• Title, Summary, Keyword: 응결시간

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Prediction of Setting Time of Concrete Using Fly Ash and Super Retarding Agent (초지연제 및 플라이애쉬를 사용한 콘크리트의 응결시간 예측)

  • Han, Min-Cheol
    • Journal of the Korea Concrete Institute
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    • v.18 no.6
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    • pp.759-767
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    • 2006
  • This paper presents a method to estimate the setting time of concrete using super retarding agent(SRA) and fly ash(FA) under various curing temperature conditions by applying maturity based on equivalent age. To estimate setting time, the equivalent age using apparent activation energy($E_a$) was applied. Increasing SRA content and decreasing curing temperature leads to retard initial and final set markedly. $E_a$ at the initial set and final set obtained by Arrhenius function showed differences in response to mixture type. It is estimated to be from $24{\sim}35KJ/mol$ in all mixtures, which is smaller than that of conventional mixture ranging from $30{\sim}50KJ/mol$. Based on the application of $E_a$ to Freisleben-Hansen and Pederson's equivalent age function, equivalent age is nearly constant, regardless of curing temperature and SRA contents. This implies that the concept of maturity is applicable in estimating the setting time of concrete containing SRA. A high correlation between estimated setting time and measured setting time is observed. Multi-regression model to determine appropriate dosage of SRA reflecting FA contents and equivalent age was provided. Thus, the setting time estimation method studied herein can be applicable to the concrete containing SRA and FA in construction fields.

Estimation of Setting Time of Chlorine By-pass System Dust Mortar using Setting Time Estimation (현장용 응결시간추정계를 이용한 고염화물 모르타르의 응결시간 추정)

  • Lee, Hyuk-Ju;Han, Jun-Hui;Hyun, Seong Yong;Shin, Yong-Seop;Lee, Jun-Seok;Han, Min-Choel
    • Proceedings of the Korean Institute of Building Construction Conference
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    • pp.6-7
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    • 2018
  • In the previous study, durometer, namely rubber hardness tester Was used to confirm the possibility of using the setting time of concrete for determination. in this study, the possibility of using condensation time judgment condensation estimation system by comparing the measuring station setting estimation system Measuring needle of the proctor penetration resistance tester by newly making a measurement needle and refining the coagulation estimation system Want to make sure. As a result of this study, it was possible to use one condensation estimation system showing similar correlation between the two types of durometer showing high correlation with the penetration resistance value of proctor testers, It is considered to be fruitful to use the dew condensation estimation system for determining the setting time.

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Estimation of the Setting Time of the High Flowing Concrete Using Durometer (Durometer를 이용한 고유동 콘크리트의 응결시간 판정 방법)

  • Han, Min-Cheol;Shin, Yong-Sub;Han, In-Deok
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.35 no.9
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    • pp.143-150
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    • 2019
  • The purpose of this study was to propose how to determine the setting time related to the determination of the surface finish working time of the concrete using a Durometer, which is used as a rubber hardness meter. Two different types of Durometer were used to measure the setting time of the concrete. High flowing concrete with 40% of water to binder ratio was fabricated maintaining $600{\pm}100mm$ of slump flow. The test results indicated that the application of the Durometer resulted in a high correlation with the penetration resistance tester in both mortar and concrete. When measuring the setting time of the concrete, with properly used with Durometer, evaluation of the setting time of the concrete can be available. Therefore, it is thought that the measurement of the final set of the durometer C type can be useful to decide the limit time of the finishing operation and the time of the rejuvenation of the curing process by measuring the finishing set at 40 HD in the case of the initial set and 10 HD in the case of D type.

Experimental Study on Setting Time of Cement Paste Mixed Accelerating Admixtures (급결제를 혼합한 시멘트페이스트의 응결시간에 관한 실험적 연구)

  • Heo Gweon;Choi Hong-Shik;Yi Seong-Tae
    • Journal of the Korea Concrete Institute
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    • v.17 no.6
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    • pp.879-884
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    • 2005
  • The setting time is a very important factor affecting the quality of tunnel lining and reinforcement of inclined slope etc. Currently, however, the quality criteria of accelerating admixture to improve it is not established well. In this study, evaluation on setting time measuring methods of cement mixed a accelerating admixture (AA) was performed using Gillmore and Vicat needle test methods. For both test methods, the setting time for addition at a time was better than post addition regardless of initial setting and final setting. For Gillmore needle test method, two types of measuring methods were selected and it is noted that setting time with cement type under the same accelerating admixture can be different. Accordingly, manufacturing company shall develop a less sensitive accelerating admixture to cement type. For Vicat needle test method, six types of measuring methods were used and a proper measuring method of the admixture were proposed as follows: (1) the temperature of materials used shall be controlled exactly and (2) to evaluate its properties, an admixture usage of $5\%$ (ratio of cement weight) is recommended.

Estimation of the Apparent Activation Energy of the Cement Mortar Incorporating Admixtures Considering Setting Time (혼화재치환 시멘트 모르터의 응결시간을 이용한 겉보기 활성화에너지 산정)

  • Choi, Hyun-Kyu;Son, Ho-Jung;Baek, Dae-Hyun;Lim, Choon-Keun;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.343-344
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    • 2010
  • This study compares the apparent activation energy(Ea) by ASTM C 1074 with that by setting time. As the result of this study, it is found that Ea by setting time was ranged from 15~21 KJ/mol. This value is smaller than that 30~50 KJ/mol by ASTM C 1074.

