• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.609-616
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• 2021

In this experimental, water-repellent powder, which is a metal salt-based inorganic substance, and natural zeolite powder, which is a pozzolan-based material, were mixed into cement mortar, and their physical properties and resistance to moisture were confirmed. It was confirmed that the test specimen using natural zeolite at the same time had excellent resistance in the water permeation test and the chloride penetration test as compared with the test specimen in which the inorganic metal salt-based water-repellent powder was mixed alone. When a metal salt-based water-repellent powder is used, it cannot be uniformly dispersed inside water due to its insoluble property, and is limited to the surface. When used at the same time as natural zeolite, the setting time at the initial stage of hydration is fast due to the pozzolan reaction, and the water-repellent powder adheres to the porous of the natural zeolite and is evenly distributed inside the test specimen to generate some water resistance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.20-27
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• 2019

Compared to the development and manufacturing technology of electronic goods, the development of waste glass recycling technology is relatively insufficient, leading to the acceleration of waste of resources and environmental pollution. Although waste glass recycling technology is being actively developed overseas, waste glass recycling technology is insufficient in Korea, leading to the illegal dumping or burial of waste glass. Waste glass has been confirmed to have pozzolan reaction potential when having hydration reaction with cement. Waste glass is also reported to be effective in reducing bleeding and inhibiting the development of hydration heat by improving the physical properties of concrete and the rheology properties of fresh concrete. Therefore, this paper analyzed the strength characteristics and the effect of alkalic-silica reaction on the expansion of shielding concrete that used waste glass as fine aggregate. Where, suitable admixture materials were used as a measure to suppress the expansion.

• Journal of the Korea Institute of Building Construction
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• v.22 no.5
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• pp.425-430
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• 2022

Concrete used for the foundation of high-rise buildings is often placed through in an integrated pouring to ensure construction efficiency and quality. However, if concrete is placed integrally, there is a high risk of temperature cracking during the hydration reaction, and it is necessary to determine the optimal mixing design of high-performance, high-durable concrete through the replacement of the admixture. In this study, experiments on salt damage, carbonation, and sulfate were conducted on the specimen manufactured from the optimal high-performance low-heating concrete combination determined in the author's previous study. The resistance of the cement matrix to chlorine ion diffusion coefficient, carbonation coefficient, and sulfate was quantitatively evaluated. In the terms of compression strength, it was measured as 141% compared to the structural design standard of KCI at 91 days. Excellent durability was expressed in carbonation and chlorine ion diffusivity performance evaluation. In particular, the chlorine ion diffusion coefficient, which should be considered the most strictly in the marine environment, was measured at a value of 4.09×E-12m²/y(1.2898×E-10m²/s), and is expected to be used as a material property value in salt damage durability analysis. These results confirmed that the latent hydroponics were due to mixing of the admixture and high resistance was due to the pozzolane reaction.

• Journal of the Korea Institute of Building Construction
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• v.21 no.2
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• pp.141-148
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• 2021

In this study, the characteristics of the cement mortar replaced with fly ash and ground granulated blast furnace slag generated during circulating fluidized bed combustion method and pulverized coal combustion process were investigated. As a result of the study, when mixed with circulating fluidized bed combustor fly ash and pulverized coal combustion fly ash, it is advantageous not only in terms of strength development but also in terms of durability. The circulating fluidized bed combustor fly ash contributes to the improvement of initial reactivity, and the pulverized coal combustion fly ash is involved in long-term strength development through pozzolanic reaction. Therefore, it can be seen that the mixed use of circulating fluidized bed combustor fly ash and pulverized coal combustion fly ash acts as a complementary factor for cement mortar substituted with ground granulated blast furnace slag.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.1
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• pp.72-81
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• 2024

In this study, DEIPA was used for enhancing cementitious performance of bottom ash replaced cement. By applying the partial or no-known crystal structure method to X-ray diffraction data, the amounts of amorphous bottom ash and calcium silicate hydrate(C-S-H) could be separated and quantified. In the sample without DEIPA, the bottom ash hardly reacted, resulting in low compressive strength. However, the addition of DEIPA not only altered the hydration behavior of the cement but also enhanced the pozzolanic reaction between bottom ash and calcium hydroxide, leading to the generation of additional C-S-H. This resulted in high compressive strength not only in the early stages but also in the later stages. Therefore, with the addition of DEIPA during the pulverization of the bottom ash, the reactivity of the bottom ash was significantly improved. Hence, there is potential in the development of bottom ash replacement cement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.229-240
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• 1987

