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Effect of Different Ceramic Waste Powder on Characteristics of Fly Ash-Based Geopolymer
No full textThe escalating demand for construction materials driven by rapid population growth has heightened the reliance on cement binders, resulting in increased CO2 emissions from the cement industry. Geopolymers, considered environmentally friendly alternatives, have been explored in various studies to address this challenge. This research specifically investigates the impact of different types of ceramic waste bricks (BT), floor tiles (FT), roof tiles (RT), and sanitary ceramics (ST) on the physical and mechanical properties of fly ash-based geopolymer mortar. To provide a comprehensive understanding, this research examines the compressive strength, mineral phase, chemical bonds, and microscopic evolution of fly ash geopolymer mortar incorporating varying proportions of each ceramic waste type (25% and 50% fly ash replacement). A consistent mixture of Na2SiO3and NaOH was used for the alkaline solution in all formulations. The curing process was carried out at room temperature for 7, 14, and 28 days prior to the compressive strength test. The result revealed that the inclusion of 25% BT experienced higher strength compared to the control sample after 14 days, but the strength became comparable after 28 days at 40.24 MPa. A reduction in strength was evident with the addition of other ceramic components. Moreover, higher incorporation of CWP correlated with a faster setting time for fresh geopolymers. This was also linked to the degree of gel formation, as indicated in the microstructure images. The emergence of plagioclase minerals was evident in all formulations of the geopolymer products under XRD analysis, while the bond of the geopolymer signature, Si-O-T (T = Si or Al), was identified from the infrared spectra. The microstructure of the binder showed a geopolymer matrix alongside unreacted fly ash particles. Overall, CWP replacement up to 25% can be potential in fly ash geopolymer without sacrificing significant strength loss and remaining in the range of normal strength mortar. Doi: 10.28991/CEJ-2024-010-02-06 Full Text: PD
Recycling of Eggshell Powder and Wheat Straw Ash as Cement Replacement Materials in Mortar
No full textCement is among the important contributors to carbon dioxide emissions in modern society. Researchers are studying solutions to reduce the cement content in concrete to minimize the negative impact on the environment. Among these solutions is replacing cement with other materials, such as waste, which also poses environmental damage and requires landfill areas for disposal. Among these wastes are eggshell powder ash (ESPA) and wheat straw ash (WSA), which were utilized as cement substitutes in green mortar production. Thirteen mixtures were cast, one as a reference without replacement and twelve others that included replacing ESPA and WSA (single and combined) with cement in 2%, 4%, 6%, and 8% proportions of cement's weight. The mechanical (compressive and flexural strength), microstructural (SEM), and thermogravimetric analysis (TG/DTA) properties of all mixtures were examined. The results showed a remarkable improvement in mechanical properties, and the best improvement was recorded for the (4%ESPA+4%WSA) mixture, which reached 73.3% in compressive strength and 56% in flexural strength, superior to the reference mixture. Furthermore, SEM analyses showed a dense and compact microstructure for the ESPA and WSA-based mortars. Therefore, the WSA and ESPA wastes can be recycled and utilized as a substitute for cement to produce an eco-friendly binder that significantly improves the microstructural and mechanical characteristics of mortar. In addition, combining the two materials also presents a viable option for creating a sustainable ternary blended binder (with cement) that boasts superior properties compared to using the WSA or ESPA individually. Doi: 10.28991/CEJ-2024-010-01-05 Full Text: PD
Influence of Gypsum on the Residual Properties of Fly Ash-Slag-Based Alkali-Activated Concrete
No full textHigh-temperature exposures of concrete lead to serious damage in concrete structures, resulting in the significant decay of mechanical properties and spalling of concrete. Alkali-activated concretes (AAC) of blended aluminosilicate precursors and activators have been proven to have higher thermal endurance than conventional portland cement concrete. Incorporation of gypsum (GY) in alkali-activated systems has proven to positively impact the mechanical properties when adopted in controlled amounts. GY releases SO42- to the binder system, which helps in the formation of ettringites, along with Ca2+, which leads to the formation of hydrates. This causes a reduction in porosity and improves strength gain. Incorporation of GY into the fly ash-slag-based alkali-activated system further improves thermal endurance by retaining considerable residual strengths even after 800°C exposure. In the present study, the influence of GY on the residual mechanical properties of fly ash-slag-based AAC is investigated to explore the thermal endurance of the ternary mix at elevated temperatures. The mechanical properties of fly ash (FA), Ground Granulated Blast Furnace Slag (GGBS), and gypsum (GY) ternary blended AAC subjected to elevated temperatures are studied in comparison with conventional portland cement concrete (control mix). AAC design mixes with varying proportions of GY as a replacement to FA-GGBS precursor are tested for mechanical properties to obtain the optimum mix. The residual mechanical properties of the FA-GGBS-GY optimum ternary AAC mix are obtained after exposure to elevated temperatures up to 800°C. The morphology and microstructural characteristics of AAC are studied by Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) analyses to investigate the influence of gypsum on the thermal endurance of concrete when exposed to elevated temperatures. Improved thermal endurance is observed for AAC when FA-GGBS precursors are replaced with 5% of GY as compared to the thermal endurance of conventional portland cement concrete (PCC) of the same compressive strength. Doi: 10.28991/CEJ-2024-010-03-017 Full Text: PD
