• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.37-38
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• 2023

As one of the resource recovery projects, this study aims to select natural fibers and synthetic fibers that can be used for concrete mixing among waste fibers and reuse them for the base concrete mixture. Using waste fiber, we seek a solution to the problem of reduced fluidity and hardening time of fiber-reinforced concrete and find the optimal mix of the ground concrete mixed with waste fiber.

• Journal of Conservation Science
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• v.32 no.3
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• pp.299-312
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• 2016

The Daehan Uiwon (Historic Site No. 248) in which the predecessor of Seoul National University Hospital is a crucial medical institution that built in the Korean Empire period. One of them, East 1 Affiliated Ward that attached to Daehan Uiwon was built with concrete foundation in 1908 and extended two times in 1935 and 1954. As a result of material scientific analysis for concrete foundation, all of the foundation is composed of mortar and stone aggregates, however, the mixing proportions between the aggregate and the mortar were confirmed to be different with construction periods. To determine the mixing proportion, and physical properties by ultrasonic velocity and rebound hardness, the concrete foundations by construction period were obtained. In result, 1954's mixing proportion of concrete between mortar and stone aggregate indicated the highest ratio of aggregates with 1 : 35, mean value of ultrasonic velocity and unconfined compressive strength were calculated with 450 m/s and 18.92 MPa in 1954's constructions that is the lowest values compared with other times. As a result, the difference characteristics of physical properties by construction periods are possible interpreted with porosities and mixing ratios of stone aggregates.

• Resources Recycling
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• v.29 no.1
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• pp.43-52
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• 2020

The objectives of this study were to identify the optimal mix of foam concrete with the low-strength and high-flow for the repairing ground subsidence situation emergently by utilizing a large amount of industrial by-products and evaluate the possibility by applying it to the site. The factors of the experiment were the mixing ratio of mixing water and a foaming agent and the mixing ratio of foam over paste volume. The optimal mix identified by the experiment was applied to the field and basic properties were evaluated. The results of the experiment showed that the optimal mixing ratio of mixing water and the foaming agent was 10%. Moreover, when the mixing ratio of pre-foam over paste volume was 170%, it satisfied the target. However, to ensure stable quality when applying to the field, the foam mixing ratio was set 140% for the field application. The field application test of foam concrete with the low-strength and high-flow using an eco-friendly binder satisfied all target performances. Therefore, the possibility of using it as a mixture and construction method for a ground repair system is confirmed. However, there was a quality deviation between the upper part and the lower part due to the separation between foam and paste. Consequently, further studies are needed to improve it.

• 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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.5
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• pp.147-156
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• 2006

This study is purposed to improve the performance of concrete made of recycled coarse aggregate. For this, recycled aggregate concrete was produced with SBR latex, and fluidity, dynamic performance and drying shrinkage were examined. According to the result, with mixing 6% of SBR latex, fluidity having resistance against segregation can be insured and compressive and flexural strength was increased. Especially the increment in terms of flexures was remarkable. In addition to, with above mixing ratio, drying shrinkage was reduced. Therefore there is a strong inference that superior recycled aggregate concrete can be produced with using 6% of SBR latex.

• Computers and Concrete
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• v.21 no.2
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• pp.139-147
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• 2018

Due to enhanced construction requirement, ready mixed concrete are being popular day by day. The current study aimed to develop ready mixed concrete using GBFS contained cement and determine its properties of fresh and hardened states. A real scale experiment was set up in a ready mixed plant for measuring workability and compressive strength. The workability was tested after mixing (within 5 minutes), 30, 60, 90, 120 and 150 minutes of the running of bulk carrier. The ready mixed carrier employed spinning motion i.e., rotating around its axis with 20 RPM and running on road with 1km/h speed. The mixing ratio of cement: sand:gravel, water to cement ratio, super plasticizer were, 1:1.73:2.47, 0.40 and 6% of cement, respectively. The chemical composition of raw material was determined using XRF and the properties of cements were measured according to ASTM standards. The experimental results confirm that the cement with composition of 6.89% of GBFS, 4% of Gypsum and 89.11% of clinker showed the good compressive strength and workability of concrete after 150 minutes of the spinning motion in bulk carrier.

