• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.356-362
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• 2016

Light-weight concrete uses forming agents for reducing weight and high heat insulation property. However, the forming agents make problems of decreased volume and compressive strength of the concrete. This research aims to having weight-reduction and securing heat insulation property using recycled wasted form polyurethane without any forming agents. A small quantity of admixture used for constructability and avoiding material segregation. We picked admixtures from two different companies which shows evenly dispersed of wasted form polyurethane. This research conducts a study on the effect of mixing ratio of admixture on the light-weight concrete used wasted form polyurethane. As a result of the test, increased mixing ratio of the admixtures results reduced fluidity of concrete. On the other hand, percentage of moisture content and compressive strength are increased slightly. Combustibility performance and sound insulation performance are also secured, as well.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.923-930
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• 2005

This paper was to evaluate the high strength lightweight self-compacting concrete(HLSCC) manufactured by Nan-Su, which main factor, Packing Factor(PF) for mixing design, has been modified and improved. We have examined HLSCC performance at its fresh condition as well as its mechanical properties at the hardened condition. The evaluation of HLSCC fluidity has been conducted per the standard of second class rating of JSCE, by three categories of flowability(slump-flow), segregation resistance ability(time required to reach 500mm of slump-flow and time required to flow through V-funnel) and filling ability(U-box test) of fresh concrete. The compressive strength of HLSSC at 28 days has come out to more than 30MPa in all mixes. The relationship between the compressive strength-splitting tensile strength and compressive strength-modulus of elasticity of HLSSC were similar those of typical lightweight concrete. Compressive strength and dry density of HLSCC at 28 days from the multiple regression analysis resulted as $f_c=-0.16LC-0.008LS+50.05(R=0.83)\;and\;f_d=-3.598LC-2.244LS+2,310(R=0.99)$, respectively.

• Journal of the Korea Institute of Building Construction
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• v.8 no.5
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• pp.59-65
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• 2008

In the evaluation method of KS on the activity factor of fly ash, same amount of cement should be replaced with fly ash. Therefore, contradictory effects on concrete strength exist, i. e. strength decease due to low content of cement and strength increase of strength due to filling-pore-function of fly ash. European Committee for Standardization (CEN) specifies the method 1 to 4. adding fly ash without reducing the content of cement, for the evaluation method on activity factor of fly ash. This study investigates the applicability of the method 2 of CEN to mix design of concrete. The followings are derived ; There is a key ratio of f)y ash mixing which enhances the incremental ratio of mixing water to improve fluidity of mortar. The incremental ratio of mixing water is maximized about 11% ratio of fly ash mixing. Compressive strength most slightly increases at that ratio of fly ash mixing. Activity factor of fly ash increases as water-cement ratio becomes low and contents of fly ash becomes high. Moreover, quality of fly ash and condition of mix design affect the applicable amount of fly ash and available range of water-cement ratio. However, this method has some problems for practical purpose because activity factors of fly ash for some cases are over 1.0. Further research should be conducted to develop more useful method of evaluating activity factor of fly ash.

• Journal of the Korea Institute of Building Construction
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• v.10 no.6
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• pp.145-154
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• 2010

As buildings have become higher and larger, the use of high performance concrete has increased. With this increase, interest in and use of ultra fine powder admixture is also on the rise. The silica fume and BSF are the admixtures currently being used in Korea. However, silica fume is exclusively import dependent because it is not produced in Korea. In the case of BFS, it greatly improves concrete fluidity and long-term strength. But a problem exists in securing early strength. Furthermore, air-cooled slag is being discarded, buried in landfills, or used as road bed materials because of its low activation energy. Therefore, we investigated in this study the usability of nano-slag (both rapidly-chilled and air-cooled) as an alternative material to the silica fume. We conducted a physic-chemical analysis for the nano-slag powder and performed a mortar test to propose quality standards. The analysis and testing were done to find out the industrial usefulness of the BFS that has been grinded to the nano-level.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.435-444
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• 2016

In Korea, approximately 48% of all households live in apartments, which are a form of multi-unit dwellings, and this figure increases up to 58%, when row houses and multiplex houses are included. As such, majority of the population reside in multi-unit dwellings where they are exposed to the problem of floor impact noise that can cause disputes and conflicts. Accordingly, this study was conducted to manufacture a high-weight, high-stiffness foamed concrete in order to develop a technology to reduce the floor impact noise. For the purpose of deriving the optimum mixing ratio for the foamed concrete that best reduces the floor impact noise, the amounts of the foaming agent, lightweight aggregate and binder were varied accordingly. Also, the target characteristics of the concrete to be developed included density of over $0.7t/m^3$, compressive strength of over $2.0N/mm^2$ and thermal conductivity of under 0.19 W/mK. The results of the experiment showed that the fluidity was very excellent at over 190 mm, regardless of the type and input amount of foaming agent and lightweight aggregate. The density and compressive strength measurements showed that the target density and compressive strength were satisfied in the specimen with 50% foam mixing ratio for foamed concrete and in all of the mixtures for the lightweight aggregate foamed concrete. In addition, the thermal conductivity measurements showed that the target thermal conductivity was satisfied in all of the foamed concrete specimens, except for VS50, in the 25% replacement ratio case for Type A aggregate, and all of the mixtures for Type B aggregate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.68-69
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• 2019