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Prediction of Setting Time of the Cement Mortar Considering Equivalent Age (등가재령에 의한 시멘트 모르터의 응결시간 예측)

  • Choi, Hyun-Kyu;Son, Ho-Jung;Baek, Dae-Hyun;Lim, Choon-Keun;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.331-332
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    • 2010
  • This paper present a method to estimate the setting time of cement mortar incorporating admixtures under various curing temperature conditions by appling maturity based on equivalent age. It is indicated that equivalent age using setting time can be a proper method to predict setting time and it also exhibited comparable relativity between prediction value and measurement value.

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Setting Estimation of Cement Paste Using New-type Embedded Sensor (매입형 센서를 활용한 시멘트 풀의 응결 시간 측정)

  • Shin, Kyung-Joon;Lee, Do-Keun;Seo, Dong-Wan;Yoo, Chul-Min;Lim, Min-Hyuk;Lim, Sung-Hwan
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.4 no.4
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    • pp.483-488
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    • 2016
  • The present study proposes an economical embedded ring-sensor that can measure a strain behavior of cement paste and mortar in early age. Using the proposed ring-sensor, the experimental method is proposed that can measure the setting time of the cement paste and mortar conveniently. The experimental study has been conducted using the mixtures of which W/C are 0.30, 0.35, 0.40, and 0.45. From the test result, the setting times measured by convectional test methods such as vicat method and penetration resistance method are compared with the setting time proposed by this study. The result reveals that the proposed ring-sensor can effectively measure the early age behavior so that can evaluate the time when the contraction starts. In addition, the contraction starting time can be regarded as a rational setting time, which is similar to the initial setting of convectional test methods.

An Experimental Study on the Effects of Early-age Vibrations for Properties of Concrete (진동이 양생초기 콘크리트에 미치는 영향에 관한 연구)

  • 오병환;송혜금;조재열
    • Magazine of the Korea Concrete Institute
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    • v.10 no.5
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    • pp.81-87
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    • 1998
  • 최근 들어 교통난 해소를 위한 도로확폭 공사나 파일항타 및 발파 등의 공사가 많이 진행되고 있으며, 이러한 경우 진동의 영향으로 콘크리트의 품질 저하에 영향을 미칠 것으로 예상된다. 이에 따라 본 연구에서는 진동과 굳지 않은 콘크리트에 미치는 영향을 평가하기 위하여 실험변수를 진동속도, 진동발생점등으로 나누어, 콘크리트의 압축강도, 부착강도를 측정하였다. 또한 응결시간을 측정하여 외부 진동용인이 응력에 미치는 영향을 평가하였다. 진동속도는 0.25cm/sec ~4.2cm/sec까지 변화시켰고, 진동가력시점은 타설 직후(0시간)부터 타설 후 2, 4, 6, 12 시간 후 에 진동을 가하였다. 본 연구의 실험 결과 진동속도 0.25cm/sec 에서는 압축 강도와 부착강도가 증가하는 반면에 진동속도 0.5cm/sec 이상에서는 압축강도는 5~12% 정도 감소하고 부착강도도 이와 유사하게 감소하는 것으로나타나고 있다. 응결시간은 0.25cm/sec의 작은 진동에서는 영향이 거의 없으나 0.5cm/sec 이상에서는 타설 직후의 진동시 응결시간이 다소 빨라지는 것으로 나타났다. 본 연구 결과, 양생초기 콘크리트의 진동 허용치는 약 0.3~0.4cm/sec 로 나타나고 있으며, 이것은 앞으로 실제 구조물의 시공시 진동규제치로서 하나의 유용한 자료가 될 수 있을 것으로 사료된다.

Evaluation of Optimum Mix Proportion and Strength of Volcanic Ash based Geopolymer (화산재 기반 지오폴리머의 최적배합 도출 및 강도 특성)

  • Nam, Chang-Sik
    • 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.

Estimation of Setting Time of Concrete Using Rubber Hardness Meter (고무경도계를 이용한 콘크리트의 응결시간 추정 가능성 분석)

  • Han, Min-Cheol;Han, In-Deok;Shin, Yong-Sub
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.4
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    • pp.358-366
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    • 2019
  • The purpose of this study is to explore the possibility of estimating optimum surface finishing work time of the fresh concrete placed at the job site by applying a surface hardness test meter(Durometer). Tests are carried out by measuring and comparing the Proctor penetration resistance test and hardness test by Durometer. Correlations between Procter penetration test and hardness test by Durometer were obtained. Two different types Durometer were applied to estimate setting time. Test results indicate that the measurement of the Durometer and the test of the Proctor penetration resistance are highly correlated. When measuring the initial setting time with Durometer, initial setting time is reached when the hardness value by the type C Durometer is reached around 42HD, and when final setting is measured with the type D Durometer, the surface finishing work time limit and curing time can be estimated with 10HD of Durometer.