• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2007.04a
• /
• pp.19-23
• /
• 2007

In this paper, the period for the strength correction was determined with each region of south Korea based on the meteorological data of KMA(Korea meteorological administration) by applying KASS-5 regulation. In case of 28 days of strength control age, the period for strength correction with 6MPa was calculated to 50-60 days and, with 3 MPa. to around 80 days. The period for the strength correction was shown to be decreased with the rise of altitude. The period to consider the delay of the strength development due to low temperature including the period of cold weather concrete was nearly 7 months around 1 year. References for determining the strength correction factors with each region of south Korea was provided in this paper.

• Journal of the Korean Geotechnical Society
• /
• v.33 no.8
• /
• pp.17-27
• /
• 2017

Gangwon province which is located in northeast of Korea is the coldest region where average daily temperature is below zero during winter while the other regions are above zero. However, there have been insufficient researches on the insulation design and the effect of the insulation on the freezing damages, even though freezing damages were reported consistently in the lining of road tunnel during winter. In this study, to investigate the effect of insulations on the reduction of freezing damages, numerical analysis was performed considering geotechnical and meteorological characteristics in Gangwon province during winter. As a result, it was found that thickness of concrete and shotcrete in lining had negligible effect on the freezing depth while the insulation had significant effect on it. In addition, because the freezing depth is greatly affected by the thermal conductivity of the ground behind the lining in the period of cold weather, these effects should be considered in the estimation of the insulation thickness.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.7
• /
• pp.342-347
• /
• 2016

This study examined the effects of the coarse aggregate maximum size and grading of fine aggregates to acquire the characteristics of very low shrinkage on normal strength concrete mixed in the field. In addition, the shrinkage characteristics of concrete under construction were evaluated in accordance with the curing temperature. The compressive strength and drying shrinkage tests were performed for nine mixing factors composed of the coarse aggregate size (13, 20, and 25 mm), types of fine aggregate (see sand, crushed sand, and blended sand), and curing temperatures (5, 20, and $35^{\circ}C$). To acquire low shrinkage properties under $350{\mu}{\varepsilon}$ strain on normal strength concrete, a 25 mm maximum of coarse aggregate was available, and the grading of fine aggregate affected the shrinkage of concrete. In addition, very low shrinkage properties were acquired in the curing temperature range except cold and hot weather concrete.

• Journal of the Korea Concrete Institute
• /
• v.28 no.3
• /
• pp.309-316
• /
• 2016

In this study, performance of hardening accelerator types which promote setting and hardening of cement has been reviewed in order to develop early age strength of concrete with compressive strength of 21~27 MPa after examination of strength development of the concrete at early age according to curing temperature and unit cement(binder) content. As results, soluble mineral salt showed better hardening acceleration effect than organic salt in the scope of this study. Also, hydration reaction accelerating effect of $C_3S$ by Soluble mineral salt is effective on development of early age compressive strength and it was shown that the Pt's hydration reaction accelerating effect was the best. Construction duration reduction can be expected by securing compressive strength for prevention of early aged freezing damage in 25hour-curing time under curing temperature at $15^{\circ}C$. Also, it was shown that compressive strength of specimen cured at $5^{\circ}C$ was similar with plain specimen cured at $10^{\circ}C$. Therefore, it is expected that fuel costs and carbon dioxide can be reduced when the same construction duration is considered.

• International Journal of Highway Engineering
• /
• v.1 no.2
• /
• pp.155-168
• /
• 1999

Asphalt pavement tends to rut in high temperature and to crack in cold temperature. The performance of asphalt pavement can be deteriorated by korean weather condition which has the four distinct seasons. In this study, the typical sections that may minimize rutting and fatigue were analyzed through the numerical model tests. The layered elastic theory , finite element method and visco elastic theory were utilized for these numerical model tests. From the various numerical model tests, it is found that an optimum design procedure was recommended. It was increasing the thickness of asphalt stabilized base with fixing the wearing course as 5cm the minimum specified thickness. The section was most beneficial in resting rutting and fatigue. From the analysis of the relative index on tensile strain and cost analysis, it was recommended that the thickness ratio of subbase and asphalt concrete is 1.0$\sim$2.5.

