• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.695-698
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• 2005

Ever since man learnt to build homes and cities around 10,000 years ago, clay materials has undoubtedly been one of the most widely-used construction materials in the world. However, the clay has poor strength, water resistance and durability, thus being limitedly used as calcined clay after being calcined. Pozzolan materials is to improve the strength and the durability of concrete as a result of the pozzolanic reaction. Therefore, the purpose of this study is to analyzes ingredient about clay mineral about Chung-buk area 10 places and to examine the application of clay minerals for the concrete admixtures.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.307-308
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• 2009

The ultra high strength concrete classed 80 MPa for Lotte Town at pusan has many hydrated materials due to low water to binder ratio and high admixture contents and improved void structure caused by C-S-H gel corresponding to pozzolan and latent hydraulicity of FA and BS. Moreover, durability of the concrete is superior because there was no penetration of carbon dioxide, chloride and chloric ion caused by its fine internal constitution.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.109-110
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• 2013

The purpose of this study was to investigate pozzolanic activity according to the firing temperature of the rice straw ash. In order to measure amount of SiO2 of rice straw ash, XRF(X-ray fluorescence) analysis was tested. Also to evaluate properties of mortars using rice straw ash, mortar flow, cement setting time, compressive strength was tested. As a results, as the mortar with a mixture ratio of rice straw ash up to 15% was found to have a compressive strength superior to that of plain mortar.

• Clean Technology
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• v.7 no.2
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• pp.109-117
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• 2001

Whereas commonly used to make concrete having rich water contents as binder or mineral admixture, blast furnace slag has been rarely applied to manufacture in concrete based products having poor water contents. This study, for the multi-recycling of blast furnace slag, is to analyze strength enhancement mechanism of concrete based products using blast furnace slag. The results of this study are following. We found that blast furnace slag is very effective mineral admixture to manufacture high strength spacer having over $400kgf/cm^2$ in compressive strength. Also, enhancement of strength by blast-furnace slag are responsible to densified grading and pozzolanic reaction.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.753-756
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• 2006

This paper discussed pozzolanic reaction properties of classified fly ashes by using of electrostatic precipitator. Blaine values of fly ashes at hoppers are respectively about 3000(ordinary), 5000(fine) and 8000cm2/g(super-fine). The pozzolanic reactivity of fly ash at early stage and at later stage are respectively related to the related to the fineness and the glass content of fly ash. But the early hydration of cement was retarded by addition of super fine fly ashes. the adiabatic temperature rise of mortar containing fly ash is increased with the fineness of fly ashes.

• Magazine of the Korea Concrete Institute
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• v.6 no.5
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• pp.131-139
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• 1994

The min aim of thls study was to evaluate the effect of particle slze of the fly ash as a cement additive. Experimental work was carried out with three different sizes of fly ash. 18.58, 8.95 and 4.02{$mu}m$ in average radius. Namely, the effect of particle size variation of fly ash on the physical properties of cement paste was investigated. The jluidity was decreased with increasing the addition of fly ash to cement paste regardless of the particle size variation. The decrement of the fluidity of the pulverized fly ash was higher than that of the spherical fly ash. On the other hand, the pozzolan reactivity increased with lowering particle size. In the case of specimens with 5% up to 10% addition of fly ash having a particle size of 4.02{$mu}m$. the compressive strength was increased as compared with the plain specimens before curing for 28 days and showed higher value above 800kg /$cm^2$ when cured for 60 days.This increased compressive strength was ascribed to both the closer packlng of fine particles and the pozzolan reactivity of fly ash. These results were comfirmed by measuring both the porosity of the specimens and Ca(OH ), contents remained in specimens. This work showed that could be effectively ut~lized as a blending material without any de crease in the strength of early hydration stage if we can control the particle size of fly ashes by sizing or pulverizing.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.2
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• pp.47-53
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• 2010

Very-early strength latex-modified concrete (VES-LMC) was developed with a focus on workability, strength development and long-term durability that would allow for opening a bridge to traffic only 3 hours after concrete placement, which would be useful when repairing concrete bridge deck overlays. However, even though usage of latex in VES-LMC improves the durability, it has a disadvantage that it produces lots of entrained air. Therefore, specific plan is necessary since it is weak for freezing and thawing in air-void structure. In the present study ultra-fine fly ash (UFFA) was used. Test results are follows ; Air content of VES-LMC UFFA (VES-LMC using UFFA) concrete was decreased since major pozzolan reaction was happened in one day. It was also found that total air content of concrete was decreased with pozzolan reaction since air content in 28 days was the same with one day air content. The addition of calcium hydroxide increased entrained air which is smaller than size of 200 ${\mu}m$. It was effective to improve the air-void structure of VES-LMC since spacing factor can be confirmed as smaller than size of 200 ${\mu}m$ using more than 15% of UFFA.

