• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.197-207
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• 1996

Maturity is expressed as the integral of time and temperature of concrete above a datum temperature. The maturity concept proposes that concrete of the same mix at the same maturity has the same strength, whatever combination of temperature and time makes up that maturity. In this study, the Nurse-Saul function which was proposed to account for the effects of temperature and time on strength developrnent is used in computing maturity. After existing various functions are considered to relate concrete strength to the maturity value, new strength-maturity function is proposed. Tests ;ire conducted in order to determine d datum temperature and compare prechction value with measured concrete strength. The constants in proposed prediction equation are determined from test results, and the equation is adopted to predict the strength of slab. The slab was cast in the laboratory from the same batch of mold, and cores are cut from slab in order to estimate the actual strength. These values are used to compare with predicted value. The present study allows more realistic determination of early-age strength of concrete and can be efficiently used to control the quality in actual construction.

• 레미콘
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• no.4 s.51
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• pp.25-35
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• 1997

• Magazine of the Korea Concrete Institute
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• v.10 no.5
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• pp.89-100
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• 1998

본 연구는 양생온도이력이 콘크리트 강도에미치는 영향을 평가하기 위한 것으로 물 시멘트비가 60%, 45%, 26%인 3종류의 콘크리트에대하여 5$^{\circ}C$부터 5$0^{\circ}C$까지의 항온양생과 초기재령에 고온도이력을 변수로 한 변동온도양생을 실시한 공시체의 압축강도를 측정하였다. 또한 그 실험결과에 강도평가 방법의 하나인 Maturity 개념을 도입하여 강도평가에 미치는 재령, w/c, 온도이력 등에 대한 영향을 평가하였다. 항온양생 실험결과에 따르면 물시멘트비가 낮을수록 초기재령에서의 강도발현은 높게 나타나며 양생온도 5$0^{\circ}C$인 경우를 제외하고 재령7일까지의 강도발현은 양생온도가 높을수록 크게 나타나고 있다. 한편, 변동온도양생실험결과에 의하면 초기재령에서 고온양생한 콘크리트의 강도발현은 물시멘트비의 영향을 크게 받으며, 1주 이후의 양생온도가 강도발현에 미치는 영향은 1주까지의 고온도이력에 대한 영향에 비교해 2차적이다. 기존의 Maturity개념인 Saul-Bergstrom의 함수와 Ooi의 함수를 가지고 항온 및 변동온도 양생실험결과를 분석한 결과, 전체적으로 Saul-Bergstrom식에 의한 경우가 실험값과의 차이가 작게 나타났으나 두 식 모두 Maturity 가 큰 경우에는 계산에 의한 값이 실험에 의한 값보다 크게 나타나고 있어 장기 재령시 강도평가는 한계강도 개념을 고려한 새로운 Matruity함수를 제안할 필요가 있다.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.191-202
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• 1998

The maturity method in which the strength increase of cement concrete is expressed as a function of an intergral of the curing period and temperature of the concrete has often been applied to its strength prediction. For the purpose of the application of the maturity method to the compressive strength prediction for lightweight polymer mortars using an unsaturated polyester resin as a binder, the lightweight polymer mortars with various catalyst and accelerator contents, are prepared. tested for compressive strength, and the datum temperatures for the maturity equations are estimated. The maturity is calculated by using the maturity equations with the estimated datum temperature. The compressive strengths of the lighweight polymer mortars are predicted from the maturity-compressive strength relationships.

• International Journal of Highway Engineering
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• v.7 no.1 s.23
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• pp.83-92
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• 2005

Maturity method is a non-destructive method for estimating in-place concrete strength as a function of time and temperature. The main objective is to use maturity method determining joint sawing and traffic opening time for whitetopping construction in Korea. Another objective is to investigate the influence of air temperature in the correspondence to slab temperature and maturity value. For determining the joint sawing and traffic opening time, thermachron i-button and strain gage were inserted in the fresh concrete in the slab and a maturity value was calculated at desired times. In-place strength was then estimated from a pre-established relationship between maturity values and compressive strength. The results showed that there are significant differences between the estimated strength obtained from maturity curve and in-place concrete strength. The reasons are that the gain of in-place concrete strength was influenced by several factors in the field such as curing conditions, air temperature, and wind speed etc. Also, the results showed that air temperature had significant influence on slab temperature and maturity value The slopes of maturity curves exponentially decrease as air temperature decreases. This means that maturity value sharply dropped as air temperature decreases.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.177-183
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• 2004