Carbonation of concrete is one type of a chemical process. The reaction mechanism is very complex for the case when low-calcium fly ash and blast furnace slag is added. When fly ash and blast furnace slag is used as an admixture in concrete, they improve compressive strength in the long term, permeability and chemical resistance of concrete by a pozzolanic reaction and latent hydraulic property. On the other hand, the pozzolanic reaction of fly ash and latent hydraulic property of the blast furance slag leads to a reduction of the alkalinity of the concrete. It has been pointed out that this will accelerate the carbonation of the concrete and the corrosion of reinforcement steel embedded in the concrete. In order to clarify the effect of fly ash and blast furance slag on the carbonation of concrete, an accelerated carbonation testing of concrete was carried out by varying the conditions of concrete and the initial curing period in water. The test results of accelerated carbonation were compared to the carbonation test results of concrete stored for 15 years in open air, but protected from rain. As a result, the equation for the rate of carbonation based on compressive strength of concrete was proposed.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.749-755
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• 2004

Fluosilicic acid ($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicate salts prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicate salts to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. In this study, two-component fluosilicate salt based chemical admixtures (MZ) of $4\%,\;6\%$, and $8\%$ concentration were prepared by the reaction of $H_2SiF_6$ ($25\pm2\%$) and metal salts. The effect of concentration of MZ at a constant adding ratio on the hydration and watertightness of cement were investigated respectively. In a cement containing MZ, metal fluorides such as $CaF_2$ and soluble silica by hydrolysis were newly formed during hydration. The total porosity of the hardened cement was lower in the presence of U because of packing role of metal fluoride and pozzolanic reaction of soluble $SiO_2$. Consequently, the watertightness of the hardened paste containing MZ was more improved than non-added (plain) due to an odd hydration between cement and MZ.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.578-584
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• 2021

This study comparatively analyzed the properties of hydration reaction and strength development of four types of pond ash(PA) and fly ash(FA), aiming for the effective use of PA. The PA whose chlorine content was highest due to the seawater movement method had a faster setting time, higher cumulative heat, and greater initial strength development than those of FA due to the acceleration of the cement hydration reaction. However, the activity factor increase rate decreased after seven days of curing due to the rapid generation of early hydrates. The PA that contained impurities, such as a large amount of unburned carbon, had a delayed setting time due to the lower hydration reaction. Moreover, the strength was degraded in all curing ages. The PA whose chlorine content was lower due to the freshwater movement method and the amorphous content exhibited similar hydration reactivity and strength development characteristics compared to that of FA. The thermogravimetric analysis results verified that it had a similar level of Ca(OH)₂ consumption and pozzolanic reactivity with that of FA. Conclusively, it is necessary to expand the application of the freshwater movement method and manage the ignition loss to raise PA's usability.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.540-549
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• 2002

In this work, the hydration behaviour of portland cement pastes containing fly ash, blast-furnace slag and silica fume is investigated by Impedance Spectroscopy(IS). As fly ash or blast-furnace slag was added to portland cement, the values of R$_{t(s+1)}$ and R$_{t(s+1)}$ were decreased in the early hydration period. It showed that hydration of cement containing blending components was slower than it of the reference cement paste with the same W/C ratio. However, the cement paste containing silica fume had a large value of R$_{t(s+1)}$ and R$_{t(int)}$due to very rapid pozzolanic reactivity of silica fume in the hydration time. In OPC-fly ash system, a characteristic plateau region appeared between straight-line and semicircle. The plateau region continued to grow in range with the content of fly ash and the hydration time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.59-67
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• 2016

Concrete is a very useful construction material for the sealing disposal of hazardous substances. In general, mass concrete is applied to these structures. And, the mineral admixtures are recommended for the long term performance. Calcium leaching could be happened due to the contact with pure water in underground structures. Thus, it is needed to evaluate the resistance of calcium leaching for concrete mixed with mineral admixtures. From the test results, the mineral admixtures are effective to the improvement of long term compressive strength and chloride diffusion coefficient in concrete members. When calcium leaching is happened, however, the reduction of compressive strength and chloride penetration resistance is severe than OPC case, the micro pore distribution is adversely affected. Consequently, when the mineral admixtures are applied to underground structures which is exposed to calcium leaching environment, it is desirable to reduce water-to-binder ratio, to expose after the sufficient pozolanic reaction, and to use BFS than FA.