• Journal of the Korea Institute of Building Construction
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• v.12 no.2
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• pp.161-168
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• 2012

The purpose of this study was to investigate the influence of recycled aggregates powder (RP) contents on recycled aggregates (RA) using fly-ash (FA) mortar in a condition of zero cement targeting earth filling materials, and the results can be summarized as follows. First, there was a tendency that as RP contents increased, W/B and air contents increased also. In the case of compressive strength, the strength was hardly developed at the early age, which was prior to 14 days; however, with the starting point of 14 days of age, strength of around 1.5~2.0 MPa was developed when it arrived at 28 days. At a curing temperature of $20^{\circ}C$, the more RP contents increased, the more the compressive strength increased in comparison with FA 100% at all levels except RP 100 %, showing the highest compressive strength at RP 25 %. At a curing temperature of $35^{\circ}C$, the temperature-dependence appeared to be large, as the RP contents were decreased compared to the curing temperature of $20^{\circ}C$. In addition, based on SEM analysis, this study was able to confirm that a pozzolanic reaction formed by an alkali stimulus of RA with the lapse of certain days even in 100 percent FA, causing the densification of tissues, and with RP 25%, hydrate was created the most densely by the hydration of unhydrated cement particles and pozzolanic reaction of FA.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.53-60
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• 2017

Fly ash(FA) which is a byproduct in the coal combustion in thermal power plant contributes to pore structure densification due to pozzolanic reaction, and this leads to long-term strength development and excellent resistance to chloride penetration. In the work, compressive strength and chloride resistance in OPC(Ordinary Portland Cement) and FA-based concrete are evaluated, and the relationships are investigated considering ages. For the work, 3 different W/B (Water to Binder) ratios of 37%, 42%, and 47% are prepared, and 3 substitution ratio of fly ash(0%, 30%, and 50%) are considered as well. At the age of 28 days and 180 days, test results of compressive strength, diffusion coefficients based on Tang's method, and passed charges referred to ASTM C 1202 and KS F 2711 are obtained. With increasing replacement ratio of FA and decreasing W/B, the resistances to chlorides(diffusion coefficient and passed charge) are improved, and the results at the age of 180 days decrease to only 15% level at the age of 28 days due to pozzolanic reaction in FA 50 mixture, which shows that resistance to chloride is much dependent on age effect than strength development. After 180 days, more clear linear relationships are observed between strength and resistance to chloride.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.1
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• pp.49-57
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• 2013

Recently, recycling of industrial by-products and CO2 reduction have been important issues in the world. In this reason, applications and reuse of Fly ash as a binder for concrete, which is generated in thermoelectric power plant, have been one of the effective recycle methods. In order for Fly ash to be applied to concrete, Korean Standard(KS) has selected and managed quality such as $SiO_2$, fineness, specific gravity, ignition loss and activity index. However, there is a limits for activity index, whose test period required is at least 28 days or 91 days. Activity index is the critical indication standard to determine mechanical strength of concrete that contained Fly ash. To complement the disadvantage of test method, this research provided "API test method", which quickly measure Pozzolanic reaction of Fly ash can be considered as a alternative of activity index. Then, the adaptable API test method need to be investigated through comparative analysis with the test result of API, activity index and K-value. The test method can make evaluation of Fly ash quality faster and more accurate. As a result, most Fly ash produced in Korea has not been satisfied in the KS quality standard except water content and specific gravity, and especially fluidized bed boiler ash has its characteristics. Also, API, activity index and K-value have superior interrelationship. The interrelationship between API and activity index and K-value gets increased as the material age gets higher, so API test can be considered as very useful test method for Pozzolanic reaction evaluation of Fly ash.