• Title/Summary/Keyword: water cement ratio

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Effect of Air Void Organization to Frost-Resistance in High-Strength Concrete (고강도 콘크리트의 동해저항에 관한 기포조직의 영향)

  • 김생빈;홍찬홈
    • Proceedings of the Korea Concrete Institute Conference
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    • 1991.10a
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    • pp.5-10
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    • 1991
  • This study was performed to find out the effect about the spacing factor and durability factor to evaluate the durability of concrete in high-strength concrete with freezing and thawing as following each condition, 1) unit cement content : 500kg/$\textrm{m}^3$, 550kg/$\textrm{m}^3$ 2) water/cement ratio : 25%, 30%, 35% 3) air content : below 1.5%, 1.6~3.5%, 4~6%, over 7% From the results tested, a variation of air content was more effective to the durability of concrete than that of water/cement ratio and unit cement content.

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The Effect of Aerated Concrete containing Foam Glass Aggregate on the Floor Impact Sound Insulation (발포유리 혼합기포 콘크리트의 바닥충격음 차단성능 영향에 관한 연구)

  • Yun, Chang-Yeon;Jeong, Jeong-Ho;Kim, Myung-Jun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.5
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    • pp.414-422
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    • 2013
  • As structure-borne sound, the floor impact sound is one of the serious noises in residential building. Most of heating system applied to the typical Korean residential building is floor heating system which is called ondol. The ondol usually consists of finishing material, mortar with heating coil, light-weight aerated concrete and reinforced concrete. This study focused on the isolation of heavy-weight impact sound and modification of mortar and light-weight aerated concrete. Specifically the glass foam aggregate was added on light-weight aerated concrete. Also, water-cement ratio and amount of cement on mortar were revised. The sound pressure level of heavy-weight impact was measured in reverberation chamber using both bang-machine and impact ball. The size of specimen was 1 m by 1 m. Substitution ratio of glass foam aggregate on light-weight aerated concrete shows relationship with heavy-weight impact sound pressure level. In addition, heavy-weight impact sound pressure level was decreased with increment of water-cement ratio and amount of cement on mortar.

Model for simulating the effects of particle size distribution on the hydration process of cement

  • Chen, Changjiu;An, Xuehui
    • Computers and Concrete
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    • v.9 no.3
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    • pp.179-193
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    • 2012
  • The hydration of cement contributes to the performance characteristics of concrete, such as strength and durability. In order to improve the utilization efficiency of cement and its early properties, the particle size distribution (PSD) of cement varies considerably, and the effects of the particle size distribution of cement on the hydration process should be considered. In order to evaluate effects of PSD separately, experiments testing the isothermal heat generated during the hydration of cements with different particle size distributions but the same chemical composition have been carried out. The measurable hydration depth for cement hydration was proposed and deduced based on the experimental results, and a PSD hydration model was developed in this paper for simulating the effects of particle size distribution on the hydration process of cement. First, a reference hydration rate was derived from the isothermal heat generated by the hydration of ordinary Portland cement. Then, the model was extended to take into account the effect of water-to-cement ratio, hereinafter which was referred to as PSD hydration model. Finally, the PSD hydration model was applied to simulate experiments measuring the isothermal heat generated by the hydration of cement with different particle size distributions at different water-to-cement ratios. This showed that the PSD hydration model had simulated the effects of particle size distribution and water-to-cement ratio on the hydration process of cement with satisfactory accuracy.

Physical Properties Variation of Grout Materials Based on the Water to Cement Ratio and the Mixing Speed (물시멘트비 및 혼합속도에 따른 주입재의 물성변화 연구)

  • Chun, Byung-Sik;Kim, Jin-Chun;Jang, Bui-Woong;Lee, Jun-Woo
    • Journal of the Korean GEO-environmental Society
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    • v.1 no.1
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    • pp.87-96
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    • 2000
  • Generally, OPC(ordinary portland cement) is used for grouting in Korea, and bentonite has usually been added to prevent the deposition of cement particles. The dispersion of CB(cement bentonite) grout is influenced by variable factors i.e. water to cement ratio, particle size of cement, kind of bentonite, adding volume, method of adding, viscosity of CB grout materials and curdling time. Among variable factors, the viscosity of CB grout materials is influenced by the dispersion, and dispersion is improved as the speed of grout mixer increase. In this paper, the specification of construction was derived by estimating physical characteristics of CB grout materials and confirming the sate of dispersion. The results show that the engineering characteristics of CB grout materials vary with the water to cement ratio and the mixing speed.

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The Analysis of Skin Friction on Small-scale Prebored and Precast Piles Considering Cement Milk Influence (시멘트풀의 영향을 고려한 축소모형 매입말뚝의 거동분석)

  • Park, Jong-Jeon;Jung, Gyung-Ja;Jeong, Sang-Seom
    • Journal of the Korean Geotechnical Society
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    • v.33 no.1
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    • pp.5-15
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    • 2017
  • Skin friction may be one of the most critical factors in designing the prebored and precast pile. Special attention was given to the interface behavior of cement milk-surrounding soil during the installation of prebored and precast pile. Small-scale field model pile test was conducted for the case of single pile. The size and geometry of the small-scale field model piles were designed with pile length 1.3m, boring diameter 0.067 m. Quick maintain-load test was conducted for the cases of boring diameter 150, 125, 90, 86, 74 mm and water-cement ratio 90, 70, 60%. It was shown that the bearing capacity of the pile increased as the cement-water ratio and cement milk thickness increased. Considering the scale effect between the small-scale model test and the actual construction site, it was found that cement milk thickness of 0.1~0.4D (50~200 mm) was reasonable for the stability of the structure. Also, the proper cement paste water / cement ratio was about 70% when considering the results of this study and quality control.

