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The Influence of Recycled Coarse Aggregate Content on the Properties of High-Fly-Ash Self-Compacting Concrete
Get PDFIn Vietnam, solid waste from construction activities significantly impacts environmental pollution. Recycled concrete aggregate (RCA), derived from waste concrete, can serve as a coarse aggregate in concrete production. However, compared to natural aggregates, RCA exhibits distinct characteristics, including lower strength, higher water absorption, and an increased angular and rough surface. These properties may influence concrete's workability, compressive strength, and durability. This research investigates the influence of RCA on the properties of High-Fly-Ash Self-Compacting Concrete (SCC). The study explores various replacement levels of natural coarse aggregate with RCA (0%, 50%, 75%, and 100%), alongside a 50% volume fraction of fly ash. Key concrete properties evaluated include workability, compressive strength, flexural strength, and chloride ion permeability. The findings reveal that using 100% RCA in combination with a high fly ash content (50%) produces SCC that meets workability requirements according to EFNARC standards. However, there are trade-offs: the compressive strength decreases by 4.61%, the flexural strength decreases by 3.1%, and chloride ion permeability increases by 57.57% compared to the control sample (using natural aggregates). Notably, the chloride ion permeability of SCC using 100% RCA falls into the category of low permeability. Doi: 10.28991/CEJ-SP2024-010-04 Full Text: PD
Sustainable Concrete Production: Utilizing Cow Dung Ash and Corn Stalk Ash as Eco-Friendly Alternatives
Get PDFThis study aims to determine whether it is feasible to replace conventional materials used in manufacturing concrete with waste materials, namely cow dung ash and corn stalk ash. This study proposes to assess the possibility of using these agricultural by-products to improve the sustainability of concrete while simultaneously tackling the environmental issues related to the manufacture of conventional concrete. The research aims to assess the mechanical qualities, optimize the mix proportions, and examine the ecological implications of using these substitute materials. This research aims to mitigate environmental challenges like carbon dioxide emissions, resource depletion, and the accumulation of agricultural waste by combining agricultural waste and lowering dependency on traditional cement. The study investigates the use of cow dung ash (CDA) and corn stalk ash (CSA) as alternatives for conventional Portland cement (OPC) in mortar mixes at varying quantities, ranging from 5% to 25% CDA and 2.5% to 10% CSA. Chemical composition reveals that CDA and CSA predominantly comprise O, Mg, Al, Si, P, K, and Ca. The workability, hardened characteristics, and microstructure of CDA and CSA were assessed. Increasing CDA and CSA percentages reduced mortar workability; nevertheless, replacing 8% to 10% CDA and 7.5% CSA maintained compressive, tensile, and flexural strengths comparable to control mixes. However, more significant CDA and CSA proportions resulted in lower mortar strength. For example, 10% CDA-enriched mortar had a compressive strength of 31.77 N/mm2, a tensile strength of 3.42 N/mm2, and a flexural strength of 3.61 N/mm2, whereas 7.5% CSA-enriched mortar had a compressive strength of 28.4 N/mm2, a tensile strength of 3.04 N/mm2, and a flexural strength of 3.7 N/mm2. According to the findings, CDA and CSA can replace OPC by up to 10% and 7.5% in mortar manufacturing, making cementitious material alternatives viable. Doi: 10.28991/CEJ-SP2024-010-02 Full Text: PD
Assessment of Ground Penetrating Radar for Pyrite Swelling Detection in Soils
Get PDFPyrite swelling in soils below buildings is a major issue. It leads to severe deformations in floor foundations. A survey is carried out at a selected site in the city of Laval, Quebec, to assess the usefulness of ground-penetrating radar (GPR) to detect deformations that may be indicative of the presence of pyrite. Four soil samples are taken from the aforementioned site to determine the soil type below the concrete slab. The results indicate the presence of limestone, moor clay, and shale sediments, which are prone to pyrite swelling. The GPR data were collected using the GSSI SIR 4000 with a high frequency antenna and processed using RADAN software. The GPR data indicate the presence of severe deformation in many locations of the concrete slab. The most important wave reflections indicative of pyrite swelling are the rebar reflections, showing interesting pushed-up and dropped-down reflections. These reflections appear in two forms. The first is the attenuated reflections that may occur due to pyrite-rich materials. The second is the high amplitude reflections that occur because of the air void, which can be formed due to heaving the concrete slab because of pyrite swelling. As a result, GPR appears to be an effective method for assessing and mapping the effect of pyrite swelling below concrete slabs. Doi: 10.28991/CEJ-2024-010-03-05 Full Text: PD
Analysis and Prediction of Rainfall with Oceanic Nino Index and Climate Variables Using Correlation Coefficient and Deep Learning
