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2007 research outputs found
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Analysis of Rock Quarry Sand and Bottom Ash Reinforced by Randomly Distributed PET Rings
No full textThe study presented deals with determining the shear strength and deformation properties of coarse-grained waste materials, such as rock quarry sand (RQS) and bottom ash (BA), which can be improved using randomly distributed reinforcements made of polyethylene terephthalate (PET) rings. The tests were executed for a degree of reinforcement n, i.e., a ratio of a PET ring weight to the weight of the dry parent materials, which equals about n = 0.25%, 0.5%, and 1.0% in the case of RQS, and n = 0.5%, 1.0%, and 1.5% in the case of BA. The results showed that the most effective improvement in the shear strength properties can be achieved for n = 0.25 - 0.5% in the case of RQS and n = 0.5 - 1.0 % in the case of BA. Reinforcing RQS by n = 1.0% or BA by n = 1.5% led to a significant decrease in the 1D deformation modulus. The positive effect of randomly distributed PET ring reinforcements on the properties of RQS and BA materials was also demonstrated using physical modeling. An embankment model made of RQS and reinforced by PET rings (n = 0.25 %) can carry up to a 2.8 times greater load than an embankment model made of the parent RQS. An embankment model made of BA with PET rings (n = 0.5%) can carry up to a 2.3 times greater load than an embankment model made of the parent BA. Doi: 10.28991/CEJ-2025-011-05-06 Full Text: PD
Influence of Bacillus Subtilis Bacteria on Strength and Durability of Concrete with Silica Fume
No full textThis study investigates the influence of Bacillus subtilis bacteria on the strength and durability properties of M30 concrete with and without silica fume. The experimental study was conducted on four concrete mix series: conventional concrete (B1), conventional concrete with silica fume (B2), bacterial concrete without any admixtures (B3), and bacterial concrete with silica fume (B4). Silica fume was incorporated at replacement levels of 5% and 10% by weight of cement for the B2 and B4 mix series to evaluate its effect on bacterial activity and concrete performance. The study measured compressive strength, split tensile strength, and water absorption to assess mechanical and durability properties. Results reveal that bacterial concrete (B3 and B4) exhibits improved strength and durability compared to conventional concrete (B1 and B2). Furthermore, silica fume enhances the performance of bacterial concrete due to its pozzolanic action, which refines the microstructure and provides additional nucleation sites for calcium carbonate precipitation by Bacillus subtilis. Among all mixes, B4 with 10% silica fume achieved the highest strength and durability, demonstrating the synergistic effect of bacteria and silica fume. This research highlights the potential of bacterial concrete with silica fume as an innovative material for sustainable construction, offering improved mechanical performance and reduced permeability. Doi: 10.28991/CEJ-2025-011-05-013 Full Text: PD
Crack Pattern Analysis and Reinforcement Strain Development in UHPSFRC-Strengthened RC Joints
No full textThis study assesses the effectiveness of ultra-high performance steel fiber-reinforced concrete (UHPSFRC) in improving the seismic behavior of reinforced concrete (RC) exterior joints, emphasizing crack patterns and reinforcement strain development. Three full-scale specimens (a conventional RC control joint and two UHPSFRC-strengthened versions with 800 mm and 1025 mm strengthening lengths) were subjected to reversed cyclic loading to mimic seismic forces. Crack progression and strain distribution were examined through visual observations, strain gauges, and displacement data, offering a detailed evaluation of joint performance. Findings indicate that UHPSFRC enhances shear resistance, reduces crack widths significantly (<0.5 mm compared to >2 mm in the control), and modifies failure modes: the 800 mm length shifts damage to beam flexural failure, while the 1025 mm length increases peak capacity (231.4 kN vs. 185.8 kN) but reverts to joint shear failure. The novelty lies in UHPSFRC's ability to replace transverse reinforcement in congested joint zones, enhancing ductility and easing construction difficulties. This research provides fresh insights into optimizing UHPSFRC application length, delivering practical guidance for seismic retrofitting, and contributing to design standards for robust RC frames in seismic regions. Doi: 10.28991/CEJ-2025-011-04-014 Full Text: PD
