• Title/Summary/Keyword: 기건단위질량

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Size Effect of Concrete Compressive Strength Considering Dried Unit Weight of Concrete (콘크리트의 기건단위질량을 고려한 콘크리트 압축강도의 크기효과)

  • Sim, Jae-Il;Yang, Keun-Hyeok;Yi, Seong-Tae
    • Journal of the Korea Concrete Institute
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    • v.27 no.2
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    • pp.169-176
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    • 2015
  • Since the size effect law announced currently has been based on the normal weight concrete, for light weight concrete having different fracture characteristics, its application is questionable. Accordingly, in this study, a model equation to predict the effect of dried unit weight of the concrete on size effect of its compressive strength was developed and a database using existing research results was created. After determining the experimental constants of prediction models of Ba${\check{z}}$ant based on nonlinear fracture mechanics, Kim and Eo, and this study using the database, their results are mutually compared. Finally, it was found that the prediction model of this study considered dried unit weight of concrete predicted well the test results for light weight concrete than that of the models of Ba${\check{z}}$ant and Kim and Eo.

The Study on the Physical and Strength Properties of Lightweight Concrete by Replacement Ratio of Artificial Lightweight Aggregate (인공경량골재 혼합비율에 따른 경량 콘크리트의 물성 및 강도특성에 관한 연구)

  • Choi, Se-Jin;Kim, Do-Bin;Lee, Kyung-Su;Kim, Young-Uk
    • Journal of the Korea Institute of Building Construction
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    • v.19 no.4
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    • pp.313-322
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    • 2019
  • This study is to compare and analyze the physical and strength properties of lightweight concrete using domestic lightweight aggregate by replacement ratio of artificial lightweight fine and coarse aggregate after considering low cement mixture and pre-wetting time. The slump, unit weight, compressive strength and split tensile strength of lightweight concrete with domestic lightweight aggregate were measured. As test results, the slump of lightweight concrete by replacement ratio of lightweight fine aggregate increased as the replacement ratio of lightweight fine aggregate increased. The unit weight of lightweight concrete using 100% of lightweight fine aggregate was about 10.4% lower than that of the lightweight concrete with natural sand. In addition, the unit weight of lightweight concrete by replacement ratio of lightweight coarse aggregate increased with the increase of the ratio of LWG10(5~10mm). The compressive strength of lightweight concrete with lightweight fine and coarse aggregate increased as the replacement ratio of lightweight fine aggregate increased. The compressive strength of lightweight concrete with natural sand and LWG10 was 30 to 31MPa regardless of the replacement ratio of the lightweight coarse aggregate after 7 days.

A Proposal of Tensile Strength Prediction Models Considering Unit Weight of Concrete (콘크리트의 기건 단위질량을 고려한 인장강도 예측모델 제안)

  • Sim, Jae Il;Yang, Keun Hyeok
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.16 no.4
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    • pp.107-115
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    • 2012
  • The present study evaluates the validity of different equations specified in code provisions and proposed by the existing researchers to predict the concrete tensile capacities (direct tensile strength, splitting tensile strength and modulus of rupture) using a comprehensible database including 361 lightweight concrete (LWC), 1,335 normal-weight concrete (NWC) and 221 heavy-weight concrete (HWC) specimens. Most of the equations express the concrete tensile strengths as a function of its compressive strength based on the limited NWC concrete test data. However, the present database shows that the concrete tensile capacities are significantly affected by its unit weight as well. As a result, the inconsistency between experiments and predictions by the different models increases when the concrete unit weight is below 2,100 kg/$m^3$ and concrete compressive strength is above 50 MPa. On the other hand, new models proposed by the present study considering the concrete unit weight predict the tensile strengths of concrete with more accuracy.

The Unit Weight and Compressive Strength Properties of Lightweight Concrete by the Mixing Ratio of Artificial Lightweight Coarse Aggregate (인공경량굵은골재 혼합비율에 따른 경량콘크리트의 기건단위질량 및 압축강도 특성)

  • Kim, Do-Bin;Kim, Young-Uk;Oh, Tae-Gue;Kim, Joung-Hyeon;Ban, Jun-Mo;Choi, Se-Jin
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2018.05a
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    • pp.218-219
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    • 2018
  • This study analyzed the unit weight and compressive strength properties of lightweight concrete using high volume blast furnace slag powder by the mixing ratio of lightweight coarse aggregate to investigate the properties of lightweight concrete using domestic artificial lightweight aggregate.

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Mechanical Properties of Lightweight Aggregate Concrete according to the Substitution Rate of Natural Sand and Maximum Aggregate Size (천연모래 치환율과 경량 굵은 골재 최대 크기에 따른 경량 골재 콘크리트의 역학적 특성)

  • Sim, Jae-Il;Yang, Keun-Hyeok
    • Journal of the Korea Concrete Institute
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    • v.23 no.5
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    • pp.551-558
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    • 2011
  • The effect of the maximum aggregate size and substitution rate of natural sand on the mechanical properties of concrete is evaluated using 15 lightweight aggregate concrete mixes. For mechanical properties of concrete, compressive strength increase with respect to age, tensile resistance, elastic modulus, rupture modulus, and stress-strain relationship were measured. The experimental data were compared with the design equations specified in ACI 318-08, EC2, and/or CEB-FIP code provisions and empirical equations proposed by Slate et al., Yang et al., and Wang et al. The test results showed that compressive strength of lightweight concrete decreased with increase in maximum aggregate size and amount of lightweight fine aggregates. The parameters to predict the compressive strength development could be empirically formulated as a function of specific gravity of coarse aggregates and substitution rate of natural sand. The measured rupture modulus and tensile strength of concrete were commonly less than the prediction values obtained from code provisions or empirical equations, which can be attributed to the tensile resistance of lightweight aggregate concrete being significantly affected by its density as well as compressive strength.

