• International Journal of Concrete Structures and Materials
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• v.5 no.2
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• pp.113-117
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• 2011

The purpose of this work is the comparative study for grinding of two cement clinkers. X-ray fluorescence, physical and granulometric tests and optical microscopy were used to characterize the clinkers. Also grinding tests were carried out for ten samples to determine the parameters influencing grindability of its clinkers. The results of calculation of the energies of grinding according to the law developed by Von Rittinger and the study of the microstructure of the two clinkers shows good agreements. Indeed, frequent clusters of belite which indicate a lack of uniformity and fineness have an effect on lowering the grindability. The obtained analyses and the results enabled us to interpret the granulometry and the microstructure of clinker to control quality and resistance.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.888-893
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• 1998

Calcium sulfoaluminate, $C_4$A$_3$$\bar{S}$, was prepared for reutilizing industrial by-products, such as II-CaSO$_4$, Al(OH), CaF$_2$ and cement sludge wastes. Mixed powder was fired at 1,15$0^{\circ}C$. $C_4$A$_3$$\bar{S}$ clinkers fired at 1,15$0^{\circ}C$ were analyzed by SEM and XRD. Also were added in cement paste and mortar and characterized as setting time, flow values and compressive strength. $C_4$A$_3$$\bar{S}$ could be found in the X-ray diffraction pattern. The setting time of cement pastes added clinkers fired at 1,15$0^{\circ}C$ was shorter than that of ordinary portland cement. Also the compressive strengths of the cement mortar added clinkers was higher than those of ordinary portland cement.

• Journal of the Korean Ceramic Society
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• v.44 no.4 s.299
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• pp.224-229
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• 2007

To evaluate the cooling rate of clinker quantitatively, several clinkers with different cooling rate were made in the laboratory. The X-ray diffraction pattern of Ferrite 002 reflection were measured and the parameters were calculated by using split type pseudo-Voigt function. The X-ray diffraction patterns of the Ferrite phase in the clinkers from cement manufacturing plant were analyzed by using the parameters and the analysis program was developed to calculate the cooling rate quantitatively. The cooling rate coefficients of the clinkers were calculated by using the profile fitting method of the program and the influence of cooling rate on strength was evaluated. The results show that there is a close relation between the cooling rate of clinker and the strength of cement.

• Journal of the Korean Ceramic Society
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• v.12 no.4
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• pp.3-8
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• 1975

Hydration processes of the rapid hardening cement clinkers, which were synthesized from domestic alunite for major alumina source, limestone, kaolin and fluorite, were investigated by means of x-ray diffraction analysis, thermal analysis and microscopic observation etc. The clinkers were composed mainly of alite, calcium fluroaluminate (C11A7.CaF2) minerals. While the hydratio processes of the clinkers are altered by concentration of SO3 in the paste, calcium aluminate hydrates such as C4AH13, CAH10 and calcium monosulfate hydrate (C3A.CaSO4.12H2O) are formed at first and then some of them are transformed into ettringite(C3A.3CaSO4.32H2O) within 30~60 min. when the concentration of SO3 in the paste are enough. However the formed ettringite are changed slowly into calcium monosulfate hydrate as the concentration of SO3 become lowered, and the paste is hardened with these close-packed minerals. When the content of SO3 in clinker is so enough, calcium sulfoaluminate hydrates are found without any addition of anhydrite or hemi-hydrite.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.514-519
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• 2020

In this study, cement clinkers were sintered at each temperature by replacing some of the clay components of cement clinkers with coal materials. The mineral phase change of sintered cement clinker was quantitatively analyzed by XRD-Rietveld method. As the sintering temperature of cement clinker increased, the amount of belite decreased, the amount of alite increased, and the amount of free-CaO decreased. The form of alite and belite could be distinguished at sintering temperature of 1450℃ or higher. The crystal size was greatly increased at 1500℃ sintering. It was confirmed that the excessive sintering was progressed. Free-CaO decreased with the increase of sintering temperature. At 1450 ℃ or higher, it was less than 0.5%. In 1450℃ or greater, it is determined that enough sintering is included. Therefore, the application of fly ash as a raw material of cement clinker was judged to be usable as a source of chemical components of alumina and iron raw materials.

