• Advances in concrete construction
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• v.11 no.3
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• pp.207-217
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• 2021

This study relates to a production of Quaternary Cement Concrete (QCC) prepared by using Micro Silica (MS), Marble Dust (MD) and Rice Husk Ash (RHA), followed by an investigation towards fresh and hardened properties of blended concrete. A total of 39 mixes were cast by incorporating different percentages of MS (6%, 7% and 8%), MD (5%, 10% and 15%) and RHA (5%, 10%, 15% and 20%) as partial replacement of Ordinary Portland Cement. The workability of fresh concrete was maintained in the range of 100±25 mm by adding 0.7% of Super Plasticizer in the mix. Optimum mechanical strength was observed at combination of 8% MS+5% MD+10% RHA. Marble dust replacement from 10 to 15% and Rice husk ash replacements from 15 to 20% depicted a substantial reduction in compressive strength at all ages. Durability parameter with respect to water absorption at 28 days shows an increasing trend as the percentage of blending increases.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.119-120
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• 2022

This study investigated the use of different amounts of BFS and POFA. In all mixture systems, 60% cement was replaced with POFA and BFS as a substitute for Ordinary Portland Cement. The results show that with the addition of POFA and BFS, although the early compressive strength will be reduced, the strength will be significantly improved at 28 days. In the ternary system, the 28-day strength is negatively correlated with increasing POFA content.

• Journal of the Korean Ceramic Society
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• v.55 no.3
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• pp.224-229
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• 2018

OPC production requires high calorific value and emits a large amount of $CO_2$ through decarbonation of limestone, accounting for about 7% of $CO_2$ emissions. To reduce $CO_2$ emissions during the Ordinary Portland Cement (OPC) production process, there is a method of reducing the consumption of cement or lower temperature calcination for OPC product. In this study, for energy consumption reduction, we prepared Hauyne-belite cement by calcination at a low temperature compared to that used for OPC and studied the early hydration properties of the synthesized Hauyne-belite cement. We set the ratios of Hauyne and belite to 8 : 2, 5 : 5 and 3 : 7. For the hydration properties of the synthesized Hauyne-belite cement, we tested heat of hydration of paste and the compressive strength of mortar, using XRD and SEM for analysis of hydrates. As for our results, the temperature for optimum synthesis of Hauyne-belite is $1,250^{\circ}C$. Compressive strength of synthesized Hauyne-belite cement is lower than that of OPC, but it is confirmed that compressive strength of synthesized Hauyne-belite cement with mixing in of some other materials can be similar to that of OPC.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.57-61
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• 2005

Cement paste is originally the basic material and crucial factor consisting concrete. This study investigates the relationship between flow apparatuses, which are ring flow(R-F), flow cone(F-C) and mini slump(M-S), in order to estimate the fluidity of cement Paste. For quantitatively evaluating the measured data this study also investigated the calibration of the rheology consistent, such as yield value and plastic viscosity, of cement paste using viscometer For this purpose the present work discussed the influence of 3 type of ordinary portland cement with different companies, affecting the fluidity of cement paste. and it also demonstrated the influence of the various kinds of mineral admixtures, such as fly ash(FA), blast furnace slag(BS) and silica fume(SF) and that of incorporating ratio. The author concluded that using R-F apparatus is the most effective flow test method of cement paste and it is exactly proportional to other apparatus' rheological properties.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.573-576
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• 2006

To predict service life of concrete structures exposed to chloride attack, surface chloride concentration, diffusion coefficient of chloride ion, and chloride corrosion threshold value in concrete, are used as important factors. of these, as the diffusion coefficient of chloride ion for concrete is strongly influenced by concrete quality and environmental conditions of structures and may significantly change the service life of structures, it is considered as the most important factor for service life prediction. The qualitative factors affecting the penetration and diffusion of chloride ion into concrete are water-binder(W/B) ratio, age, cement type and constituents, chloride ion concentration of given environment, wet and dry conditions, etc. In this paper the influence of cement type on the diffusion characteristics of chloride ion in concrete was investigated through the chloride ion diffusion test. For this purpose, the diffusion characteristics in concrete with cement type such as ordinary portland cement(OPC), binary blended cement(BBC), and ternary blended cement(TBC) were estimated for the concrete with W/B ratios of 32% and 38%, respectively. It was observed from the test that the difussion characteristics of BBC containing OPC and ground granulated blast-furnace slag was found to be most excellent of the cement type used in this study.

