• The Journal of Advanced Prosthodontics
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• v.14 no.3
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• pp.162-172
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• 2022

PURPOSE. The present study aims to analyze the effect of abutment neck taper and types of cement on the amount of undetected remnant cement of cement-retained implant prostheses. MATERIALS AND METHODS. Three neck taper angles (53°, 65°, 77°) and three types of cement (RMGI: resin-modified glass ionomer, ZPC: zinc phosphate cement, ZOE: zinc oxide eugenol cement) were used. For each group, the surface percentage was measured using digital image and graphic editing software. The weight of before and after removing remnant cement from the abutment-crown assembly was measured using an electronic scale. Two-way ANOVA and Duncan & Scheffe's test were used to compare the calculated surface percentage and weight of remnant cement (α = .05). RESULTS. There were significant differences in remnant cement surface percentage and weight according to neck taper angles (P < .05). However, there were no significant differences in remnant cement surface percentage and weight on types of cement. No interaction was found between neck taper angles and types of luting cement (P > .05). The wide abutment with a small neck taper angle showed the most significant amount of remnant cement. And the types of luting cement did not influence the amount of residual cement. CONCLUSION. To remove excess cement better, the emergence profile of the crown should be straight to the neck taper of the abutment in cement-retained implant restoration.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.99-106
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• 1991

Result of an experimental study on the manufacture, the mechanical properties and waterightness of pitch-based carbon fiber reinforced fly ash.cement composites are presented in this paper. The carbon fiber reinforced fly ash.cement composites using early strength cement, silica powder and a small amount of stylene butadiene rubber latex are prepared with carbon fiber, foaming agents and mixing conditions. As a result, the mechanical and plysical properties such as compresive, tensile and flectural strengths, watertightness and cement composites are improved by using a small amount of stylene butadiene rubber latex.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.290-294
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• 1996

High-Belite cement had a better slump flow characteristics than type I cement and slag cement, and its varation of slump flow with time was also excellent. As the amount binder added was increased, the strength increased while material separation decreased. This phenomena was obvious when the amount of cement was abobe 500kg/$\textrm{m}^3$ . When the amount of cement and S/a were 516kg/$\textrm{m}^3$ and 52% respectively, the application strength of 600kg/$\textrm{m}^3$ was satisfied. Since, however, the aggreate size of 25mm was somewhat unsatisfactory, the characteristics of high performance concrete could be obtained by the addition of the viscosity-enhancing agent.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.189-196
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• 2003

Soil-cement column is often used as a contaminant barrier. This study presents the results of experimental study performed to investigate the changes of properties of soil-cement column under the attack of acids. Sulfuric nitric, and ascetic acid were used as contaminants. Specimen were made of clayey and sandy soils with addition of cement and water Permeability of soil-cement decreased with time during permeability test. When significant amount of acid percolated the specimen, permeability increased and compressive strength decreased due to the dissolution and leaching of cement and its chemical reaction compounds. Sulfuric and nitric acid were more effective than ascetic acid in deteriorating soil-cement column. Amount of acid required to lower the pH of soil cement below 12 was calculated from the results of permeability tests. This leads to a conclusion that, under the conditions employed in this study, the chemical stability of soil-cement column could be maintained against acid attack for longer than generally accepted lifetime of contaminant barriers.

• Computers and Concrete
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• v.19 no.2
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• pp.217-226
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• 2017

This paper summarizes the results of experimental research, and artificial intelligence methods focused on determination of compressive strength of lightweight cement mortar with silica fume and fly ash after sulfate attack. The artificial neural network and the support vector machine were selected as artificial intelligence methods. Lightweight cement mortar mixtures containing silica fume and fly ash were prepared in this study. After specimens were cured in $20{\pm}2^{\circ}C$ waters for 28 days, the specimens were cured in different sulfate concentrations (0%, 1% $MgSO_4^{-2}$, 2% $MgSO_4^{-2}$, and 4% $MgSO_4^{-2}$ for 28, 60, 90, 120, 150, 180, 210 and 365 days. At the end of these curing periods, the compressive strengths of lightweight cement mortars were tested. The input variables for the artificial neural network and the support vector machine were selected as the amount of cement, the amount of fly ash, the amount of silica fumes, the amount of aggregates, the sulfate percentage, and the curing time. The compressive strength of the lightweight cement mortar was the output variable. The model results were compared with the experimental results. The best prediction results were obtained from the artificial neural network model with the Powell-Beale conjugate gradient backpropagation training algorithm.

• Journal of the Korean Ceramic Society
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• v.40 no.3
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• pp.219-224
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• 2003

Fly ashes containing 6.1~16.5 wt% of unburned carbon were treated thermally at 500$^{\circ}C$ for 3 h and thus, the content of unburned carbon was decreased below 2.1 wt%, the range of particle size distribution became narrower and the mean particle size became smaller. Besides, the properties of particles in fly ashes were improved, particularly the particle shape became close to a spherical type. The fluidity of cement pastes containing fly ashes treated previously at 500$^{\circ}C$ for 3 h was increased much than that of cement pastes containing original fly ashes. When the added amount of superplasticizer was over the saturation amount, there was no correlation between the amount of unburned carbon in fly ashes and the apparent viscosity of cement pastes actually. On the contrary, when the added amount of superplasticizer was below the saturation amount, there was a correlation.

• Cement Symposium
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• no.1
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• pp.31-40
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• 1973

Cement industry in Korea, has made a remarkable progress in recent years and now annual production capacity is about 9,000,000 tons. However, this large amount of cement is only one kind of general portland cement type I, and it is urgent problem for ceme

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.164-165
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• 2019

Light-weight foamed concrete using cement as a raw material consumes a lot of energy and generates $CO_2$ because of the high temperature firing process in the manufacturing process of cement. This study was carried out to evaluate the use of blast furnace slag through the properties analysis by substituting a certain amount of blast furnace slag as an industrial by-product as a substitute for cement. The experimental results showed similar characteristics to those of using only cement when the blast furnace slag fine powder was used in an appropriate amount. Therefore, if a certain amount of cement is replaced with blast furnace slag powder, it can maintain similar quality, reduce natural resources and energy consumption, and reduce carbon dioxide emissions.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.265-266
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• 2018

In recent years, active loess cement has been used instead of cement in order to reduce the amount of cement and industrial byproducts that are the main cause of environmental pollution. We also used polysilicon sludge as a by-product to reduce the amount of cement used and to improve the environmental pollution due to the reduction of carbon dioxide. Polysilicon is a raw material used in the production of panels for solar power generation. When producing 1 ton of polysilicon, 2 tons of sludge is generated. It is an experiment to reduce sludge treatment and cement usage. This study analyzed basic characteristics of polysilicon sludge and active loess cement according to replacment ratio.

• Korean Journal of Microbiology
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• v.12 no.3
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• pp.147-148
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• 1974

A small amount of Duco cement or Elmer's clear cement was dropped on a slide glass and immediately spread with a glass rod or woden stick a thin film on the surface. After approximately 1 minute a small amount of rubber cement was spread on the top of the film of Duco cement using the same method as described earlier. It was important that the rubber cement be smeared before the Duco cement dried out. These two kinds of cements must not be mixed. It was better to make the film of the rubber cement slightly thicker than the film of Duco cement. This composite film may be used up to several months after preparation. The sample leaf was placted on the slide, prepared with adhesive and the leaf surface was passed on the film with the thumb. The pressing was done so the leaf surface was completely in contact with the film. Then the leaf was peeled from the slide.