• Title/Summary/Keyword: initial curing time

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MECHANICAL PROPERTIES AND MICROLEAKAGE OF COMPOSITE RESIN MATERIALS CURED BY VARIABLE LIGHT INTENSITIES (가변 광도에 따른 복합레진의 기계적 물성 및 변연누출도 변화)

  • Han, Seung-Ryul;Min, Kyung-San;Shin, Dong-Hoon
    • Restorative Dentistry and Endodontics
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    • v.28 no.2
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    • pp.134-145
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    • 2003
  • Mechanical properties and microleakage of two composites [conventional hybrid type DenFil (VERICOM Co., Anyang, Korea) / micro matrix hybrid type Esthet X (Dentsply Caulk, Milford, DE, U.S.A.)] were evaluated to assess whether variable light intensity curing is better than conventional curing technique. Curing was done for 40 seconds in two ways of 2 step soft-start technique and 5 step ramping technique. Three kinds of light intensities of 50, 100, $200{\;}mW/\textrm{cm}^2$ were initially used for 10, 20, 30 seconds each and the maximum intensity of $600 {\;}mW/\textrm{cm}^2$ was used for the rest of curing time in a soft-start curing tech nique. In a ramping technique, curing was done with the same initial intensities and the light intensity was increased 5 times with the same rate to the maximum intensity of $600{\;}mW/\textrm{cm}^2$. After determining conditions that showed no different mechanical properties with conventional technique, Esthet X composite was filled in a class V cavity, which dimension was $4{\times}3{\times}1.5{\;}mm$ and cured under those conditions. Microleakage was evaluated in two ways of dye penetration and maximum gap estimation through SEM observation. ANOVA and Spearman's rho test were used to confirm any statistical significance among groups. The results were as follows : 1 Several curing conditions of variable light intensities resulted in the similar mechanical properties with a conventional continuous curing technique, except conditions that start curing with an initial light intensity of $50{\;}mW/\textrm{cm}^2$. 2. Conventional and ramping techniques were better than soft-start technique in mechanical properties of microhardness and compressive strength. 3. Soft-start group that started curing with an initial light intensity of $100{\;}mW/\textrm{cm}^2$ for 10 seconds showed the least dye penetration. Soft-start group that started curing with an initial light intensity of $200{\;}mW/\textrm{cm}^2$ for 10 seconds showed the smallest marginal gap, if there was no difference among groups. 4. Soft-start technique resulted in better dye-proof margin than conventional technique(p=0.014) and ramping technique(p = 0.002). 5. There was a very low relationship(p=0.157) between the methods of dye penetration and marginal gap determination through SEM evaluation. From the results of this study, it was revealed that ramping technique would be better than conventional technique in mechanical properties, however, soft-start technique might be better than conventional one in microleakage. It was concluded that much endeavor should be made to find out the curing conditions, which have advantages of both aspects or to solve these kinds of problems through a novel idea of polymerization.

Estimation of Setting Time and Compressive Strength of the Concrete According to Curing Conditions Using a Hybrid Meter (하이브리드 미터를 이용한 양생조건에 따른 응결 및 압축강도 추정)

  • Park, Jae-Woong;Jeong, Jun-Taek;Lim, Gun-Su;Han, Jun-Hui;Kim, Jong;Han, Min-Cheol
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2023.11a
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    • pp.187-188
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    • 2023
  • This study aimed to evaluate a feasibility of estimating setting time and compressive strength of curing conditions using a Hybrid meter. As a result, It was determined that the measured hardness value at the initial set, final set and at 5MPa of the Hybrid meter were not affected by curing conditions. And the Hybrid meter(A) is confirmed to have a higher correlation, so it is judged to be more suitable for pratical use.

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Strength Characteristics of Concrete Subjected ta Vertical Continuous Vibration during Initial Curing Period (초기양생 중에 수직방향 연속진동을 받은 콘크리트의 강도특성)

  • Kim Jong-Soo;Jang Hee-Suk;Kim Myung-Sik;Kim Hee-Sung
    • Journal of the Korea Concrete Institute
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    • v.17 no.2 s.86
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    • pp.273-297
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    • 2005
  • In construction site, there are some occasions where concrete under initial curing is being affected by nitration from nearby vibration sources. To study these effects, in this paper, strength characteristics of concrete specimens subjected to continuous vibration up to 12 hours in vertical direction after concrete placement were observed. And through the vibration time control experiment where a number of time combinations consisted of times before and after applying vibration during initial curing period were used as experimental parameters, possibility of concrete strength improvement was investigated. From the experimental results, it could be seen that the concrete strengths were mostly decreased due to the increase of vibration velocity during initial curing period. But fluctuation ratio of concrete strength did not have any close correlations with the vibration times. And results of vibration time control experiment showed that if times before applying vibration sustains at least more than 3 hours, subsequent vibrations after that hours do not affect the concrete strength in any unfavorable ways.

