• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.77-78
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• 2020

In Korea, more than 30,000 tons of waste Styrofoam are produced every year. Styrofoam is spent more than 500 years decomposing during the reclamation process, so it needs to be recycled. The recycling rate of waste styrofoam continues to be the third highest in the world, but it is lower than that of Germany and Japan. Therefore, measures are needed to increase the recycling rate of waste Styropol. Another problem is that cement is mainly used in existing lightweight foam concrete. However, large amounts of CO2 from cement-producing processes cause environmental pollution. Currently, Korea is increasing its greenhouse gas reduction targets to cope with energy depletion and climate change, and accelerating efforts to identify and implement reduction measures for each sector. In 2013 alone, about 600 million tons of carbon dioxide was generated in the cement industry. Therefore, this study replaces CO2 generation cement with furnace slag fine powder, uses crude steel cement for initial strength development of bubble concrete, and manufactures hardening materials to study its properties using waste styrofoam. As a result of the experiment, the hardening agent replaced by micro powder of furnace slag was less intense and more prone to absorption than cement using ordinary cement. Further experiments on the segmentation and strength replenishment of furnace slag are believed to contribute to the manufacture of environmentally friendly lightweight foam concrete.

• Magazine of the Korea Concrete Institute
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• v.6 no.5
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• pp.149-157
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• 1994

보통 포틀랜드 시멘트와 수용성 고분자 물질인 hydroxy propyl methyl cellulose(HPMC), 미세골재 및 혼화재료를 사용하여 W/C=0.1이 되도록 물을 첨가하고 twin roll mill로 혼합 성형한 후 60일간 양생하여 고강도 시멘트 경화체를 제조하였다. 이 경화체에 대한 휨강도 및 파괴인성을 검토하였다. SiC 분말 및 백색시멘트를 첨가한 경우 휨강도는 약 100MPa정도, 탄성계수는 80-95GPa의 값을 나타내었다. 실리카흄을 첨가한 경우 휨강도는 80MPa, 탄성계수는 60GPa의 값을 나타내었다.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.25-28
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• 2006

This study investigated pre-mixed cement combined with ordinary portland cement, BF and SF, in order to manufacture cement binder, which is possible to produce 150MPa ultra high strength concrete. The BF used in this study reduces and control hydration heat. It can also improve concrete fluidity, while AP increases hydration product and accelerates reaction of BF. SF has micro filler effect and makes pozzolanic reaction. It also fabricates high density internal organization. This developed pre-mixed cement can reduce hydration heat and increase hydration product. It is possible to fabricate high density organization and to secure homogeneity. The mock-up test of ultra high strength concrete showed excellent dispersibility and workability and indicated compressive strength more than 150MPa at 28 days.

• Geomechanics and Engineering
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• v.33 no.2
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• pp.211-219
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• 2023

This study analyzes the changes in the physical properties of grout by irradiating it with ultrasonic energy and assesses the injectability of the grout into deep rock fractures. The materials used in the research are OPC (Ordinary Portland Cement) and MC (Micro Cement), and are irradiated depending on the water/cement ratio. After irradiating the grout with ultrasonic energy, viscosity, compressive strength, and particle size are analyzed, and the results of the particle size analysis were applied to Nick Barton's theory to evaluate the injectability of the grout into deep rock fractures under those conditions. It was found that the viscosity of the grout decreased after ultrasonic wave irradiation, and the rate of viscosity reduction tended to decrease as the water/cement ratio increased. Additionally, an increase in compressive strength and a decrease in particle size were observed, indicating that the grout irradiated with ultrasonic energy was more effective for injection into rock fractures.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.138-139
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• 2021

The MiDF Cement Composite is a high-performance construction material with low defects that dehydrates surplus water through pressurization and minimizes air gap between particles. In other words, the performance expression of the MiDF cement complex is affected by pressurized conditions. Thus, this study analyzed the physical characteristics of MiDF cement complex according to the power and pressure of the ga-power and the time of application and intends to use it as a basic data for optimal mixing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.140-141
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• 2020

Concrete has a lower thermal conductivity or thermal diffusion coefficient compared to other building materials, so it is widely used as fireproof compartment material or refractory material for structures. However, in the event of thermal damage such as fire, cement curing agents and aggregates act differently, resulting in heat generation or deterioration of tissue due to dehydration, resulting in deterioration of physical properties and fire resistance. Therefore, in this study, the processing structure of cement paste is measured through nitrogen absorption method. The test specimen is a cement paste of 40% W/C and is set at 1000 ℃ under heating temperature conditions. As the temperature rose, the micro-pore mass below was reduced based on about 0.01 감소m, but the air gap above that was increased.Thus, in the range of pores measured in nitrogen adsorption, the air mass tended to decrease under high temperature conditions.

