• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.692-697
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• 2015

In this study, the reduction efficiencies of leachate heavy metal levels were investigated by adding $Al_2O_3$ and CaO to the bottom ash to observe their effects on the heavy metals leachate reduction efficiency. The ratio of $Al_2O_3$ and CaO contents were varied by 10~40% (W/W) alongside different curing time of 7 and 28 days. The reduction efficiencies of leachate heavy metal levels were estimated to be 69.3% for Cu and 52.1% for Pb during the curing time of 7 days. For the curing time of 28 days, the efficiencies changed to 85.2 and 100% for Cu and Pb, respectively. It was thus confirmed that the high reduction efficiency could be obtained as the curing time increased.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.247-254
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• 1999

The effect of manufacturing parameters such as molding and curing conditions on friction characteristics of friction materials were studied using a pad-on-disk type friction tester. The optimal manufacturing rendition for the best friction characteristics were investigated using friction materials containing 15 ingredients employing Taguchi robust design experiment. The friction characteristics were strongly affected by pressing time, pressing temperature, pressing pressure, curing time, curing temperature.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.77-80
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• 2005

The surface of concrete tiles is weak in moisture that it occurrenced efflorescence, but in the former study we found that it is possible to ensure moisture stability of concrete surface by autoclaving. So this study is to discuss the moisture stability and Physical Properties of high-strength glossy concrete according to time and temperature of autoclave curing. As the results, by increasing time and temperature of autoclave curing, compressive strength and surface hardness increased and glossiness decreased. In the case to 3 hour and $180^{\circ}C$ of autoclave curing, there is not effloescences in mosture stability test.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10c
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• pp.185-190
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• 1998

Corrosion of steel reinforcement is the most significant factor of deterioration in reinforced concrete structures. Chloride ion is considered one of the most common culprits on the corrosion of steels in concrete. The main objective of this study is understanding behavior of chloride ion in hardened cement pastes at different stages of curing. Cement pastes with water-cement ratio of 0.5 are allowed to hydrate in sealed containers for 28, 70, 180 days. And than pore solution is expressed. It was found that the $Cl^-$ concentrations in pore solution is decreased with increasing curing time in all Nacl addition level, the $OH^-$ concentrations is increased to 70 days but decrease at 180 days in all Nacl addition level. The $Cl^-$/$OH^-$ in pore solution is increased with increasing curing time in all Nacl addition level, however $Cl^-$/$OH^-$ of maximum Nacl addition level(Nacl 0.54% by weight of cement) is under the onset of depassivation level 0.3.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.489-494
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• 2010

A geo-composite soil (GCS) is a stabilized mixture of bottom ash, cement and dredged soil. Various samples with different mass ratios of mixtures were tested under curing time of 7 and 28 days to investigate physical properties and compressive strength. This paper focused on the effect of bottom ash on the strength characteristics of Busan marine dredged soil. Cement has been added as an additive constituent to enhance self-hardening of the blended mixture. The unconfined compressive strength of GCS increases with an increase in curing time due to pozzolanic reaction of the bottom ash. The strength after 28 days of curing is found to be approximately 1.3 to 2.0 times the strength after 7 days of curing, regardless of mixture conditions. The secant modulus of GCS is in the range of 55 to 134 times the unconfined compressive strength. The correlation of unconfined compressive strength with bottom ash content and initial void ratio are suggested.