• Geomechanics and Engineering
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• v.35 no.1
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• pp.95-108
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• 2023

Soft soil ground is a crucial factor limiting the development of the construction of transportation infrastructure in coastal areas. Soft soil is characterized by low strength, low permeability and high compressibility. However, the ordinary treatment method uses Portland cement to solidify the soft soil, which has low early strength and requires a long curing time. Microbially induced carbonate precipitation (MICP) is an emerging method to address geo-environmental problems associated with geotechnical materials. In this study, a method of bio-cementitious mortars consisting of MICP and cement was proposed to stabilize the soft soil. A series of laboratory tests were conducted on MICP-treated and cement-MICP-treated (C-MICP-treated) soft soils to improve mechanical properties. Microscale observations were also undertaken to reveal the underlying mechanism of cement-soil treated by MICP. The results showed that cohesion and internal friction angles of MICP-treated soft soil were greater than those of remolded soft soil. The UCS, elastic modulus and toughness of C-MICP-treated soft soil with high moisture content (50%, 60%, 70%, 80%) were improved compared to traditional cement-soil. A remarkable difference was observed that the MICP process mainly played a role in the early curing stage (i.e., within 14 days) while cement hydration continued during the whole process. Micro-characterization revealed that the calcium carbonate filling the pores enhanced the soft soil.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.115-116
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• 2023

This study aims to investigate and improve the carbon dioxide sequestration capability and the mechanical properties of non-hydraulic low calcium silicate cement especially designed for CO₂ reaction and ordinary Portland cement subjected to the carbonation curing facilitating pH swing method. Nitric acid (HNO₃) was utilized as an liquid for the mixing of cement paste to enhance the initial dissolution of Ca ions from the cements by promoting low pH environment and prevent the direct precipitation of Ca with the anion, owing to the high solubility of Ca(NO₃)₂ in water. The results presented that the higher the concentration of HNO₃, the higher the compressive strength and CO₂ sequestration (until 0.1 M). Ca dissolution caused by the harsh acid attack onto the anhydrous cement particle lead to the higher carbonation reaction degree, forming abundant CaCO₃ crystals after the reaction. However, cement paste mixed with excessively high concentration of HNO₃ presented deterioration due to the too harsh pH environment and abundant NO₃- ions which are known to retard the reaction of cement.

• International Journal of Concrete Structures and Materials
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• v.5 no.2
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• pp.125-131
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• 2011

Five all-lightweight alkali-activated (AA) slag concrete mixes were tested according to the variation of water content to examine the significance and limitation on the development of cementless structural concrete using lightweight aggregates. The compressive strength development rate and shrinkage strain measured from the concrete specimens were compared with empirical models proposed by ACI 209 and EC 2 for portland cement normal weight concrete. Splitting tensile strength, and moduli of elasticity and rupture were recorded and compared with design equations specified in ACI 318-08 or EC 2, and a database compiled from the present study for ordinary portland cement (OPC) lightweight concrete, wherever possible. Test results showed that the slump loss of lightweight AA slag concrete decreased with the increase of water content. In addition, the compressive strength development and different mechanical properties of lightweight AA slag concrete were comparable with those of OPC lightweight concrete and conservative comparing with predictions obtained from code provisions. Therefore, it can be proposed that the lightweight AA slag concrete is practically applicable as an environmental-friendly structural concrete.

• International Journal of Concrete Structures and Materials
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• v.9 no.4
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• pp.427-438
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• 2015

The present work proposes a new image analysis method for the evaluation of the multi-walled carbon nanotube (MWNT) distribution in a cement matrix. In this method, white cement was used instead of ordinary Portland cement with MWNT in an effort to differentiate MWNT from the cement matrix. In addition, MWNT-embedded cement composites were fabricated under different flows of fresh composite mixtures, incorporating a constant MWNT content (0.6 wt%) to verify correlation between the MWNT distribution and flow. The image analysis demonstrated that the MWNT distribution was significantly enhanced in the composites fabricated under a low flow condition, and DC conductivity results revealed the dramatic increase in the conductivity of the composites fabricated under the same condition, which supported the image analysis results. The composites were also prepared under the low flow condition (114 mm < flow < 126 mm), incorporating various MWNT contents. The image analysis of the composites revealed an increase in the planar occupation ratio of MWNT, and DC conductivity results exhibited dramatic increase in the conductivity (percolation phenomena) as the MWNT content increased. The image analysis and DC conductivity results indicated that fabrication of the composites under the low flow condition was an effective way to enhance the MWNT distribution.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.737-740
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• 2003

In this study, the influence of cement factor on the early strength gain and the other properties of concrete is discussed. According to the result, the setting time is faster in order of alumina cement(AC), high-early-strength cement(HSC) and ordinary Portland cement(OPC), and when OPC are replaced with HSC and AC, the final setting time is faster than when only OPC is used. At 10% replacement of AC, the instant setting happens. As the particle of cement is minute, setting time is shortened. As the properties of hardened concrete, the time when compressive strength of 5㎫, which the form can be removed, is gained is about 18 and 16 hours in the case of OPC and HSC respectively, and in the case of AC, it is about 5 hours. It also shows 16 hours at the replacing ratio of HSC of 50%, and 26 and 72 hours at the replacing ratio of AC of 5 and 10% respectively. And it shows 21, 16 and 12 hours with variation of fineness of cement, so early strength gain is fast with an increase of fineness. The coefficient of correlation between compressive strength and the rebound value is over 0.97, is very favorable. Therefore, if the rebound value of P type Schmidt hammer is more than 25, it is thought that the side forms can be removed.