Effects of Cement Alkalinity on the Time-to-Corrosion of Reinforcing Steel in Concrete under Chloride Exposure

  • Nam, Jingak;Hartt, William H.;Kim, Kijoon
    • Corrosion Science and Technology
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    • v.3 no.6
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    • pp.245-250
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    • 2004
  • A series of classical G109 type concrete specimens was exposed to cyclic wet and dry ponding with 15 w/o NaCl solution for approximately five years. Mix design variables included 1) three cement alkalinities (EqA of 0.97, 0.52, and 0.36) and 2) three water-cement ratios (0.50, 0.41, and 0.37). To determine the corrosion initiation time, corrosion potential and macro-cell current between top and bottom bars were monitored. Subsequent to corrosion initiation, specimens were autopsied and visually inspected. Concrete powder samples were collected from top rebar trace and chloride concentration was measured. Also, time-to-corrosion, $T_i$, for specimens of the individual mix designs was represented using Weibull analysis. Time-to-corrosion was a distributed parameter; and because of this, corrosion initiation of four identical specimens for each mix varied, often over a relatively wide range. Specimens fabricated using the lowest water cement ratio and the highest alkalinity cement exhibited the longest time-to-corrosion initiation and the highest chloride threshold levels. Time-to-corrosion did not increase monotonically with cement alkalinity, however, presumably as a consequence of relatively high $Cl^-$ binding in the lower pore water pH range. The chloride threshold level, $Cl_{th}$, increased with increasing $T_i$ and, consequently, was greatest for the highest cement alkalinity specimens.

Effect of Water-Soluble Polymer on the Properties of High Strength Hardened Cement Paste (고강도 시멘트 경화체의 특성에 미치는 수용성 폴리머의 영향)

  • 김정환;최상흘;한기성
    • Journal of the Korean Ceramic Society
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    • v.26 no.5
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    • pp.698-704
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    • 1989
  • Basic investigation for the flexural strength and water stability of hardened cement pastes using ordinary portland cement with water-soluble polyer (hydroxypropyl methyl cellulose ; HPMC) was carried out with 0.2 of water cement ratio. For molding of the specimen, the paste was mixed by twin roll mill. According to increase in the content of HPMC, the setting time of cement paste was delayed and the flexural strength was increased. The maximum flexural strength of hardened cement paste with 5.0wt% of HPMC was about 330 kg/$\textrm{cm}^2$. The expansion of the hardened cement paste immersed in water was increased with the content of water soluble polymer(HPMC). Consequently, the strength and the water stability of the hardened cement pastes were remarkably reduced by the expansion of them.

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An Experimental Study on the Physical Characteristics of Cement Mortar with Cellulose Fiber and Diatomite (목질섬유 및 규조토 혼입 시멘트 모르터의 물성에 관한 실험적 연구)

  • 김경민;박석근;이수용
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2003.05a
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    • pp.103.2-108
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    • 2003
  • The purpose of this study is to understand the Physical characteristics of cement mortar about humidity control on indoors and wall crack restraint. Experiments were conducted on the strength, water absorption coefficient, drying-shrinking crack, length change, cracks of mortar plaster bases according to mixture rate by mixing cellulose fiber and diatomite into cement mortar. The excellent tensile & bending reinforcement efficiency of cellulose fiber and void filling ability of diatomite proved to be suppressing cracks of cement. And diatomite seems to improve moisture-protection efficiency of cement mortar because of its high water absorption ratio and slow drying speed.

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Compressive Strength and Optimal Mixing Ratio of Alkali Activated Cement Concrete Containing Fly Ash (플라이 애쉬를 활용한 알칼리 활성시멘트 콘크리트의 압축강도와 최적혼합비)

  • Han, Sang-Ho;Park, Sang-Sook;Kang, Hwa-Young
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.11 no.4
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    • pp.152-158
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    • 2007
  • This is a fundamental research to utilize alkali activated cement(AAC) in concrete. The compressive strength of AAC concrete were measured for the various mixing ratios of activator/fly ash, and the mixing ratios of water glass, NaOH, and water among the activators. The mixing ratio of fine and coarse aggregates was maintained constantly. The relationships between the compressive strength and mixing ratios were analyzed to find the optimal mixing ratio of AAC concrete. As the results, the optimal mixing ratio of activator/fly ash in AAC concrete was 0.7, and that of water glass, NaOH, water among the activator was 4.0:1.0:2.5 for the maximum compressive strength.

Dimensional Stability of Cement-Bonded Boards Manufactured with Coffee Chaff

  • AJAYI, Babatunde
    • Journal of the Korean Wood Science and Technology
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    • v.34 no.5
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    • pp.52-58
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    • 2006
  • Coffee chaff for manufacturing of the 6 mm thick cement-bonded boards was obtained from a coffee processing industry at Omuo-Ekiti, in Ekiti State, Nigeria. Boards were produced with three levels of cement to coffee chaff ratio of 1.5:1, 2.5:1 and 3.5:1; and at three levels of mixing curing reagent of 2.0%, 2.5% and 3.0%. Three dimensional properties of thickness swelling (TS), water absorption (WA) and linear expansion (LE) were investigated after 48 hours immersion in water. The mean values obtained for TS, WA and LE ranged from 0.46% to 1.47%, from 11.52% to 24.00%, from 0.19% to 0.35%, respectively. The most dimensionally stable boards were produced at the highest mixing levels of curing reagent and cement to coffee chaff ratio of 3.0% and 3.5:1, respectively. The coffee chaff is suitable as raw material for the manufacture of cement-bonded composites and it would be able to stimulate and activate the use of other agro-byproducts for the manufacture of value-added panels.