• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.1
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• pp.15-20
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• 2014

In this research, the geopolymer was fabricated using municipal solid waste incineration ash (denoted as MSWIA) slag and alkali activator, NaOH and its properties were analyzed. Particularly, the effects of NaOH molarity, particle size of MSWIA, and liquid/solids ratio on the compressive strength of geopolymers were investigated. The compressive strength of geopolymers fabricated increased with finer grain size of MSWIA, and optimum value of the liquid/solids ratio was identified as 0.13. As the molarity of the NaOH increased, the compressive strength of geopolymers was increased. Even more the 20 M of NaOH, but the strength was not increased. The calcium aluminum silicate and calcium aluminum silicate hydrate zeolites were generated in the geopolymer fabricated with more than 20 M of NaOH, with some unreacted silica and unknown crystals remained. The highest compressive strength, 163 MPa, of geopolymer was appeared at conditions of curing temperature $70^{\circ}C$, and 20 M of NaOH, indicating that the high concentration of NaOH accelerates the geopolymer reaction and dense microstructure. The high-strength geopolymer fabricated in the present study is expected to contribute significantly to develop the field of cement alternative substances and to improve the recycling rate of MSWIA slag.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.310-315
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• 2019

This study conducted a series of studies to find alternative ways to use Chlorine Bypass System-dust(CBS-dust) in cement production. The results of engineering characteristics of CBS-dust are summarized as follows. First of all, the density of CBS-dust is 2.40, lighter than cement and the pH was 12.50 which was strong alkaline. In terms of particle size, it was 11.70 ㎛ which was finer than cement. With chemical properties, calcium oxide(CaO) was the highest as 35.10%, potassium oxide(K₂O) was 32.43%, potassium chloride(KCl) was 19.46%, sulfur oxide(SO₃) was 6.81%, and the remaining chemical components are SiO₂, Fe₂O₃, Al₂O₃, MgO, and the like. Therefore, if CBS-dust is used as early-strength chemical admixtures in the concrete secondary products that use a large amount of mineral admixtures without rebar, it can be an effective method for increasing the strength of concrete as an alkali activator and preventing early-frost damage of Cold Weather Concrete.

• Resources Recycling
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• v.27 no.6
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• pp.59-67
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• 2018

Efflorescence is a white deposit of powders in the surface of cement concrete which can also occur in geopolymers. Efflorescence occurs when sodium ions in alkali activator react with atmospheric carbon dioxide to form sodium carbonate components. In this study, we investigated whether the secondary efflorescence can be reduced by controlling the Na/Al mole ratio or by changing the curing temperature and heat curing time in fly ash-based geopolymers. The 28 days compressive strength in geopolymers having Na/Al ratio of 1.0 was higher than geopolymers having Na/Al ratio of 0.8. The strength increased with the increasing curing temperature and longer heat curing time. On the other hand, efflorescence was lower when the curing temperature was high and the heat curing time was longer in the geopolymers having Na/Al ratio of 1.0. The geopolymers having Na/Al ratio of 0.8 showed accelerated efflorescence occurrence than the geopolymers having Na/Al ratio of 1.0. In order to reduce the occurrence of the secondary efflorescence of fly ash-based geopolymers, it will be advantageous to maintain the Na/Al ratio at 1.0, increase the curing temperature, and lengthen the heating curing time.