• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.781-784
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• 2006

This paper investigates the fundamental properties of light weight foamed concrete with the variances in unit weight of concrete and adding ratio of stability agent(SA). Test showed that concrete adding SA slightly decreased fluidity but secured stable flow appearances without segregation of concrete components. All specimens in a standard condition represented that a sinking depth was not observed, while, in the wet condition, a specimen adding SA decreased the sinking depth $2{\sim}4mm$ more than control concrete. Compressive strength values of control concrete showed $0.03{\sim}0.3MPa$ higher than the concrete adding SA. As for the tensile strength, the specimen adding SA also had lower value, while the ratios of comp. to tens. strength presented $0.43{\sim}0.62$, which is relatively higher than ordinary concrete.

• Journal of the Korea Institute of Building Construction
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• v.9 no.3
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• pp.73-78
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• 2009

Coal ash is a by-product of the combustion of pulverized coal, and much of this is dumped in landfills. The disposal of coal ash is one of the major issues for environmental problems. In this paper, the effects of the kinds and replacement ratio of coal ash on the durabilities of concrete mixtures are investigated. Fine aggregate was replaced with coal ash(fly ash and bottom ash) in five different ratios, of 0%, 10%, 20%, 35%, and 50% by volume. Test results indicated that the compressive strength increased with the increase in fly ash percentage. The loss of compressive strength of bottom ash concrete mixes after immersion in sulphuric acid solution was less than in the control mix(BA0). In addition, the carbonation depth of fly ash concrete mixes was lower than the control mix(FA0).

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.33 no.3
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• pp.44-51
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• 2001

Sedimentation characteristics such as SS, $BOD_5$, COD removal efficiency of waste water in the toilet paper mill using milk carton were examined. Optimum dosage of coagulant, rapid mixing time and slow mixing time were determined by turbidity, SS, COD, $BOD_5$ and then equation for treatment efficiency was suggested. Mechanical strength of floc was determined by turbidity. For the coagulant, polyacrylamide (PAM) is more efficient for removing pollution than the aluminium sulfate. Effective mixing ratios of PAM and aluminum sulfate to remove pollution are 70:30 and 30:70. The lowest turbidity was showed when rapid mixing at 300 rpm after coagulant injection was applied. That which indicates the highest point of flocs mechanical strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.3
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• pp.261-268
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• 1999

The seismic performance of precast concrete panel structures tested previously has been evaluated in this paper. Hysteretic curves of test specimens are idealized to elasto-plastic curves to get reliable yielding and ultimate displacements. For the idealized curves, ductility and energy dissipation capacity of specimens have been evaluated using a few guide lines. In addition, the strength capacity of specimens is checked for the strength demand caused by the design earthquake load including overturning moment effects. The result shows while the strength of specimen with joint box for vertical continuity is little bit lower than that of specimen connected by welding, the ductility of the former is higher than that of the latter. The energy dissipation ratios of PC specimens are ranged from 83% to 96% of that of Re specimen and the average of those are shown 90%.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.241-248
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• 2006

By Testing tension coupon, deviation of yield strength & tensile strength of SS and SM is big but the that of SN is small relatively. So Designing weak beam type frame by using SN could be reflected well the original intention. As the strength ratios of beam and column becomes large, the absorption energy is large. The increase quantity was linear relationship, the y=0.46x+0.62 $(R^2=0.82)$

• Computers and Concrete
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• v.23 no.3
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• pp.155-160
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• 2019

The use of recycled aggregate concrete for the purpose of environmental and resource conservation has gained increasing interest in construction engineering. Nevertheless, few studies have reported on the bonding performance of the bars in recycled aggregate concrete after exposed to high temperatures. In this paper, 72 pull-out specimens and 36 cubic specimens with different recycled coarse aggregate content (i.e., 0%, 50%,100%) were cast to evaluate the bond behavior between recycled aggregate concrete and steel bar after various temperatures ($20^{\circ}C$, $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$). The results show that the recycled aggregate concrete pull-out specimens exhibited similar bond stress-slip curves at both ambient and high temperature. The bond strength declined gradually with the increase of the temperature. On the basis of a regression analysis of the experimental data, a revised bond strength mode and peak slip ratios relationship model were proposed to predict the post-heating bond-slip behavior between recycled aggregate concrete and steel bar.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.64-65
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• 2020

Oyster shells are difficult to grind, while oyster shell powders have coarse and coarse grains, whereas egg shell powder, the same high calcium material, has small and soft particles and has opposing properties. In order to study the change in flexural and compressive strength by designing different mixing ratios using 50% of oyster shell powder and egg shell powder as a filling material. As a result of the experiment, there is almost no difference in the result.