• Journal of the Korean Ceramic Society
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• v.55 no.5
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• pp.480-491
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• 2018

Calcium phosphates (CaP) were prepared by a wet chemical method. Micro-crystalline dicalcium phosphate (DCPD) was precipitated at $37^{\circ}C$ and pH 5.0 using $Ca(OH)_2$ and $H_3PO_4$. The precipitated DCPD solution was kept at $37^{\circ}C$ for 96 h. Artificial bone cement was composed of DCPD, $Ca(H_2PO_4)_2{\cdot}H_2O$ (MCPM), and $CaSO_4{\cdot}1/2H_2O$, $H_2O$ and aqueous poly-phosphoric acid solution. The wet prepared CaP powder was used as a matrix for the bone cement recipe. With the addition of aqueous poly-phosphoric acid, the cement hardening reaction was started and the CaP bone cement blocks were fabricated for the mechanical strength measurement. For the tested blocks, the mechanical strength was measured using a universal testing machine, and the microstructure phase analysis was done by field emission scanning electron microscopy and X-ray diffraction. The cement hardening reaction occurred through the decomposition and recrystallization of MCPM and $CaSO_4{\cdot}1/2H_2O$ added on the surface of the wet prepared CaP, and this resulted in grain growth in the bone cement block.

• 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.

• Economic and Environmental Geology
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• v.43 no.2
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• pp.177-184
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• 2010

When cement grout is used for waterproofing of grounds, important roles are played by fluidity, particle size and bleeding. The most important element which determines their characteristics is the water/cement ratio of grout. Moreover in order to improve the efficiency of soil permeation, micro cement with a smaller average diameter is used in addition to ordinary portland cement. Besides the mixing ratio and cement diameter, the condition of ground is also of fundamental importance in the efficiency of permeation. In order to evaluate grout in terms of permeation ability into ground, we need a field test of grounting, which is cost and time consuming. In this paper we present a laboratory test method in which the suitability and efficiency of grouts are simply and more practically tested. In Korea neither a test standard nor devices are available to simulate grouting in a laboratory. We devised a grout injection equipment in which grouting was reproduced in the same condition with different materials, and suggested a standard for the production of specimens. Our tests revealed that the efficiency of injection increases with the water/cement ratio. We also found that more efficiently injected is the grout with the order of decreasing size; MS8000, micro cement, and ultra fine cements, and colloidal super cement.

• Restorative Dentistry and Endodontics
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• v.36 no.2
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• pp.132-138
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• 2011

Objectives: The purpose of this study was to evaluate curing degree of three dual-cure resin cements with the elapsed time in self-cure and dual-cure mode by means of the repeated measure of micro-hardness. Materials and Methods: Two dual-cure self-adhesive resin cements studied were Maxcem Elite (Kerr), Rely-X Unicem (3M ESPE) and one conventional dual-cure resin cement was Rely-X ARC resin cement (3M ESPE). Twenty specimens for each cements were made in Teflon mould and divided equally by self-cure and dual-cure mode and left in dark, $36^{\circ}C$, 100% relative humidity conditional-micro-hardness was measured at 10 min, 30 min, 1 hr, 3 hr, 6 hr, 12 hr and 24 hr after baseline. The results of micro-hardness value were statistically analyzed using independent samples t-test and one-way ANOVA with multiple comparisons using Scheffe's test. Results: The micro-hardness values were increased with time in every test groups. Dual-cure mode obtained higher micro-hardness value than self-cure mode except after one hour of Maxcem. Self-cured Rely-X Unicem showed lowest value and dual-cured Rely-X Unicem showed highest value in every measuring time. Conclusions: Sufficient light curing to dual-cure resin cements should provided for achieve maximum curing.