• Steel and Composite Structures
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• v.45 no.2
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• pp.281-291
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• 2022

Surmounting complexities in analyzing the mechanical parameters of concrete entails selecting an appropriate methodology. This study integrates a novel metaheuristic technique, namely satin bowerbird optimizer (SBO) with artificial neural network (ANN) for predicting uniaxial compressive strength (UCS) of concrete. For this purpose, the created hybrid is trained and tested using a relatively large dataset collected from the published literature. Three other new algorithms, namely Henry gas solubility optimization (HGSO), sunflower optimization (SFO), and vortex search algorithm (VSA) are also used as benchmarks. After attaining a proper population size for all algorithms, the Utilizing various accuracy indicators, it was shown that the proposed ANN-SBO not only can excellently analyze the UCS behavior, but also outperforms all three benchmark hybrids (i.e., ANN-HGSO, ANN-SFO, and ANN-VSA). In the prediction phase, the correlation indices of 0.87394, 0.87936, 0.95329, and 0.95663, as well as mean absolute percentage errors of 15.9719, 15.3845, 9.4970, and 8.0629%, calculated for the ANN-HGSO, ANN-SFO, ANN-VSA, and ANN-SBO, respectively, manifested the best prediction performance for the proposed model. Also, the ANN-VSA achieved reliable results as well. In short, the ANN-SBO can be used by engineers as an efficient non-destructive method for predicting the UCS of concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.131-132
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• 2023

Recently, the construction industry has seen the emergence of interior and exterior finishes using ultra-high performance concrete (UHPC) and colored concrete products using precast concrete (PC). However, the excessive amount of pigment used for coloring reduces the strength of the concrete. There is a need to improve the durability and chromaticity of colored concrete, and further analytical studies on the properties of colored concrete are also required. Therefore, in this paper, colored ultra-high strength cement composites (C-UHSCC) containing red and green inorganic pigments were prepared, and the compressive strength and color of the specimens were measured according to the age, and the correlation between strength and color was analyzed by simple linear regression analysis using R² value. The results showed that the red color was highly correlated with L^* and a^*, and the green color was highly correlated with a^*. These results can be considered for various concrete formulations, but research is needed to suggest the optimal pigment mixing ratio for proper strength and color development.

• Structural Engineering and Mechanics
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• v.88 no.2
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• pp.179-188
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• 2023

The mechanical behaviours of biopolymer-treated soil depend on the formation of soil-biopolymer matrices. In this study, various biopolymers(e.g., xanthan gum (XG), locust bean gum (LBG), sodium alginate (SA), agar gum (AG), gellan gum (GE) and carrageenan kappa gum (KG) are selected to treat three types of natural soil at different concentrations (e.g., 1%, 2% and 3%) and curing time (e.g., 4-365 days), and reveal the reinforcement effect on natural soil by using unconfined compression tests. The results show that biopolymer-treated soil obtains the maximum unconfined compressive strength (UCS) at curing 14-28 days. Although the UCS of biopolymer-treated soil has a 20-30% reduction after curing 1-year compared to the maximum value, it is still significantly larger than untreated soil. In addition, the UCS increment ratio of biopolymer-treated soil decreases with the increase of biopolymer concentration, and there exists the optimum concentration of 1%, 2-3%, 2%, 1% and 2% for XG, SA, LBG, KG and AG, respectively. Meanwhile, the optimum initial moisture content can form uniformly biopolymer-soil matrices to obtain better reinforcement efficiency. Furthermore, the best performance in increasing soil strength is XG following SAand LBG, which are significantly better than AG, KG and GE.