The maturity concept is based on the fact that concrete gains strength with time as a result of the cement hydration and, thus the strength of concrete is related to the degree of hydration of the cement in concrete. The rate of hydration, as in any chemical reaction, depends primarily on the concrete temperature during hydration. Therefore, the aim of the study is to investigate of the correlation between strength of high-strength concrete and maturity that is expressed as a function of an integral of the curing period and temperature.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.82-89
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• 2014

The purpose of this study is to propose a simple model to evaluate the compressive strength development of concrete with various supplementary cementitious materials (SCMs) and cured under different temperatures. For the generalization of the model, the ACI 209 parabola equation was modified based on the maturity function and then experimental constants A and B and 28-day compressive strength were determined from the regression analysis using a total of 265 data-sets compiled from the available literature. To verify the proposed model, concrete specimens classified into 3 Groups were prepared according to the SCM level as a partial replacement of cement and curing temperature. The analysis of existing data clearly revealed that the 28-day compressive strength decreases when the curing temperature is higher and/or lower than the reference curing temperature ($20^{\circ}C$). Furthermore, test results showed that the compressive strength development of concrete cured under $20^{\circ}C$ until an early age of 3 days was marginally affected by the curing temperature afterward. The proposed model accurately predicts the compressive strength development of concrete tested, indicating that the mean and standard deviation of the ratios between predictions and experiments are 1.00 and 0.08, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.3
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• pp.167-173
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• 2023

The cash flow matching problem(CFMP) aims to minimize the initial investment by paying the total amount due for the T-year in principal and interest of bonds or bank deposits without paying the full amount in cash. Linear programming(LP) is the only known way to solve CFMP. The linear programming method is a problem that optimizes T linear functions, and it cannot be solved by handwriting, so LINGO, which is a solution to the linear programming method, is used. This paper proposes an algorithm that obtains the solution of CFMP solely by handwriting without the help of LINGO. The proposed algorithm determines the amount of bond purchases by covering payments until the previous year of the next maturity bond in the order that the maturity date falls from the longest to the short term. In addition, until the year before the maturity of the shortest maturity bond, the amount of deposit covered by the principal and interest of the bank deposit was determined. As a result of applying the proposed algorithm to two experimental data, it was shown that more accurate results can be obtained compared to the linear programming method.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.2
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• pp.147-156
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• 1981

Most of the currently available rice threshers in Korea are of head-feeding type originally developed for threshing paddy at grain moisture content of 15 to 17% on wet basis. And prevailing rice harvesting system is swathing or cutting and bundling upright rice crop at a maturity stage of grain moisture content of ca. 28 to 20%, followed by transient natural drying in the field and threshing at grain moisture content of about 17%. The system often allows rather high field loss of rice both quantitatively and qualitatively. These necessitate use of a preharvest desiccant, and diquat has been registered recently as a rice desiccant. Aim of the present study is to determine the best time and rate of diquat application and to evaluate its utility as a rice desiccant under its optimal usage conditions in Korea. Diquat was not so effective for japonica rice varieties while it was very effective for the new varieties bred from indica x japonica crosses. The best time of application was the period from 2 days before to 3 days after physiological maturity of grain (moisture content of 28% w.b.) and the optimal rate was about 330g of diquat ion/ha. Applying diquat at the right time and rate dropped grain moisture to 15 to 16% (w.b.) within a week after treatment in contrast to that of 20 to 24% in untreated rice. Desiccation of rice crop with diquat resulted in 10 to 15% increase in grain resistance to shattering and significant reduction in percent green rice. However, there was no reduction in milled rice yield and percent whole kernel and was no change in the percent chalky rice and percent tinted rice. Diquat use appears highly desirable, if there is no residue problem which has not been studied in the present study.

• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.365-372
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• 2014

Technologies for rapid concrete curing using elevated temperature are important for saving cost and time when constricting concrete structures. Recently, a microwave heating form was developed. In this study the early strength of concrete cured by the developed form was experimentally investigated. Large scale mock up tests were conducted six times, and the results were analyzed based on the maturity theory. Logarithmic correlation curves were generated based on the measured strength and estimated maturity. It was confirmed that the strength development of the concrete cured by microwave heating form can be estimated by the equivalent age theory usually applied to steam-curing technology. By using the microwave heating form, one day at most is enough to get the required strength for the safe removal of forms, even in cold weather.