Integrating 3D printing into architecture is gaining attention because it allows construction of construction structures without formwork. Among them, 3D printing construction materials must have high flow performance and at the same time ensure the performance that does not collapse during lamination. Therefore, in this study, we tried to determine the fluidity and lamination properties of mortar formulations, and set the thickener incorporation ratio as the formulation parameters. As a result of this experiment, it was confirmed that the lamination performance was secured from the thickening agent mixing rate of 1.5%.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.127-128
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• 2020

This research is part of the research for unifying the mass concrete and utilizing the rate of super retarding agent. We analyzed the performance of super retarding agent 20℃ conditions. It was found that there was no deterioration in fluidity and air quality due to the change in the super retarding agent mixing rate. It was found that when super retarding agent was mixed up to 0.5 %, it was delayed for 22.3 hours at 20℃. Therefore in order to ensure the performance required at the site, the super retarding agent mixing rate must be determined by fully considering the situation at the site. In addition it will be analyzed that super retarding agent performance analysis at high temperature will be required in subsequent studies.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.83-90
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• 2006

This paper investigates experimentally the fire resistance performance and spatting resistance of high performance reinforced concrete column member subjected to fire containing polypropylene fiber(PP fiber) and cellulose fiber(CL fiber). An increase in PP fiber and CL fiber contents, respectively resulted in a reduction of fluidity due to fiber ball effect. Air content is constant with m increase in fiber content. Compressive strength reached beyond 50 MPa. Based on fire resistance test, severe failure occurred with control concrete specimen, which caused exposure of reinforcing bar. No spall occurred with specimen containing PP fiber. This is due to the discharge of internal vapour pressure. Use of CL fiber superior to control concrete in the side of spatting resistance, localized failure at comer of specimen was observed. Corner of specimen had deeper neutralization than surface of specimen. Specimen containing PP fiber had the least damaged area due to spatting. Neutralization depth ranged between 6 and 8 mm Residual compressive strength of specimen containing PP fiber maintained 40%, which is larger than control concrete with 20% of residual strength. Specimen containing CL fiber had 25% or residual strength.

• Journal of the Korea Institute of Building Construction
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• v.12 no.3
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• pp.284-290
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• 2012

Cement Fineness Modulus (CFM) is a method of expressing the distribution of particle sizes of cement in numeric form. If CFM is controlled through crush process of cement without modifying the chemical components or mineral composition of cement, it is judged to be able to produce a cement satisfying various requirements because it is estimated to enable various approaches to cement such as high early strength, moderate heat, low heat cement and so on. Therefore, in this study, as basic research for manufacturing special cement utilizing the controls of CFM, the intention was to review the impacts of CFM on the fundamental properties of concrete. To summarize the result, as mixture characteristics of fresh concrete, ratio of small aggregate and unit quantity were gradually increased, securing greater fluidity, with an increase in CFM, while the amount of AE and SP were reduced gradually. In addition, setting time was delayed as CFM increased. Furthermore, compression strength was relatively high during initial aging as CFM became smaller, but as time passed, compression strength became smaller, and it showed the same level of strength as aging time passed about three years.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.173-179
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• 2014

This is an experimental study for recycling coal ash left over from coal use as a potential fine aggregate in concrete. Coal ash is generally divided into either fly ash or bottom ash. Fly ash has been utilized as a substitution material for cement in concrete mixes. On the other hand, bottom ash has the problem of low recycling rates, and thus it has been primarily reclaimed. This study partially substituted fine concrete aggregates with bottom ash to increase its application rate and therefore its recycling rate; its suitability for this purpose was confirmed. The concrete's workability dropped noticeably with increasing bottom ash content when a fixed water-cement ratio of concrete mix was used. Thus, concrete mixes with higher ratio levels are required. To address this problem, concrete was mixed using a polycarboxylate high-range water reducing agent. The fluidity and air entrainment immediately after mixing the concrete and 1 h after mixing were measured, thereby replicating the time concrete is placed in the field when produced either in a ready-mixed concrete or in a batch plant. As a result of this research, the workability and air entrainment were maintained 1 h after mixing for a concrete mixture with approximately 30% of its fine concrete aggregates substituted with the bottom ash. A slight drop in compression strength was seen; however, this confirmed that potential of using bottom ash as a fine aggregate in concrete.