• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.163-169
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• 1998

The strength and freeze-thaw test were carried out in order to use recycled aggregate as crushed aggregate in concrete. The recycled concrete had a lower flexture and compressive strengths than ordinary concrete, but the inclusion of fly ash shows similar results in both concretes. The resistance of freeze-thaw was strongly influenced by W/C ratio, content of recycled aggregate and fly ash, and it was also found that the resistance was higher when W/C ratio and fly ash content was lower. and was superior when replacement level of recycled aggregate reached to 80%.

• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.129-137
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• 2005

In Korea, due to the insufficiency of natural aggregates and increasing needs of crushed stones, it is necessary to examine the alkali-silica reaction of the crushed stones. The reaction produces an alkali-silica reaction gel which can imbibe pore solution and swell to generate cracks that are visible In affected concrete. In general, crushed stones are tested by petrograptuc examination, chemical method and mortar-bar method, but the most reliable method Is mortar-bar test. This study tested alkali-silica reactivity of crushed stones of various rock types using ASTM C 227 and C 1260, and compared the results of two test methods. This study also analyzed effects of particle size and grading of reactive aggregate on alkali-silica reaction expansion of mortar-bar. The effectiveness of mineral admixtures to reduce detrimental expansion caused by alkali-silica reaction was investigated through the ASTM C 1260 method. The mineral admixtures used were nv ash, silica fume, metakaolin and ground granulated blast furnace slag. The replacement ratios of 0, 5, 10, 15, 25 and $35\%$ were commonly applied for all the mineral admixtures and the replacement ratios of 45 and $55\%$ were additional applied for the admixtures that could maintain workability. The results indicate that replacement ratios of $25\%$ for ay ash, $10\%$ for silica fume, $25\%$ for metakaolin or $35\%$ for ground granulated blast furnace slag were most effective to reduce alkali-silica reaction expansion under the experimental conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.829-836
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• 1999

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.53-59
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• 2009

The purpose of this research is particle shape evaluation of granular soil and aggregate using Digital Image Process(DIP). DIP is very useful to measure the roughness and particle shape of aggregates. Couple of aggregates, like standard sand, two different crushed stones, and two different marine aggregates, have been employed. Shape factor of two different marine aggregates is ranged 0.35 to 0.54. Crushed stone I is that of 0.74 which is highly flat, but standard sand is elongated shape. Especially, two marine aggregate showed a big difference of width and length which meaned a long shape. There is any significant difference of elongation ratio and flakiness for each aggregate with different measuring system, like direct measurement of vernier calipers and DIP method. Within the limited test results, DIP is one of useful to get the particle shape of aggregate with limitation of measuring errors and to apply the particle distribution curve.

• Journal of the Korean GEO-environmental Society
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• v.6 no.3
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• pp.17-23
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• 2005

In Korea, the production of reclaimed concrete materials has been increased due to the increase in the concrete structures taken down every year. The reclaimed concrete materials have been reused as road materials. However, the studies on their mechanical and environmental properties have been very limited. The recycled rate of the materials is currently low in Korea. This paper presents the investigation of mechanical and environmental properties of the reclaimed concrete materials, as well as the comparisons with those of gravel. For the evaluation of the mechanical and environmental characteristics, following tests were conducted on both reclamed materials and gravel; liquid limit, plasticity index, CBR, sand equivalent test, abrasion test, pH test, and column leaching test. The test results showed that the reclaimed concretes satisfy the requirements for use as roadbase, subbase, and subgrade materials, except base materials. The pH of reclaimed concrete materials was less than 11 and the leaching test results satisfied the regulatory requirement of Waste Management Act in Korea. Based on the investigations, it appears that the reclaimed concrete materials are environmentally safe and applicable for use as road materials.

• Cement Symposium
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• no.21
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• pp.102-107
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• 1993

• Tunnel and Underground Space
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• v.26 no.5
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• pp.418-430
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• 2016

In this study, experimental study on cement grout materials containing anti-washout admixtures or accelerators in grout column for reinforcement technology in groundwater-saturated mining cavity was conducted. As a result, the cement milk containing anti-washout admixtures was suitable for mixed aggregates, and the cement mortar containing anti-washout admixtures and the cement milk containing accelerators were suitable for crushed stone aggregate in terms of forming grout column. Especially, in the case of crushed stone aggregate injecting the cement milk containing accelerators, the diameter of the grout column was greatest and the void of the crushed stone aggregate was filled with grout materials. Therefore the case of crushed stone aggregate injecting the cement milk containing accelerators is considered for optimal grout materials and aggregate.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.385-392
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• 2005

The object of this study is to prove the quality and reliability of recycled aggregate concrete by finding a way to improve the durability of the material through the experiment on the accelerated carbonation, freezing and thaw, and drying shrinkage, analysing the influence on the durability to Promote more active use of recycled aggregate concrete. The result of study as follows. (1) Resistibility to the freeze and thaw of the recycled aggregate concrete showed relative dynamic modulus of elasticity over $90\%$ which is very good, and all cycles show $99.2{\~}91.0\%$ dynamic modulus of elasticity which is improved compared with the $97.5{\~}90.6\%$ relative dynamic modulus of elasticity of ordinary concrete made of broken stone. (2) Carbonated thickness of the recycled aggregate concrete and the normal concrete was similar or it appeared with the tendency which it diminishes more or less. (3) Length change rate in drying contraction of the recycled aggregate concrete made of the recycled aggregate was lower than the ordinary concrete made of the broken stone by $18.5{\~}3.9\%$ in all blending.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.83-90
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• 2008

The purpose of this study is to attempt to use broken red brick, which is categorized as impurities of circular aggregate to thick aggregate, as a replacement for concrete. Through the material test and performance test for each mixing rate of the broken red brick (0%, 30%, 60%), the following conclusion was reached by studying the material and structural characteristics of circular aggregate to the concrete. Even though broken red brick, which is categorized as impurities of circular aggregate, is mixed 30% with normal rubble, the compression strength, intensity strength, and curving strength was similar to that of concrete that uses normal rubble. Therefore, concrete beam made with broken red brick can be applied to the real construction field. Also, the study regarding the cutting test of the concrete that uses broken red brick and regarding applying and mixing admixture that can increase the ductility factor will be required in the future.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.249-254
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• 2002

In Korea, due to the shortcomings of natural aggregates and increasing needs of crushed stones, it is necessary to examine the alkali-aggregate reaction of the crushed stones. The purpose of this study is to analyze petrographic properties and alkali-aggregate reaction of crushed stones This study was peformed to investigate the alkali-aggregate reaction of crushed stones using chemical analysis, physical properties, XRD, XRF and mortar-bar method.