• Steel and Composite Structures
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• v.50 no.4
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• pp.443-458
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• 2024

The construction industry, one of the biggest producers of greenhouse emissions, is under a lot of pressure as a result of growing worries about how climate change may affect local communities. Geopolymer concrete (GPC) has emerged as a feasible choice for construction materials as a result of the environmental issues connected to the manufacture of cement. The findings of this study contribute to the development of machine learning methods for estimating the properties of eco-friendly concrete, which might be used in lieu of traditional concrete to reduce CO₂ emissions in the building industry. In the present work, the compressive strength (f_c) of GPC is calculated using random forests regression (RFR) methodology where natural zeolite (NZ) and silica fume (SF) replace ground granulated blast-furnace slag (GGBFS). From the literature, a thorough set of experimental experiments on GPC samples were compiled, totaling 254 data rows. The considered RFR integrated with artificial hummingbird optimization (AHA), black widow optimization algorithm (BWOA), and chimp optimization algorithm (ChOA), abbreviated as ARFR, BRFR, and CRFR. The outcomes obtained for RFR models demonstrated satisfactory performance across all evaluation metrics in the prediction procedure. For R² metric, the CRFR model gained 0.9988 and 0.9981 in the train and test data set higher than those for BRFR (0.9982 and 0.9969), followed by ARFR (0.9971 and 0.9956). Some other error and distribution metrics depicted a roughly 50% improvement for CRFR respect to ARFR.

• Advances in concrete construction
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• v.17 no.3
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• pp.167-177
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• 2024

Disposal of waste glass derived from bottle or packaging glass, flat glass, domestic glass is one of the major environmental defies. Moreover, the remnants of bricks resulting from the remnants of buildings are also considered an important factor in polluting the environment due to the difficulty of filling or getting rid it. The aim of this study is to valorize these wastes through chemical activation to be an environmentally friendly material. The Microstructure, compressive strength, setting time, drying shrinkage, water absorption of different pastes produced by clear glass (CG), green glass (GG) and brick waste (BP) activated were tested and recorded after curing for 3, 7, 28 and 365 days. Five samples of pastes were mixed in proportions represented by: 100% GP (GP), 100% GGP (GGP), 100% BP (BP), 90% GP + 10% BP (GPB) and 90% GGP + 10% BP (GGPB). Various parameters considered in this study include sodium hydroxide concentrations (10 mol/l); 0.4 as alkaline liquid to binder ratio; 2.5 as sodium silicate to sodium hydroxide ratio and cured at 60℃ for 24 hours. Experimental results revealed that the addition of 10% of BP resulted in an increased strength performance of geopolymer paste especially with GGPB compared to GGP in 365 days. In addition, the 10% amount of BP increases the absorption and shrinkage rate of geopolymer pastes (GPB and GGPB) by reducing the setting time. SEM results revealed that the addition of BP and GP resulted in a dense structure.

• Advances in concrete construction
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• v.17 no.1
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• pp.45-52
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• 2024

In this study, the fresh properties of paraffin-mixed concrete, compressive strength, resistance to frost damage, and resistance to composite deterioration under freeze-thaw and salt environment were investigated. The compressive strength of paraffin-mixed concrete was almost the same as that of unmixed concrete, and no decrease in strength was observed, unlike the concrete with entrained air in consideration of freeze-thaw resistance. Concerning the freeze-thaw resistance of paraffin-mixed concrete, the relative dynamic modulus of elasticity (RDME) did not decrease even without entrained air. In addition, no decrease in the RDME was observed in the combined deterioration with salt damage, and it was confirmed that the mass reduction was suppressed compared to the concrete without paraffin. The freeze-thaw resistance of concrete when paraffin is mixed may be improved due to the reduction in the amount of frozen water and the mixed paraffin particles exist in the concrete as pore fillers with a size of 200 ㎛ or less, which act as substitutes for air voids. This resulted in reduction of the apparent air void spacing and thereby relieving the pore pressure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.117-124
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• 2015

Currently, Eco-friendly construction materials are widely utilized for reducing $CO_2$ emission in construction. Furthermore various engineering fibers are also added for improving a brittle behavior in concrete. In the paper, concrete specimens with 10% and 20% replacement ratio with RHA (Rice Husk Ash) are prepared, and engineering behaviors in RHA and OPC concrete are evaluated with different addition of coconut fiber from 0.125~0.375% of volume ratio. Several basic tests including compressive strength, tensile strength, flexural strength, impact resistance, and bond strength are performed, and crack width and deflections are also measured in flexural test. RHA is evaluated to be very effective in strength development and 0.125% of fiber addition leads significant improvement in tensile strength, ductility, and crack resistance. RHA and coconut fiber are effective construction material both for reutilization of limited resources and performance improvement in normal concrete.

