• Journal of environmental and Sanitary engineering
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• v.14 no.3
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• pp.22-30
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• 1999

This study was carried out to examine the compressive strength characteristics of solids solidified with the lead sludge with mixture of cement and fly ashes as additive. And the additives are commercial fly ash and ESP(Electrostatic precipitator) fly ash. The compressive strength of solidified lead sludge solid was increased by adding fly ash up to 46~62%, which was the results of pozzolanic reaction. When replaced the cement with 10%of commercial fly ash, the solid showed the highest value $210{\;}kg/cm^2$, and the solidification conditions were 0.55 of the water/cement ratio and curing for 14 days. Also, the results of leaching test by EPT(Environmental Protection Agency-Toxicity Test) were showed that the solidified lead has leached out under 10%, which was less than 0.173 mg/L of EPA standard. As leaching solutions, the demineralized water, 0.1N acetic acid solution, and synthetic brine were used. and the observations by SEM of the solidified lead-laden solid after EPT leaching test were indicated the severe erosion on solid surface.

• International Journal of Concrete Structures and Materials
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• v.7 no.2
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• pp.111-117
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• 2013

Heavy oil fly ash (HOFA) is a byproduct generated by the burning of heavy fuel oil. Chemical analysis showed that HOFA is mainly composed of unburned carbon with a significant amount of heavy metals. Due to toxicity, management of this waste poses a challenge to the industry personal. The present study investigates the possible use of HOFA as a black pigment or admixture in cement mortar aiming to produce ornamental brick. In order to investigate the change of cement mortar strength when HOFA is added, the standard compressive strength test with 50 mm cubes was performed. The results showed that the addition of 2-5 % of HOFA in cement mortar does not affect its strength. The leaching behavior of trace elements within HOFA and HOFA mixed mortar were investigated through laboratory batch leaching experiments. The results confirmed that HOFA can be utilized as a black pigment in ornamental brick, which is environmentally safe and provides good balance between color and brick properties.

• Ecology and Resilient Infrastructure
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• v.2 no.2
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• pp.147-153
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• 2015

Various adverse effects can occur due to direct exposure from toxic substances when toxic materials are used to restore river ecosystems. Thus, this study performed analysis on the development of toxicity in terms of survival and abnormality rates using embryos of Bombina orientalis living in Korea to analyze the toxicity of materials used in the river projects. The results showed that the toxicity in cement (C group) was the strongest whereas the toxicity in plant-based polyurethane (P1 group) was the weakest. Survival rates of B. orientalis embryos were 100%, 94 - 95%, 66 - 89% and 0% in control, P1, polyurethane (P2) and C groups, respectively. Abnormalities of embryos were 10.5%, 5.3 - 10.5%, 26.3 - 27.8% and 35.7% in control, P1, P2 and C groups, respectively. Furthermore, we verified that having a sufficient curing time reduced toxic substances that were extracted. The above result suggest that cement and polyurethane hamper the early development of amphibians. In conclusion, it is highly important to review biological safety with respect to the selection of materials used to restore rivers. This study shows the importance of the selection of eco-friendly materials and processes.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.22 no.1
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• pp.47-59
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• 2019

This study was composed of four treatments [no treatment, phosphate + limestone layer treatment, phosphate + sodium bicarbonate + cement layer treatment, and phosphate + sodium bicarbonate + limestone layer treatment] for figuring out vegetation effects on the acid drainage slope. Treated acid neutralizing techniques were effective for neutralizing acidity and vegetative growth in order of [first: phosphate + sodium bicarbonate + limestone layer treatment, second: phosphate + sodium bicarbonate+cement layer treatment, third: phosphate + limestone layer treatment and fourth: no treatment] on the acid drainage slope. We found out that sodium bicarbonate treatment was additory effect on neutralizing acidity and increasing vegetaive growth besides phosphate and neutralizing layer treatments. In neutralizing layer treatments, Limestone layer was more effective for vegetation and acidity compared to cement layer treatment. Cement layer showed negative initial vegetative growth probably due to high soil hardness and toxicity in spite of acid neutralizing effect. Concerning plants growth characteristics, The surface coverage rates of herbaceous plants, namely as Lotus corniculatus var. japonicus and Coreopsis drummondii L were high in the phosphate + sodium bicarbonate + limestone layer treatment while Festuca arundinacea was high in the phosphate + sodium bicarbonate + cement layer treatment. We also figured out that soil acidity affected more on root than top vegetative growth.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.10 no.S_2
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• pp.89-95
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• 2001

The solidification and leaching characteristics of cyclone ash collected from an industrial incineration plant were investigated. Cement and calcium hydroxide were used as the solidifying materials. The leaching characteristics of the solidified cyclone ash were found to vary depending on both the quantitative and the qualitative aspects of the solidifying materials. Except for copper and lead, all the heavy metal ions in the leachate of the solidified material composed of 10~20 % cement or 10~20 % calcium hydroxide were found to be within their standard limit. Moreover, all the heavy metal ions were also observed to be within satisfactory limits in the leachate obtained from the solidified material composed of 30 % cement or 30 % calcium hydroxide. Therefore, to satisfy the standard compressive intensity and permissible limits of heavy metal ions leached from solidified material, it would appear that a 30 % proportion of either additive in the solidification product can meet the required standard for the leachate. The cost of solidifying cyclone ash per ton for ash-30 % cement and ash-30 % lime was calculated as 26,750 and 26,070 won, respectively. Accordingly, significant reduction in the waste toxicity and mobility as well as an improvement in the engineering properties of the solidified products were successfully achieved.

