• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.83-88
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• 1997

In this paper, we described the basic elements (relative flowing area ratio and funeling velocity ratio in mortar, flowability and self-compactibility in concrete, and etc.) required for the maximum mix design of the super flowing concrete (SFC) using manufactured sand. Also, manufactured sand and fly ash were used for investigating characteristics of SFC through various experiments (replacement ratio of manufactured sand, optimum mix condition) before producing the concrete in batch plant. As the result of this project, the SFC using manufactured sand up to 50% showed high flowability and self-compactibility in fresh concrete. Furthermore, its compressive strength is higher than normal concrete without manufactured sand. From now on, this study may suggest how to apply manufactured sand in the SFC.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.375-382
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• 1999

The use of compaction grouting system(C.G.S) evolved in the 1950's to correct structural settlement of buildings. Over the almost 50 years, the technology has developed and is currently used in wide range of applications. Compaction Grouting, the injection of a very stiff 'zero-slump' mortar grout under relatively high pressure, displaces and compacts soils. It can effectively repair natural or man-made soil strength deficiencies in variety of soil formations. Major uses of Compaction Grouting include densifying loose soils or fill voids caused by sinkholes, poorly compacted fills, broken utilities, improper dewatering, or soft ground tunneling excavation. Other application include preventing liquefaction, re-leveling settled structures, and using compaction grout bulbs as structural elements of minipiles or underpinning. So, on the basis of the case history constructed in recent year, a study has been performed to analyze the basic mechanism of the Compaction Grouting and verify the effectiveness of the ground improvement.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.185-188
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• 2004

The effect of fly ash to prevent detrimental expansion due to alkali -silica reaction was investigated through the ASTM C 1260 method that is one of the most commonly used method because results can be obtained within about 16 days. Reactive aggregate used is a netamorphic rock and sedimentary rock. The replacement proportions of portland cement by fly ash were respectively 0, 5, 10, 15, 25 and 35 percent. Expansion of mortar bars due to alkali-silica reaction decreased with the increase of fly ash content. The results show that the expansion due to alkali-silica reaction is dramatically reduced in the presence of high volume fly ash. When the fly ash content examine from all angles (strength and a flow), the replacement proportions of fly ash is about $25\%$ in order to control on expansion.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.10-19
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• 2013

Recently, researches related to precast modular construction have been actively conducted for nuclear power plant, LNG gas tank, and small-medium PCCV as well as bridges and buildings. In this study, the precast panel cast with steel mesh reinforced mortar (SRM) which is similar reinforced ferrocement was developed for efficient precast construction, construction time reduction, and easy transportation. Mortar mixture with high strength and flowability was obtained from various case studies using silica fume and GGBS. Also, $1,200{\times}600{\times}150mm$ SRM and reinforced concrete (RC) panels were manufactured with reinforcing ratio of 2% and 4%. To verify structural performance of the SRM specimen, the basic material tests, free shrinkage test, and 3-point flexural test with a line loading were carried out. From the test results, it was determined that SRM specimens showed outstanding flexural capacity and ductility. However, the 4% reinforced SRM specimens must consider shear reinforcing to be used as a precast modular member.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.119-126
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• 2012

Portland cement production-1.5billion tonnes yearly worldwide-contributes substantially to global atmospheric pollution(7% of total of $CO_2$ emissions). Attempts to increase the utilization of fly ash, by-products from thermal power plant to partially replace the cement in concrete are gathering momentum. But most of fly ash is currently dumped in landfills, thus creating a threat to the environment. Many researches on alkali-activated concrete that does not need the presence of cement as a binder have been carried out recently. Instead, the sources of material such as fly ash, that are rich in Silicon(Si) and Aluminium(Al), are activated by alkaline liquids to produce the binder. Hence concrete with no cement is effect reduction of $CO_2$ gas. In this study, we investigated the influence of the compressive strength of mortar on alkaline activator and curing condition in oder to develop cementless fly ash based alkali-activated concrete. In view of the results, we found out that it was possible for us to make alkali-activated mortar with 70MPa at the age of 28days by using alkaline activator manufactured as 1:1 the mass ratio of 9M NaOH and sodium silicate and applying the atmospheric curing after high temperature at $60^{\circ}C$ for 48hours.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.1-9
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• 2020