• Journal of the Korean Society of Safety
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• v.20 no.2 s.70
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• pp.84-90
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• 2005

This study is to use results of the experiment on the influence to the strength by mixing powders of wasted tires into regular remicon within a range of little effectiveness in durability, applicability, economic aspect, and workability, to put it to practical use and to apply as basic data from a view of recycling wasted tires as construction materials. And the concrete, which was mixed with 10mm particles with ratio of $0.5\%\;and\;1.0\%$ respectively at 270 of mixing strength, was reduced by $27\%$ in compressive strength compared to normal concrete, whereas concrete mixed with other than 10mm particles showed lower decrease ratio compared to the former by reducing only $1.0\%\~1.5\%$. it is found that as strength increases, the less in quantity of aggregate and the more increase in quantity of cement. When considered to the above result, it is estimated that concrete mixed with wasted tire particles could be better used in conditions of compressive force rather than tensile force, and could also be used for structures with flexural strengths as well. In conclusion, higher strengths could be made using waste tire mix.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.585-588
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• 2006

The environment-friendly building material, photocatalyst/scoria/loess concrete, was prepared using scoria and loess (which have merits as building materials) and photocatalyst (which has the functions to compose the environmental contaminants and of self cleaning). In order to apply this material as a building material, the compressive and flexible strengths, and water absorptivity (which have been set by Korea Industrial Standard) were measured. The optimum mixing ratio of photocatalyst/scoria/loess concrete was obtained at the condition of $393kg/m^3$ of coarse aggregate, $802kg/m^3$ of fine aggregate in case of scoria, $80kg/m^3$ of loess, $12kg/m^3$ of photocatalyst, $400kg/m^3$ of cement, and $2kg/m^3$ of AE water reducing agent. The photocatalyst/scoria/loess concrete prepared by above mixing ratio of raw materials showed 25 MPa of compressive strength, $3.8{\sim}4.6$ MPa of flexible strength and $11.4{\sim}12.0%$ of water absorptivity, indicating that the quality of this material was suitable for Korea Industrial Standard (more than 21 MPa for compressive strength, more than 2.0 MPa for flexible strength in case of lightweight aggregate, and less than 15 % for water absorptivity in case of clay brick) for using as a building material.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.713-716
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• 2008

In about the concrete application which recycles Ash the research came to be advanced as research in compliance with researchers relation actively in about cement substitutional concrete mixing ratio and burglar quality of existing. The research which it sees as fundamental research the research which it follows in cement substitutional concrete mixing ratio of existing and it researched different Bottom-Ash recycling qualities in about cup aggregate partial substitution Bottom-Ash application.

• Journal of the Korea Institute of Building Construction
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• v.8 no.5
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• pp.35-42
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• 2008

In this study, a sample was fabricated according to the recycled aggregate replacement level(0%, 30%, 60%), and the steel fiber mixing status in order to use recycled aggregate as a concrete alternative coarse aggregate, and then the materials and structural characteristics of recycled aggregate and steel fiber which impacted the reinforced concrete were analyzed. A conclusion was derived as follows. After considering the results of various material experiments and mock-up test, when a flexural strength and a ductility factor is increased and the replacement level is increased through mixing the steel fiber with the recycled aggregate concrete, the ductility and flexural strength reduction seems to be inhibited by adding the steel fiber. Also, it is indicated that the recycled aggregate has almost-similar compressive strength, tensile strength flexural strength and ductility capacity to the concrete which using the general gone even though the steel fiber is used and the replacement level is increased to 30%. Accordingly, the reinforced concrete frame using the steel fiber mixture and recycled aggregate seems to apply to the actual structure.