• Advances in concrete construction
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• v.11 no.1
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• pp.73-80
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• 2021

Rice Husk Ash (RHA) geopolymer paste activated by sodium aluminate were characterized by X-ray diffractogram (XRD), scanning electron microscope (SEM), energy dispersion X-Ray analysis (EDAX)and fourier transform infrared spectroscopy (FTIR). Five series of RHA geopolymer specimens were prepared by varying the Si/Al ratio as 1.5, 2.0, 2.5, 3.0 and 3.5. The paper focuses on the correlation of microstructure with hardened state parameters like bulk density, apparent porosity, sorptivity, water absorption and compressive strength. XRD analysis peaks indicates quartz, cristobalite and gibbsite for raw RHA and new peaks corresponding to Zeolite A in geopolymer specimens. In general, SEM micrographs show interconnected pores and loosely packed geopolymer matrix except for specimens made with Si/Al of 2.0 which exhibited comparatively better matrix. Incorporation of Al from sodium aluminate were confirmed with the stretching and bending vibration of Si-O-Si and O-Si-O observations from the FTIR analysis of geopolymer specimen. The dense microstructure of SA2.0 correlate into better performance in terms of 28 days maximum compressive strength of 16.96 MPa and minimum for porosity, absorption and sorptivity among the specimens. However, due to the higher water demand to make the paste workable, the value of porosity, absorption and sorptivity were reportedly higher as compared with other geopolymer systems. Correlation regression equations were proposed to validate the interrelation between physical parameters and mechanical strength. RHA geopolymer shows comparatively lower compressive strength as compared to Fly ash geopolymer.

• Structural Engineering and Mechanics
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• v.77 no.6
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• pp.819-830
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• 2021

To evaluate the performance of concrete load bearing walls in a structure under horizontal loads after being exposed to real fire, two steps were followed. In the first step, an experimental study was performed on the thermo-mechanical properties of concrete after heating to temperatures of 200-1000℃ with the purpose of determining the residual mechanical properties after cooling. The temperature was increased in line with natural fire curve in an electric furnace. The peak temperature was maintained for a period of 1.5 hour and then allowed to cool gradually in air at room temperature. All specimens were made from calcareous aggregate to be used for determining the residual properties: compressive strength, static and dynamic elasticity modulus by means of UPV test, including the mass loss. The concrete residual compressive strength and elastic modulus values were compared with those calculated from Eurocode and other analytical models from other studies, and were found to be satisfactory. In the second step, experimental analysis results were then implemented into structural numerical analysis to predict the post-fire load-bearing capacity response of the walls under vertical and horizontal loads. The parameters considered in this analysis were the effective height, the thickness of the wall, various support conditions and the residual strength of concrete. The results indicate that fire damage does not significantly affect the lateral capacity and stiffness of reinforced walls for temperature fires up to 400℃.

• Advances in concrete construction
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• v.13 no.1
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• pp.11-23
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• 2022

Conventional concrete needs some improvement in the mechanical properties, which can be obtained by different admixtures. However, making concrete samples costume always time and money. In this paper, different types of hybrid algorithms are applied to develop predictive models for forecasting compressive strength (CS) of concretes containing metakaolin (MK) and fly ash (FA). In this regard, three different algorithms have been used, namely multilayer perceptron (MLP), radial basis function (RBF), and support vector machine (SVR), to predict CS of concretes by considering most influencers input variables. These algorithms integrated with the grey wolf optimization (GWO) algorithm to increase the model's accuracy in predicting (GWMLP, GWRBF, and GWSVR). The proposed MLP models were implemented and evaluated in three different layers, wherein each layer, GWO, fitted the best neuron number of the hidden layer. Correspondingly, the key parameters of the SVR model are identified using the GWO method. Also, the optimization algorithm determines the hidden neurons' number and the spread value to set the RBF structure. The results show that the developed models all provide accurate predictions of the CS of concrete incorporating MK and FA with R² larger than 0.9972 and 0.9976 in the learning and testing stage, respectively. Regarding GWMLP models, the GWMLP1 model outperforms other GWMLP networks. All in all, GWSVR has the worst performance with the lowest indices, while the highest score belongs to GWRBF.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.4
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• pp.65-72
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• 2022

For sustainable development in the construction industry, blast furnace slag has been used as a substitute for cement in concrete. In contrast, ferronickel slag, which is the by-product generated during smelting to ferronickel used in the manufacturing of stainless steel and nickel alloys, has a limitation to use as a binder and an aggregate due to its expansive characteristics. Recently, stabilization technology of ferronickel slag has been improved and studies have been carried out to utilize ferronicke slag as fine aggregate in concrete. Therefore, in this study, basic mechanical properties of concrete used in ferronickel slag aggregate was evaluated. The compressive strength (24, 30, 40 MPa) and replacement rate of ferronickel slag aggregate (0, 10, 25, 50%) were considered as experimental variables. As a result of test, concrete replaced fine aggregate with 25% ferronickel slag aggregate showed superior performance in the compressive strength and flexural strength.

