• Architectural research
• /
• 제15권1호
• /
• pp.53-58
• /
• 2013

High strength concrete is being used increasingly in mass structure projects. The purpose of this study is to investigate the influence of temperature during mixing, placing and curing on the strength development, hydration products and pore structures of high strength concrete in mass structures. The experiments were conducted with two different model walls, viz.: 1.5 m and 0.3 m under typical summer and winter weather conditions. The final part of this study deal with the clarification of the relationship between the long-term strength loss and the microstructure of the high strength concrete at high temperatures. Test results indicated that high elevated temperatures in mass concrete structures significantly accelerate the strength development of concrete at the early ages, while the long-term strength development is decreased. The long-term strength loss is caused by the decomposition of ettringite and increased the total porosity and amount of small pores.

• Advances in concrete construction
• /
• 제1권2호
• /
• pp.151-162
• /
• 2013

The performance characteristics of high-strength and high-performance concrete are discussed in this review. Recent developments in the field of high-performance concrete marked a giant step forward in high-tech construction materials with enhanced durability, high compressive strength and high modulus of elasticity particularly for industrial applications. There is a growing awareness that specifications requiring high compressive strength make sense only when there are specific strength design advantages. HPC today employs blended cements that include silica fume, fly ash and ground granulated blast-furnace slag. In typical formulations, these cementitious materials can exceed 25% of the total cement by weight. Silica fume contributes to strength and durability; and fly ash and slag cement to better finish, decreased permeability, and increased resistance to chemical attack. The influences of various mineral admixtures such as fly ash, silica fume, micro silica, slag etc. on the performance of high-strength concrete are discussed.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1991년도 가을 학술발표회 논문집
• /
• pp.140-145
• /
• 1991

Tests were conducted to get a mix proportioning of high strength concrete between σ28 and (C/W) using low quality materials easily purchased in situ. Superplasticizer was used as a chemical admixture to compensate low slump of base concrete keeping it up about 15±2㎝. General material properties such as modulus of elasticity, poisson's ratio, unit weight and stress-strain characteristic of high strength concrete were obtained. Test results show that mix proportioning of high strength concrete proposed in this paper have reasonable validity and these can be used as a design criteria in high strength concrete construction.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
• /
• pp.442-445
• /
• 1997

With increasing use of high strength concrete tied columns in structural engineering, it becomes necessary to examine the applicability of related sections of current design codes. High strength concrete has an advantage of strength capacity and stiffness especially for column elements. This paper presents an experimental study of high strength concrete tied columns subjected to eccentric loading. The main variables included in this test were concrete compressive strength, steel amount, eccentricity, and slenderness ratio. The concrete compressive strength varied from 34.9Mpa(356kg/$\textrm{cm}^2$ ) to 93.2Mpa(951kg/$\textrm{cm}^2$ ) and the longitudinal steel ratios were between 1.1% and 5.5%. The eccentricity was selected for the different failure modes, i.e., compression control, balanced point, and tension control. The slenderness ratio varied from 19 to 61. The column specimens with same slenderness ratio but with different concrete compressive strength were constructed and tested. The purpose of this paper is to show failure modes of high strength reinforced concrete columns.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.204-207
• /
• 2004

In this paper, mechanical properties of the high strength lightweight self-compacting concrete with simple mixed design method was investigated. Experimental tests were performed as such compressive strength, splitting tensile strength, modulus of elasticity and density of high strength lightweight self-compacting concrete. The 28 days compressive strength of high strength lightweight self-compacting concrete with the LC replacement ratio of $100\%$ reduces about $31\%$ but LF replacement ratio of $100\%$ increase about $20\%$ compared that of the control concrete. The structural efficiency of high strength lightweight self-compacting concrete increase with proportional to the replacement into of LF. The relationship between the splitting tensile strength and 28 days compressive strength can be represented by the equation $f_s=0.076f_{ck}+0.5582$. The modulus of elasticity was found to be lower than that of normal weight concrete, ranging form 24 to 33 GPa.

