• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.39-48
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• 2020

The present study investigates the chemical reaction and performance of ternary blended binders by mixing ferronickel slag. Cement was replaced using ground granulated blast furnace slag and ferronickel slag, combined up to 50% of the replacement rate. The blended cements were tested by setting times, length change, compressive strength at 1, 3, 7, 28 days. X-ray diffraction and scanning electron microscope were conducted for detecting hydration products while the MIP and microhydation heat were used for examining morphological characteristics. The results showed that by adding ferronickel slag, Pozzolanic reaction occurred, forming a dense pore structure and the effect of reducing hydration heat and dry shrinkage was also found. The compressive strength at 28 days was lower than that of 100% OPC control specimen (OSP0), but ternary blended cements showed no significant difference compared to binary blended (OSP50). If the optimal mix is derived later and used for the purpose, the potential for use as a cement binder is expected.

• Journal of the Korea Institute of Building Construction
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• v.9 no.5
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• pp.119-125
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• 2009

In this paper, the engineering properties and estimation of drying shrinkage of concrete incorporating fly ash (FA), blast furnace slag (BS) and cement kiln dust (CKD) were discussed. FA, BS and CKD contents ranged from 0% to 20%. Water to binder ratio (W/B) also ranged from 40 to 50 %, with a 5% interval. For estimating drying shrinkage, an exponential model proposed by the author was applied, According to results, the use of FA, BS and CKD resulted in a decrease of flowability and air contents. As expected, the use of admixtures also decreases the early age strength of concrete, while at later age, due to a pozzolanic reaction of FA and BS, the compressive strength was recovered to a value comparable with that of plain concrete. For drying shrinkage, the use of admixtures led to an increase in the drying shrinkage of concrete. The exponential model suggested by the author showed good agreement between the calculated and experimental values both at early age and at later age.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.152-159
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• 2010

Recently, the public interest in eco-friendly material and structure has been increasing and many Hwang-toh researches are being actively performed. Hwang-toh is one of the traditional environment friendly construction materials used as a construction and plastering material. Hwang-toh has many advantages as construction material due to its high heat storage capacity, auto-purification, antibiotic ability, and infrared ray emission characteristics. But, currently it has not been developed into construction material and used in modern construction due to its low strength and dry shrinkage cracking prone characteristics. According to the recent researches and study results, Hwang-toh can be used as a natural pozzolanic material like fly-ash or pozzolan. In this study, mechanical properties and structural flexure behavior experiments of slag, recycled PET fiber, and Hwang-toh added concrete are carried out. The test results showed that drying shrinkage of concrete mixed with Hwang-toh has lower compressive strength and elastic modulus than those of control cement concrete specimen, but it has the similar flexural behavior in reinforced concrete beams.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.769-774
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• 2005

Fluosilicic acid(H2SiF6) is recovered as an aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded H3PO4 or HF. Generally, fluosilicates are the salts produced by the reaction of H2SiF6 and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. This study was performed to know mechanical properties and watertightness using fluosilicates based composite made from fluosilicates and other compounds. Mix proportions for experiments were modulated at 0.45 of water to cement ratio and $0.0-2.0\%$ of adding ratio of fluosilicates based composite. Evaluation for mechanical properties of concrete was conducted to know fresh state of concrete, hardening state of concrete, and watertightness. Evaluation for watertightness of concrete was carried out permeability, absorption test and porosity analysis. In addition. Scanning Electron Microscopy(SEM) and Energy Dispersive X-Ray(EDX) used for investigating micro-structure and atomic component distributed in hardened concrete. It is ascertained that characteristics of mechanical properties and watertightness was more improved than non-added because of packing role of fluosilicates based composite and pozzolanic reaction of soluble $SiO_2$. Also, concrete added fluosilicates based composite had a tendency to delay setting time and only $0.5\%$ addition of fluosilicates based composite delayed 150 minutes compared with non-added.

• Geomechanics and Engineering
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• v.22 no.2
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• pp.143-152
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• 2020

In this research, soil samples of the Kerman sedimentary basin, Iran, were investigated through laboratory tests such as petrography (Scanning Electron Microscopy (SEM), X-Ray Fluorescence Spectroscopy (XRF) and X-Ray Diffraction (XRD)), physical and mechanical characteristics tests. The soil in this area is dominantly CL. The petrography results showed that the dominant clay mineral is Illite. This soil has made some problems in the earth dams due to the low shear strength. In this study, a set of samples were prepared by adding different amounts of lime. Next, the petrography and strength tests at the optimum moisture content were performed. The results of SEM analysis showed substantial changes in the soil structure after the addition of lime. The primary structure was porous and granular that was changed to a uniform and solid after the lime was added. According to XRD results, dominant mineral in none stabilized soil and stabilized soil are Illite and calcite, respectively. The pozzolanic reaction resulted in the reduction of clay minerals in the stabilized samples and calcite was known as the soil hardener material that led to an increase in soil strength. An increase in the hydrated lime leads to a decrease in their maximum dry unit weight and an increase in their optimum moisture content. Furthermore, increasing the hydrated lime content enhanced the Unconfined Compressive Strength (UCS) and soil's optimum moisture. An increase in the strength is significantly affected by the curing time and hydrated lime contents, as the maximum compressive strength is achieved at 7% hydrated lime. Moreover, the maximum increase in the California Bearing Ratio (CBR) achieved in clay soils mixed with 8% hydrated lime.

