• 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.

• Journal of the Korea Construction Safety Engineering Association
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• s.35
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• pp.72-78
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• 2006

• Korean Architects
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• no.5 s.87
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• pp.6-10
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• 1976

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.1
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• pp.19-28
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• 2018

The time for form removal is an important factor for ensuring the safety and economical efficiency of concrete structures, because it affects the quality, period, and cost of construction. Although local specifications suggest the form curing time, there is a problem of low quality of concrete due to early removing of form. This is because they do not fully understand effect of curing condition, and they want to shorten construction period in the field. Therefore, this research evaluates the effect of curing condition according to the time for form removal by testing specimen. As a result, the concrete compressive strength at the age of 28 days decreased about 40% in the condition of form removal after 12 hours, while the strength in the condition of form removal after 28 days decreased about 7%. Finally, this paper suggests an estimating equation for the concrete compressive strength due to the time for form removal considering various curing temperatures as equivalent ages. The proposed equation can be used in the field for evaluating the strength after form removal.

• Journal of the Korea Institute of Building Construction
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• v.18 no.3
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• pp.259-266
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• 2018

In recent years, the early strength of concrete is important in order to shorten the time of form removal at the construction site. The purpose of this study is to analyze the moment of form removal as investigating the amount of cement contents and the physical properties and strength of the concrete according to types of admixture in the curing temperature of $10^{\circ}C$ for concrete of 21 to 27 MPa. As a result, it was found that compressive strength of concrete could not be secured 5 MPa by 36 hours even if the amount of cement contents were increased to $360kg/m^3$ with plain admixture. Also, it was confirmed that the strength improvement rate was excellent when using the accelerating agent with polycarboxylic acid type, and the moment of compressive strength of 5 MPa was estimated at 30 hours.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.61-62
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• 2019

With development of IT technology, the ubiquitous has been realized in various industry. In construction industry, as well, end-edge techniques have been introduced such as managing technique the temperature and compressive strength of the concrete placed in structure in domestic and abroad project sites. However, several problems were found during application at the actual field regarding difficulties of connecting Bluetooth communication due to the short communication range, diffuse reflection caused by aluminum formwork, and high cost by using one-time sensor. Therefore to recover these shortages, and improve the performances, the wireless sensor network based concrete IoT management system for concrete early-age quality management was developed.

• Journal of Environmental Science International
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• v.15 no.2
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• pp.185-191
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• 2006

In this paper, removal time of side form from concrete using OPC(ordinary Portland cement) and FAC(fly ash cement) are proposed by appling logistic model, which evaluates the strength development of concrete with maturity. W/B, types of cement and curing temperatures are adapted as test parameters. The estimation of strength development by logistic model has a good agreement between calculated values and measured ones. As for the removal times of form works suggested in this paper, as W/8 increases, curing temperature decreases and fly ash is used, removal time of side form is prolonged. Removal time of form from concrete using OPC suggested in this paper is shorter $2.5\~3.5$ days than those of KASS-5 (Korean Architectural Standard Specifications-5) in the range of over $20^{\circ}C$. And in the range of $10\~20^{\circ}C$ removal time of form is shorter than that of KASS-5 by as much as $4\~4.5$ days. The use of FAC results in an increase in removal time of form compared to that of OPC by about 1 day.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.163-168
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• 2000

In this paper, removal times of from from concrete using OPC( Ordinary Portland Cement) and BSC(Blast-furnace Slag cement) are suggested by appling logistic curve, which evaluates the strength development of concrete with maturity. W/B, kinds of cement and curing temperatures are selected as test parameters. According to the results, the estimation of strength development by logistic curve has a good agreement between calculated values. As for the removal time of from suggested in this paper, as W/B increase, curing temperature decrease and BSC in used, removal they times of from are shown to be kept longer. Removal times of from from concrete using OPC suggested in this paper are shorter by about 2~3day than those of standard specifications provided in KCI in the rang of over $20^{\circ}C$, while they takes 4~5 day shorter compared with those of standard specifications Provided in KCI in the range of 10~$20^{\circ}C$. Removal times of from for concrete using OPC are longer than those using BSC by about 1 day.

• Journal of the Korea Institute of Building Construction
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• v.21 no.1
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• pp.21-29
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• 2021

The objective of this study is to evaluate the effect of the application of double layered bubble sheet on the curing of slab and wall concrete placed at the job site in cold weather and to offer a feasibility of Concrete IoT Management System(CIMS), which is wireless sensor network developed by the authors, to manage early age quality of the concrete in terms of temperature, maturity and strength development. Test results indicated that the application of bubble sheet enhances the insulation performance, which results in an increase of the temperature by around 1~20. 6℃. It is found that CIMS can gather the temperature, maturity and strength development data from the sensors embedded from 30 m far from CIMS successfully. Predicted compressive strengths by CIMS had good agreement with measured ones within 2 MPa error level until 7 days. It is thought that the combination of the bubble sheet application for cold weather protection and CIMS for quality management tool in cold weather concreting contributes to shorten the time for the form removal by one day.