• Structural Engineering and Mechanics
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• v.83 no.3
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• pp.387-400
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• 2022

The practice of using encased steel-concrete columns in medium to high-rise structures has expanded dramatically in recent years. The study evaluates existing methodologies and codal guidelines for estimating the ultimate load-carrying characteristics of concrete-encased short columns experimentally. The present condition of composite column design methods was analyzed using the Egyptian code ECP203-2007, the American Institute of Steel Construction's AISC-LRFD-2010, Eurocode EC-4, the American Concrete Institute's ACI-318-2014, and the British Standard BS-5400-5. According to the codes, the axial load carrying characteristics of both the encased steel and concrete sections was examined. The effect of load-carrying capacities in different forms of encased steel sections on encased steel-concrete columns was studied experimentally. The axial load carrying capacity of twelve concrete-encased columns and four conventional reinforced columns were examined. The conclusion is that the confinement was not taken into account when forecasting the strength and ductility of the encased concrete, resulting in considerable disparities between codal provisions and experimental results. The configuration of the steel section influenced the confining effect. Better confinement is achieved with the laced and battened section than with the infilled steel tube reinforced and conventionally reinforced section. The ECP203-2007 code reported the most conservative results of all the codes used.

• Computers and Concrete
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• v.26 no.4
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• pp.327-342
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• 2020

The objective of this study is to manufacture environmentally-friendly synthetic lightweight aggregates that may be used in the structural lightweight concrete production. The cold-bonding pelletization process has been used in the agglomeration of the pozzolanic materials to achieve these synthetic lightweight aggregates. In this context, it was aimed to recycle the waste fly ash by employing it in the manufacturing process as the major cementitious component. According to the well-known facts reported in the literature, it is stated that the main disadvantage of the synthetic lightweight aggregate produced by applying the cold-bonding pelletization technique to the pozzolanic materials is that it has a lower strength in comparison with the natural aggregate. Therefore, in this study, the metakaolin made of high purity kaolin and calcined kaolin obtained from impure kaolin have been employed at particular contents in the synthetic lightweight aggregate manufacturing as a cementitious material to enhance the particle crushing strength. Additionally, to propose a curing condition for practical attempts, different curing conditions were designated and their influences on the characteristics of the synthetic lightweight aggregates were investigated. Three substantial features of the aggregates, specific gravity, water absorption capacity, and particle crushing strength, were measured at the end of 28-day adopted curing conditions. Observed that the incorporation of thermally treated kaolin significantly influenced the crushing strength and water absorption of the aggregates. The statistical evaluation indicated that the investigated properties of the synthetic lightweight aggregate were affected by the thermally treated kaolin content more than the kaoline type and curing regime. Utilizing the thermally treated kaolin in the synthetic aggregate manufacturing lead to a more than 40% increase in the crushing strength of the pellets in all curing regimes. Moreover, two numerical formulations having high estimation capacity have been developed to predict the crushing strength of such types of aggregates by using soft-computing techniques: gene expression programming and artificial neural networks. The R-squared values, indicating the estimation performance of the models, of approximately 0.97 and 0.98 were achieved for the numerical formulations generated by using gene expression programming and artificial neural networks techniques, respectively.

• Fire Science and Engineering
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• v.26 no.6
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• pp.45-50
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• 2012

The spalling causes the sever reduction of the cross sectional area with the exposure of the reinforcing steel, which originates a problem in the structural behaviour. By coating surface of high strength concrete with fireproof mortar, the high strength concrete is protected from the spalling in fire and the method to constrain the temperature increase of steel bar within the concrete. The purpose of this study is to investigate the temperature history properties of lightweight mortar using perlite and polypropylene fiber for fire protection covering material. For this purpose, selected test variables were the contents and length of polypropylene fiber. As a result of this study, it has been found that addition of polypropylene fiber to mortar modifies its pore structure and this causes the internal temperature to rise. And it has been found that a new lightweight mortar can be used in the fire protection covering material.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.315-325
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• 2017

This study aims to provide information for the design and use of structural lightweight concrete (SLWC) for floating concrete structures in a marine environment. An experimental program was set up and comprehensive experimental campaign were carried out to determine SLWC mix proportions that can satisfy specified concrete strength, density, and slump values all of them were determined from previous research. Comparisons with previous SLWC mix designs that have been utilized for actual floating concrete structures were made. Key aspects needed to be considered regarding to the use of SLWC for floating marine concrete structures were discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.201-204
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• 2004

