• Korean Journal of Agricultural Science
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• v.14 no.2
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• pp.373-383
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• 1987

No-fines concrete is concrete from which the fine aggregate fraction has been omitted. The concrete so formed, consisting only of coarse aggregate, cement, and water, has large voids uniformly distributed through its mass. This study was performed to obtain the basic data which can be applied to the use of no-fines concrete. The data was based on the properties of no-fines concrete depending upon various mixing ratios. The results obtained were summarized as follows. 1. Test result of the consistency, suitable water-cement ratio was increased with the increasing of mixing ratio. 2. At the suitable water-cement ratio, the highest strengths were showed. But it gradually was decreased with the increasing of mixing ratio and strengths are considerably lower than that of conventional portland cement concrete. 3. The relations between compressive and tensile strength were highly singnificant as a straight line shaped. The strength ratio was decreased with the increasing of mixing ratio and considerably lower than of conventional portland cement concrete. 4. Bulk density was decreased with the increasing of the mixing ratio, and was similar to that of the conventional portland cement concrete at mixing ratio 1:4. 5. The relations between strength and bulk density were highly significant as a straight line shaped. The decreasing ratio of strengths was higher than that of bulk density.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.695-702
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• 2002

Shotcrete (or Sprayed concrete) has been used as an important support material in New Austrian Tunnelling Method (NATM). Since the mid of 1990, permanent shotcrete tunnel linings such as Single-shell, NMT (Norwegian Method of Tunnelling) has been constructed in many countries for reducing the construction time and lowing construction costs instead of conventional in-situ concrete linings. Among essential technologies for successful application of permanent shotcrcte linings, high performance shotcrete providing high strength, high durability, better pumpability has to be developed in advance as an integral component. This paper presents the Ideas and first experimental attempts to increase early strength and bond strength of wet-mixed Steel Fiber Reinforced Shotcrete(SFRS) in sump water condition. In order to increase early strength, a new approach using high-early strength cement with liquid alkali-free accelerator has been investigated From the results, wet-mix SFRS with high-early strength cement and alkali-free accelerator exhibited excellent early strength improvement compared to the ordinary portland content and good bond strength even under sump water condition.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.163-166
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• 1999

In this paper, strength development of concrete using blast-furnace slag cement(BSC) and ordinary portland cement(OPC) are discussed under varius W/C and curing temperatures. According to the experimental results, strength development of BSC concrete is lower than that of OPC concrete in low temperature at early age and maturity. In high curing temperature, BSC concrete has higher strength development than that of low temperature regardless of the elapse of age and maturity. BSC has much effect on the strength development of concrete at the condition of mass concrete, hot weather concreting and the concrete products with the steam curing, which is influenced by high temperature.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.823-828
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• 1999

Blast furnace slag cement(BSC) has many merits in relation to its prodution cost or environmental problem of these days, but it has still some limitation in broad use mainly because it has the lower early hydration strength than the normal portland cement(PC) has. In the present study, several different experimental concepts to improve its low strength in the early hydration stage were tried out which addition of the effective alkali activators such as Ca(OH)2 and limestone powder, fly ash in existing BSC. It was found that the addition of suitable quantity the effective alkali activators such as Ca(OH)2 and limestone powder, fly ash in BSC can be a possible way to get enough early strength compared with the PC and existing BSC.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.217-222
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• 1994

Generally speaking, grouting on the base stabilizes the ground as the aspects of mechanic and engineering properties, with drilling hole at any depth of the earth, and pressuring the cement milk or special chemical grouting material in it. The purpose of grouting on the base is waterproofness and solidification of the ground by earth concreting that the cement milk pass through paticles of soil or crack of rock. This report shows the fundamental properties of microcement compared with those of ordinary portland cement in a point of grouting. It also describes that experimental applications on the treatment of the weathered rock at the constructior of Taegu subway and Boryong earth filled dam site, south of chungchung province, resulted in success.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.620-623
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• 2004

Waste concrete powder(WCP) has been estimated with a great value-added material as by-product of waste concrete manufactured to fine and coarse aggregate for concrete, because it is able to utilized for cement clinker and concrete admixture. In the experimental results for this study, chemical composition of WCP was similar to that of cement, and specific gravity of WCPs were 2.46 and 2.48 due to internal micro-void of WCP. Final setting of paste with WCP was delayed, and flow value of mortar with WCP was tendency to reduced in comparison with that of paste and mortar with only ordinary portland cement as replacement ratio of WCP increased. Furthermore, sorptivity of mortar with WCP was increased as replacement ratio of WCP increased. Compressive strength of mortar with $15\%$ WCP was developed about 27MPa at 28days.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.193-196
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• 2003

In this paper, the experimental investigation for the setting properties of cement paste, the consistency and strength properties of mortar with steel furnace slag dust was performed and compared with those of cement paste and mortar with ground granulated blast furnace slag. When steel furnace slag dust was replaced with normal portland cement, setting time and flow value indicated to good results like as mortar with ground granulated blast furnace slag. However, mortar with steel furnace slag dust expressed to appreciably strength devaluation according to containing ratio, and did not indicate the pozzolanic reaction like as ground granulated blast furnace slag.

• Computers and Concrete
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• v.21 no.4
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• pp.367-376
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• 2018

This study reports the results of nondestructive monitoring of macro void developments in mortars manufactured with both ordinary Portland cement and sulfate resistant cement. Two types of curing were utilized; tap water curing and another curing environment that contains 5% $Na_2(SO_4)$ solution. Being the primary objective of this study, macro void developments of the mortar specimens were monitored by X-ray Medical Computerized Tomography. Compressive strength tests and water absorption tests were conducted on specimens that were kept in both curing environments for a duration of 560 days. Data analyses yielded consistent results among the three tests used in this experimental study. Macro void ratios of mortars decreased at the beginning of experiments for a certain period; afterwards, macro void ratios increased. The objective of this study was accomplished as anticipated since X-CT image analysis was able to nondestructively monitor macro void development process in cement mortars.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.271-276
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• 1999

This study is performed to evaluate an elastic properties and acid-resistance of concrete using pine needle ash(PNA). Materials used for this experiment are PNA , normal portland cement, natural fine and coarse aggregate. Test results show that the highest ultrasonic pulse velocity , dynamic and static modulus of elasticity is achieved by 5% PNA filled PNA concrete, which has showed similar with those of thei normal cement concrete. Acid-resistance of PNA concrete is increased with increase of the contnet of PNA , it is 1.29 times of the normal cement concrete by 5% PNA fille PNA concrete an d2.57 times by 15% PNA filled PNA concrete . Accordingly , PNA concrete wil greatly improve the properties of concrete.

• Journal of the Korean GEO-environmental Society
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• v.25 no.5
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• pp.15-19
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• 2024

This study aimed to develop high-efficiency grouting techniques under deep-depth conditions by experimentally verifying the applicability of various injection materials. Particle size analysis and injection model experiments were conducted with Ordinary Portland Cement (OPC) and Micro Cement (MC) to evaluate the injection performance of each material. Using Barton's Cubic Network theory, the rock fracture spacing was calculated for domestic deep-depth standards, specifically below 40 meters underground. The analysis of particle size passability under selected conditions showed that MC could pass through the rock fracture gaps, while OPC could not. According to the results of the injection model experiments using experimental devices and area calculation software, OPC failed in injection due to its larger particle size, whereas MC was capable of injection even under high-viscosity conditions. Based on these findings, the study quantitatively and visually derived the applicability of grouting materials under deep-depth conditions, and high-viscosity MC material is expected to be effective for waterproofing enhancement in deep-depth rock fracture surfaces.