• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.47-52
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• 2000

Recently, it is very necessary the development of the manufacturing techniques for high strength concrete(HSC) for the large-scale size and good quality of civil structure. But, the manufacture and quality control of HSC of which shrinkage, heat of hydration and workability at construction filed are considered, is very difficult due to its low water-cement ratio and high quantity of unit cement content. In the present study, we tried to know and assess the influences of chemical and physical properties of cement on the material properties of HSC. We analyzed basic properties of 4 kinds of cement whose chemical and physical properties are different each other through various tests such as chemical analysis and mortal test. Also, we performed the assessment of the material properties of HSC for each dement by the test for the conditions of same mix design and similar compressive strength. From the results in the study, the assessment of the important quality factors of cement influencing the properties of HSC may be utilized to quality control of applied cement to manufacture the HSC of high quality.

• Journal of the Korean Ceramic Society
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• v.29 no.4
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• pp.298-304
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• 1992

Flexural strength, microstructure, hydration reaction and moisture sensitivity in macro defect-free (MDF) cement, which basically prepared of high alumina cement (HAC) and hydroxypropyl methylcellulose (HPMC) and polyvinylalcohol (PVA) as water soluble polymer were investigated. Cement composites based on HAC-PVA system were improved in flexural strength than that of HAC-HPMC system especially, the strength of specimens added to 10 wt% of polyvinylalcohol was 160 MPa. These improvements of flexural strength were attributed to not only the effect of water soluble polymer in elimination of macropores (above 100 $\mu\textrm{m}$) and cement grain bridging, but the effect of unhydrate cement as an aggregate. Moisture sensitivity and flexural strength in wet condition of MDF cement composites immersed in water at 80$^{\circ}C$ for 3 days were decreased.

• Journal of the Korean Ceramic Society
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• v.43 no.12 s.295
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• pp.846-851
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• 2006

This paper discuss the adsorption and fluidity properties of recycled cement powder with different hydration hysteresis and particle size. Reactivity of hydrated fine powder was negligible low. Therefore, the adsorption and fluidity properties with super-plasticizer for hydrated recycled cement powder was very important for using additive material. Adsorption amount of super-plasticizer was increased by the finer hydrated recycled cement powder addition. And the fluidity of hydrated recycled cement powder was very poor than un-hydrated cement powder. To Improve the fluidity of hydrated recycled cement powder, PC super-plasticizer is the more effective than NS super-plasticizer.

• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.861-868
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• 1990

Investigation for the preparation of high strength hardened cement paste using ordinary portland cement, hydroxypropyl methyl cellulose(HPMC) with SiC powder was carried out. The cement paste was mixed with 0.1 of water cement ratio by twin roll mill and cured 60 days in humidity chamber. The hydration degree of cement paste cured with W/C=0.1 in 60 days was about 30% and most pores in the paste were found to be existed as gel pores of diameter less than 0.01㎛. The maximum flexural strength of hardened cement paste was about 960kg/㎠. When the SiC powder was added to the paste, the flexural strength was 1000∼1100kg/㎠ and the Young's modulus was 8∼9×105kg/㎠.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.232-235
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• 2004

This study aims to manufacture non-sintering cement(NSC) by adding phosphogypsum(PG) and waste lime(WL) to granulated blast furnace slag(GBFS) as sulfate and alkali activators. This study also investigates the basic physical properties and hydration reaction of NSC, and evaluates its reusing possibility as construction material. Results obtained from this study have shown that GBFS was affected by $So_4^{2-}$ in waste PG and stimuli under wet condition, left slag components, created Ettringite and CSH gels, and eventually started being hydrated. These hydrated creations formed dense structures like CSH based on Ettringite and contributed in allowing the mortar to reveal high strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.525-528
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• 2006

This study performed an experimental test to derive the characteristics of compressive strength, het of hydration and creep of roller compacted concrete. The main variable of strength test are cement content and fly ash content. The heat of hydration test was performed using MARUTO CH-50-CA and dreep test was carried out according to KS F 2453.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.264-269
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• 1996

Thermal cracks are occurred when thermal stress due to the hydration of cement exceeds the tensile strength of concrete. In this study, the thermal stresses are investigated at the massive concrete like an anchorage of suspension bridge. The thermal crack can be controlled by considering the placing height, concrete type, pre-cooling and pipe cooling in the design stage.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.267-274
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• 2006

Greenhouse gas reduction will be highlighted as the most pending question in the cement industry in future because the production of Portland cement not only consumes limestone, clay, coal, and electricity, but also release waste gases such as $CO_2,\;SO_3$, and NOX, which can contribute to the greenhouse effect and acid rain. To meet the increase of cement demand and simultaneously comply with the Kyoto Protocol, cement that gives less $CO_2$ discharge should be urgently developed. This study aims to manufacture non-sintering cement(NSC) by adding phosphogypsum(PG) and waste lime(WL) to granulated blast furnace slag(GBFS) as sulfate and alkali activators. This study also Investigates the hydration reaction of NSC through analysis of scanning electron microscopy(SEM), X-ray diffraction(XRD), differential thermal analysis(DTA), and pH. Results obtained from analysis of the hydrate have shown that the glassy films of GBFS are destroyed by the activation of alkali and sulfate, ions eluted from the inside of GBFS react with PG and produce ettringite, and consequently the remaining component in GBFS slowly produced C-5-H(I) gel. Here, PG is considered not only to play the role of simple activator, but also to work as a binder reacting with GBFS.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.3
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• pp.51-60
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• 2007

This study was performed to evaluate void ratio, compressive and flexural strengths, and pH properties according to the content ratio of rice husk ash, aggregate size, and neutral treatment time of porous concrete with content of rice husk ash produced as an agricultural by-product. The SEM results for cement mortar with a 5% rice husk ash for the weight of cement formed more C-S-H hydrates due to the $SiO_2$ of rice husk ash. In the XRD test, cement mortar with a 5% rice husk ash for the weight of cement registered a higher peak point of approximately $2{\theta}=20{\sim}25^{\circ}$ compared to cement mortar without rice husk ash. According to the results of the XRD and SEM tests, the $SiO_2$ that was a major chemical element of rice husk ash generated a large amount of calcium hydroxide in the early stage of the hydration process of cement leading to the formation of ettringite. The void ratio of porous concrete with rice husk ash decreased with increasing content ratio of rice husk ash. In addition, the void ratio of porous concrete with rice husk ash decreased compared to porous concrete without rice husk ash. The compressive and flexural strength of porous concrete with a 5% and 10% content ratio of rice husk ash slightly increased compared to concrete without rice husk ash. The pH value of porous concrete rapidly decreased immediately after neutral treatment. Then, it gradually increased and decreased again after 14 days. However, the pH value was nearly the same regardless of neutral treatment time in 28 curing days. Also, for neutral treatment, the pH value of porous concrete showed appropriate pH levels (less than 9.5) in all mixtures for planting at 28 curing days.

• Proceedings of the Korean Ceranic Society Conference
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• 2004.04b
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• pp.52.1-52.1
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• 2004