• Resources Recycling
• /
• v.19 no.6
• /
• pp.36-42
• /
• 2010

Researches on resources recycling in the field of construction have made an extensive progress such as recycled aggregate of waste concrete and recycling of asphalt. On the other hand, there are almost never researches on pavement method with used waste frying oil. In South Korea, 0.2 million ton used waste frying oil is discharged every year. It is guessed that about 0.1 million ton used waste frying oil can be collected. If used waste frying oil is recycled, it is expected that disuse cost will be reduced and water pollution of rivers will be prevented. Therefore, the purpose of the study was to evaluate on mechanical features (strength, water resistance, chemical resistance, abrasion resistance, freezing and thawing resistance and permeable coefficient) whether dense graded permeable concrete mixing silica sand with flexible alkyd resin manufactured by making ester reaction with collected used waste frying oil to make alkyd resin could be applied to road pavement for non-roadway. The results of the study were as follows. In flexural strength, it had 1.6 times as much as road design standard 4.5MPa. In water resistance, chemistry resistance and freezing and thawing resistance, they had lack of strength in early age. As age went by, they didn't have large changes. And curing temperature had phenomenon of increase in strength at rather low temperature than high temperature by glass transition temperature of resin. Therefore, considering workability, strength and durability when it was applied to road pavement, it was reasonable that the mixing ratio of flexible alkyd resin was 10~15% in comparison with silica sand weight.

• Journal of the Korea Concrete Institute
• /
• v.20 no.2
• /
• pp.193-202
• /
• 2008

Seismic design for bridge columns of the current Korea Highway Bridge Design Specifications which adopt full ductility design concept results in reinforcement congestion problems in construction site. It is due to large amount of confining steel is required even for small ductility demand which is a normal case in low and moderate seismicity regions like Korean peninsular. Therefore a new seismic design method based on limited ductility concept was proposed, which is called ductility demand based design method. It uses the new confining steel design equation considering ductility demand and aspect ratio of the column as well as material strength. The purpose of this study is to verify safety of the ductility demand based design method by the confining steel design equation. Eighty nine circular column test results are selected and investigated in terms of ductility factor and its safety. The safety factor for the circular column test results ranges between 1.11 and 3.98, and the average is 1.90. In this paper, the basic concept and detailed design procedure of the ductility demand based design method are also introduced as well as the investigation of the safety with respect to the major variables in confining steel design.

• Journal of the Korea Concrete Institute
• /
• v.25 no.2
• /
• pp.209-215
• /
• 2013

This study is aimed to identify the method to use the CaO-$Al_2O_3$ system of rapidly cooled steel making slag (RCSS) as the environment-friendly inorganic accelerating agent by analyzing its physical and chemical properties. The fraction of rapidly cooled steel making slag is distinguished from its fibrous, and the contents of CaO and $Fe_2O_3$ are inversely proportional across different fractions. In addition, as the content of CaO decreased and the content of $Fe_2O_3$ increased, the loss ignition tended to become negative (-) and the density increased. The pore distribution by mercury intrusion porosimetry is very low as compared to the slowly cooled steel-making slag, which indicates that the internal defect and the microspore rate are remarkably lowered by the rapid cooling. To analyze the major minerals the rapidly cooled steel-making slag, XRD, f-CaO quantification and SEM-EDAX analysis have been performed. The results shows that f-CaO does not exist, and the components are mainly consisted of $C_{12}A_7$ and reactive ${\beta}-C_2S$.

• Journal of the Korea Concrete Institute
• /
• v.18 no.4 s.94
• /
• pp.569-576
• /
• 2006

PC-type copolymers were synthesized using MPEG(polyethylene glycol methyl ether methacrylate, Mn=2080) to different mole ratios of mono-carboxylic acid(AA : acylic acid). The mole ratios of AA were 2, 3, 4 and PC-type terpolymers were synthesized using mono-, dicarboxylic acid(ITA : itaconic acid MAL : maleic acid) with the same graft chain. To investigate effects of PC-type co-, ter-polymers on the hydration of cement experiments involving FT-IR, XRD, DSC, SEM have been analysed with cement paste specimens to 1, 3, 28 day. The hydration reaction rate of cement paste was slightly delayed at 1 day, due to increase in molar ratio of [AA]/[MPEG], it was recovered in the days after and the copolymer was more active than the terpolymer, because of low carboxylic acid content PC-type copolymers applied 2AA-type were fastest copolymer on hydration reaction of cement paste to 3 day and the more AA mole ratios increased, the more hydration was retarded.

