• Journal of the Korean Geotechnical Society
• /
• v.23 no.12
• /
• pp.25-32
• /
• 2007

This study is to evaluate the effect of chemical attack on durability and deterioration of lining concrete in tunnel. Surface examination, nondestructive inspection, uniaxial compressive strength test, carbonation test, chloride diffusion test, micro-structural analysis were performed to analyze the deterioration of lining concrete in tunnel constructed 70 years ago. From surface examination results, the tunnel had been repaired and reinforced in several times. It has many cracks, water-leakage, efflorescence and exploitation. Compressive strengths obtained from nondestructive inspection and uniaxial compressive strength test have measured $17.5{\sim}34.7MPa$, and $12.8{\sim}40.3MPa$, respectively. Carbonation depth specimen cored from concrete lining has ranged from 3mm to 27mm. From chloride diffusion test, most specimens have low permeability. And the XRD analysis was able to detect ettringite and thaumasite, which were confirmed by SEM and EDS results to be the causes for the deterioration of lining concrete.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.28 no.1
• /
• pp.12-23
• /
• 2024

In this study, a structural concrete square beam was developed using the centrifugal molding technique. In order to secure the bending stiffness of the cross section, the hollow rate of the cross section was set to 10% or less. Instead of using the current poor mixture of concrete and a concrete mixing ratio with a high slump (150-200) and a design strength of 100 MPa or more was developed and applied. In order to investigate the durability of centrifugally formed PSC square beams to be used as the superstructure of the avalanch tunnel or ramen bridge, the durability performance of ultra-high-strength centrifugally formed concrete with a compressive strength of 100 MPa was evaluated in terms of deterioration and chemical resistance properties.Concrete durability tests, including chloride penetration resistance, accelerated carbonation, sulfate erosion resistance, freeze-thaw resistance, and scaling resistance, were performed on centrifugally formed square beam test specimens produced in 2022 and 2023. Considering the information verified in this study, the durability of centrifugally molded concrete, which has increased watertightness in the later manufacturing stage, was found to be superior to that of general concrete.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.12
• /
• pp.27-33
• /
• 2012

The purpose of this study is to evaluate the field applicability of Quantum Stick in scale deposit prevention for subway tunnels in Seoul. This technology was installed into drainpipes and its performance was monitored through occasional site visits. SEM and EDS were also performed on scale collected from these drain pipes. Results showed a decrease in scale deposits due to Quantum Stick treatment. In the field test, the device was found to be effective in preventing scale formation in new pipes as well as reducing existing scale in previously installed pipes. However, further investigations are necessary to account for various environmental conditions. In conclusion, the results indicate that molecular Vibration technology is effective in suppressing scale formation.

• Resources Recycling
• /
• v.26 no.6
• /
• pp.38-44
• /
• 2017

As by-pass dust (BPD) made from cement manufactured process is designated waste, it is required to bury as high cost. The main component of BPD is potassium chloride (KCl), and used for the fertilizer. For using KCl to the fertilizer, the pH value of KCl is required as neutral or weak acid. However, it is not suitable to apply BPD into the fertilizer directly without any other treatment because BPD's pH value is shown 12.0~12.5; a high base. In this study, the carbon dioxide ($CO_2$) was used for removing calcium oxide (CaO) and reducing pH value during manufacturing process of KCl. We fixed inner condition of the carbon test chamber as $25^{\circ}C$-50RH%, and retained 0~7 hours under the 20 vol% of $CO_2$ atmosphere. After experiment, we analyzed the content of CaO and pH value from each samples. The more time exposed to $CO_2$, the content of CaO and pH value are shown. Furthermore, pH value exposed in 6 hours nearly reached 7.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.3
• /
• pp.367-374
• /
• 2021

In this study, the applicability of mechanochemical process for the manufacture of self-healing admixtures and the effect of mechanochemical process on the self-healing performance were evaluated. The self-healing admixtures were adopted as a highly reactive materials(expansive agent, swelling material and crystal growth agent) for mechanochemical processes. The self-healing admixtures for the mechanochemical process application were evaluated by X-Ray Diffraction and Fourier Transform Infrared Spectroscopy analysis, water permeability performance was used to evaluate self-healing performance of mortar. As a result of the evaluation, the self-healing performance of the WM(With-Mortar)3 sample to which mechanochemical process increased by 4.1% compared to the WM1 sample that was not treated, and the average healing index was 94.3%.