The purpose of this study is recycling of sewage sludge and fly-ash. In this experiment, green aggregates, which is a mixture of sewage sludge and clay and fly-ash, with different content of sewage sludge (up to $80wt\%$). Then they were burned in different soak temperatures from $1190^{\circ}C\;to\;1290^{\circ}C$ with changed soak time and heating rate at 5, 7, 10 minutes and $20^{\circ}C/min$, $30^{\circ}C/min$ respectively in order to produce lightweight aggregate (LWA). Data of both experiment series were generated to evaluate the quality of LWA as well as the relationship between burning condition and product's quality.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.280-281
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• 2014

Recently, it is certain that the increase of heating and cooling energy consumption by radical change in climate condition has caused serious problems related to environmental and energy concerns associated with increase of fossil fuel usage and carbon dioxide production as well as global warming. Therefore, various actions to reduce greenhouse gas and energy consumption have been prepared by world developed countries. The energy consumption by buildings approximately reaches 25% of total korea energy consumption. The greatest part in the buildings of the energy consumption is building facade. But a few research projects on concrete comprising more than 70% of outsider of buildings has been tried. This research is structural insulation concrete what improved insulation performance using micro form admixture and calcined diatomite powder and lightweight aggregate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.40-41
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• 2013

The energy consumption by buildings approximately reaches 25% of total korea energy consumption. The greatest part in the buildings of the energy consumption is building facade. but a few research projects on concrete compising more than 70% of outsider of buildings has been tried. This research is structural insulation concrete what improved insulation performance using micro form admixture and calcined diatomite powedr and lightweight aggregate.

• Advances in nano research
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• v.13 no.5
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• pp.499-512
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• 2022

This study investigates the efficiency of ensemble machine learning for predicting the lightweight-aggregate concrete (LWC) characteristics. A stacking ensemble (STEN) approach was proposed to estimate the dry density (DD) and 28 days compressive strength (Fc-28) of LWC using two meta-models called random forest regressor (RFR) and extra tree regressor (ETR), and two novel ensemble models called STEN-RFR and STEN-ETR, were constructed. Four standalone machine learning models including artificial neural network, gradient boosting regression, K neighbor regression, and support vector regression were used to compare the performance of the proposed models. For this purpose, a sum of 140 LWC mixtures with 21 influencing parameters for producing LWC with a density less than 1000 kg/m³, were used. Based on the experimental results with multiple performance criteria, it can be concluded that the proposed STEN-ETR model can be used to estimate the DD and Fc-28 of LWC. Moreover, the STEN-ETR approach was found to be a significant technique in prediction DD and Fc-28 of LWC with minimal prediction error. In the validation phase, the accuracy of the proposed STEN-ETR model in predicting DD and Fc-28 was found to be 96.79% and 81.50%, respectively. In addition, the significance of cement, water-cement ratio, silica fume, and aggregate with expanded glass variables is efficient in modeling DD and Fc-28 of LWC.

• Fire Science and Engineering
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• v.25 no.5
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• pp.8-13
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• 2011

High strength concrete is the occurrence of explosive spalling associated with high temperature such as a fire. The spalling causes the sever reduction of the cross sectional area with the exposure of the reinforcing steel, which originates a problem in the structural behaviour. The purpose of this study is to investigate the mechanical properties of lightweight mortar using perlite and polypropylene fiber for fire protection covering material. For this purpose, selected test variables were the ratio of water to cement, the ratio of cement to perlite, contents of polypropylene fiber. As a result of this study, it has been found that addition of perlite and polypropylene fiber to mortar modifies its pore structure and reduces its density. And it has been found that a new lightweight mortar can be used in the fire protection covering material.

• Journal of the Korea Institute of Building Construction
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• v.13 no.5
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• pp.491-497
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• 2013

The objective of the present study is to establish a straightforward mixture proportioning procedure for structural lightweight aggregate concrete (LWAC), and evaluate the selection range of the targeted dry density of concrete against the designed concrete compressive strength. In developing this procedure, mathematical models were formulated based on a nonlinear regression analysis over 347 data sets and two boundary conditions of the absolute volume and dry density of concrete. The proposed procedure demonstrated the appropriate water-to-cement ratio and dry density of concrete to achieve the designed strength decrease with the increase in volumetric ratio of coarse aggregates. This trend was more significant in all-LWAC than in sand-LWAC. Overall, the selection range of the dry density of LWAC exists within a certain range according to the designed strength, which can be obtained using the proposed procedure.