An Experimental Study on the Effects of Vertical Vibration during the Initial Curing on the Concrete Strength (수직진동이 초기양생중인 콘크리트의 강도에 미치는 영향에 관한 실험적 연구)

  • Kim Kwang-Soo;Han Kyung-Bong;Park Sun-Kyu;Park Jeong-Su
    • Journal of the Korea Concrete Institute
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    • v.16 no.5 s.83
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    • pp.645-650
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    • 2004
  • As time passes, bridge structures require extension work on bridge in use from various effects such as social economical, or traffic environment change. When the concrete is poured at the connection of extension work initial curing concrete is influenced by vibration of vehicles that are passing through the old bridge superstructure. Concrete at early curing stage in construction site should be properly protected, enough to have established sufficient integrity to withstand outside vibration, impact etc. Currently there is no standard specification or regulation in our country. In this paper, experimental variables were divided by vibration velocity and time of loading, and concrete compressive strength and bond strength were measured.

Evaluation on Uniaxial Compression Strength of SSG Method with Curing Condition (양생조건에 따른 SSG공법의 일축압축강도 평가)

  • Choi, Yong-Sung;Kim, Byoung-Il;Moon, In-Jong;Heo, Jun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.2
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    • pp.15-20
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    • 2016
  • The grouting method, which can be used to effectively improve small areas within a short amount of time, may have different injection effects depending on the ground conditions and the levels of a water table. In particular, for ground with a relatively large permeability, the strength of the ground and the water proof ability can decrease over time due to the leaching process. To solve this problem, a "self-healing smart grouting (SSG) method", which was designed to maintain the initial strength of the ground by minimizing the leaching process, was developed recently. In this study, uniaxial compression tests were carried out on SSG samples to understand the strength of SSG over curing time where two different curing temperatures have been applied for comparison. The uniaxial compression strength of SSG was further compared with the samples prepared using conventional methods (LW and SGR). The test results showed that the uniaxial compression strength of SSG was higher at both high and low curing temperatures compared to that of the samples prepared using conventional methods. The initial strength of SSG was also relatively higher.

The Study on the Strength Properties of High Volume Fly-Ash Concrete (플라이애시를 다량 사용한 콘크리트의 강도특성에 관한 연구)

  • Paik, Min-Su;Lee, Young-Do;Jung, Sang-Jin
    • Journal of the Korea Institute of Building Construction
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    • v.2 no.4
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    • pp.169-176
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    • 2002
  • To study of binder and fine aggregate a lot of replacement fly-ash concrete, initial characteristics, standard environment of curing temperature $20^{\circ}C$, hot-weather environment, cold weather environment of curing temperature $5^{\circ}C$. Flash concrete tested slump, air contest, setting and Hardening concrete valuated setting period of form, day of age 3, 7, 28 compression strength in sealing curing. Underwater curing specimen compression strength of age 3. 7, 28day used strength change accordingly fly-ash concrete curing temperature. Purpose of study is consultation materials in field that variety of fly-ash replacement concrete mix proportion comparison and valuation. (1) Setting test result, fly-ash ratio of replacement higher delay totting time. Same volume of fly-ash ratio of replacement is lower fly-ash ratio of replacement fine aggregate delay setting time. Setting test in curing temperature $35^{\circ}C$ over twice fast setting in curing temperature $20^{\circ}C$ and all specimen setting delay in curing temperature $5^{\circ}C$. F40 specimen end of setting about 30 time. (2) Experiment result age 28day compression strength more fisher plan concrete then standard environment in curing temperature $20^{\circ}C$, cold weather environment in curing temperature $5^{\circ}C$, most strength F43 is hot-weather environment in curing temperature $35^{\circ}C$ replacement binder 25%, fine aggregate 15%. (3) Hot-weather environment replacement a mount of fly-ash is a same of plan concrete setting period of form. Age 28day compression strength replacement a mount of fly-ash more hot-weather concrete then plan concrete.