• Journal of the Korean Ceramic Society
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• v.32 no.8
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• pp.873-880
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• 1995

In order to prepare the modified belite (C2S-C4A3S-C4AF-CS) cement with low energy, clinkers were synthesized by converter slag, limestone, gypsum and clay. The synthesized clinkers were characterized and the hydration processes were investigated by XRD, SEM and microconduction calorimetry. The hydrates were mainly C-S-H and ettringite. The needle-like ettringite formed by the hydration of C4A3S at the early stage of hydration was filled in the inner vacant spaces of the hardened body and it might contribute to the rapid-hardening phenomena. The hardened body became stronger due to the hydration of C2S at the later period. The compressive strengths of the cement-3 mortars hydrated for 3, 7 and 28 days were 115, 128 and 211 Kgf/$\textrm{cm}^2$, respectively.

• Journal of the Korean Ceramic Society
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• v.37 no.8
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• pp.768-773
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• 2000

Alnite clinker, which is based on CaO-SiO2-CaCl2 system, was synthesized by recycling Cl-containing waste, and its hydraulic properties were onvestigated. Alinite coinkers with two different chemical compositions were burned for 10∼30 minutes in the range of temperature, 1350∼1450$^{\circ}C$. The microstructures of those clinkers were characterized by powder X-ray diiffracuion analysis, optical microscope, and scanning electronic microscope and heat of hydration of alinite cements which was measured in order to investigate hydraulic properties. X-ray analysis shwoed that f-CaO in both clinkers with different compositions significantly was decreased with transforming C2S(belite) to C3S(alite). From the results of microscopy and scanning electron microscopy(SEM), crystal of synthesized alite(C3S) was larger and better crystallinity than that of ordinary portland cement.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.490-494
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• 2011

This paper reports the use of supplementary cementing materials (SCMs) derived from local resources, for the partial replacement of Portland cement to reduce $CO_2$ emission during cement production. Replacement of Portland clinkers up to 20 wt.% with SCMs in normal cements reduced $CO_2$ emission by 0.18 kg $CO_2$/kg. The compressive strength exceeded the standard specification for Portland cement ASTM C-150. Blended cement samples containing 20% Portland clinker replacement had compressive strengths of 37 MPa after 28 days of curing time. The microstructure evolution of blended cement at a composition of 80:20 was similar to that of the 100% Portland cement, where the structure between days 28 and 56 reached a steady state. Blended cements with compositions of 70:30 and 60:40 still showed progress of CSH plate formation and the lack of massive structure development. It is shown that the use of supplementary cementing materials could be as one of alternative ways to reduce $CO_2$ emissions during cement production.

• Advances in Computational Design
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• v.3 no.2
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• pp.147-163
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• 2018

Cementitious composites are multiphase heterogeneous materials with distinct dissimilarity in strength under compression and tension (high under compression and very low under tension). At macro scale, the phenomenon can be well-explained as the material contains physical heterogeneity and pores. But, it is interesting to note that this dissimilarity initiates at molecular level where there is no heterogeneity. In this regard, molecular dynamics based computational investigations are carried out on cement clinkers and calcium silicate hydrate (C-S-H) under tension and compression to trace out the origin of dissimilarity. In the study, effect of strain rate, size of computational volume and presence of un-structured atoms on the obtained response is also investigated. It is identified that certain type of molecular interactions and the molecular structural parameters are responsible for causing the dissimilarity in behavior. Hence, the judiciously modified or tailored molecular structure would not only be able to reduce the extent of dissimilarity, it would also be capable of incorporating the desired properties in heterogeneous composites. The findings of this study would facilitate to take step to scientifically alter the structure of cementitious composites to attain the desired mechanical properties.

• Journal of the Korean Ceramic Society
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• v.18 no.4
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• pp.237-246
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• 1981

The effects of impurities, included in the by-produced phosphogypsum from the dihydrate process, on the hydration of portland cement were studied. Six gypsums were adopted in this study; four different raw phosphogypsums from domestic fertilizer plants, a reprocessed phosphogypsum and a reagent grade pure gypsum. Cements with differing $SO_3$ content, were synthesized by grinding two different commercial clinkers and the above six gypsums together. The effects of the impurities were investigated by measuring the setting time, the non-evaporable water coatent, X-ray phase analysis of cement pastes and the compressive strength of cement mortar specimens. It was found that the soluble $P_2O_5$ known as one of injurious impurities on the hydration of portland cement, included in the demestic raw phosghoypsum cxneedigply by far the specified amounts of the Korean Industrial Standards (L9005), and retarded the setting time severely, thus the strength development of cement was delayed at the earlier stage of hydration.