• Advances in concrete construction
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• v.3 no.3
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• pp.203-221
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• 2015

This paper presents the results of a study undertaken to investigate the enhancement of concrete strength using Silpozz and Rice Husk Ash (RHA). The total percentage of supplementary cementitious material (SCM) substituted in this study was 20%. Six different concrete mixes were prepared such as without replacement of cement with silpozz and RHA (0% silpozz and 0% RHA) is treated as conventional concrete, whereas in other five concrete mixes cement was replaced by 20% of silpozz and RHA as (0% silpozz and 20% RHA), (5% silpozz and 15% RHA), (10% silpozz and 10% RHA), (15% silpozz and 5% RHA) and (20% silpozz and 0% RHA) with decreasing water-binder (w/b) ratio i.e. 0.375, 0.325 and 0.275 and increasing super plasticiser dose. New generation polycarboxylate base water reducing admixture i.e., Cera Hyperplast XR-W40 was used in this study. The results of this research indicate that as w/b decreases, super plasticiser dose need to be increased so as to increase the workability of concrete. The effects of replacing cement by silpozz and RHA on the compressive strength, split tensile strength and flexural strength were evaluated. The concrete mixture with different combination of silpozz and RHA gives higher strength as compared to control specimen for all w/b ratios and also observed that the early age strength of concrete is more as compared to the later age strength. It is also observed that the strength enhancement of concrete mixture prepared with the combination of cement, silpozz and RHA is higher as compared to the concrete mixture prepared with cement and silpozz or cement and RHA.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.720-727
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• 2017

This study determined the optimum mix proportions for volcanic-ash-based geopolymer by analyzing the flow, setting time, and compressive strength. $Na2SiO_3$ and NaOH were used as alkali activators, and NaOH concentrations of 2, 4, 6, and 8M were used for different experimental cases. The A/B ratios examined were 0.25, 0.3, 0.35, 0.4, and 0.45, and the ratios of volcanic ash to blast furnace slag binder were 7:3, 6:4, and 5:5. In the experiment, the flow and setting time tended to decrease and the compressive strength increased as the molarity of NaOH in the geopolymer increased. The optimum molarity of NaOH was determined to be 4M. As the A/B ratio increased, the setting time decreased and the compressive strength increased. The most advantageous A/B ratio for the setting time and strength was 0.35. Increasing the ratio of volcanic ash resulted in a longer setting time and lower compressive strength. The optimum binder ratio was chosen as 6:4 based on the setting time and compressive strength. Thus, 4M of NaOH, an A/B ratio of 0.35, and binder ratio of 6:4 are considered as the proper parameters for the volcanic-ash-based geopolymer.

• Proceedings of the Korean Institute of Building Construction Conference
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• v.y2004m10
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• pp.71-76
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• 2004

This paper investigate that the effect of the concrete containing mineral admixtures(pozzolanic materials such as fly-ash, ground granulated blast-furnace slag, silica fume and meta kaolin) on the resistance properties to chloride ion invasion. The purposed testing procedure was applied to the concrete added mineral admixtures for $3\sim4$ replacement ratios under W/B ratios ranged from 0.40 to 0.55. Specimens were immersed in $3.6\%$ NaCl solution for 330 days, and penetration depth, water soluble chloride contents and acid soluble chloride contents were measured in 28, 91, 182 and 330 days. Then, diffusion coefficient were calculated using total chloride contents. As a results. the kinds of mineral admixture and replacement ratios had a great effect on the resistance property of the concrete to chloride ion invasion compared with the plain concrete. And the optimal replacement ratios of mineral admixture had a limitation for each admixtures. The amount of acid soluble chloride ions and water soluble chloride ions were varied with the kinds of mineral admixtures and the penetration depth from the concrete skin. Chloride diffusion coefficient of each concretes decreased with the time elapsed. and the diffusion coefficients of the concrete immersed salt water for 330 days had a establishment with the compressive strength measured before immersing.