• Proceedings of the Korea Concrete Institute Conference
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• 1990.04a
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• pp.11-15
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• 1990

Results of an experimental study on the manufacture and the mechanical properties of carbon fiber reinforced fly ash-cement composites are presented in this paper. The carbon fiber reinforced fly ash-cement composites using silica powder and a small amount of Ethylene vinyl acetate emulsion are prepared with carbon fiber, foaming agents and curing conditions. As a result, the manufacturing process technology of carbon fiber reinforced fly ash-cement composites is developed. And the mechanical properties such as compressive, tensile and flexural strengths and drying shrinkage of lightweight carbon fiber reinforced fly ash-cement composites are improved by using a small amount of Ethylene vinyle acetate emulsion. The development and applications of precast products and the design systems of lightweight carbon fiber reinforced fly ash-cement composites are expected in the near future.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.203-208
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• 1999

The purpose of this study is to examine the bond properties of polymer cement mortar. Generally, cement mortar using polymer has been used that recovering the deteriorative concrete structure performance. In this case, it is very important problem to become a monolithic construction by bonding property. In this study, it is evaluated with other properties that adhesion strength between polymer cement mortar and concrete substrate. And polymer cement mortar was compared with plain cement mortar by scanning electron microscope.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.75-79
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• 1995

The results of an experimental study on the manufacture and the mechanical properties of fiber reinforced calcium silicates-cement composites utilizing by products (fly ash or cement sludge) for construction materials are presented in this paper. As the test results show, compressive, tensile, and flexural strength, fracture toughness of fiber reinforced calcium silicates-cement composites were improved by increasing the fly ash and fiber contents, but were decreased by increasing cement sludge contents. Somehat, especially increasing fiber contents the fracture toughness of the composites were remarkably increased. Also, the mechanical properties of the composites reinforcing alkali-resistance GF were higher than those of the composites reinforcing Samoa Pulp.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.136-141
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• 2000

Concrete has been used for many years as a composite material that has excellent mechanical properties and durability for construction. However, concrete ia a poor electrical conductor, especially under dry conditions. Concrete that is excellent in both mechanical and electrical conductivity properties may have important applications in the electrical, electronic, military and construction industry (e.g for de-icing road from snow). The purpose of this investigation is to improve the electrical conductive of cement mortar preparared with graphite as filler. From the test result, as the ratio of graphite/cement increased, fluidity, fluidity and strength decreased but resistivity decreased. The resistivity of electrical conductive cement mortar is effect by water/cement ratio and water content of specimen. From this study, it is enough to assure the use of graphite as a conductive filler for electrical conducive cement mortar.

• Journal of the Korean Ceramic Society
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• v.46 no.4
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• pp.365-371
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• 2009

It is well known that the properties of concrete such as the compressive strength, water permeability, water tightness and durability are affected by micro-structure in hardened cement paste. Especially, for durability of concrete, watertightness of cementitious materials is the most critical property among various properties. Recently, many types of materials as organic and/or inorganic materials are used for watertightness of concrete. In this study, The effect of Stearic Acid at $0.5\;wt%{\sim}3.0\;wt%$ adding ratios on the hydration and watertightness property of cement were investigated. And we also discussed the changing of microstructure in hardened cement paste by addition of Stearic Acid. Cement paste with Stearic Acid showed improvement of watertightness by reducing of cement total pore volume and decomposition of Stearic Acid.

• Journal of Industrial Technology
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• v.19
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• pp.163-172
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• 1999

This study is conducted on the flexural toughness and flexural fatigue test to fine the mechanical properties of steel fiber reinforced rapid-set cement concrete. Experimental investigation is examined according to fiber contents(0, 0.4, 0.7, 1.0, 1.5%), fiber aspect ratio(58, 60, 83), fiber type (hooked, crimped fiber), and cement type (normal portland & rapid-set cement). The principal results obtained through this study are as follows; toughness and fatigue resistance tend to considerably increase with fiber contents, fiber aspect ration. And hooked fiber is improved better than crimped fiber. Concrete using rapid set cement is increased strength properties compared with concrete using normal portland cement, but relative strength properties behavior and fatigue resistance show a tendency to decrease a little.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.100-105
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• 1995

The aim of this study is to developed water proofing properties of cement mortar this study the effect of mix proportion on the basic characteristics of cement mortar was investigated. Also water absorption and permeability properties of mortar using several admixtures were tested. from this results, Physical properties of mortar is improved by using the sand witch has a broad particle size distribution. Also the sililca alumina powder is effective for decreasing the water permeability of mortar and zinc stearate is in creasing the water repellence property.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.667-675
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• 2006

Concrete is much more easily damaged by various parameters than by the only one and performance reducing mechanism grows more complicated in that condition. In addition, the factors which really act in concrete structure tend to be activated in turn and the degradation of concrete is very rapidly progressed. The purpose of this study is to evaluate the properties of polymer cement mortars under combined cures. The polymer cement mortars are prepared with various polymer types, polymer-cement ratios and cement-fine aggregate ratio, and tested for compressive and flexural strengths, accelerated carbonation, chloride ion penetration and acid resistance test, and freezing-thawing test. The properties of polymer cement mortars under combined cures is discussed. From the test results, polymer cement mortars have superior strengths compared with plain cement mortar under combined cures. The strengths of polymer cement mortars are markedly increased at curing condition II and V, however strengths are not improved at curing condition I and IV irregardless of polymer types. The carbonation and chloride ion penetration depths of polymer cement mortars tend to decrease in curing conditions, III-C, IV-B, V-A order, and decrease with increasing polymer cement ratios. It is concluded that polymer cement ratio of 10 to 15% are considered optimum for the preparation of such polymer cement mortars.

• Journal of the Korean Ceramic Society
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• v.34 no.12
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• pp.1261-1267
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• 1997

Four kids of powder admixtures(A, B, C, D) based on anhydrite were manufactured by mixing at a fixed rate of II-anhydrite, fly ash and active silica as an industrial by-product. Fluidity properties of cement paste such as mini-slump, apparent viscosity with elapsed time, as well as setting time of cement pastes of these admixtures substituted up to 11wt% of cement were compared to those of cement paste(SS) substisuted by marketed high-strength powder admixture(S). Among these powder admixtures, the fluidity of cement pastes(PA, PC) substituted by A and C powder admixtures manufactured from II-anhydrite and fly ash had an excellent property than that of cement paste substituted by marketed powder admixture and also a good fluidity-retention effect with elapsed time by adding of superplasticizer. The setting time of cement paste substituted by powder admixtures based on anhydrite slightly retarded than that of cement paste substituted by marketed powder admixture.

• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.833-840
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• 1990

For the development of multi-functional materials which has water reducing power, air entraining power and waterproofing power as well as blending additive in cement mortar the coal ash was modified with asphalt-stearic acid or asphalt-boiled oil mixtures by mechanical treatment. And the physical properties of cement mortar blended with modified coal ashes were compared with those of the water-tightness-cement mortar and the ordinary-portland-cement mortar added with AE.water reducing agent. The mortar of coalash-blend-cement modified with asphalt-stearic mixture was increased acid about 20% in initial strengths and decreased about 20% in water absorption ratio than those of ordinary coalash-blend-cement. The mortar of coalash-blend-cement modified with asphalt-bolied oil mixture was similar to the cement mortar added with AE.water reducing agent in water reduction ratio, air entraining conents and the initial strengths, also was similar to the water-tightness-cement mortar in water absorption and water permeability ratios.