• Journal of the Korean Geosynthetics Society
• /
• v.23 no.3
• /
• pp.31-42
• /
• 2024

Coastal sand dunes are formed by the transport and deposition of sands by wind, and play a role in conserving ecosystems and safeguarding against natural disasters. While dunes possess a self-recovering ability from erosion, the ongoing reduction in coastal zones necessitates the countermeasures of coastal sand erosion. The potential of microbially induced carbonate precipitation (MICP) technology, which enhances the ground's strength and stiffness, in increasing the erosion resistance of coastal sand dunes is explored in this study. A wind tunnel testing system was used to simulate the erosion behavior of coastal dune. Untreated and MICP-treated sands were prepared for the erosion tests. Using a 3D scanner, pre- and post-wind eroded sand surfaces were surveyed. The erosion behaviors and corresponding erodibility parameters were analyzed based on the wind tunnel testing results. The level of cementation was quantified by acid-washing the treated sands. Experimental results indicated an increase in CaCO₃, strength, and erosion resistance with higher MICP treatments. This study proposed a correction coefficient to correlate the shear stress by wind with the one by water. This study confirms the potential of applying MICP technology to mitigate wind-induced erosion in coastal sand dunes.

• Korean Journal of Poultry Science
• /
• v.31 no.4
• /
• pp.273-281
• /
• 2004

A feeding trial was conducted with Euglena strains grown under different media. The effect of supplementation of Euglena on the performance, nutrient availability and fatty acid composition of breast muscle was studied. In experiment I, two hundred ten hatched broiler chicks (Ross) were assigned to seven dietary treatments for 5 weeks. Each treatment consisted of 3 replications with 10 birds each. Control diet was formulated to have $22\%$ CP and 3,150 kcal ME/kg for starter diet, $19\%$ CP and 3,200 kcal ME/kg for finisher diet. Euglena gracilis Z. (EG) was added to control diet at the plevel of 0.25, 0.5, $1.0\%$ and Euglena gracilis Z. bleached and DHA enriched (EGBD; a strain mutated by streptomycin and cultivated in DHA enriched medium) at the level of 0.5, 1.0, $2.0\%$ in the diet. In experiment 2, two hundred fifty hatched broiler chicks (Ross) were assigned to five dietary treatments: T1; Control, T2; T1 + Euglena gracilis Z. DHA enriched (EGD; cultivated in DHA enriched medium) $0.5\%$, T3; T1 + EGD $1.0\%$, T4; T1 + EGBD $0.5\%$, T5; T1 + EGBD $1.0\%$. The weight gain and feed consumption were measured weekly. Fatty acid composition of breast muscle was determined. In experiments I and 2, Euglena supplementation had no significant effects on weight gain, feed intake and feed conversion ratio. In experiment 1, EGBD treatments significantly increased DHA concentration but decreased concentration of linoleic acid and arachidonic acid in breast muscle. EGBD 2% treatment showed the highest DHA concentration (14.27%) which is 3.9 times of that of the control ($3.66\%$). In experiment 2, $1.0\%$ EGBD treatment showed highest EPA, lignoceric acid and DHA level in breast muscle (P<0.05). Also, EGD treatments significantly increased DHA and EPA concentration. It was concluded that EGBD and EGD can be supplemented to broiler diet to produce DHA enriched broiler meat.

