might be effectively used as 20% of the partial replacement of FA. With the addition of FA to the mixture, the load-bearing capacity of RCB increases. The increase in the WGA percentage by more than 10% might cause a considerable reduction in the capacity of the RCBs, especially when the longitudinal reinforcement ratio is high. Furthermore, the digital image correlation method was used to show the cracks/micro-cracks and to define displacement in RCBs.
Citation - WoS: 13
Citation - Scopus: 15
Effect of Gbfs Ratio and Recycled Steel Tire Wire on the Mechanical and Microstructural Properties of Geopolymer Concrete Under Ambient and Oven Curing Conditions
(Elsevier, 2024) Celik, Ali Ihsan; Karalar, Memduh; Aksoylu, Ceyhun; Mydin, Md Azree Othuman; Althaqafi, Essam; Yilmaz, Fatih; Umiye, Osman Ahmed
In this study, the effects of waste steel wire ratios, granulated blast furnace slag (GBFS) ratios, and different curing methods on geopolymer concrete (GPC) were investigated. For this purpose, 12 mixtures were produced and eight of them were cured under ambient conditions and the remaining four were cured in an oven. Steel wire ratios and GBFS ratios were added to GPC as 0-1-2-3 % and 0-10-20 % by volume and weight, respectively. As a result of the mixtures, cubes, cylinders, and beams were obtained and these elements were subjected to compression, tensile, and flexural tests. As a result of the tests, the compressive strengths of the specimens were obtained as 8.5%, 19.7%, and 24.9% for ambient curing and 10.4%, 23.2%, and 32.2% for oven curing, respectively, as the steel wire fiber increased from 0 % to 3 %. The maximum compressive strength of the oven-cured specimen with 3% steel wire fiber was measured as 42.56 MPa. The tensile strength of GPC also increased as the steel wire increased. The highest tensile strength was obtained with 3 % steel wire. In addition, oven curing conditions increased the tensile strength more than ambient curing. The flexural strength (FS) increased by 21.3 %, 29.4%, and 33.8 % with increasing steel wire ratios of 1 %, 2 %, and 3 %, respectively. The FS was further increased by oven curing conditions and the maximum FS was achieved with 3 % steel wire. In ambient curing conditions, a successful geopolymerization was achieved due to the high calcium content in the samples containing 20 % GBFS. This allowed to obtain similar strengths between ambient curing and oven curing. Although the oven curing values were higher, similar results were obtained for the samples cured in an ambient containing 20 % GBFS. As a result of the study, mixtures containing 3 % steel wire and 20% GBFS provided sufficient strength without oven curing and increased the usability of GPC under ambient conditions.
Effect of Stirrup Spacing and Recycled Steel Wires on the Shear and Energy Dissipation of Pultruded GFRP Hybrid Beams
(Sage Publications Ltd, 2025) Ozkilic, Yasin Onuralp; Kalkan, Ilker; Aksoylu, Ceyhun; Madenci, Emrah; Umiye, Osman Ahmed; Althaqafi, Essam; Beskopylny, Alexey N.
The contribution of Recycled Steel Wires (RSW) to the shear strength and behavior of pultruded glass fiber reinforced polymer (P-GFRP) hybrid composite beams with reinforced concrete infill, denoted as P-GFRP beams, was investigated experimentally and analytically in the current study. A total of six specimens with varying RSW ratio and stirrup spacing of the reinforced concrete (RC) core and a fixed shear span-to-beam depth ratio were tested to failure. The addition of RSW to concrete was established to have greater contribution to the beam strength with increasing stirrup spacing, that is, decreasing transverse reinforcement ratio. The contribution of RSW to energy dissipation capacity was found to be more pronounced in the elastic range of beam response as compared to the inelastic range. The theoretical calculations indicated that the RC core prevented the P-GFRP encasement from complete failure due to shear-induced material rupture at the initial stages of loading. By maintaining their integrity, the reinforced concrete-filled box beams (RCFB) were able to resist loading until complete failure associated with flexure-induced material rupture and web compression buckling. A strut-and-tie model providing accurate strength estimates for P-GFRP beams was also proposed.