• Journal of the Korean Ceramic Society
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• v.40 no.7
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• pp.702-708
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• 2003

Cement paste, mortar or concrete specimens, substituting the content of Portland cement with fly ash up to 50 wt%, were prepared to investigate the effect of fly ash on the temperature, free lime content and strength etc. of mortar/concrete. Being compared with the concrete made of ordinary Portland cement, temperature increment of the concrete containing 50 wt% fly ash reduced, according to appropriate conversion formulae, to about 45％ at the 7 days curing time: the temperature increment of the former amounted to 33.4$^{\circ}C$, while that of the latter only to 18.7$^{\circ}C$. On the other hand, it is better to control the content of fly ash in the cement that is used for reinforced concrete not to exceed 30 wt％. In this study, more than 28 days curing time is necessary in order that the strength of concrete made of fly ash cement will be higher than that of pure Portland cement. In addition, 28-days concrete strength higher than 360 kg/$\textrm{cm}^2$ could be easily achieved even with 50 wt% fly ash cement.

• Proceedings of the Korean Institute of Building Construction Conference
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• v.y2004m10
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• pp.71-76
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• 2004

This paper investigate that the effect of the concrete containing mineral admixtures(pozzolanic materials such as fly-ash, ground granulated blast-furnace slag, silica fume and meta kaolin) on the resistance properties to chloride ion invasion. The purposed testing procedure was applied to the concrete added mineral admixtures for $3\sim4$ replacement ratios under W/B ratios ranged from 0.40 to 0.55. Specimens were immersed in $3.6\%$ NaCl solution for 330 days, and penetration depth, water soluble chloride contents and acid soluble chloride contents were measured in 28, 91, 182 and 330 days. Then, diffusion coefficient were calculated using total chloride contents. As a results. the kinds of mineral admixture and replacement ratios had a great effect on the resistance property of the concrete to chloride ion invasion compared with the plain concrete. And the optimal replacement ratios of mineral admixture had a limitation for each admixtures. The amount of acid soluble chloride ions and water soluble chloride ions were varied with the kinds of mineral admixtures and the penetration depth from the concrete skin. Chloride diffusion coefficient of each concretes decreased with the time elapsed. and the diffusion coefficients of the concrete immersed salt water for 330 days had a establishment with the compressive strength measured before immersing.

• 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.

• Computers and Concrete
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• v.29 no.4
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• pp.263-278
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• 2022

Limestone calcined clay cement (LC³) is a low carbon alternative to conventional cement. Literature shows that using limestone and calcined clay in LC³ increases the thermal degradation of LC³ pastes and can increase the magnitude of fire risk in LC³ concrete structures. Higher thermal degradation of LC³ paste prompts this study toward understanding the fire performance of LC³ concrete and the associated magnitude of fire risk. For fire performance, concrete prepared using ordinary Portland cement (OPC), pozzolanic Portland cement (PPC) and LC³ were exposed to 16 scenarios of different elevated temperatures (400℃, 600℃, 800℃, and 1000℃) for different durations (0.5 h, 1 h, 2 h, and 4 h). After exposure to elevated temperatures, mass loss, residual ultrasonic pulse velocity (rUPV) and residual compressive strength (rCS) were measured as the residual properties of concrete. XRD (X-ray diffraction), TGA (thermogravimetric analysis) and three-factor ANOVA (analysis of variance) are also used to compare the fire performance of LC³ with OPC and PPC. Monte Carlo simulation has been used to assess the magnitude of fire risk in LC³ structures and devise recommendations for the robust application of LC³. Results show that LC³ concrete has weaker fire performance, with average rCS being 11.06% and 1.73% lower than OPC and PPC concrete. Analysis of 106 fire scenarios, in Indian context, shows lower rCS and higher failure probability for LC³ (95.05%, 2.22%) than OPC (98.16%, 0.22%) and PPC (96.48%, 1.14%). For robust application, either LC³ can be restricted to residential and educational structures (failure probability <0.5%), or LC³ can have reserve strength (factor of safety >1.08).

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.112-119
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• 2022

Recently, as carbon neutrality has been important factor in the construction industry, many studies have been conducted on the high-volume fly ash concrete. High volume fly ash concrete(HVFC) is usually made by replacing more than 50% of cement with fly ash. However, HVFC has a disadvantage of low compressive strength in early age. To overcome this shortcoming of HVFC, improve this, interest in techonolgy using nanomaterials is increasing. Nano silica is expected to improve the early age strength of HVFC as a pozzolanic material. This study investigated the effect of nano silica on the early hydration reaction and microstructure of HVFC. The early hydration reaction of HFVC was analyzed through setting time, isothermal calorimeter, compressive strength and thermal weight analysis. In addition, the microstructure of HVFC was measured by mercury intrusion porosimetry. From the test results, it was confirmed that nano silica increased the early age strength and improve the microstructure of HVFC.