Chloride ion, which penetrates into the cement composites from the outside, generally diffuses by the concentration gradient. Chloride ions are adsorbed by the chemical reaction with cement hydrates. Recent studies have shown that anion exchange resin (AER) powder can effectively adsorb the chloride ion in the cement composites, and thus, the cement composites containing AER have a high chloride adsorption capacity and a good resistance for chloride penetration. In this study, the chloride adsorption ability of the AER powder was investigated under the conditions of distilled water and calcium hydroxide saturated solution to determine if the AER powder is less effective to increase the chloride adsorption ability after grinding process. The chloride adsorption ability of AER powder was compared with the previous research about the chloride adsorption of AER bead. In addition, the compressive strength, chloride diffusion coefficient (using NT Build 492 method), and the chloride profile of cement mortar substituted with AER powder were investigated. There was no decrease in the chloride adsorption capacity of AER powder but increase in the kinetic property for chloride adsorption after the grinding process. The AER powder could absorb the chloride ion in the mortar quickly, and showed better chloride ion adsorption ability than the cement hydrates.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.713-718
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• 2009

Advanced industries-IT, BT, NT and ET are rapidly developing in 21 century. And the cement industry is becoming the principal factor in air pollution because of the creation of $CO_2$ during manufacturing. Also, the cement industry will be faced with a crisis due to the exhaustion of natural resources. In this study, nano cement by Bottom-up method of a chemical synthesis was developed. The generation of $CO_2$ during the plasticization process of cement manufacturing was avoided. The purpose was to produce building materials that have both high strength and durability as the high value-added growth engine industry of the 21 century. The nano cement was developed using hydrothermal synthesis. This is a method of mixing after ripening, by manufacturing the high density gel and low gel, which does not require special test equipment or pressure conditions to produce. Particle size, SEM, EDX, and porosity tests were conducted. This study investigated the compressive strength of concrete with various compositions. Specimens were tested for compressive strength at 3, 7, 14 and 28 days. The medium-sized (50% by weight) cement particles created by chemical synthesis were less than 168 nm. The compressive strength of the mortar prepared using this cement was 53.9 MPa. But it was judged that succeeding study will be necessary for development of nano building materials with high ability and economical analysis.

• Journal of the Korea Concrete Institute
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• v.13 no.1
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• pp.54-61
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• 2001

As a part of the movement of natural resources conservation, there have been doing many recycling research works for obsolete aged tire, wasted plastic materials, etc. The purpose of this experimental study is to develop glass concrete by recycling wasted glasses as a cementitious constituent in concrete. First of all, the optimum replacement ratio of powdered waste glasses(PWG) can be determined through pilot compressive strength test on normal and high strength concrete cylinders, which have been made in various mix proportions by changing the replacement ratio of PWG. Then, further tests have been done to figure out mechanical properties of most desirable glass concrete with optimum replacement ratio of PWG, such as static modulus of elasticity, compressive and tensile strengths, flexural strength. On the other hand, the alkali-silica reactions by the mortar-bar method(KS F 2546) have been experimentally doing in various grain sizes of PWG, since the alkali in the cement has a tendency to react with the silica in the PWG. In can be confirmed from the test that glass concrete can have better workability than concrete with silica fume, and they are alike in compressive strength. It is concluded that wasted glasses can be used as pratical additives for economic and environmentally friendly concrete.

• Resources Recycling
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• v.22 no.3
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• pp.36-42
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• 2013

According to the recent community-based structures enlargement, specification, and diversification. It needs appropriate construction materials in terms of intensity and environmental aspects. Thus, in manufacturing the cement using micro limestone powder which is main material. It is also expected to save energies and reduces $CO_2$, by using the blast furnace slag and fly ash which are mitigated environmental load construction materials that emerged. In this research, The durability aspect tries to be grasped considering the chemical property according to the coherence of the hydration product. Consequently, The compressive strength was measured over 30 Mpa on 3rd. In addition, according to the content of the limestone powder, the setting time is promoted. It has the feature expanded in the length change. And it is determined because the possibility of replacing the existing for construction material such as it is measured compared with the time to use the portland cement usually that flexural strength is high with the age 7 days ago, so it is sufficient.

• Journal of the Korea Institute of Building Construction
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• v.10 no.6
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• pp.61-66
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• 2010

As global warming has had harmful effects on the environment, the construction industry has made efforts to reduce the amount of $CO_2$ generated in the process of cement production. There is an urgent need for an alternative material that can replace cement. To improve the initial strength and economical efficiency pointed out as problems, this research was conducted for Blast Furnace Slag (BFS), an industrial byproduct. Non-sintering cement (NSC) was used by minimizing the amount of high-priced alkali activators. By using Nano-technology, fineness has been maximized, to enhance the initial strength of BFS. This research is based on non-sintered cement replaced by nano-slag using alkali activators, and the fundamental properties and quality of the non-sintered cement were investigated. A variety of activators were used, up to 10 percent of the slag weight. This research aims to present fundamental data through a comparative analysis of flexural strength, compressive strength, time of setting, diabetic temperature, and rising heat.