• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.67-75
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• 2008

An engineered cementitious composite produced with slag particles (Slag-ECC) had been developed based on micromechanical principle. Base grain ingredients were properly selected, and then the mixture proportion was optimized to be capable of achieving robust tensile ductility in the hardened state. The rheological design is performed in the present study by optimizing the amount of admixtures suitable for self-consolidating casting and shotcreting process in the fresh state. A special focus is placed on the rheological control which is directly applicable to the construction in field, using prepackaged product with all pulverized ingredients. To control the rheological properties of the composite, which possesses different fluid properties to facilitate two types of processing (i.e., self-consolidating and shotcreting processing), the viscosity change of the cement paste suspensions over time was initially investigated, and then the proper dosage of the admixtures in the cement paste was selected. The two types of mixture proportion were then optimized by self-consolidating & shotcreting tests. A series of self-consolidating and shotcreting tests demonstrated excellent self-consolidation property and sprayability of the Slag-ECC. The rheological properties altered through this approach were revealed to be effective in obtaining Slag-ECC hardened properties, represented by pseudo strain-hardening behavior in uniaxial tension, allowing the readily achievement of the desired function of the fresh Slag-ECC. These ductile composites with self-consolidating and shotcreting processing can be broadly utilized for a variety of applications, e.g., in strengthening seismic resistant structures with congested reinforcements, or in repairing deteriorated infrastructures by shotcreting process.

• Magazine of the Korea Concrete Institute
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• v.6 no.4
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• pp.131-140
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• 1994

Recently, tunnels are increasingly constructed in this country with the increased construction of highways, high-speed railways and subways. Shotcreting is one of the major processes in the tunnel construction. Many problems, however, exist in the current shotcreting practice. The purpose of the present study is, therefore, to explore the problems in the current shotcreting practice, to derive an optimum mix for efficient shotcreting, To this end, extensive experimental study has been conducted. Optimum mixes with high quality and economy were derived. The present study provides a firm bast: in our country to apply high-quality shotcrete in tunnel construction.

• Proceedings of the Korean Geotechical Society Conference
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• 1995.10a
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• pp.17.1-24
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• 1995

In tennelling lattice girders have basically the same function as steel arch supports. They serve as elements of temporary lining and in some cases also as part of the permanent lining. Also lattice girders are closely connected with that of the shotcreting lining technique. This paper presents the results of modelling test for analysing shorcrete rebound, shotcreting time and finding void spaces using the aretificial tunnel wall which consist of wood to evaluate the site applicability of lattice girders for tunnel support. Test results indicate that in case of using lattice girders as a tunnel support material, shotcrete rebound, shotcreting time and occurrence of void spaces are relatively reduced comparing to H-beam steel rib. And we can get some informations ths lattice girder has various advantages when we use it as one of tunnel support materials.

• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.121-128
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• 1999

The SHO PATCH System Mortar is a mortar shotcreting system which uses fairly small machine and equipment, and is applied for shotcrete tunnel linings, in particular for small bore tunnels of aqueducts by the TBM(Tunnel Boring Machine) method, and for reparing tunnels suffering from spring water and deterioration. This study shows the characteristics of the new mortar shotcreting system, the SHOT PATCh System Mortar, which exhibits excellent shotcrete performance.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.871-876
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• 1998

The SHOT PATCH System Remitar is a mortar shotcreting system which used fairly small machine and equipment, and is applied for shortcrete tunnel linings, in particular for small bore tunnels of aqueducts by the TBM(Tunnel Boring Machine) method, and for repairing tunnels suffering from spring water and deterioration. This study shows the characteristics of the new mortar shotcreting system, the SHOT PATCH System Remitar, which exhibits excellent shotcrete performance.

• Magazine of korean Tunnelling and Underground Space Association
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• v.4 no.4
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• pp.54-57
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• 2002

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.581-584
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• 2004

High ductile fiber reinforced mortar suitable for wet-mix shotcreting (sprayable ductile mortar) 10 the fresh state, while maintaining tensile strain-hardening behavior in the hardened state, has been developed based on micromechanics and workability control. In the development concept of sprayable ductile mortar, micromechanics is adopted to properly select the matrix, fiber, and interface properties to exhibit strain hardening and multiple cracking behaviors in the composites. Within the pre-determined micromechanical constraints, the workability is controlled by optimizing mix proportions. A series of spray tests show the excellent pumpability and sprayability of the sprayable ductile mortar. Subsequent direct tensile tests demonstrate that the tensile performance of sprayed mortar is comparable to that of cast mortar, for the same mix design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6D
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• pp.615-622
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• 2012

The aim of shotcrete is to increase the bearing capacity and to protect the excavated surface from erosion by preventing falling of rock mass. Shotcreting method is divided into two types as dry process and wet process. Since 1997, wet process method has been used more frequently than dry process method in field works. The failure to bond, so called rebound, occurs in many case during shotcrete works. The excess amount of rebound has a significant effect on the total construction cost. For example, material and craft-man cost increases, the shooting time delays due to deceleration of work execution stage, work efficiency of craft-man decreases and additional cost to remove the muck generates. In this study, therefore, the experimental analysis of rebound amount and strength was conducted by analyzing the actual construction data for wet process type of shotcreting method upon accelerator contents. Also, the effective and rational method was suggested, which can be actually implemented in the Korea construction sites.

• Journal of the Korean Institute of Educational Facilities
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• v.19 no.5
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• pp.29-36
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• 2012

The goals of this study are to develop a sprayable strain-hardening cement composite (SHCC) and to investigate the potential of the sprayable SHCC for packing the joint between existing R/C building and seismic retrofit elements. This paper provides the procedure for the development of a sprayable SHCC, test results of fresh properties required to a sprayable SHCC, and mock-up test results of developed sprayable SHCC. Control mixture of polyvinyl alcohol (PVA) fiber-reinforced SHCC (PVA-SHCC) was predetermined based on available research results. The pumpability and sprayability of the SHCC mixture were depended on the fluid property of fresh SHCC mixture. In this study, the effects of admixtures such as AE agent and fly ash on the rheological and rebound properties of control SHCC mixture were investigated to determine a sprayable SHCC mixture. Flow values and air content during shotcreting procedure of sprayable SHCC were also evaluated. The results show that flow or flowability and amount of air of three SHCC mixtures decreased almost linearly according to shotcreting procedure from mixer to nozzle. And the pumpability and sprayability of mixture with AE agent and low amounts of fly ash were superior to the those of SHCC. Mock-up test result show that developed sprayable SHCC indicates much improved workability and shotcrete construction period than conventional method(nonshrinkage mortar).

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.380-385
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• 1998

Nowadays, shotcrete plays an essential part in he construction of underground structures, and steel fiber is so useful for increasing the toughness of the concrete that is spotlighted at tunnel or pavement site. A variety of tests have been developed to measure and quantity the improvements achievable in steel fiber reinforced concrete(SFRC) and shotcrete. But Korea doesn`t have specific standards in this respect, and the only criteria that KHC(Korea Highway Corporation) applies to tunnel shotcreting are flexural strength and toughness quotient. Test results in order to manage the quality of steel fiber reinforced concrete and shocrete are very affected by various test method. Therefore, this study deals with the test methodological effects on SFRC quality. The major interests are loading method, that is, load control and displacement control, loading velocity, support condition.