Rehabilitation of Partially Corrosion-Damaged Post-Tensioned Concrete Structures Using Carbon Fiber Reinforced Polymer
No full textThis study provides a comprehensive assessment of the deterioration and rehabilitation of post-tensioned (PT) concrete structures affected by chloride-induced corrosion. Through a detailed case study in the United Arab Emirates, the research identifies moisture ingress and inadequate waterproofing as primary contributors to corrosion in PT tendons and ducts, significantly compromising structural integrity. A rigorous evaluation using nondestructive and semi-destructive testing techniques was conducted to quantify damage and determine the extent of degradation. The results revealed severe corrosion in critical structural elements, necessitating targeted intervention to restore performance and durability. To address these challenges, an integrated rehabilitation strategy was developed, incorporating structural repairs, strengthening through carbon fiber-reinforced polymer (CFRP), and advanced waterproofing techniques. The adopted approach involved enlarging load-bearing components and applying CFRP to enhance flexural strength while minimizing aesthetic alterations. Experimental findings demonstrated that CFRP reinforcement increased slab flexural strength by 30% and reduced crack widths by 23%, effectively mitigating corrosion-related deterioration and extending service life. Furthermore, micro-concrete was utilized in all enlargement locations in compliance with ACI standards, ensuring long-term durability. The proposed rehabilitation framework offers a sustainable solution for extending the service life of PT structures exposed to aggressive environmental conditions. By addressing both immediate structural deficiencies and underlying degradation mechanisms, the strategy enhances resilience and reduces future maintenance requirements. The integration of CFRP strengthening, epoxy crack injection, and advanced waterproofing measures significantly improves corrosion resistance and structural longevity
Phosphate Adsorption from Aqueous Solutions Using Eggshell and Sacha Inchi (Plukenetia volubilis) Mixture
No full textThe use of bioadsorbents for the removal of pollutants is being increasingly investigated worldwide due to their high efficiency and the potential use of various natural sources. The present study introduces a novel approach for phosphate adsorption using sacha inchi cuticle and eggshell mixture. These materials were pyrolyzed (400°C for 20 min) and mixed in a 1:10 (eggshell:cuticle) ratio. An adsorption study was carried out using synthetic phosphate solution concentrations of 0–300 mg/L and adsorbent masses of 0.1–1 g/100 mL. The temperature, pH and stirring were kept constant (25°C, pH:5 and 150 rpm) during the tests. The phosphate adsorption capacity increased as higher phosphate concentrations were used, reaching a maximum of 300 mg/L. However, differences in removal were observed when varying the amount of adsorbent used, reaching equilibrium in approximately 1 h, with a percentage of phosphate removal between 31 and 41%. The adsorption process followed a Freundlich isotherm with a correlation coefficient of 0.97, suggesting a multilayer adsorption process. According to the SEM-EDX results confirmed a high concentration of carbon and oxygen in the sacha inchi cuticle, in that sense, this by-product could be evaluated for the removal of other contaminants from water
Optimizing Waste Foundry Sand in Concrete Considering Strength Properties for Sustainable Green Structures
No full textIncorporating waste foundry sand (WFS) into concrete is a sustainable approach to enhance green construction practices. Waste foundry sand is a byproduct of the metal casting industry and is often discarded in landfills, posing environmental concerns. Using it as a partial replacement for natural sand in concrete addresses both waste management and resource conservation. In this research paper, advanced machine learning models have been reported on the soft computing of the optimal waste foundry sand in concrete based on strength properties for sustainable green structures. The machine learning techniques such as “Group Methods Data Handling Neural Network (GMDH-NN)”, “Support Vector Machine (SVM)”, “K-Nearest Neighbors (KNN)”, “Tree Decision (Tree)” and “Random Forest (RF)” were applied on a database for the compressive strength containing 397 records, for elastic modulus containing 146 records, and for split tensile strength containing 242 records. Each record contains C-Cement content (kg/m³), WFS-Waste foundry sand content (kg/m³), W-Water content (kg/m³), SP-Super-plasticizer