• Restorative Dentistry and Endodontics
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• v.37 no.4
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• pp.194-200
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• 2012

Objectives: New resin cement (NRC) has been developed as a root repairing material and the material is composed of organic resin matrix and inorganic powders. The aim of this study was to compare the rat subcutaneous tissue response to NRC and mineral trioxide aggregate (MTA) cement and to investigate the tissue toxicity of both materials. Materials and Methods: Sixty rats received two polyethylene tube-implants in dorsal subcutaneous regions, MTA and NRC specimens. Twenty rats were sacrificed respectively at 1, 4 and 8 wk after implantation and sectioned to 5 ${\mu}m$ thickness and stained with Hematoxylin-Eosin (H-E) or von-Kossa staining. The condition of tissue adjacent to the implanted materials and the extent of inflammation to each implant were evaluated by two examiners who were unaware of the type of implanted materials in the tissues. Data were statistically analyzed with paired t-test (p < 0.05). Results: In specimens implanted with both NRC and MTA, severe inflammatory reactions were present at one wk, which decreased with time. At eighth wk, MTA implanted tissue showed mild inflammatory reaction, while there were moderate inflammatory reactions in NRC implanted tissue, respectively. In NRC group, von-Kossa staining showed more calcification materials than MTA group at eighth wk. Conclusions: It was concluded that the calcium reservoir capability of NRC may contribute to mineralization of the tissues.

• Restorative Dentistry and Endodontics
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• v.14 no.1
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• pp.7-24
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• 1989

The purpose of the study was to evaluate the cytotoxic effects of polycarboxylate cements and zinc phosphate cements in vitro. Human fibroblasts were cultured in ${\alpha}$-MEM, and each cement was manually mixed and filled in glass ring cylinder (8${\times}$8mm in diameter, in height.) Cement filled cylinders were placed in the center of the dish (35mm in diameter) containing 3ml of ${\alpha}$-MEM. Millipore filters to simulate dentinal barrier were also placed between the cylinder and the dish, then stored in 5% $CO_2$ containing chamber for 1 and 2 weeks at the temperature of $36.6^{\circ}C$. The results of the experiments were analyzed by counting the cells in the period of one week and two weeks respectively, and were assessed by calculating the cell multiplication rate and the relative growth rate. The experimental groups and the control group were compared. The results of the study were summarized as follows. 1. Durelone brand of the polycarboxylate cements showed marked cytotoxicity after one week, but after two weeks the toxicity decreased remarkably. Poly-F brand exhibited moderate cytotoxicity after one week, but after two weeks the toxicity slightly decreased. HY-BOND brand was weakly cytotoxic after one week, but after two weeks the toxicity became significant. 2. The cytotoxicity of the zinc phosphate cements was negligible after one week, but after two weeks Lee Smith brand revealed considerable cytotoxicity. 3. In general, the zinc phosphate cements were less cytotoxic than the polycarboxylate cements.

• Environmental Engineering Research
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• v.14 no.4
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• pp.212-219
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• 2009

Emission characteristics of air pollutants from three commercially operating cement kilns co-burning waste were investigated. The major heavy metals emitted were mercury (Hg), zinc (Zn), nickel (Ni), chromium (Cr), lead (Pb), cadmium (Cd), and arsenic (As) Removal efficiency of the bag filter was above 98.5% for heavy metals (except Hg), and above 60% for Hg. Higher fractions of heavy metals entering the bag filter were speciated to cement kiln dust. On average, 3.3% of the -heavy metals of medium and low toxicity (Pb, Ni, and Cr) entering the bag filter were released into the atmosphere. Among highly toxic heavy metals, 0.14% of Cd, 0.01% of As, and 40% of Hg entering the bag filter were released into the atmosphere. In passing through the bag filter, the proportion of oxidized Hg in all cases increased. Emission variations of hazardous air pollutants in cement kilns tested were related to raw materials, fuel, waste feed and operating conditions. Volatile organic compounds detected in gas emissions were toluene, acrylonitrile benzene, styrene, 1,3-butadiene, and methylene chloride. Although hazardous air pollutants in emissions from cement kilns co-burning waste were within the existing emission limit, efforts are required to minimize their levels.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.3
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• pp.135-143
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• 2009

To study possibility of $Cr^{6+}$ solid solution and efficiency of admixture, leaching property of Portland cement mortar was investigated by using KSLT (Korea Standard Leaching Test), TCLP (Toxicity Characteristic Leaching Procedure), Soacking procedure, as adding excess $Cr^{6+}$. As a result, admixture of lignin type showed high compressive strength of mortar but no changing leaching property.

• Restorative Dentistry and Endodontics
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• v.4 no.1
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• pp.17-21
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• 1978

The histopathological study was made to investigate the pulp reaction of "Hipol". The toxicity against the pulp tissue was compared with the "Zinc-Oxide-Eugenol Cement." A total of 36 cavities of healthy prmanent teeth of the 3 dogs were chosen and filled with the experimental filling materials without base. The teeth were prepared at 3 intervals; a week and two, three weeks as a result of this study. 1) Both "Hipol" and "Adaptic" showed very severe to moderate pulp reactions in the all of the filled teeth. 2) There was little difference between "Hipol" and "Adaptic" in the severity of the pulp reaction. 3) After 3 weeks, the teeth filled with "Hipol" and "Adaptic" showed more or less recovery phenomena. The teeth filled with "Zinc-Oxide-Eugenol Cement" showed marked recovery phenomenon. 4) There was little difference in the histopathological result between "Universal" group and "Catalyst" group.