Citation - WoS: 6
Citation - Scopus: 6
Experimental, Theoretical and Digital Image Correlation Methods to Assess Bending Performance of RC Beams With Recycled Glass Powder Replacing Cement
(Nature Portfolio, 2025) Aksoylu, Ceyhun; Basaran, Bogachan; Karalar, Memduh; Zeybek, Ozer; Althaqafi, Essam; Beskopylny, Alexey N.; Ozkilic, Yasin Onuralp
This study investigates the use of Waste Glass Powder (WGP) as a proportional replacement for cement in sustainable concrete production. In addition, changes in the bending capacity of the Reinforced Concrete (RC) Beams were examined by adding WGP at different rates (0%, 10%, 20%, 30%) to RC Beams with different steel reinforcement ratios (rho s = 0.0077 i.e. Phi 8, rho s = 0.0121 i.e. Phi 10, rho s = 0.0174 i.e. Phi 12). To pursue this goal, 12 test specimens were evaluated and then confirmed to explore the bending productivity. The amount of longitudinal bar section area and WGP proportion were chosen as the key parameters. For this aim, experimental and analytical investigations were carried out by replacing cement with WGP in weight ratios of 10%, 20%, and 30% and considering three different longitudinal reinforcements (rho s = 0.0077 i.e. Phi 8, Phi 10, Phi 12). The test results showed that tension reinforcement section area and WGP proportion dimensions had dissimilar rupture and flexure effects on RC Beams. Furthermore, investigational tests are confirmed with the help of the Digital Imagining Method, and the image processing method was used to identify the cracks/microcracks in RC Beams. Consequently, it is observed that each WGP ratio in the concrete combination has dissimilar bending and rupture properties on the RC Beams for experimental tests-10% of partial replacement of cement. It was found that a WGP ratio of more than 10% can significantly reduce the bending capacity of RC Beams. When the experimental test beams were compared with the analytical results, it was observed that the experimental results and analytical calculations are in agreement.
Optimization of Concrete with Human Hair Using Experimental Study and Artificial Neural Network via Response Surface Methodology and Anova
(Nature Portfolio, 2025) Yildizel, Sadik Alper; Karalar, Memduh; Aksoylu, Ceyhun; Althaqafi, Essam; Beskopylny, Alexey N.; Stel'makh, Sergey A.; Ozkilic, Yasin Onuralp
The increasing demand for sustainable construction materials has prompted the investigation of non-biodegradable waste, such as human hair (HH), for concrete reinforcement. This study seeks to evaluate the impact of HH fiber on the fresh, physical, and mechanical characteristics of concrete. HH was incorporated in varying proportions (1-5% by weight of cement), along with modifications in cement content, to ascertain optimal performance conditions. An extensive experimental program was executed, succeeded by the utilization of Artificial Neural Networks (ANN) to formulate predictive models for compressive strength (CS), flexural strength (FS), and splitting tensile strength (STS). Furthermore, Response Surface Methodology (RSM) and Analysis of Variance (ANOVA) were utilized to identify statistically significant factors and optimize the mix design. The findings indicated that the mechanical performance of concrete enhanced with HH inclusion up to 3%, after which a deterioration ensued, presumably due to inadequate dispersion and workability challenges. The ANN models precisely predicted mechanical outcomes, while the RSM-derived models demonstrated strong correlations, with R2 values of 0.9434, 0.9365, and 0.9311 for CS, FS, and STS, respectively. ANOVA confirmed the significance of model inputs with p-values below 0.05. Furthermore, SEM, EDX, and XRD analyses validated the integration of HH into the concrete matrix and substantiated the observed mechanical properties. This study confirms the feasibility of HH as a sustainable fiber in concrete, enhancing critical performance metrics when applied at optimal dosages. The amalgamation of ANN, RSM, and ANOVA offers a thorough methodology for optimizing innovative concrete composites and clarifying the mechanisms underlying performance enhancement.