content (kg/m³), CA-Coarse aggregates content (kg/m³), FA-Fine aggregates content (kg/m³), TA-Total aggregates content (kg/m³), and Age-The concrete age at testing (days), considered as the input parameters and CS_WFS-Compressive strength of waste foundry sand concrete (MPa), E_WFS-Elastic modules of waste foundry sand concrete (GPa), and STS_WFS-Split tensile strength of waste foundry sand concrete (MPa), which are the output parameters. A 75/25 partitioning pattern for train/test of the database was used in line with established rules. At the end of the model operation, it can be observed that kNN, SVM, and RF were paramount in terms of performance and therefore outclassed the other models in the three-state strength condition of the WFS cement concrete. Hence, these were selected as the decisive models for the prediction of the compressive strength, elastic modulus, and splitting tensile strength of the WFS cement's concrete. The sensitivity analyses showed that Age, WFS/C and CA/C are more impactful on the compressive strength, Age, FA/TA, and W/C are more impactful on the elastic modulus; and 1000SP/C, WFS/C, and W/C are more impactful on the splitting tensile strength of the WFS cement concrete. Generally, these models provide a foundation for optimizing material use, ensuring quality, and meeting environmental goals. Industries leveraging these tools can produce eco-friendly, high-performance concrete while addressing waste management challenges and reducing their carbon footprint
Experimental and Numerical Modeling for the Impact of Freezing Temperatures Reduction on the Mechanical Properties of Frozen Sand
No full textArtificial ground freezing (AGF) is an approach that uses heat extraction to congeal in situ soil to improve soil quality temporarily. This technology is ecologically sustainable and has minimal adverse effects on soil and groundwater. AGF is widely used in subterranean construction, providing temporary support and groundwater sealing. Nevertheless, precisely simulating the mechanical characteristics of frozen soils with dependable constitutive models presents significant challenges for scientists and engineers. Frozen soil, consisting of ice, liquid water, solid particles, and pore air, is a distinctive geological substance with heightened sensitivity to temperature and external influences. Experimental studies have shown that the mechanical properties of frozen soils are significantly influenced by temperature, confining pressure, strain rate, stress path, and stress level. Numerical simulation offers a superior approach for forecasting soil qualities, particularly in artificial frozen soil technologies for excavations like tunnels and mines. This research examines the impact of varying freezing temperatures and pressures on soil characteristics. This research employs experiments and numerical analysis using Mohr-Coulomb and hardening soil models. The experimental results indicated that the elastic modulus almost increases linearly by a rate of 90000 kN/m² with 1ºC drops below 0ºC. The unconfined compressive strength increased by 2068 kN/m² for each 1°C decrease from 0 to -2°C. Within the temperature range of -2°C to -10°C, the rate of increase is 529 kN/m². The apparent cohesion increased by 238.75 kN/m² for each 1°C decrease from 0 to -2°C. Within the temperature range of -2°C to -10°C, the rate of increase is 66.25 kN/m². A nonlinear association between temperature decrease and tensile stress rise was observed. Numerical analysis shows that as confined pressure increases and temperature decreases, materials can either get stronger or weaker; the Mohr-Coulomb and HS models show stress-strain curve behavior that matches what was found in experiments
Efficacy of Plastic Waste Strips Towards Enhancement of Shear Capacity of Reinforced Concrete Beams
No full textThe amount of plastic waste produced worldwide has been steadily rising. Manufacturing processes, service industries, and municipal solid waste produce a significant amount of waste plastic. One common construction and industrial waste that could be employed as shear reinforcement in concrete beams for specified purposes is the plastic waste strips, since they have relatively high tensile strength. Such plastic strips are used to tie clay bricks, floor finishing tiles, walkway finishing blocks, curbstones, and so on in different industrial products. This study examines an approach that uses plastic waste strips in place of conventional stirrups to enhance the shear performance of reinforced concrete (RC) beams. A set of shear tests was performed on carefully constructed 150 mm width × 225 mm depth × 