• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.679-686
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• 2005

The corrosion of reinforcement induced by chloride ingress is the main deterioration cause of coastal reinforced concrete structures. In this paper, an experimental study was executed to investigate the effect of the kinds and replacement ratios of mineral admixtures (fly-ash, ground granulated blast-furnace slag silica fume and meta-kaolin), W/B and curing time on chloride diffusion of concrete by long-time immersion test in chloride solution. According to the result, the use of mineral admixtures was effective in improving the resistant to chloride ingress. The chloride penetration depth and diffusion coefficient were decreased as replacement ratios of mineral admixture were increased. The kind and replacement ratio of the mineral admixture are more important than the W/B in reducing the chloride diffusion of concrete. Chloride binding capacity of mineral admixture, which was sequenced in the order of MK

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.76-84
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• 2017

This study selected a method which uses high early strength cement as a way to reduce the curing time and curing energy source of concrete secondary products and reviewed the improvement in the initial strength of concrete secondary products setting the target strength of the concrete capable of removing the form to 15MPa and the curing time to 6 hours. As a result of the test, the only specimen which achieved the form removal strength of 15 MPa only through atmospheric curing within the target curing time of 6hours was ACC-100, and the specimens of TRC-100 and TRC-50 satisfied the values of 6 hours and 15MPa through steam curing. However, we could see that it was difficult to secure workability in the case of the specimen of ACC-100 due to its high rapid setting property and a retarder such as anhydrous citric acid was required to be used to improve the workability. When we look into the pattern following changes in the water to binder ratio, while, in the case of stream curing, OPC-100, TRC-100, and TRC-50 were all found to satisfy achievement of the form removal strength within 6hours as the water to binder ratio decreased, in the case of atmospheric curing, TRC-100, and TRC-50 achieved 15MPa within 12hours.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.21-28
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• 2017

The steel-plate concrete(SC) is used in a form of module assembly construction in the outer wall of nuclear-power plant and LNG containment. Since the steel-plate concrete modules are generally manufactured from the plant, the weight of SC has significantly effect on the total construction cost in the aspect of shipment. Therefore, the use of lightweight aggregates concrete(LWAC), which fill the inside of SC module can be a solution. However, the amount of used lightweight aggregates(LWA) is limited in the use of current concrete mixing process due to the concrete quality problems and it also determines the allowable minimum density of LWAC. In this research, the preplaced casting method is applied because of increasing the volume fraction of LWA significantly, which results from the producing process of pre-packing the LWA in the formwork and filling the interstitial voids between LWA using cement paste grout. The density and compressive strength of selected preplaced LWAC were $1,600kg/m^3$ and 30MPa and it was applied for the mock-up specimens of SC panel. It was used for the 3-point bending test for evaluating its structural performance. The results show that the preplaced LWAC can reduce the density of concrete with the adequate mechanical and structural performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.126-132
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• 2018

As means to increase the use of concrete with recycled coarse aggregate (RCA), this study aims to evaluate the applicability for flexural strengthening of reinforced concrete beam with high-strength concretes and RCA on which FRP plates, used for repair and strengthening of old and low-durability reinforced concrete structures, is applied. In order to increase the adhesive force of epoxy and FRP plate, FRP plate was installed according to Near-Surface-Mounted (NSM) method. 12 specimens were manufactured using substitution rate of RCA (30%), concrete strengths (40MPa, 60MPa), diameters of deformed bar (D10, D13), and types of FRP plate (AFRP, CFRP) as variables to analyse flexural performance according to FRP plate and substitution rate of recycled aggregate. As a result, in all specimens, specimens strengthened by FRP plate showed a maximum of 17% increase in performance compared to specimens without FRP plate and strengthening performance of CFRP was found to be higher than AFRP. When modulus of rupture was used, the value of cracking moment was similar to that of the reference equation. As bending moment of some specimens strengthened by FRP plate failed to satisfy the criteria of KCI 2012 and ACI 440-2R, additional experiment is deemed as necessary.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.6
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• pp.93-99
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• 2020

In terms of construction work, the construction cost is lower than the importance of the construction, and since it is demolished after the completion of the construction, it is treated as a relatively small proportion compared to other construction types. Construction engineers who actually worked on the site talk about the safety of the construction work as the most important work of the various processes to ensure the quality and safety of the construction work. However, it is also true that safety management is difficult for temporary construction because various types of temporary materials are installed at various sites at the same time as construction progresses, and the main construction is carried out using them. Safety accidents in construction work are not much different even if they are carried out in temporary construction. The importance and safety of construction work cannot be neglected in view of the recent trend of large-scale construction, multi-purpose, excavation of large-scale underground spaces, and construction trends that are changing to skyscrapers. The purpose of this research is to secure the safety of Dongbar among the temporary materials used in construction work by using IT convergence technology, and to propose safety management to prevent safety accidents in the construction work.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.81-88
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• 2022

In the NRC (New paradigm Reinforced Concrete) beam, steel forms, main angles used as main reinforcements, and shear angles used as basic shear reinforcements are welded and assembled in the form of vierendeel truss structures in a steel factory. After the NRC truss frame is installed at the site, additional main reinforcement and shear reinforcement are distributed. In this study, the shear performance evaluation of the NRC beam was conducted through shear tests in accordance with the type of shear reinforcement of the NRC beam (shear angle, inclined shear reinforcing bar, and U-type cover bar). As a result of the test, the initial stiffness was similar before the initial cracking of each specimen, and all specimens were shear fractured.The shear reinforcements of the specimens exhibited a yielding behavior at the time of the maximum sheat force, and the shear strengths of the specimens increased as the amount of reinforcement of the shear reinforcement increased. These results show that NRC shear reinforcements exhibit shear performance corresponding to their shear strength contribution. As a result of calculating the nominal shear strengths according to KDS 14 20 22, the experimental shear strengths of the NRC beam specimens with shear reinforcement was 37~146% larger than the nominal shear strengths, so It was evaluated as a safety side.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.111-116
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• 2022

Recently, building structures tend to be super high-rise and large-scale with the development of concrete technology. When high-rise building is constructed of reinforced concrete structure, it has a disadvantage that its own weight increases. Light weight aggregate(LWA) was developed to compensate for these shortcomings. Manufacturing concrete using these light weight aggregates has the advantage of reducing the self weight of the reinforced concrete structure, but has a disadvantage in that the strength of the concrete is reduced. In this study, an experimental study was conducted to investigate the strength characteristics of hardened cement according to the presence or absence of surface coating of lightweight aggregates. As a result, in terms of compressive strength, the surface-coated lightweight aggregate exhibited higher strength than the uncoated lightweight aggregate. Also, it was considered that this is because the interfacial voids of the surface coated lightweight aggregate mixed cement hardened body were filled with blast furnace slag fine powder particles.