The effect of combined carbonation and steam curing on the microstructural evolution and mechanical properties of Portland cement concrete

  • Kim, Seonhyeok;Amr, Issam T.;Fadhel, Bandar A.;Bamagain, Rami A.;Hunaidy, Ali S.;Park, Solmoi;Seo, Joonho;Lee, H.K.
    • Advances in concrete construction
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    • v.11 no.5
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    • pp.367-374
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    • 2021
  • The present study investigated the effect of the combined carbonation and steam curing on the physicochemical properties and CO2 uptake of the Portland cement concrete. Four different curing regimes were adopted during the initial 10 h of curing to evaluate the potential of carbonation curing as an alternative to conventional steam curing in the precast concrete industry from environmental and practical viewpoints. Four combinations of carbonation and steam curing conditions were applied as curing regimes to the samples at an early age. The test results indicated that the samples treated with the combined carbonation and steam curing exhibited higher early strength development compared to the other samples, signifying that carbonation curing can reduce the production time of precast concrete. Furthermore, the CO2 uptake capacity of the samples was calculated and found to be as high as 18% with respect to the mass of the paste samples. Hence, the simultaneous utilization of steam and CO2 for the fabrication of precast concrete members has the potential to make precast concrete greener and more cost-effective.

A Fundamental Study on The Expression of Initial Strength of Injection Materials for Steel Pipe Multi-Stage Method using Circulating Resources (순환자원을 활용한 강관다단공법용 주입재의 초기강도 발현에 대한 기초연구)

  • Sang-Huwon Song
    • The Journal of the Convergence on Culture Technology
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    • v.9 no.5
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    • pp.557-562
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    • 2023
  • This study reviewed the use of soil injection materials using circulating resources as injection materials for the steel pipe multi-stage construction method. The tests performed were homogel time and homogel compressive strength. The steel pipe multi-stage construction method is an auxiliary construction method for tunnels, and the expression of initial strength after construction is an important factor. The better the strength development in the initial stage, the more it can be used as an injection material suitable for the multi-stage steel pipe construction method. As a result of laboratory test, it was found that the homogel time of the injection material using circulating resources required more time than the mixing ratio using cement as the injection material. In addition, it was found that the initial strength curing time satisfying 2MPa was required for more than 24 hours. Therefore, it was confirmed that the injection material using recycled resources required a longer initial curing time than cement of the same mixing ratio.

Study of initial setting for solidification process of dredged soil of rural stream (농촌 소하천 고함수비 퇴적 저지의 고화처리에 대한 초기응결연구)

  • Chang, Pyung-Wuck;Woo, Chull-Woong;Kim, Seong-Pil;Kim, Jae-Hyung
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2002.10a
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    • pp.345-348
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    • 2002
  • The dredged soils of rural streams can be treated with cement for recycling. It is very important to know whether the treated soils have achieved some required qualities for further treatments if the soils are mixed with cement. In this study, fall-cone test was used to examine changes in workability and compactibility during an curing time of soil-cement mixture. Test results showed that fall-cone apparatus can be satisfactorily used for this purpose. Although there was some difference of initial curing time and cement contents, the engineering properties of treated soils were little affected.

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POLYMERIZATION SHRINKAGE OF COMPOSITE RESINS CURED BY VARIABLE LIGHT INTENSITIES (가변 광도 중합에 따른 복합레진의 중합수축에 관한 연구)

  • Lim, Mi-Young;Cho, Kyung-Mo;Hong, Chan-Ui
    • Restorative Dentistry and Endodontics
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    • v.32 no.1
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    • pp.28-36
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    • 2007
  • The purpose of this study was to compare the effect of exponential curing method with conventional curing and soft start curing method on polymerization shrinkage of composite resins. Three brands of composite resins (Synergy Duo Shade, Z250, Filtek Supreme) and three brands of light curing units (Spectrum 800, Elipar Highlight, Elipar Trilight) were used. 40 seconds curing time was given. The shrinkage was measured using linometer for 90 seconds. The effect of time on polymerization shrinkage was analysed by one-way ANOVA and the effect of curing modes and materials on polymerization shrinkage at the time of 90s were analysed by two-way ANOVA. The shrinkage ratios at the time of 20s to 90s were taken and analysed the same way. The results were as follows : 1. All the groups except Supreme shrank almost within 20s Supreme cured by soft start and exponential curing had no further shrinkage after 30s (p < 0.05). 2. Statistical analysis revealed that polymerization shrinkage varied among materials (p = 0.000) and curing modes (p = 0.003). There was no significant interaction between material and curing mode. 3. The groups cured by exponential curing showed the statistically lower polymerization shrinkage at 90s than the groups cured by conventional curing and soft start curing (p < 0.05). 4. The initial shrinkage ratios of soft start and exponential curing were statistically lower than conventional curing (p < 0.05). From this study, the use of low initial light intensities may reduce the polymerization rate and, as a result, reduce the stress of polymerization shrinkage.