Artificial Neural Network-Based Prediction of Physical and Mechanical Properties of Concrete Containing Glass Aggregates
No full textThis comprehensive study analyzes the use of crushed glass as both fine and coarse aggregate in concrete, as well as the prediction accuracy of Artificial Neural Networks (ANN). The primary objectives are to understand the interactions between concrete's constituents and to assess the accuracy of ANN models in predicting concrete's mechanical and physical properties. This is achieved using a two-decade experimental results dataset of concrete's compressive and tensile strengths, slump, density, and the corresponding mix design proportions, including waste glass aggregate. A series of 70 concrete samples were carefully built and tested, with compressive strengths varying from 12 to 71 MPa and glass aggregate percentages ranging from 0-100%. These samples served as the basis for the creation of an input dataset and ANN targets. The ANN model underwent intensive training, validation, testing, and statistical regression analysis. The ANN models are exceptionally accurate, with a continuously low error margin of roughly 2%, highlighting their usefulness in matching experimental and predicted results. Validation techniques highlight the models' dependability, with consistently high coefficients of determination (R-values), including 0.99484, demonstrating their robustness in replicating complicated concrete properties. The data analysis shows a unique pattern, with optimum glass aggregate percentages in the range of 10–20%. Beyond this range, there is a noticeable decline in concrete properties. Finally, the study confirms the efficacy of ANN in predictive modeling while also validating the potential of crushed glass to replace natural aggregates in concrete. Doi: 10.28991/CEJ-2024-010-05-018 Full Text: PD
The Hybrid System of Fluidization and Sediment Flushing for Maintenance Dredging Technique
No full textThe Hybrid System of Fluidization-sediment flushing is a dredging technique that combines the functions of fluidization and suction in the same fluidization pipe using a perforation pipe. The purpose of this study was to address an easier dredging method using fluidization pipes. 2-dimensional (2D) experimental physical modeling research and multiple linear regression analysis were used to process the test result. The results found that for optimal sediment flushing after the sediment layer was agitated by fluidization, the influence parameter was analyzed must follow the limitations of the experimental result, such as the hole diameter (Df) is not more than 5 mm (Df < 5 mm), the hole distance (É‘) is less than 5 cm (É‘/db < 5 cm), the pump head (HP) is small, and the fluidization pipe depth/sediment thickness (db) can be larger. The research findings are presented in the correlation equation which indicates the relationship of dimensionless parameters was Vs/Vw = 1/Df ((É‘/db), (HP/db), (t.(gí—0.5)/(db0.5)), (v/(g.db(S – 1)0.5)) which can be applied to 3-dimensional experiments and field experiments. One of the advantages of the hybrid system of fluidization-flushing sediment is its ease of use and lack of impact on the aquatic environment as a dredging technique. Doi: 10.28991/CEJ-2024-010-07-013 Full Text: PD
Evaluating the Efficiency of Alkaline Activator with Silica-Rich Wastes in Stabilizing Cadmium-Contaminated Soil
No full textContaminant soil remediation has potential engineering applications with various stabilization techniques addressing heavy metal contamination. Conventional soil stabilizers, however, have an environmental impact, promoting international research into environmentally friendly alternatives. Using waste byproducts to produce geopolymer binders as new green cementitious materials can provide an environmentally friendly and effective option for soil improvement. Silica-rich wastes have been advanced as a sustainable option for soil stabilization. The effectiveness of alkaline-activated silica-rich wastes in stabilizing cadmium-contaminated soil and its potential engineering utilization remain of profound significance, demanding sustained and rigorous research investigation. Cadmium was immobilized in silty clay soil by rich silica waste products”fly ash, silica fume, and rice husk ash”at various percentages with 4.5 and 6.5-molar alkaline activators. Unconfined compressive strength tests assessed soil behavior, while Toxicity Characteristic Leaching Procedure (TCLP), pH tests, X-ray diffraction, and scanning electron microscope analyses explained cadmium immobilization mechanisms. The experimental results revealed that alkali-activated silica-rich wastes enhanced strength and cementitious properties and reduced cadmium leaching in the contaminated silty clay. The Finite Element Method was also employed to analyze the bearing capacity of the stabilized contaminated soil. The numerical results support the experimental results and confirm increased soil strength and reduced compressibility, endorsing the efficacy of the stabilization techniques and environmental benefits. Doi: 10.28991/CEJ-2024-010-07-04 Full Text: PD
Utilization of Hybrid SIFCON to Improve Performance and Properties of Slab System Openings
