• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.97-100
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• 2009

This study is a basic experiment to complement the problems in decrease of strength in case we change lots of fly ash("FA" here in after) in ordinary portland cement("OPC" here in after). Mixing plaster that is known to be effective in improvement in hydration of blast furnace slag powder("BS" here in after). After FA changed concrete is mixed, the study physical proporties such as compression strength, increased proportionaly. When second-class BS 5 % and gypsum 2 % changed, compare to OPC strength approximately 120 % was recorded after one day. In FA 20 % case, according to the ratio of gypsum changed results showed similar trend, but compared to FA 10 % changed concrete, expression strength improvement was lower.

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.494-498
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• 2012

Geopolymer cements and geopolymer resins are newly advanced mineral binders that are used in order to reduce the carbon dioxide generation that accompanies cement production. The effect of additives on the compressive strength of geopolymerized class-F fly ash was investigated. Blast furnace slag, calcium hydroxide($Ca(OH)_2$), and silica fume powders were added to fly ash. A geopolymeric reaction was initiated by adding a solution of water glass and sodium hydroxide(NaOH) to the powder mixtures. The compressive strength of pure fly ash cured at room temperature for 28 days was found to be as low as 291 $kgf/cm^{-2}$, which was not a suitable value for use in engineering materials. On the contrary, addition of 20 wt% and 40 wt% of blast furnace slag powders to fly ash increased the compressive strength to 458 $kgf/cm^{-2}$ and 750 $kgf/cm^{-2}$, respectively. 5 wt% addition of $Ca(OH)_2$ increased the compressive strength up to 640 $kgf/cm^{-2}$; further addition of $Ca(OH)_2$ further increased the compressive strength. When 2 wt% of silica fume was added, the compressive strength increased to 577 $kgf/cm^{-2}$; the maximum strength was obtained at 6 wt% addition of silica fume. It was confirmed that the addition of CaO and $SiO_2$ to the fly ash powders was effective at increasing the compressive strength of geopolymerized fly ash.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.1
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• pp.35-41
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• 2013

In this study, we investigated the strength development and durability of geopolymer mortar using blast furnace slag only, and admixed with blast-furnace slag and fly ash as cementious materials in oder to develop cementless geopolymer concrete. In order to compare with the geopolymer mortar, the normal mortar using ordinary portland cement was also test. In view of the results, we found out that strength development, the resistance to freezing-thawing of the geopolymer mortar have better than the mortar using ordinary portland cement. Especially, using the combined with blast furnace slag and fly ash develop high strength of above 60 MPa, and improve the resistance of freezing-thawing of approximately 20%, but promote the velocity of carbonation of 2.2~3.5 times.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.43-44
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• 2023

This study evaluated the mechanical and electrical properties of low-cement mortar using a large amount of industrial by-products to reduce carbon emissions from the cement industry. As types of industrial by-products, blast furnace slag and fly ash, which are representative materials, were used, and ultra-high fly ash was mixed and evaluated to solve the problem of initial strength loss. In addition, in order to evaluate the electrical properties, 1% of MWCNT was incorporated relative to the powder mass. As experimental items, the compressive strength was measured on the 1st, 3rd, 7th and 28th days of age, and the rate of change in electrical resistance was measured on the 28th day of age. As a result of the experiment, the initial strength of the test specimen mixed with blast furnace slag and fly ash was significantly lower than that of 100% cement, and the specimen mixed with blast furnace slag showed strength equal to that of cement at 28 days of age. As an electrical characteristic, the electrical resistance was reduced when the load was loaded, and this reason is judged to be the effect of improving the conductivity as the connection between CNTs is narrowed by the compressive load.

• Cement
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• s.62
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• pp.49-55
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• 1976

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.297-298
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• 2023

In the concrete industry, efforts are being made to reduce CO₂ emissions, and technologies that collect, store, and utilize CO₂ have recently been studied. This study analyzed the change in compressive strength after the accelerated carbonation test of Non-Sintered Cement(NSC) mortar. Type C Fly Ash and Type F Fly Ash were mixed in a 1:1 ratio and then mixed with Blast Furnace Slag fine powder to produce NSC. The mortar produced was cured underwater until the target age. In addition, an accelerated carbonation test was conducted under the condition of a concentration of 5 (±1.0%) of CO₂ gas for 14 days. The mortar compressive strength was measured before and after 14 days of accelerated carbonation test based on the 7th and 28th days of age. As a result of the experiment, the compressive strength was improved in all binder. In general, the compressive strength of NSC mortar subjected to the accelerated carbonation test was similar to that of Ordinary Portland Cement(OPC) mortar not subjected to the accelerated carbonation test.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.687-690
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• 2005

Recently, to consider financial and constructive aspect, usage of Admixture, like Blast- Furnace Slag and Fly-Ash, are increased. These mineral admixtures, a by-product of steel industry, have many advantage, to reduce the heat of hydration, increase in ultimate strength, improve workability and etc. But it also reduces early-age strength, so it is prevented from using of Blast-Furnace Slag at cold-weather-concrete. In this study, for the purpose of increasing usage of mineral admixtures, like Blast-Furnace Slag and Fly ash, it is investigated the strength properties of concrete subjected to under low temperature According to this study, if early curing is carried out before having frost damage, the strength of concrete, subjected to frost damage, is recovered. And to consider increasing effect of strength, it is more effective to use of mineral admixtures, especially to use blast furance slag.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.135-136
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• 2019

Recently, as the interest in environmental issues increases, the construction industry needs to recycle blast furnace slag, circulating fluidized bed Combustion fly ash, etc. to solve industrial by-products, and to develop artificial stone. In this study, the strength characteristics based on blast furnace slag according to the addition rate of alkali stimulant NaOH are investigated. The experimental results showed that the flexural and compressive strengths increased with the addition of alkali stimulants. Based on these results, it will be presented as a basic research data for the manufacture of artificial stone and will be tested later.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.415-420
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• 2002

This study is intended to investigate the influence of mineral admixtures on the autogenous and drying shrinkage of high performance concrete. According to results, drying shrinkage increases with increase of fly ash content, and it does not show difference with replacement of blast furnace slag powder. It increases when incorporating silica fume or fly ash and silica fume together. The autogenous shrinkage shows increasing tendency with increase of silica fume and blast furnace slag powder content, and incorporating of silica fume or fly ash and silica fume together has effects on reducing autogenous shrinkage. Therefore, it is considered that application of both silica fume and fly ash can reduce the cracks caused by autogenous shrinkage, including enhancement in strength and placeability of high performance concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.595-598
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• 2005

Recently, owing to the development of industry and the improvement of building techniques, the concrete structure is becoming larger and higher. In hardening these large concrete, the heat of hydration gives rise to considerable thermal stress depending on the size and environmental condition of concrete, which might cause thermal cracking. Especially, the crack may cause severe damage to the safety and the durability of concrete structure. This study is investigated the thermal properties of concrete according to several binder conditions, such as OPC, Belite rich cement(BRC), slag cement(SC), blast furnace slag (BFS) added cement, fly ash added cement and BFS-fly ash added cement. As a result of this study, the concrete made with BRC, fly ash($25\%$) added cement and BFS($35\%$)-fly ash($15\%$) added cement gets superior effect in the control of heat hydration.