• Smart Structures and Systems
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• v.30 no.2
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• pp.195-207
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• 2022

Computational drawbacks associated with regular predictive models have motivated engineers to use hybrid techniques in dealing with complex engineering tasks like simulating the compressive strength of concrete (CSC). This study evaluates the efficiency of tree potential metaheuristic schemes, namely shuffled complex evolution (SCE), multi-verse optimizer (MVO), and beetle antennae search (BAS) for optimizing the performance of a multi-layer perceptron (MLP) system. The models are fed by the information of 1030 concrete specimens (where the amount of cement, blast furnace slag (BFS), fly ash (FA1), water, superplasticizer (SP), coarse aggregate (CA), and fine aggregate (FA2) are taken as independent factors). The results of the ensembles are compared to unreinforced MLP to examine improvements resulted from the incorporation of the SCE, MVO, and BAS. It was shown that these algorithms can considerably enhance the training and prediction accuracy of the MLP. Overall, the proposed models are capable of presenting an early, inexpensive, and reliable prediction of the CSC. Due to the higher accuracy of the BAS-based model, a predictive formula is extracted from this algorithm.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.21-22
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• 2020

This study is about high strength self-leveling mortar according to the mixing ratio of polymer. The self-leveling mortar currently released in Korea maintains a compressive strength of 40 Mpa as of 28 days. In addition, the level of bonding strength and flexural strength are kept the same. However, through this study, it is confirmed how the self-leveling mortar with a compressive strength of 60Mpa as of the 28th is shown according to the amount of polymer mixed. Experimental factors were configured according to the amount of polymer mixed, and the types of experiments were to confirm compressive strength, flexural strength, adhesion strength and flow. In addition, by confirming the early strength, a study was conducted to improve the quick workability compared to the self-horizontal mortar in the market.

• Advances in concrete construction
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• v.16 no.5
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• pp.255-267
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• 2023

The production of ultra-early-strength concrete (UESC) traditionally involves complexity or necessitates high-temperature curing conditions. However, this study aimed to achieve ultra-early-strength performance solely through room-temperature curing. Experimental results demonstrate that under room-temperature (28℃) curing conditions, the concrete attained compressive strengths of 20 MPa at 4 hours and 69.6 MPa at 24 hours. Additionally, it exhibited a flexural strength of 7.5 MPa after 24 hours. In contrast, conventional concrete typically reaches around 20.6 MPa (3,000 psi) after approximately 28 days, highlighting the rapid strength development of the UESC. This swift attainment of compressive strength represents a significant advancement for engineering purposes. Small amounts of steel fibers (0.5% and 1% by volume, respectively) were added to address potential concrete cracking due to early hydration heat and enhance mechanical properties. This allowed observation of the effects of different volume contents on ultra-early-strength fiber-reinforced concrete (UESFRC). Furthermore, the compressive strength of 0.5% and 1% UESFRC increased by 16.3% and 31.3%, respectively, while the flexural strength increased by 37.1% and 47.9%. Moreover, toughness increased by 58.2 and 69.7 times, respectively. These findings offer an effective solution for future emergency applications in public works.

• Advances in materials Research
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• v.13 no.1
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• pp.19-35
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• 2024

Presented Article evaluates the effect of nanoclay on permeability, compressive strength, and plasticity behavior of fine-grained soil related to the Tabriz landfill site. In this regard, comprehensive experimental study was performed on taken soil samples (42 specimens) with aim of design high-performance liners for Tabriz landfill. The samples was mixed by 0% (control) 3%, 6% and 9% nanoclay and prepared in 1, 7, 14 and 28 days before testing stage. Index tests like particle-size, permeability, atterberg limits, and uniaxial compressive strength (UCS) was conducted on samples. The results show that studied soil is classified as CL in USCS classification and atterberg limits measured as LL is 37, PL is 20.67, and PI is 16.33 which increase into 75, 45, and 30. The assessment presented the LL was increased about 20.27% based on increasing in nanoclay from 0% to 9%. These variations for PL and PI were 21.77% and 18.37%, respectively. Also, the and soil's compressive strength is increase from 120 kPa to 188 kPa and permeability is estimated as 4.25×10^-6 m/s which reduced into the 6.34×10^-9 m/s with respect the naboclay content increases form 0% to 9%.

• Advances in concrete construction
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• v.17 no.4
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• pp.211-220
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• 2024

Concrete, consisting mainly of cement, water and aggregates; is the most used construction material all over the world. Cement manufacturing industry is one of the carbon dioxide producing sources that contributes to global warming. Therefore, in the last few years, there is a growing interest in using waste materials and by-products as cement replacement materials. Using these kinds of materials as a part of cement replacement reduces the air pollution, cost and also enhances some properties of concretes. In the present work, marble dust (MD) was examined as a partial cement replacement material with seven proportions as 0%, 10%, 20%, 30%, 40%, 50%, 60% and glass powder (GP) was used as an additive, 8% by cement weight, in a 0.55 water-binder ratio concrete. In order to evaluate their effects; workability, strength (compressive, flexural and split tensile), alkalinity, sulphate resistance and ultrasonic pulse velocity tests were performed. Experimental results indicated that with MD replacement and GP addition; there is a loss in the workability but improvement in mechanical properties. With 10% replacement of MD compressive, flexural and tensile strengths increased by 10.7%, 6.2% and 5.3% respectively. Moreover, up to 30% replacement of MD reasonable strength values were obtained.

• Journal of the Korea Institute of Building Construction
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• v.24 no.4
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• pp.403-411
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• 2024

This study investigated the use of recycled aggregate from waste asphalt concrete in dry soil concrete mixed with red mud. The results showed that dry soil concrete utilizing waste asphalt recycled aggregate had relatively lower compressive strength compared to that using crushed aggregate. However, dry soil concrete mixed with red mud using waste asphalt recycled aggregate achieved a compressive strength of over 18.0MPa, meeting the highest performance standard for parking lot use, when the cement content was more than 250kg/m³.