No full textThis research aims to enhance Slurry Infiltrated Fibrous Concrete (SIFCON) by incorporating both long and short fibers, with the goal of increasing ductility and mechanical properties behavior. The study also evaluates the effectiveness of SIFCON in strengthening two-way reinforced concrete slabs with large openings. Various SIFCON mixes were created, integrating hooked-end fibers, micro steel fibers, and different volume ratios (Vf) of hybrid steel fibers (one-third, one-half, and two-thirds). A reference mix with 2% hybrid fiber-reinforced concrete (SFC) was formulated for comparison. Hybrid SIFCON samples demonstrated superior mechanical properties compared to those reinforced with hooked fibers, showing higher compressive strength, cylinder compressive strength, flexural strength, and direct tensile strength by 14%, 13.9%, 38.2%, and 58.2%, respectively, at 28 days, but a lower splitting tensile strength by 24%. Compared to micro steel fiber-reinforced samples, hybrid SIFCON exhibited higher compressive strength, cylinder compressive strength, flexural strength, and splitting tensile strength by 18.2%, 51%, 167.5%, and 43.6%, respectively, but a lower direct tensile strength by 7.4%. The study involved nine two-way square slabs with various mixtures of normal concrete, mortar-infiltrated fiber concrete, and full SIFCON. Control samples were constructed using normal-strength concrete. The application of SIFCON increased punching shear strength by 3.21% to 154.25% compared to the control samples. Doi: 10.28991/CEJ-2024-010-11-07 Full Text: PD
The Consequence of the Involvement of Flexural, Compression, and Punching Reinforcement Upon Punching Strength
No full textFlat slabs have an important role in concrete buildings due to their architectural flexibility and speed of construction. Punching shear is one of the most important phenomena to be considered during the design of reinforced concrete flat slabs, as this type of failure is brittle and does not predict previously raised alarms before failure. The main factors that affect punching strength in concrete are compressive strength, flexural reinforcement, and punching reinforcement in the form of stirrups, shear studs, or other shapes. This paper is part of a research program operated at the reinforced concrete laboratory of the Faculty of Engineering, Cairo University, to evaluate the contribution of horizontal flexural reinforcement, horizontal compression reinforcement, and vertical punching reinforcement on the punching strength of reinforced concrete flat slabs. In this research, fifteen half-scale specimens are cast and tested. The specimens had dimensions of 1100í—1100 mm and a total thickness of 120 mm. All specimens were connected to a square column of dimensions 150í—150 mm and loaded at the four corners with a supported span of 1000 mm. The main parameters considered in this research included spacing between stirrups, width of the stirrups, number of stirrup branches, ratio of the compression reinforcement, and ratio of the tension reinforcement. During testing, ultimate capacity, steel strain, cracking pattern, and deformation were recorded. The experimental results were analyzed and compared against values estimated from different international design codes. Doi: 10.28991/CEJ-2024-010-09-014 Full Text: PD
Seismic Isolators Layout Optimization Using Genetic Algorithm Within the Pymoo Framework
No full textIn most previous studies, seismic base isolation system optimization has mainly focused on determining isolation layer parameters. However, the subsequent steps of isolator device selection and positioning can significantly impact overall system performance. To address these shortcomings, we propose an alternative optimization approach demonstrated through two models: regular and irregular 8-storey reinforced concrete structures. This approach utilizes the Pymoo framework and commercially available isolators to find optimal isolator layout configurations in two steps. First, using the equivalent lateral force (ELF) procedure, an initial population of seismic isolators meeting shear strain, base shear coefficient, and buckling requirements was randomly selected from suppliers' elastomeric bearing catalogs. Second, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) was used to improve the seismic response of the models under the fast nonlinear analysis (FNA) method by minimizing peak roof acceleration, inter-story drift ratio, displacement of the isolated base layer, as well as maximizing the fundamental period. The results underscore the effectiveness of this approach in improving seismic response. Compared to fixed-base structures, the optimal solutions achieved more than double the fundamental period, reduced peak roof acceleration by over 70%, and diminished base shear force by approximately 50%. This methodology can serve as a reference for future research across various structure types, including hybrid isolation systems and steel structures. Doi: 10.28991/CEJ-2024-010-08-07 Full Text: PD
Comparison of Multi-Objective Metaheuristics for Discrete Optimization of Steel Trusses Using Direct Analysis
No full textThis study enriches structural optimization research using direct analysis for steel truss structures, which is often hampered by high computational demands. The main objective of this work is to evaluate multi-objective optimization algorithms in truss sizing optimization with discrete variables, focusing on minimizing total mass and controlling inter-story drift under multiple load combinations. Five leading multi-objective metaheuristic algorithms were assessed: SPEA2, GDE3, NSGA2, MOEA/D, and the novel MOEA/D-EpDE, which uniquely combines MOEA/D with Dynamical Resource Allocation and pbest Differential Evolution. Four performance indicators, such as Generational Distance (GD), GD Plus (GD+), Inverted GD+ (IGD+), and Hypervolume (HV), were utilized. Findings from four truss optimization problems revealed that all considered algorithms located feasible optimal solutions, but MOEA/D-EpDE excelled, consistently securing the lowest GD, GD+, IGD+, and anchor point values, along with the highest HV values in most scenarios. This indicates its superior capability in addressing the problem efficiently. NSGA2 and MOEA/D also performed well, outperforming GDE3 and SPEA2. This study is pioneering in its application of these algorithms to steel truss optimization via direct analysis, highlighting the potential for advanced computational techniques in structural engineering. Doi: 10.28991/CEJ-2024-010-12-07 Full Text: PD