• Journal of the Korean Geosynthetics Society
• /
• v.20 no.4
• /
• pp.85-93
• /
• 2021

The seventy percentage of Korean Peninsular is covered by the mountainous area, and the depth of west sea and south sea is relatively shallow. Therefore, a large scale land reclamation from the sea has been implemented for the construction of industrial complex, residental area, and port and airport facilities. The common problem of reclaimed land is consisted of soft ground, and hence it has low load bearing capacity as well as excessive settlement upon loading on the ground surface. The hollow concrete block has been used to reinforce the loose and soft foundation soil where the medium-high apartment or one-story industrial building is being planned to be built. Recently the earthquakes with the magnitude of 4.0~5.0 have been occurred in the west coastal and southeast coastal areas. Lee (2019) reported the advantages of hollow concrete block reinforced shallow foundation through the static laboratory bearing capacity tests. In this study, the dynamic behavior of hollow concrete block reinforced sandy ground with filling the crushed stone in the hollow space has been investigated by the means of shaking table test with the size of shaking table 1000 mm × 1000 mm. Three types of seismic wave, that is, Ofunato, Hachinohe, Artificial, and two different accelerations (0.154 g, 0.22 g) were applied in the shaking table tests. The horizontal displacement of structure which is situated right above the hollow concrete block reinforced ground was measured by using the LVDT. The relative density of soil ground are varied with 45%, 65%, and 85%, respectively, to investigate the effectiveness of reinforcement by hollow block and measured the magnitude of lateral movement, and compared with the limit value of 0.015h (Building Earthquake Code, 2019). Based on the results of shaking table test for hollow concrete block reinforced sandy ground, honeycell type hollow block gives a large interlocking force due to the filling of crushed stone in the hollow space as well as a great interface friction force by the confining pressure and punching resistance along the inside and outside of hollow concrete block. All these factors are contributed to reduce the great amount of horizontal displacement during the shaking table test. Finally, hollow concrete block reinforced sandy ground for shallow foundation is provided an outstanding reinforced method for medium-high building irrespective of seismic wave and moderate accelerations.

• Korean Journal of Soil Science and Fertilizer
• /
• v.44 no.4
• /
• pp.527-533
• /
• 2011

Decomposition of compost applied to soils is affected basically by its biological stability; but, many other chemical properties of the compost may also influence compost organic-C mineralization. This study was conducted to investigate the principal substrate quality factors of composts that determine C mineralization of compost with similar stability degree (SD). Three composts samples with similar SD but different chemical properties such as pH, C/N, $K_2SO_4$-extractable C, and molar ratio of $NH_4^+$ to $NO_3^-$ were mixed with an acid loamy soil and $CO_2$ emission was monitored during the laboratory incubation for 100 days. Temporal pattern of cumulative compost organic-C mineralization expressed as % of total organic C ($C_{%\;TOC}$) followed double exponential first order kinetics model and the $C_{%\;TOC}$ ranged from 4.8 to 11.8% at the end of incubation. The pattern of C%TOC among the composts was not coincident with the SD pattern (40.1 to 58.6%) of the composts; e.g. compost with the lowest SD resulted in the least $C_{%\;TOC}$ and vice versa. This result indicates that SD of compost can not serve as a concrete predictor of compost mineralization as SD is subject not only to maturity of compost but also to characteristics of co-composting materials such as rice hull (low SD) and sawdust (high SD). Meanwhile, such pattern of $C_{%\;TOC}$ collaborated with pH, C/N, $K_2SO_4$-extractable C, and molar ratio of $NH_4^+$ to $NO_3^-$ of the composts that are regarded as chemical indices of the progress of composting. Therefore, for better prediction of compost mineralization in soils, it is necessary to consider both SD and other chemical indices (pH, C/N, and molar ratio of $NH_4^+$ to $NO_3^-$).

• Journal of the Korea Concrete Institute
• /
• v.23 no.5
• /
• pp.683-692
• /
• 2011

In piloti-type low-rise RC residential buildings, severe damages have been usually concentrated at piloti stories under the earthquake. In this study, a piloti story was retrofitted by installation of buckling-restrained braces (BRB's) to increase strength and stiffness of piloti story and by application of fiber reinforced polymer (FRP) sheet on columns to avoid the brittle shear and axial failure of columns. To verify this retrofit performance, reversed cyclic lateral load tests were performed on 1:5 scale bare and retrofitted frames. The test results showed that yield strength (43.2 kN) appeared to be significantly larger than design value (30 kN) due to the increase of strength in the compression side, but the stiffness value (11.6 kN/mm) turned out to be approximately one-half of the design value (24.2 kN/mm). The reasons for this difference in stiffness were due to slippage at joint between the frame and the BRB's, displacement and rotation at footing. The energy absorption capacity of the retrofitted frame was 7.5 times larger than that of the bare frame. The change of the number of load cells under the footing from 2 to 1 reduced lateral stiffness from 11.6 kN/mm to 6 kN/mm, which was only three times larger than that of the bare frame (2.1 kN/mm).