Citation - WoS: 1
Citation - Scopus: 2
Shear and Flexural Performance of Reinforced Concrete Beams with Recycled Concrete Aggregates
(De Gruyter Poland Sp ZOO, 2025) Ozkilic, Yasin Onuralp; Althaqafi, Essam; Karalar, Memduh; Aksoylu, Ceyhun
This study investigates the effects of recycled concrete aggregate (RCA) content and stirrup spacing on the structural performance of reinforced concrete beams (RCBs) under flexural and shear loading. A total of 24 RCB specimens were cast with RCA replacement ratios of 0, 10, 20, and 40%, and tested under four different stirrup spacings: 100, 160, 200, and 270 mm. The experimental program evaluated key structural parameters, including load-bearing capacity, stiffness, ductility, and energy dissipation. The results demonstrated that increasing the RCA content generally led to reductions in both flexural and shear strength. The most significant shear strength loss (46.86%) occurred at 40% RCA with 270 mm stirrup spacing, while the highest flexural load reduction (11.24%) was observed in beams with & Oslash;10 longitudinal reinforcement and 40% RCA. Moreover, although higher RCA content generally reduced stiffness, ductility, and energy dissipation, specimens with wider stirrup spacing exhibited relatively better performance under shear, suggesting that transverse reinforcement can partially mitigate RCA-induced performance losses in shear-dominated beams. These findings suggest that while RCA can be used in RCBs, proper detailing of transverse and longitudinal reinforcement is essential to maintain adequate structural performance.
Citation - WoS: 3
Citation - Scopus: 3
Shear and Flexural Performance of Reinforced Geopolymer Concrete Beams Cured Under Ambient and Oven Conditions With Environmentally Friendly Waste Steel Tire Wire Additives
(Nature Portfolio, 2025) Ozkilic, Yasin Onuralp; Celik, Ali Ihsan; Aksoylu, Ceyhun; Karalar, Memduh; Mydin, Md Azree Othuman; Althaqafi, Essam; Umiye, Osman Ahmed
In this study, the effects of Granulated Blast Furnace Slag (GBFS) and Waste Steel Wire (WSW) admixtures on the flexural and shear performances of Reinforced Geopolymer Concrete Beams cured under oven and ambient conditions were investigated experimentally and analytically in detail. The research used 100 mm and 270 mm stirrup spacings and changed GBFS and WSW with 0%, 10%, 20%, and 1%, 2%, and 3%, respectively. To evaluate flexural and shear strength of reinforced GPC, 100 x 150 x 1000 mm samples were made. The results showed how material proportions affect flexural, and shear beam mechanical performance and ductility. In flexural beams, increasing the GBFS ratio to 10% enhanced load bearing capability and preserved ductility. However, 20% of GBFS reduced load bearing capability and brittle fractures. It was found that mixtures with GBFS of 10% and WSW of 3% are optimum for flexural beams. For shear beams, brittle fracture was observed for all GBFS and WSW ratios and ductile behavior was not achieved. Increasing GBFS content to 10% boosted capacity from 2.05 to 19.37%, however increasing it to 20% dropped capacity from 2.72 to 15.10%. Increasing WSW content enhanced load bearing capability, however increasing GBFS content over 10% did not. It is emphasized that different materials and design methods should be investigated to ensure ductile behavior in shear beams. Increasing the WSW ratio from 0 to 3% boosted energy consumption capacity by 2.78 times. But raising the GBFS ratio to 20% reduced energy consumption capacity by 66%. In addition, AS3600 predicted beam damage more correctly in different conventional computations. This study shows that the GBFS ratio should be limited to 10% and the WSW ratio to 3%. This combination maintains ductility in flexural beams and gives a safe design limit in shear beams while increasing load bearing capability. The results obtained provide important information that will shed light on new designs.