• Journal of Urban Science
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• v.11 no.1
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• pp.21-28
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• 2022

Raman spectroscopy is effective to investigate functional groups via molecular vibration. The technique offers the structural information of compounds including subtle changes in the chemical composition of local atomic coordination without critical damage. Thus, the effect of carbonation on the hydration characteristics of Portland cement under pre-curing conditions for carbonation was investigated via Raman spectroscopy in the present study. Gaseous CO₂ was injected within 60 seconds, and the reaction time was varied from 0 minute to 90 minutes. The test results indicated that the Ca/Si ratio of C-S-H reduced immediately after mixing and then the C-S-H with a relatively high Ca/Si ratio coexisted as the reaction time increased. The calcium carbonates formed in the present study included calcite and amorphous calcium carbonates. The test results via Raman spectroscopy provide valuable information about the carbonation characteristics of OPC under pre-curing conditions for carbonation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.223-224
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• 2023

This study compared the curing temperature of the bubble sheet and the photothermal insulation sheet incorporating carbon-based photothermal materials to reduce concrete curing time as a part of shortening construction period. As a result of the experiment, bubble sheet with photothermal material B is judged to be effective in shortening the curing time under hot environment.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.347-350
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• 2005

The strength level for removal of lining concrete in tunnel is increased from 2.94MPa to 4.9MPa in 2004. This result in the increase of concrete curing time, and construction time would be delayed. In this study, in order to improve the efficiency of construction cycle and satisfy the strength criterion, a curing method is adopted, which is considering the hydration heat in the lining concrete member. As a result, it is shown that the concrete curing time for form removal is about 20hrs without the adjustment of concrete mix design. And construction cycle time is not changed compared to that before the change of strength criterion.

• The Journal of Advanced Prosthodontics
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• v.3 no.3
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• pp.126-131
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• 2011

PURPOSE. The aim of this in vitro study was to examine the curing efficiency of various resin-based materials polymerized through ceramic restorations with 3 different thicknesses. Curing efficiency was evaluated by determining the surface microhardness (VHN) of the resin specimens. MATERIALS AND METHODS. Four kinds of resin materials were used. Z350 (3M ESPE $Filtek^{TM}$ Z350: A2 Shade), Z250 (3M ESPE $Filtek^{TM}$ Z250: A2 Shade) and $Variolink^{(R)}$ II (VL: Ivoclar vivadent, base: transparent) either with or without a self-curing catalyst (VLC: Ivoclar vivadent, catalyst: low viscosity/transparent) were filled into the silicone mold (10 mm diameter, 1 mm thick). They were cured through ceramic discs (IPS e.max Press MO-0 ingot ivoclar vivadent, 10 mm diameter, 0.5, 1 and 2 mm thicknesses) by LED light-curing units for 20 and 40 seconds. Vicker's microhardness numbers (VHNs) were measured on the bottom surfaces by a microhardness tester. Data were analyzed using a 3-way analysis of variance (ANOVA) at a significance level of 0.05. RESULTS. The thickness of ceramic disc increased, the VHNs of all four resin types were decreased (P<.05). The mean VHN values of the resins light cured for 40 seconds were significantly higher than that of LED for 20 seconds in all four resin materials (P<.05). VLC showed significantly higher VHN values than VL regardless of other conditions (P<.05). Z350 and Z250 showed higher values than VL or VLC (P<.01). CONCLUSION. Thinner ceramic disc with increased curing time resulted higher VHN values of all resin materials. The use of a catalyst produced a greater hardness with all polymerization methods. Restorative resin materials (Z350, Z250) showed higher VHN values than resin cement materials (VL, VLC).

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.67-74
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• 2000

The usage of nondestructive testing on early-aged concrete leads to enhacned safty and allows effective scheduling of construction, thus making it possible to maximize the time and cost efficiencies. In this study, a reliable nondestructive strength evaluation method for early-aged concrete using the longitudinal wave velocity is proposed. Compression tests were performed to examine factors influencing the velocity-strength relationship of concrete, such as water-cement (w/c) ratio, fine aggregate ratio, curing temperature, and curing condition. The test results show that a change in the w/c ratio and curing temperature has minor effect on the velocity-strength relationship/ However, curing condition significantly influences the velocity-strength relationship of early-aged concrete. Moreover, the longitudinal wave velocity increases with decreasing fine aggregate ratio. It is concluded from this study that the strength evaluation of early-age concrete can be achieved by a nonlinear equation which considers the effects of curing condition and fine aggregate ratio.