• The Korean Journal of Physiology
• /
• v.1 no.1
• /
• pp.67-72
• /
• 1967

Present paper is attempted to introduce the phenomenon of 'after contraction' in isolated cardiac-muscle. Papillary muscles were removed from cat right ventricle and were used as a preparation. The muscle strip was Placed in tissue bath which is kept in steady temperature of around $25^{\circ}C$ and was perfuced by Tyrode solution, saturated with 95% $O_2$ and 5% $CO_2.$ under the condition of high calcium (8.2-10.0 mM/l), low sodium (72.4-70.0 mM/l) perfusion with the administration of epinephrine (1-2 mg/l) into tile tissue bath normally triggered muscle contraction was followed by oscillatory, repetitive contractions - after contraction. The phenomenon of after contraction was augumented by decrease in tissue bath temperature and by increase in number of preceding beats and in driving rate. Authors were able to maintain the phenomenon in prominent and steady state giving proper experimental conditions such as fixed bath temperature (ranged from $22^{\circ}C\;to\;27^{\circ}C$), suitable driving rate (20 per minute in average) and perfusion of high calcium, loll sodium and 1-2 mg/l of epinephrine. In some preparations, the strength of after contraction (second contraction) reached up-to 80% of normally triggered contraction and five repetitive contractions were observed as largest number of after contractions. Intracellular action potential measured in the muscle which was beating regulary showing steady after contraction revealed no oscillating after potential in most parts of the muscle but in few cases oscillating changes of after potentials were detectable. In electrogram of the muscle preparation recorded by means of contact electrode prominent, oscillating after potentials were observable when the recorder was set at highest sensitivity. It still is not clear that whether after contraction is the phenomenon which corresponds to those changes in action potential, oscillating after potential, of the muscle preparation. Possible mechanism of the phenomenon of after contraction relating with after potential changes was proposed. Detailed results obtained from further studies on after contraction and concrete discussion on the phenomenon will be reported by authors.

• Economic and Environmental Geology
• /
• v.51 no.5
• /
• pp.429-438
• /
• 2018

Since concrete is a hardened aggregates of various materials, it needs to be crushed for chemical analyses. However, the effect of sample crushing on the analytical results has not been precisely assessed till today. In this study, we prepared concrete test pieces using Portand cements and fly ashes as binding materials, and ponded ashes and sands as aggregates and analyzed the heavy metals of the test pieces using Standards for Fair Testing of Soil Contamination (SFTSC) and Wastes (SFTW). For this, each test piece was partially crushed at first and sieved for separation of grains of <0.15 mm, 0.15-0.5 mm, and 0.5-5 mm from the same crushed samples (Crushing Method I). Results of those samples using SFTSC showed a clear trend that analyzed heavy metal concentrations are higher in the finer fractions. Particularly, fractions with <0.15 mm indicated much higher concentrations than the theoretical ones, which were calculated based on the concentrations of individual materials and their mixing fractions. In contrast, the analytical results were generally comparable with the theoretical ones when the test pieces were totally pulverized such that all the crushed grains were <0.15 mm in size (Crushing Method II). These results are associated with the fact that cement materials and fly ashes, which are high in heavy metals relative to other materials, are enriched in the fine fractions. The analytical results using the SFTW derived very low concentrations in most of parameters and did not indicate the dependence of concentrations on the crushing methods due to using distilled water as leaching agent.

• International Journal of Highway Engineering
• /
• v.17 no.3
• /
• pp.49-58
• /
• 2015

PURPOSES : The use of environmentally friendly construction methods has been recently encouraged to reduce fuel consumption and the effects of global warming. For this purpose, the roller compacted concrete pavement (RCCP) construction method has been developed. RCCP is more environmentally friendly and economically efficient than general concrete by reducing the amount of CO2 generated through the application of a smaller amount of cement. RCCP has a number of advantages such as an easy construction method, low cost, high structural hydration performance, and aggregate interlocking. However, mix design standards and construction guidelines of RCCP are required for domestic application. In addition, a study on aggregate selection, which has an effect on the characteristics of RCCP, is necessary owing to a limited number of researches. Thus, the aggregate effect on the performance of RCCP in securing the required strength and workability was evaluated in consideration of domestic construction. METHODS : Sand and coarse aggregates of both 19mm and 13mm in maximum size were used in this study. Four types of aggregate gradations (s/a = 30%, 58%, and 70% for the sand and coarse aggregate of 19mm in maximum size, and s/a = 50% for a combination of the three types of aggregates) were set up to investigate the effects of the PCA band on the RCC characteristics. The conditions of s/a = 30% and 70% were evaluated to check the gradation effect outside of the recommended band. The conditions of s/a = 58% and 50% were used because they are the optimum combination of the two and three types of aggregates, respectively. RCCP gradation band was suggested gradation with a proper construction method of RCCP by synthetically comparing and analyzing the correlation of optimum water content, maximum dry density, and strength of requirements through its consistency and compaction test. RESULTS : The lower and upper limit lines are insufficient to secure a relatively strong development and workability compared to an aggregate gradation in the RCCP gradation band region. On the other hand, the line in the RCCP gradation band and the 0.45 power curve in the RCCP gradation band region were satisfactory, ensuring the required strength and workability. CONCLUSIONS : The suitable aggregate gradation on RCCP process should meet the RCCP gradation band area; however, fine particles passing through a #60 sieve do not need to be within the recommended gradation band because the influence of this region on such fine particles is small.