Citation - WoS: 13
Citation - Scopus: 15
Shear Performance in Reinforced Concrete Beams With Partial Aggregate Substitution Using Waste Glass: a Comparative Analysis Via Digital Imaging Processing and a Theoretical Approach
(AMER CHEMICAL SOC, 2024) Zeybek, Özer; Basaran, Bogachan; Aksoylu, Ceyhun; Karalar, Memduh; Althaqafi, Essam; Beskopylny, Alexey N.; Stel'makh, Sergey A.
The usage of waste glass aggregate (WGA) associated with the replacement of fine aggregate (FA) and coarse aggregate (CA) is observed to reduce the number of raw materials for sustainable concrete. For this aim, a total of 15 beams were produced, and then investigational experiments were implemented to observe the shear performances. The stirrup spacing and WGA proportion were chosen as the main parameters. FA and CA were exchanged with WGA with weight proportions of 0, 10, and 20%. The experimental investigation results showed that changing stirrup spacing and WGA proportion affected the fracture and shear properties of reinforced-concrete-beams (R-C-Bs). Furthermore, the findings of the test results revealed that the proportion of WGA could be efficiently consumed as 20% of the partial replacement of FA. With the addition of FA to the mixture, the load carrying capacity of R-C-Bs increases. On the other hand, increasing the WGA ratio by more than 10% using CA, together with increasing the stirrup spacing, can significantly reduce the capacity of R-C-Bs. It was observed that the calculated shear strengths of R-C-Bs with inadequate stirrup spacing, based on ACI 318 and EC2 design codes, can be up to 52 and 79% higher than the experimental results for R-C-Bs containing coarse glass aggregate and 21 and 56% higher for R-C-Bs containing fine glass aggregate, respectively. Additionally, an image processing method was applied to describe the damages/microdamages in R-C-Bs. At that point, the findings obtained from the experimental part of the study were confirmed by the results of the image processing method. Although the strains obtained with the image processing method are reliable, it has not been determined exactly where the crack will occur due to the very sudden development of the shear crack at the moment of beam failure.
Citation - WoS: 14
Citation - Scopus: 17
Utilizing Recycled Glass Powder in Reinforced Concrete Beams: Comparison of Shear Performance
(Nature Portfolio, 2025) Karalar, Memduh; Basaran, Bogachan; Aksoylu, Ceyhun; Zeybek, Ozer; Althaqafi, Essam; Beskopylny, Alexey N.; Ozkilic, Yasin Onuralp
In this research, the effect of using waste glass powder (WGP) as a partial replacement for cement on the flexural behavior of reinforced-concrete-beams (R-C-Bs) was investigated. For this aim, a total of 9 specimens were produced, and investigational experimentations were conducted to evaluate the flexural performances of R-C-Bs. Subsequently, the cement was partially replaced with WGP with weight percentages of 0%, 10%, 20% and 30%. Furthermore, the influence of stirrup spacing (SS) in the longitudinal reinforcement on productivity was also examined. The results presented indicate that the efficient WGP percentage might be considered as 10% of the partial replacement of cement. Increasing the WGP percentage within the cement by more than 10% may considerably reduce the ability of the R-C-Bs, noticeably when the lengthwise reinforcement proportion is high. Additionally, the experimental shear strengths of R-C-Bs attained from the flexural tests were compared with the shear capacities estimated using Eurocode 2 and ACI 318 - 19 regulations. It was concluded that the shear capacities calculated with ACI318-19 are much lower than the values calculated with EC2. Furthermore, it may be observed that ACI318-19 calculates the shear capacities of R-C-Bs to be 15-51% higher than those of the experimental results. Furthermore, the Digital Image Correlation (DIC) was used to study the flexural cracks/micro-cracks in R-C-Bs. Comparisons indicate that DIC has similar deformations and fracture properties for the R-C-Bs as the experimental tests. Finally, it was considered that the optimum consumption quantities determined by the results of the present research would be a guide for future investigation.