• Korean Journal of Poultry Science
• /
• v.31 no.4
• /
• pp.283-291
• /
• 2004

Feeding trials were conducted with Euglena strains grown under different media. The effect of supplementation of Euglena on the laying performance, egg quality and fatty acid composition of egg yolk was studied. In experiment I, two hundred eighty 32-wk-old ISA Brown layers were randomly assigned to seven dietary treatments for 4 wks. Each treatment consisted of 4 replications with 10 birds each housed in two birds cages. Control diet was formulated to have $17\%$ CP and 2,750 kcal ME/kg. Euglena gracilis Z. (EG) was added to control diet at the level of 0.25, 0.5, $1.0\%$ and Euglena gracilis Z. bleached and DHA enriched (EGBD; a strain mutated by streptomycin and cultivated in DHA enriched medium) at the level of 0.5, 1.0, $2.0\%$ in the diet. In experiment 2, three hundred 84-wk-old ISA brown layers were randomly assigned to five dietary treatments: T1; Control, T2; T1 + EGBD $0.5\%$, T3; T1 + Euglena gracilis Z. DHA enriched (EGD; cultivated in DHA enriched medium) $0.5\%$, T4; T1 + EGD $1.0\%$, T5; T1 + EGD $2.0\%$. Each treatment had 5 replication of 12 birds each housed in two birds cages. In experiments 1 and 2, Euglena suppplementation did not significantly affect egg production but increased egg weight and feed intake. In experiment 1, EG was more effective in increasing egg yolk color score than EGBD. Egg yolk color of EG $1\%$ treatment showed the highest score. EGBD supplementation increased DHA concentration of egg yolk. EGBD $2\%$ treatment showed the highest DHA and the lowest palmitic and stearic acids concentration in the egg yolk. In experiment 2, EGBD $0.5\%$ treatment showed highest DHA level in egg yolk (P<0.05). It was conducted that EGBD is a single cell protein source rich in DHA, that can be used to produce DHA enriched eggs.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.4
• /
• pp.45-56
• /
• 2013

In this study, a blast furnace slag with latent hydraulic property is used to cement granular soils without using Portland cement. When the blast furnace slag reacts with an alkaline activator, it can cement soils. The effect of amounts of blast furnace slag and types of alkaline activator on soil strength was investigated for resource recycling. Four different amounts of slag and six different activators (two naturals and four chemicals) were used for preparing specimens. The specimens were air-cured for 3 or 7 days and then tested for unconfined compressive strength (UCS). The UCS of cemented sand with slag increased, in the order of specimens mixed with potassium carbonate, calcium hydroxide, sodium hydroxide and potassium hydroxide. Chemical alkaline activator was better than natural alkaline activator. The maximum UCS of 3-days cured specimens was 3 MPa for 16% of slag with potassium hydroxide, which corresponded to 37% of one with 16% of high-early strength portland cement. As the amount of slag increased, the UCS and dry density of a specimen increased for all alkaline activator cases. As the curing time increased from 3 days to 7 days, the UCS increased up to 97%. C-S-H hydrates were found in the cemented specimens from XRD analyses. Cement hydrates were more generated with increasing amount of slag and they surrounded sand particles, which resulted in higher density.

• Journal of Animal Environmental Science
• /
• v.13 no.1
• /
• pp.13-20
• /
• 2007

Sawdust biofiltration is an emerging bio-technology for control of ammonia emissions including compost odors from composting of biological wastes. Although sawdust is widely used as a medium for bulking agent in composting system and for microbial attachment in biofiltration systems, the performance of agitated bed composting and sawdust biofiltration are not well established. A pilot-scale composting of hog manure amended with sawdust and sawdust biofiltration systems for practical operation were investigated using aerated and agitated rectangular reactor with compost turner and sawdust biofilter operated under controlled conditions, each with a working capacity of approximately $40m^3\;and\;4.5m^3$ respectively. These were used to investigate the effect of compost temperature, seed germination rate and the C/N ratio of the compost on ammonia emissions, compost maturity and sawdust biofiltration performance. Temperature profiles showed that the material in three runs had been reached to temperature of 55 to $65^{\circ}C$ and above. The ammonia concentration in the exhaust gas of the sawdust biofilter media was below the maximum average value as 45 ppm. Seed germination rate levels of final compost was maintained from 70 to 93% and EC values of the finished compost varied between 2.8 and 4.8 ds/m, providing adequate conditions for plant growth.