An Experimental Study on the High Strength Lightweight Self-Compacting Concrete (고강도경량 자기충전콘크리트에 관한 실험적 연구)

  • Choi Yun-Wang;Kim Yong-Jic;Moon Han-Young
    • Journal of the Korea Concrete Institute
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    • v.17 no.6 s.90
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    • pp.923-930
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    • 2005
  • This paper was to evaluate the high strength lightweight self-compacting concrete(HLSCC) manufactured by Nan-Su, which main factor, Packing Factor(PF) for mixing design, has been modified and improved. We have examined HLSCC performance at its fresh condition as well as its mechanical properties at the hardened condition. The evaluation of HLSCC fluidity has been conducted per the standard of second class rating of JSCE, by three categories of flowability(slump-flow), segregation resistance ability(time required to reach 500mm of slump-flow and time required to flow through V-funnel) and filling ability(U-box test) of fresh concrete. The compressive strength of HLSSC at 28 days has come out to more than 30MPa in all mixes. The relationship between the compressive strength-splitting tensile strength and compressive strength-modulus of elasticity of HLSSC were similar those of typical lightweight concrete. Compressive strength and dry density of HLSCC at 28 days from the multiple regression analysis resulted as $f_c=-0.16LC-0.008LS+50.05(R=0.83)\;and\;f_d=-3.598LC-2.244LS+2,310(R=0.99)$, respectively.

An Experimental Study on the Engineering Characteristics of Ternary Lightweight aggregate Mortar Using Recycling Water (회수수를 사용한 3성분계 경량 골재 모르타르의 공학적 특성에 관한 실험적 연구)

  • Lee, Jae-In;Bae, Sung-Ho;Kim, Ji-Hwan;Choi, Se-Jin
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.10 no.1
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    • pp.48-55
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    • 2022
  • This study uses the recovered water as mixing water and artificial lightweight aggregate pre-wetting water as part of a study to increase the recycling rate and reduce greenhouse gas of the ready-mixed concrete recovered during the concrete transport process, and cement fine powder of blast furnace slag(BFS) and fly ash(FA). The engineering characteristics of the three-component lightweight aggregate mortar used as a substitute were reviewed. For this purpose, the flow, dry unit mass, compressive strength, drying shrinkage, neutralization depth, and chloride ion penetration resistance of the three-component lightweight aggregate mortar were measured. When used together with the formulation, when 15 % of BFS and 5 % of FA were used, it was found to be positive in improving the compressive strength and durability of the mortar.

Effect of Substituting Normal-Weight Coarse Aggregate on the Workability and Mechanical Properties of Heavyweight Magnetite Concrete (중량 자철석 콘크리트의 유동성 및 역학적 특성에 미치는 보통중량 굵은골재 치환율의 영향)

  • Mun, Jae-Sung;Mun, Ju-Hyun;Yang, Keun-Hyeok;Lee, Ho
    • Journal of the Korea Concrete Institute
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    • v.25 no.4
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    • pp.439-446
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    • 2013
  • The objective of this study is to evaluate the workability and various mechanical properties of heavyweight magnetite concrete and examine the reliability of the design equations specified in code provisions. The main parameters investigated were the water-to-cement ratio and substitution level of normal-weight coarse aggregate (granite) for magnetite. The oven-dried unit weight of concrete tested ranged between 2446 and $3426kg/m^3$. The measured mechanical properties included compressive strength development, stress-strain curve, splitting tensile strength, moduli of elasticity and rupture, and bond stress-slip relationship of concrete. Test results revealed that the initial slump of heavyweight magnetite concrete increased as the substitution level of normal-weight coarse aggregate increases. The substitution level of normal-weight coarse aggregate had little influence on the compressive strength and tensile resistance capacity of heavyweight concrete, while it significantly affected the modulus of elasticity and stress-strain curves of such concrete. The design equations of ACI 349-06 and CEB-FIP provisions mostly conservatively predicted the mechanical properties of heavyweight magnetite concrete, but the empirical equations for modulus of elasticity and splitting tensile strength need to be modified considering the unit weight of concrete.

Physical Properties of Lightweight and Normal Weight Concretes due to Water-Cement Ratio Changes (물-시멘트비 변화에 따른 경량콘크리트와 일반콘크리트의 물리적 성질)

  • Lee, Chang-Soo;Kim, Jae-Nam;Lim, Youn;Ma, Moon-Hak
    • Journal of the Korean Society of Hazard Mitigation
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    • v.9 no.4
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    • pp.11-20
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    • 2009
  • By using the artificial lightweight aggregate for the natural aggregate depletes and destruction of environment and the application of lightweight concrete in structure, the lightweight concrete is manufactured. The fundamental characteristics by the waterbinder ratio was evaluated. It is suggested the method to control of pre-absorbed water of the lightweight aggregate. Lightweight concrete with pre-absorbed aggregate has similar characteristics compared to normal weight concrete regardless of water-binder ratio. According to the water-binder ratio, the drying condition, and the rebar, the unit mass of the lightweight concrete showed the reduction of 14.6${\sim}$21.0% as the range of 1,668${\sim}$1,998 $kg/m^3$ in comparison to the normal weight concrete. The lightweight aggregate pre-absorbed water showed the deferent evaporation quantity according to the water-binder ratio. As the water-binder ratio is lower, the oven dry vapour water is larger, therefore the internal curing water is increasing. In the same water-binder, comparing the normal concrete the lightweight concrete shows lower compressive strength which is due to the different strength of an aggregate. In the air dry curing, the normal weight concrete has a lower strength improvement effect in w/c 0.3 than the ratio 0.4 and 0.5. However, the strength improvement effect has increasing as the water-binder ratio was low in the light concrete.