• Cement Symposium
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• s.35
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• pp.242-248
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• 2008

• Cement Symposium
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• no.25
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• pp.66-72
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• 1997

• Cement Symposium
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• no.25
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• pp.206-210
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• 1997

• Cement Symposium
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• no.16
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• pp.21-31
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• 1988

• Cement Symposium
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• no.21
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• pp.51-59
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• 1993

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.233-239
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• 2007

The main objective of this study was to evaluate the effect of recycled PET fiber made from waste PET bottle on the control of plastic shrinkage cracking of cement based composites. PET is blown as a plastic material and used in a variety products such as a beverage bottle. However, waste PET bottles are thrown after the usage, raising huge problems in terms of the environment. Thus, the research on the method to recycle the PET bottles indicates important aspects in environment and economy. The method to recycle waste PET bottles as a reinforcing fiber for cement based composites is one of effective methods in terms of the recycle of waste PET bottles. In this research, the effect of recycled PET fiber geometry and length on the control of plastic shrinkage was examined through thin slab tests. A test program was carried out to understand the influence of fiber geometry, length and fiber volume fraction. Three type of recycled PET fibers including straight, twist crimped and embossed type. Three volume fraction and two fiber length were investigated for each of the three fiber geometry. Test results indicated that recycled PET fibers are effective in controlling plastic shrinkage cracking in cement based composites. In respect to effect of length of fiber, longer fiber was observed to have efficient cracking controlling with low volume fraction in same fiber geometry while shorter fiber controled plastic shrinkage cracking efficiently as addition rate increase. Also, embossed type fibers were more effective in controlling plastic shrinkage cracking than other geometry fiber at low volume fraction. But, for high volume fraction, straight type fibers were most effective in plastic shrinkage cracking controlling in cement based composites.

• Tunnel and Underground Space
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• v.27 no.5
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• pp.312-323
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• 2017

In this study, an influence of mixing ratio among firing oyster shell, non-firing oyster shell, magnetic separated converter steel slag and fly ash used as admixtures on strength properties of soil cement was evaluated by correlation analysis among compressive strength, deformation modulus and mixing ratio of admixtures. As a result, the strength of the specimens containing non-firing oyster shells was found to be larger than that of firing oyster shells, and it was confirmed that firing oyster shells could negatively affect the strength of soil cement specimens unlike previous studies. In addtion, there was a positive correlation between the ratio of magnetic separated converter slag and strength properties, so it is confirmed that it can be used as an admixture.

• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.819-825
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• 2004

The characteristic analysis of cement clinker using light microscope can evaluate not only the quality of cement but also making process. Thus this study analyzed clinkers having different burning conditions by reflective light microscope. As heating and cooling rates is decreased, alite and belite minerals grew and especially cooling rate had an effect on the growth of belite. Futhermore as the retention time in max. temperature got longer by twenty minutes, alite and belite minerals grew more about 5 $\mu\textrm{m}$. In the case of temperature 1400$^{\circ}C$ in max, the size of belite was suitable but alite was not suitable with the size of 10～15 $\mu\textrm{m}$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6A
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• pp.1033-1039
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• 2006

The purpose of this study are to evaluated bond, flexural properties and control of plastic shrinkage cracking of crimped type synthetic fiber with amplitude 6 mm and height 1.8 mm reinforced cement based composites. Bond and flexural test were conducted in accordance with the JCI-SF 8 and JCI SF-4 standard, respectively. The plastic shrinkage cracking test was conducted for evaluating the effect of fiber in reducing shrinkage cracking in cement based composites. Test results indicated that the crimped typel synthetic fibers performed significantly better than the straight type fiber in terms of interface toughness and pullout load and the crimped type synthetic fibers improved the flexural toughness of concrete. Also, the increasing the crimped type synthetic fiber volume fraction from 0.00% to 1.00% improved the plastic shrinkage cracking resistance. Specially, the effect of control of plastic shrinkage cracking is excellent at the more than 0.5% fibre volume fraction.

• Cement
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• s.36
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• pp.43-48
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• 1970