• 콘크리트학회지
• /
• 제10권6호
• /
• pp.169-178
• /
• 1998

고성능 belite 시멘트 콘크리트에 대한 부착특성에 대하여 코\ulcorner리트의 강도, 슬럼프, 배근위치, 피복두께 등의영향요인을 보단부시험체와 이음길이 보시험체를 통해 연구하였다. 동일한 압축강도의 1종 보통 포틀랜드 시멘트 콘크리트에 비해 부착강도는 약 10%증가하였고 압축강도 600kg/$\textrm{cm}^2$의고강도 belite 콘크리트에서 부착강도가 대체로 {{{{ SQRT { f'c} }} }}에 비례하였다. 유동성에 있어서 높은 슬럼프에 비해 ACI 318-95 규준에서 제시하는 상부근 계수 1.3이하의범위에 있었으며 이것은 고유동 belite 콘크리트가 블리이딩이나 골재분리가 적은 것으로 보여졌다. 또한 고강도 belite시멘트 콘크리트를 사용한 이음길이 보시험체에서 부착강도는 기존 예측식의 값보다다소 높게 나타났으며, 실리커흄, 플라이애쉬를 사용한 고강도 콘크리트 부착강도의 기존연구결과인 낮은 값과 차이를 보였다. 이상의 결과로 고유동, 고강도 belite 시멘트 콘크리트는 철근과의 부착성능이 다른 재료에 비해 양호한 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1998년도 봄 학술발표회 논문집(I)
• /
• pp.141-146
• /
• 1998

In the present study, we have developed high strength concrete which is adequate for the long span PC beam above 40 meters. We have selected the most adequate materials for high strength concrete through laboratory tests and in-situ mock-up applications. We verified and decided the best curing condition of high strength concrete, and suggests the optimum mix design of high strength concrete. In the future, we will verify the properties-fresh and hardened concrete- of high strength concrete and its serviceability, and also apply the high strength concrete to newly-constructed real bridge structure.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
• /
• pp.897-902
• /
• 2001

Recently, structure performance is maximized by using high strength concrete. In design of structure, concrete need combination with reinforcement, but use of common strength reinforcement make member complex bar placement, so high strength concrete members require increased strength reinforcement. If common strength reinforcement replaced by equal tension area of high strength reinforcement, reinforcement ratio increase and brittle failure of member may occur by material change. So, adequate upper limit of strength ratio is required to affirm ductile behavior in application of high strength reinforcement. In this study, ductility behavior was analysed by factor of reinforcement ratio, strength of concrete and reinforcement. The result indicate that ductile failure is shown under 0.35 $\rho_{b}$ in any reinforcement strength of same section and high strength concrete of 800kg/$cm^{2}$ used commonly is compatible with reinforcement of 5500kg/$cm^{2}$.

• Advances in concrete construction
• /
• 제13권6호
• /
• pp.411-422
• /
• 2022

Aggregates mineralogical, and petrographic properties directly affect the mechanical properties of the produced high strength. This study is focused on the effects of magmatic, sedimentary, and metamorphic aggregates on the performance of high strength concrete. In this study, the effect of the mineralogical properties of aggregates on the compressive strength and modulus of elasticity of high-strength concrete was estimated by Artifical Neural Network (ANN). To estimate the compressive strength and elasticity modules, 96 test specimens were produced. After 28 days under suitable conditions, tests were carried out to determine the compressive strength and modulus of elasticity of the test specimens. This study also focused on the application of artificial neural networks (ANN) to predict the 28-day compressive strength and the modulus of elasticity of high-strength concrete. An ANN model is developed, trained, and tested by using the available test data obtained from the experimental studies. The ANN model is found to predict the modulus of elasticity, and 28 days compressive strength of high strength concrete well, within the ranges of the input parameters. These comparisons show that ANNs have a strong potential to predict the compressive strength and modulus of elasticity of high-strength concrete over the range of input parameters considered.

• Steel and Composite Structures
• /
• 제14권2호
• /
• pp.133-153
• /
• 2013

The concrete-filled steel tube (CFT) columns have several benefits of high load-bearing capacity, inherent ductility and toughness because of the confinement effect of the steel tube on concrete and the restraining effect of the concrete on local buckling of steel tube. However, the experimental research into the behavior of square CFT columns consisting of high-strength steel and high-strength concrete is limited. Six full scale CFT specimens were tested under flexural moment. The CFT columns consisted of high-strength steel tubes ($f_y$ = 325 MPa, 555 MPa, 900 MPa) and high-strength concrete ($f_{ck}$ = 80 MPa and 120 MPa). The ultimate capacity of high strength square CFT columns was compared with AISC-LRFD design code. Also, this study was focused on investigating the effect of high-strength materials on the structural behavior and the mathematical models of the steel tube and concrete. Nonlinear fiber element analyses were conducted based on the material model considering the cyclic bending behavior of high-strength CFT members. The results obtained from the numerical analyses were compared with the experimental results. It was found that the numerical analysis results agree well with the experimental results.