1400 mm length beam specimens to evaluate failure mechanisms, modes of failure, crack patterns, and shear strength. All beams have the same flexural requirements, so they were ensured to fail by exceeding their shear strength under the applied load. This study examined five concrete beams that were reinforced internally using plastic waste strips in the shear region, as well as one control beam. The tested beams were reinforced using various strip spacings and configurations. The results of the tests indicated that increasing the plastic waste strips improved the concrete section shear strength. As the number of plastic strips in the section increases, the distance between each strip is drastically reduced, increasing the shear capacity of the beam. The experimental results indicate that the beam with six vertical plastic waste strips in its section has a 75% higher shear strength capacity than the reference beam without any transverse reinforcement. In addition, shear resistance is higher in the beam with plastic strips at 45° and 135° inclined angles than in the beam with vertical plastic strips in the same amount of plastic strips. Based on these findings, reinforced concrete beams can be utilized for specific purposes by employing plastic waste strips as transverse reinforcement to resist internal shear forces
Fragility Assessment of Cable-Stayed Bridge Towers Under Scaled Earthquakes
No full textCable-stayed bridges exhibit exceptional vulnerability to seismic excitation, particularly under combined vertical and horizontal ground motions in tectonically active regions. This study characterizes the seismic fragility of cable-stayed bridge towers using comprehensive probabilistic assessment methodologies. The framework integrates fragility curve development and Monte Carlo simulation, employing 30 earthquake ground motion records to construct robust statistical models of structural response. Fragility functions quantify the probability of exceeding predefined damage states across varying seismic intensity measures, while Monte Carlo analyses capture the stochastic nature of behavior and highlight response clustering around mean performance levels for distinct classifications. The findings reveal pronounced structural vulnerabilities within cable-stayed bridge systems, shaped by both epistemic and aleatory uncertainties that may lead to progressive collapse under extreme seismic events. Computational results indicate that although responses converge statistically around expected values, considerable scatter persists across limit states. For instance, at Sa(T1) = 1.0 g, exceedance probabilities diverge significantly: OP is almost certain (>99.9%), IO reaches 86.5%, DC 46.9%, and CP only 10.9%. Under more severe shaking (2.0 g), DC exceedance exceeds 98%, while CP remains 31%, illustrating substantial variability in fragility across thresholds. These results underscore the urgent need for improved seismic design philosophies in cable-stayed infrastructure within hazardous environments. The research advances bridge engineering practice by clarifying fundamental vulnerability mechanisms and guiding the development of innovative material systems, retrofit strategies, and structural health monitoring protocols aimed at enhancing seismic resilience
Evaluation of Using Slag Powder as a Filler for Asphalt Concrete
No full textFiller materials have a significant effect on the performance of asphalt concrete by filling the voids and modifying the binder viscosity. Many types of filler have been used; the Ordinary Portland Cement (OPC) is the most used due to its properties, which align with the required properties. The cost, production emissions, and drain for natural resources formed negative points of its usage. Accordingly, this study is dedicated to evaluating the asphalt concrete properties using byproduct material as a mineral filler. The Electric Arc Furnace Slag Powder (EAFSP) has been selected to replace the OPC with ratios from zero to 100% with an increment of 25%. Marshall and Indirect Tensile Strength (ITS) results in different testing conditions were employed to evaluate the use of EAFSP. The results revealed that using EAFSP as a filler material improved asphalt concrete strength and resistance to moisture effects, especially at high temperatures. More binder content was needed, about 0.6%, the voids in the total mix were reduced by about 1%, and the stiffness increased by about 0.5 kn/mm when replacing the OPC with EAFSP. Based on that, it's recommended that the replacement ratio should be proposed according to the weather condition, materials availability, and cost-benefit analysis