• Journal of the Korea Institute of Building Construction
• /
• v.15 no.4
• /
• pp.367-373
• /
• 2015

In this study, fundamental properties of cement were reviewed to apply high fineness cement at low temperature environment. The classified high fineness cement has large proportion of particles below $10{\mu}m$ which affects early hydration: an overall reaction of cement hydration faster. As a result of using high fineness cement, setting time of concrete was reduced and compressive strength was higher than OPC at all ages. Especially, compressive strength was more than double its value compared with OPC after three days curing in low temperature. Faster reaction and higher heat of hydration was verified by calorimetry early and maximum heat of hydration was analyzed by adiabatic temperature raising test. The analysis of this study confirmed that high fineness cement can be suitable to be used in low temperature environment.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.3
• /
• pp.279-285
• /
• 2017

In this study, the development of concrete preventing initial frost damage and durability about that were evaluated by using anti-aging agent and admixture(reduced slag). As a result of experiment, initial hydration heat was increased by $C_{12}A_7$ of reduced slag components but it was not effective to development of strength. Also fluidity decreased with increasing replacement of reduced slag. This suggested that fluidity was low by rapid setting due to absent of gypsum in reduced slag components. In case of CR2G specimen that added 4% gypsum, the flow ability was higher than plain. It is considered that concrete developed using reduced slag should use $SO_3$. Result of durability experiments, the durability decreased with increasing replacement amount of reduced slag.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.4
• /
• pp.310-315
• /
• 2019

This study conducted a series of studies to find alternative ways to use Chlorine Bypass System-dust(CBS-dust) in cement production. The results of engineering characteristics of CBS-dust are summarized as follows. First of all, the density of CBS-dust is 2.40, lighter than cement and the pH was 12.50 which was strong alkaline. In terms of particle size, it was 11.70 ㎛ which was finer than cement. With chemical properties, calcium oxide(CaO) was the highest as 35.10%, potassium oxide(K₂O) was 32.43%, potassium chloride(KCl) was 19.46%, sulfur oxide(SO₃) was 6.81%, and the remaining chemical components are SiO₂, Fe₂O₃, Al₂O₃, MgO, and the like. Therefore, if CBS-dust is used as early-strength chemical admixtures in the concrete secondary products that use a large amount of mineral admixtures without rebar, it can be an effective method for increasing the strength of concrete as an alkali activator and preventing early-frost damage of Cold Weather Concrete.

• Journal of the Korea Institute of Building Construction
• /
• v.18 no.4
• /
• pp.347-354
• /
• 2018

This paper verifies the superiority of warming work in winter by applying the insulation gang-form to the apartment housing site and analyzes the economic feasibility of the application. According to the experimental results, the actual cost of warming work was about 52 million won less than planned, and 160 million won less than the existing average.(Note - The cost of gang form material increased from 260 million won to 310 million won after the change) As a result, the construction cost could be reduced by about 110 million won. As the costs of warming work can change depending on the number of floors, the building number, and the area of each site, it is deemed necessary to conduct a thorough review in advance at the site where the cost of warming work is to be applied.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.2
• /
• pp.149-155
• /
• 2017

In this research, the surface covered curing method using the double-layered bubble sheet was evaluated. This double-layered bubble sheet has outstanding insulating performance with its low heat conductivity and high economic feasibility with its high durability. However, in the case of wall-typed building construction, the area of exposed rebar is curious on curing performance with the double-layered bubble sheet in spite of the double-layered bubble sheet showed favorable performance for slab. Therefore, in this research, regarding the actually constructed wall-typed apartment building, the most efficient curing method was suggested based on the evaluation of curing performance depending on temperature distribution depending on various location of covered or exposed rebar. As a result, the D method was determined as the most efficient curing method without any concern of early-age frost damage. However, by considering easiness of construction, the B method of covering the pieced double-layered bubble sheet on gap between rebars can be another option of desired result.