Get PDFThis article presents the relationship between the Oceanic Nino Index (ONI) and monthly rainfall on the southern and eastern coast of Thailand, specifically in Narathiwat, Pattani, and Yala provinces, where influences have been commonly observed. This research aims to study the relationship between the Oceanic Nino Index (ONI) and monthly rainfall to develop a model for predicting monthly rainfall. Despite previous related research, there has been no in-depth study on the relationship between the Oceanic Nino Index (ONI) and monthly rainfall in areas adjacent to the sea. The correlation coefficient was used to determine the relationship, revealing that the ONI value is significantly correlated with the amount of rainfall in the current month and the following month. This correlation paved the way for developing a model to predict monthly rainfall. Multiple linear regression, recurrent neural networks, and long short-term memory models were employed for this purpose. The study found that utilizing a recurrent neural network yielded the best prediction efficiency, with Mean Absolute Error (MAE) values of 112.76 mm for Narathiwat province, 81.06 mm for Pattani province, and 97.67 mm for Yala province. Doi: 10.28991/CEJ-2024-010-05-01 Full Text: PD
Ultimate Strength of Internal Ring-Reinforced KT Joints Under Brace Axial Compression
Get PDFInternal ring stiffeners are frequently used to improve the ultimate strength of tubular joints in offshore structures. However, there is a noticeable absence of specific design guidance regarding the assessment of their ultimate strengths in prominent offshore codes and design guides. No equations are available to determine the ultimate strength of internal ring-reinforced KT joints. This work developed equations to determine the ultimate strength and the strength ratio of internal ring-reinforced KT joints based on numerical models and parametric studies comprising ring parameters and joint parameters. Specifically, a finite element model and a response surface approach with eight parameters (λ, δ, ψ, ζ, θ, Ï„, γ, and β) as inputs and two outputs (ultimate strength and the strength ratio) were evaluated since efficient response surface methodology has been proven to give precise and comprehensive predictions. KT-joint with parameters λ=0.9111, δ=0.2, ψ=0.7030, ζ=0.3, θ=45°, Ï„=0.90, γ=16.25, and β=0.6 has the maximum ultimate strength, and the KT-joint with parameters: λ=1, δ=0.2, ψ=0.8, ζ=0.5697, θ=45°, Ï„=0.61, γ=24, and β=0.41 has the maximum strength ratio. The KT-joints with the optimized parameters were validated through finite element analysis. The percentage difference was less than 1.7%, indicating the applicability and high accuracy of the response surface methodology. Doi: 10.28991/CEJ-2024-010-05-012 Full Text: PD
Utilizing GIS and Machine Learning for Traffic Accident Prediction in Urban Environment
Get PDFTraffic accident prediction is crucial to preventive measures against accidents and effective traffic management. Identifying hotspots can facilitate the selection of the most critical survey points to note the contributing features. In this research, an effort has been made to identify hotspots and predict traffic accident occurrences in an urban area. Accident data was obtained from the Rescue 1122 Emergency Services of Faisalabad, and hotspots were identified using Moran's I in ArcGIS. Results showed that most hotspots were located around the General Transport Stand (GTS) area due to the maximum number of road users. The temporal investigations showed that the accident occurrence was significant from 1 to 2 p.m. The identified hotspots were further investigated by conducting a field survey. Essential features such as road geometric features, road furniture, and traffic data were used for developing Machine Learning Algorithms for accident prediction. Using Computer Vision, traffic data was extracted from recorded videos. Random forest, linear regression, and Decision tree algorithms were developed using Python in the Jupyter Notebook environment. The decision tree algorithm showed a maximum accuracy of 84.4%. The analysis of contributing factors revealed that road measurements had the maximum effect on accident occurrence. Doi: 10.28991/CEJ-2024-010-06-013 Full Text: PD
Investigating the Hydraulic Behaviours of an Alluvial Meandering River Reach Between Two Barrages
Get PDFThe Abassia-Shammia is a meandering stream in Najaf province. Predicting and estimating the flow behavior of meandering rivers is crucial for designing hydraulic structures in an accurate manner in the vicinity and conducting environmental and ecological studies. The hydraulic properties of an alluvial stream are typically subject to change due to its location between two barrages. In this study, HEC RAS 2D, developed by the Hydrologic Engineering Center's River Analysis System, was employed to simulate the hydraulic performance of the Euphrates River reach between two series of barrages, i.e., Abbassia and Shammia. Reliable input data, such as Digital Elevation Models (DEMs), land cover classification, and data for the 2023 hydrograph as a boundary condition, were utilized to develop the hydraulic model. The model was calibrated by using the observed water surface elevation from field measurements downstream of Abbassia to match the ones calculated by the model. Hence, the hydraulic model of the Euphrates River was created using an appropriate Manning roughness coefficient value (n = 0.04) based on the most suitable values of statistical indices, correlation coefficient (R²), and root mean squared error (RMSE) to assess the agreement between the observed and simulated data throughout the calibration and validation phases. To visualize the HECRAS2D output, the hydraulic maps for the study region were presented. The ten cross-sections from the field study (investigated at the same period of flow hydrograph) were presented for modeling to emphasize the river's hydraulic behaviors. Based on the results, the water surface elevation ranged between 19.1–29.2 m.a.s.l., and the flow velocity was 2.50 m/s. Meanwhile, the values of bed shear stress (Pa) and the water depth (m) ranged between 0.1 Pa and 8.93 m for the entire river. The results also proved the superiority of the HEC RAS2D model to reliably represent the hydraulic performance of the Euphrates River reach located between the two barrages. Doi: 10.28991/CEJ-2024-010-05-013 Full Text: PD
