• 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.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.137-147
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• 2002

Maturity models involving curing temperature and curing ages have been widely used to predict concrete strength, which can accurately estimate concrete strength. However, they may not consider physical quantities such as the characteristics of hydrates and the capillary porosity of microstructures associated with strength development. In order to find out the effects of both factors on a strength increment, the hydration model and the estimation method of the amount of capillary porosity were established, and the compressive strength test of concrete nth various water/cement ratios was carried out considering two test parameters, curing temperature and curing age. In this study, by analyzing the experimental results, a strength estimation model for early-age concrete that can consider the microstructural characteristics such as hydrates and capillary porosity was proposed. Measured compressive strengths were compared with estimated strengths and good agreements were obtained. Consequently, the proposed strength model can estimate compressive strength of concrete with curing age and curing temperature within an acceptable error.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.136-141
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• 1995

The early evaluation on strength of concrete is useful to achieve on quality control and improvement of properties of concrete. Especially, we could say that the confidence of construction is increased by the increase durability and safety building, due to early evaluation. In this study, was proposed to ultra-sonic pulse method as a early evaluation method for strength of concrete with main parameter, sush as W/C ratio and S/A ratio. The experiment results are summarized to follow as : $\circled1$ The ultra-sonic pulse was decreased as the increase of W/C ratio. $\circled2$ The maximum value for the ultra-sonic pulse velocity and compressive strength was presented in the case of 40% S/A ratio and these value was decreased as the change of S/A ratio over 40% $\circled1$ The relationship of the ultra-sonic pulse velocity and compressive strength on 28days according to the change of W/C and S/A ratio is to be: $F_{28} = -209193R^2 + 384417R - 1763441$(W/C Ratio) $F_{28} = 1726R^2 - 774R - 502 (S/A Ratio)

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.325-328
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• 2008

Recently increasing interest in high-rise building around the world for more than 100 floor, the trend is the increasing use of high-strength and high-flowable concrete so as of productivity improvements and cost savings to improve the performance of the early strength development. This study is to reach the optimal combination by reviewing the performance of high-rise building which is required. The results, lower the ratio of W/B was an increase in compressive strength and early strength in the use of admixture decreased in the combination of higher replacement ratio of admixture.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.5
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• pp.609-624
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• 2013

The objective of this study was to get a comprehensive understanding of how genes in chicken shell gland modulate eggshell strength at the early stage of active calcification. Four 32-week old of purebred Xianju hens with consistent high or low shell breakage strength were grouped into two pairs. Using Affymetrix Chicken Array, a whole-transcriptome analysis was performed on hen's shell gland at 9 h post oviposition. Gene ontology enrichment analysis for differentially expressed (DE) transcripts was performed using the web-based GOEAST, and the validation of DE-transcripts was tested by qRT-PCR. 1,195 DE-transcripts, corresponding to 941 unique genes were identified in hens with strong eggshell compared to weak shell hens. According to gene ontology annotations, there are 77 DE-transcripts encoding ion transporters and secreted extracellular matrix proteins, and at least 26 DE-transcripts related to carbohydrate metabolism or post-translation glycosylation modification; furthermore, there are 88 signaling DE-transcripts. GO term enrichment analysis suggests that some DE-transcripts mediate reproductive hormones or neurotransmitters to affect eggshell quality through a complex suite of biophysical processes. These results reveal some candidate genes involved with eggshell strength at the early stage of active calcification which may facilitate our understanding of regulating mechanisms of eggshell quality.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.78-83
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• 2010

This paper presents the feasibility of incorporating ultrafine particles collected in the separator bag filter (separator bag filter cement, SBFC) during the cement manufacturing process as an substitution material for cement. SBFC does not require additional processes needed in the existing processes to manufacture high early strength cement such as modifying mineral components and adjusting the firing temperature. Moreover, it can also solve the issue of efficiency decrease resulted from the increase of the grinding time applied in the existing process of manufacturing microcement. Therefore, this research has examined the characteristics of SBFC and fresh properties and mechanical properties after making paste and mortar using SBFC in order to use SBFC as a material to gain early strength of concrete. For results, analyzing the chemical composition and physical properties of SBFC, its blaine value was $6,953cm^3/g$, about double than that of OPC, but its chemical composition showed no significant difference. According to the result of the paste and mortar examination, the paste and mortar mixed with SBFC showed a lower flowability, earlier setting time, and higher compressive strength than that with OPC. The result of microstructure analysis of paste, the paste mixed with SBFC indicated about 9% lower internal porosity at an early age than that of OPC. The compressive strength and flexural strength of mortar were higher in the order of SBFC ratio of 100, 50 and 0% SBFC.

• Land and Housing Review
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• v.4 no.2
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• pp.193-200
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• 2013

Construction duration in construction project is an important factor which affects project cost. Advanced countries have reduced project cost by time shortening. Even though domestic construction companies have tried to time shortening, they yet failed to find systematic method for time shortening. Typically, duration of structural framework is affected by stripping time of form. Therefore, it need to shorten the stripping time of form for time shortening of structural framework. In this study, specimens of high-early-strength concrete were manufactured with variety conditions and compressive strength was tested. This study proposed stripping time of side and slab forms using test results. The stripping time of form was shortened when using high-early-strength concrete in structural framework by the test results. The result of this study will be useful for time shortening of structural framework.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.795-798
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• 2002

Recently. the properties of early-age concrete are increasingly important because these properties directly influence the behavior of early-age concrete structures including stress and cracking behavior. Nevertheless, the studies on early-age concrete are limited to strength and temperature development. The purpose of present study is to propose a simple and rational method which can predict the stress and strain behavior of young age concrete. A series of test have been done to measure the temperature development, strains and stresses in concrete members. The concept of equivalent age was used to define the degree of hydration and this degree of hydration was used to calculate the strength and elastic modulus. The present study indicates that the calculated stresses correlate fairly well with measured stresses. The consideration of critical degree of hydration in calculating stresses gives more accurate results. The present study provides useful method and data in evaluating early-age behavior of concrete structure.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.317-318
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• 2009

In this study, The development characteristic of Modulus of Elasticity required to considering large deflection due to early the removal of forms for the reduction of working period of concrete is investigated. As a result of this study, it is found that the high early strength concrete is advantageous to compare with plain concrete on the early deflection.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.793-796
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• 2008

Recently early strength concrete has been required for economical assurance and the prevention of frost damage in winter through air reduction in construction of concrete structures. This study presented the optimum condition revealing compressive strength 5MPa which has the possibility of removal of form in 24 hours, and researched the changes of unit weight of cement types of high early strength AE water reducing agents, characteristic of compressive strength expression as cure temperature conditions and slump or airspace. Test results showed at $15^{\circ}C$ with compressive strength of 5MPa that premature removal of form was possible in case of using highly early strength PC water reducing agent with unit weight of cement 360 ; 22hours faster than 10, unit weight 360 ; 20hours faster than 7, unit weight 390 ; 18 hours faster than 4 comparing with OP water reducing agent. And at $5^{\circ}C$ in case of using highly early strength PC water reducing agent with unit weight of cement 330 ; 32hours faster than 10, unit weight 360 ; 30hours faster than 7, unit weight390 ; 27hours faster than 4 comparing with OP water reducing agent. Therefore as the temperature rises $10^{\circ}C$, compressive strength of 5MPa reaching hour shortens 10 hours.