• Advances in concrete construction
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• v.6 no.4
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• pp.323-344
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• 2018

The study herein reports the impact of Steel Fiber (SF) and Ground Granulated Blast Furnaces slag (GGBFS) content on the fresh and hardened properties of fly ash (FA) based Self-Compacting Geopolymer Concrete (SCGC). Two series of self-compacting geopolymer concrete (SCGC) were formulated with a constant binder content of $450kg/m^3$ and at an alkaline-to-binder (a/b) ratio of 0.50. Fly ash (FA) was substituted with GGBFS with the replacement levels being 0%, 25%, 50%, 75%, and 100% by weight in each SCGC series. Steel fiber (SF) wasn't employed in the assembly of the initial concrete series whereas, within the second concrete series, an SF combination was achieved by a constant additional level of 1% by volume. Fresh properties of mixtures were through an experiment investigated in terms of slump flow diameter, T50 slump flow time, V-funnel flow time, and L-box height ratio. Moreover, the mechanical performance of the SCGCs was evaluated in terms of compressive strength, splitting tensile strength, and fracture toughness. Furthermore, a statistical analysis was applied in order to judge the importance of the experimental parameters, like GGBFS and SF contents. The experimental results indicated that the incorporation of SF had no vital impact on the fresh characteristics of the SCGC mixtures whereas GGBFS aggravated them. However, the incorporation of GGBFS was considerably improved the mechanical properties of SCGCs. Moreover, the incorporation of SF with the total different quantity of GGBFS replacement has considerably increased the mechanical properties of SCGCs, by close to (65%) for the splitting strength and (200%) for compressive strength.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.49-55
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• 2011

In order to analyze feasibility of replacing a conventional 6-mm Ti bar with a 5-mm bar, a series of rotating bending fatigue tests were carried out on Ti-6Al-4V bars by strengthening the fatigue performance using a special technique called UNSM (Ultrasonic Nanocrystal Surface Modification). The results of S-N curves clearly showed that the performance of the 5-mm titanium specimen was similar to that of the 6-mm specimen when the UNSM treatment was applied. The 5-mm treated specimen converged with small scattering band into the linear line of the non-treated 6-mm one. Below the fatigue life of $10^5$ cycles, the UNSM treatment did not show any significant superiority in the bending stress and fatigue life. However, over the fatigue life of $10^5$ cycles, the effect of UNSM was superior for each fatigue life, and the bending stress became longer and higher than that of the untreated one. In the case of 6-mm Ti-bar with UNSM, the fatigue limit was about 592 MPa, and there was fatigue strength increase of about 30.7% at the fatigue life of $10^4$ cycles compared to the untreated 6-mm bar. Therefore, the compressive residual stress made by the UNSM in Ti-6Al-4V increased the fatigue strength by more than 30%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.7-15
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• 2017

The purpose of this study was to evaluate the properties of recycled aggregate concrete (RAC) using low quality recycled aggregate with or without washing before usage. The recycled aggregate concrete evaluated in this study contained various amounts of low quality recycled aggregate, viz. 30%, 60% and 100%. To evaluate the performance of the recycled aggregate concrete, various test methods were employed to assess its compressive strength, absorption, surface resistance, ultrasound velocity, chloride ion resistance, etc. The properties of the RAC with 30% and 60% washed recycled aggregate were similar those of the natural aggregate. However, the properties of the RAC with 100% washed recycled aggregate were slightly lower than those of the other versions. Also, the RAC with the non-washed recycled aggregate exhibited lower performance results. The results showed that the RAC with washed recycled aggregate had similar properties to normal concrete (concrete using natural aggregate). This implies that the recycled aggregate should be washed to improve the RCA.