Comparison of Thermophysical Properties of PIM Feedstocks with Polyoxymethylene and Wax-Polyolefin Binders
Get PDFOne of the high-performance technologies for the serial production of small-sized metal and ceramic complex-profile parts is powder injection molding (PIM). The most industrially demanded types of polymer binder in PIM technology are polyoxymethylene-based compositions and wax-polyolefin mixtures. Despite the large number of studies devoted to different compositions of polymer binder for PIM technology, the actual task is still a comparative analysis of the properties of different binder types to determine their advantages and disadvantages, as well as the optimization of the used compositions. In this regard, this study aims at a comparative analysis of the thermophysical properties of the most demanded feedstocks with binder based on polyoxymethylene and wax-polyolefin mixtures under the condition of using identical steel powder filler. The specific heat capacity, temperatures, and heat of phase transitions, as well as the thermal inertia and effective thermal conductivity of the compared types of feedstocks, were determined as a result of the calculation-experimental study. The obtained data can replenish the knowledge bases necessary for simulation modeling and optimizing powder molding processes of various products made of 42CrMo4 steel. As a result of a comparative analysis of the thermophysical properties of feedstocks with identical powders, the kinetic effects in the thermal processes of forming feedstocks with polyoxymethylene are less significant than those in analogs with wax-polyolefin binder, which facilitates their moldability. Thus, the feedstock with polyoxymethylene has a significantly higher rate of temperature field leveling than the analogs with wax-polyolefin binder. Because of the insignificant difference in specific heat capacity, feedstocks based on polyoxymethylene have 1.5 times higher effective thermal conductivity and approximately 20% higher thermal inertia than feedstocks with identical powder filler and binder in the form of a wax-polyolefin mixture. The technological advantages of feedstocks with a wax-polyolefin binder include the possibility of processing at lower temperatures. Doi: 10.28991/CEJ-2024-010-06-05 Full Text: PD
Evaluation of an Outdoor Pilot Scale Hybrid Growth Algal-Bacterial System for Wastewater Bioremediation
Get PDFSynergistic cooperation and interaction between algae and bacteria had made it easy by using one single step only to efficiently eliminate the impurities found in wastewater. High pollution levels triggered by the disposal of untreated wastewater and the harsh social and economic conditions, together with high construction and operation costs of conventional wastewater treatment systems, made it vital to find simple, efficient, cost-effective treatment systems. In this research work, a hybrid microalgae-bacteria pilot outdoor system comprised of a series of Algaewheel® rotating algae contactors (RACs) that receive preliminary treated domestic wastewater at a hydraulic retention time (HRT) of 8 hours was monitored for a period of 5 months. An average dissolved oxygen (DO) value of 3.04 ± 1.02 mgL⻹ was obtained in the effluent-treated wastewater. While the average removal efficiencies recorded for the parameters monitored were 90.73% for BOD5, 89.10% for COD, 93.45% for TSS, 77.05% for NH3-N, and 70.40% for TN. All the effluent values for the parameters monitored were below the limits of both the local and international standards. The pilot system was found to be suitable and adaptable for small communities with low discharges of 5000 m³/day or less due to its low operation and maintenance requirements, as its electricity consumption is 80% less compared with the conventional wastewater treatment systems. Doi: 10.28991/CEJ-2024-010-11-09 Full Text: PD
Experimental Study on the Effect of Flow Velocity and Slope on Stream Bank Stability (Part I)
Get PDFThe erosion of riverbanks is a significant and capricious national concern. The Al Muwahada channel in Iraq experiences instability in its banks, resulting in failure, retreat, and morphological alterations. These issues are mostly caused by factors such as the velocity of the flow, the angle of the slope, and type of soil. This study investigated the behavior of canal bank soil in response to erosion and variations in slope angle. Therefore, a physical model of a case study was established in the laboratory. Additionally, a slope angle of 26Ëš is being utilized, which has not been previously studied in the laboratory. This angle will be tested with five different velocity values: 0.101 m/s, 0.116 m/s, 0.12 m/s, 0.13 m/s, and 0.135 m/s. The bank's deformation was measured for a period of 12 hours, which was divided into 4 equal intervals for each velocity. The study determined that a riverbank with a slope of 26Ëš is more resistant to erosion when the velocity of the water is below 0.12 m/s. Velocities equal to or greater than 0.12 m/s have a substantial impact on the erosion of the riverbed. According to this study, a velocity of 0.12 m/s or higher leads to increased erosion of the riverbank. This is equivalent to a velocity of 0.804 m/s in the prototype channel. The section of the riverbank that has suffered the greatest damage due to erosion is the upper two-thirds. The used methodology supports global efforts to increase information about the behavior of river banks with unexplored rivers that have different flow velocities and bank slope angles. Doi: 10.28991/CEJ-2024-010-08-013 Full Text: PD