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Volume 14 (4); 25 December, 2024
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Research Paper
Prediction of Compressive Strength and Design Parameters of C30/37, C35/45 and C40/50 Concrete Classes by ANN
Kars F, Ozcan G, Gulbandilar E, and Kocak Y.
J. Civil Eng. Urban., 14(4): 356-367, 2024; pii:S225204302400040-14
DOI: https://dx.doi.org/10.54203/jceu.2024.40
Abstract
The quality of concrete used in the construction sector is increasing day by day with ready-mixed concrete production. The quality of concrete is directly related to its compressive strength and the related tests are labor-intensive and time-consuming. Therefore, different artificial intelligence-based models are used to predict the compressive strength of concrete. In this study, compressive strength and design parameters of concrete classes C30/37, C35/45 and C40/50 were predicted by ANN model. A total of 240 compressive strength results obtained from concretes produced in a ready-mixed concrete plant for the construction of columns, beams, decks and stairs. 70% of these data were used for training and remaining 30% of data were reserved for testing. The prediction accuracy of the ANN model was evaluated by R2, MAPE and RMSE statistical methods. According to results, the compressive strengths of concrete classes C30/37, C35/45 and C40/50 could be predicted with errors of -0.70%, 1.25% and 0.17% for 7 days and 0.99%, 0.03% and -0.69% for 28 days, respectively. Depending on the design parameters, it was found that prediction performance could be made with almost 100% accuracy for all concretes except high-performance superplasticizer admixture. As a result, it was concluded that ‘very good’ or ‘high accuracy’ predictions can be made with ANN models.
Keywords: ANN, Compressive Strength, Concrete, Design Parameters.
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Research Paper
Condition Assessment of Metsimotlhabe River Bridge using Non-Destructive Testing and Non-Contact Procedure
Kgafela M.P., and Adewuyi A.P.
J. Civil Eng. Urban., 14(4): 368-377, 2024; pii:S225204302400041-14
DOI: https://dx.doi.org/10.54203/jceu.2024.41
Abstract
A process of in-service infrastructure health assessment using non-destructive testing and evaluation (NDT&E) techniques is crucial for prompt, accurate and quantitative identification of damage in civil infrastructure. The aim of this study was to assess the structural performance of Metsimotlhabe River Bridge through NDT&E and load testing techniques. Schmidt rebound hammer was utilized to determine the compressive strength of the bridge, total station was used to monitor the profile of the bridge girder level for differential deformation, and a non-contact global positioning system (GPS) technology was employed to measure the dynamic displacement of the bridge under random operational traffic loading conditions. Finally, the dynamic behavior of the bridge was evaluated based on displacement, strain and acceleration response data. There was a perfect linear correlation between rebound number and compressive strength of concrete from different contact surfaces. The compressive strength of the bridge superstructure from random sampling was 39.48 N/mm2 (CoV = 19.22%). The normal distribution of the bridge levels at the northern and southern levels depicted differential displacement that indicated torsional deformation. The displacement of the bridge girder was simultaneously monitored at the supports, quarter-spans and mid-span using GPS technology. The results showed functional elastomeric bearings at the supports, perfect correlation at the quarter spans and maximum dynamic flexural displacement of 21.5 mm at the mid-span. The modal decomposition acceleration and displacement response data produced the first three flexural modal frequencies of 6.44 Hz, 9.10 Hz and 19.56 Hz. It can be concluded that while the bridge was in good condition in terms of its compressive strength, elastomeric bearings and fibre strain, the differential displacement at the northern-southern edges of the bridge was a clear indication of torsional deformation of the superstructure.
Keywords: Bridge monitoring, non-destructive testing, compressive strength, rebound hammer, global positioning system (GPS), total station, displacement response, torsional deformation
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Review
A Review of Lightweight Concrete in Civil Engineering
Omran Ş.
J. Civil Eng. Urban., 14(4): 378-404, 2024; pii:S225204302400042-14
DOI: https://dx.doi.org/10.54203/jceu.2024.42
Abstract
Lightweight concrete, defined as concrete with a dry density below 2000 kg/m³, has become increasingly prominent in modern advanced concrete technology and constructions due to its low density, superior thermal insulation, and sustainability benefits owing to the use of industrial by-products and waste materials in the process of its production. This study presents a comprehensive overview of lightweight concrete, covering its historical development, material composition, and performance characteristics. The fresh properties, such as workability, slump, and water absorption, are discussed alongside its mechanical properties, including compressive, flexural, and tensile strength; modulus of elasticity; ductility; and fatigue resistance. The durability characteristics, such as water and chemical permeability, freeze-thaw resistance, carbonation, shrinkage behavior, and reinforcement corrosion, are also evaluated. In addition, the microstructural characteristics, including density, porosity, and aggregate-cement matrix interfacial transition zone (ITZ), are examined using SEM, XRD, TGA, and FTIR analyses. The study also considers the environmental performance of lightweight concrete, assessed through life cycle assessment, including the impact of adding waste and recycled aggregates. Various types of natural and synthetic lightweight aggregates, along with mineral admixtures, nanomaterials, and reinforcing fibers, are reviewed to evaluate their impact on the performance of lightweight concrete. Although lightweight concrete typically exhibits lower mechanical strength than normal concrete, its compressive, tensile, and flexural strength, elastic modulus, ductility, and fatigue resistance can be improved under optimized conditions. As reported in various studies, the addition of pozzolanic and nano-admixtures, along with optimized fiber reinforcement, can enhance both the microstructure and overall durability of lightweight concrete. These improvements can be achieved through the integration of industrial by-products such as fly ash, slag, or agricultural waste.
Keywords: Lightweight concrete (LWC), Pozzolanic admixtures, Lightweight aggregate, Artificial aggregate, Mechanical properties, Durability properties, Fiber reinforcement.
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Review
Glass Fiber Reinforced Concrete in Construction: A Review of Advances, Challenges, and Future Prospects
Baybure H.
J. Civil Eng. Urban., 14(4): 405-422, 2024; pii:S225204302400043-14
DOI: https://dx.doi.org/10.54203/jceu.2024.43
Abstract
In this study, the material compliterosition, mechanical strength (tensile strength, bending strength), alkali strength and durability properties of glass fiber reinforced concrete (GRC) and its sustainable place in construction technologies are evaluated based on a review of the literature. GRC is a composite material that stands out with its high mechanical performance, which is widely used especially in facade elements. In the research, it has been found that glass fibers positively affect the mechanical performance (tensile strength, bending strength) of concrete by preventing the formation of cracks in its microstructure, and its resistance to aging and environmental factors increases with pozzolanic and nanomaterial additives. In addition, the effects of fiber type, fiber content and fiber dimensions on GRC performance were compared; the gains achieved in both environmental sustainability and mechanical properties through the use of recycled materials and waste materials were emphasized. Experimental and theoretical studies in the literature have shown the increasing importance of GRC in the modern construction sector.
Keywords: Glass reinforced concrete, Mechanical properties, Durability, Nano materials, Pozzolanic materials, Water/ conjugate ratio, Micro crack development
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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0)