• Computers and Concrete
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• 제32권2호
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• pp.185-206
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• 2023

This article aimed to explore the optimization of mineral admixtures and retarding admixture for high-performance concrete. In essence, fresh concrete can be regarded as a mixture in which both coarse and fine aggregates are suspended in a cement-based matrix paste. Based on this view, the test procedure was divided into three progressive stages of binder paste, mortar, and concrete to explore their rheological behavior and mechanical properties respectively. At each stage, there were four experimental control factors, and each factor had three levels. In order to reduce the workload of the experiment, the Taguchi method with an L9(3⁴) orthogonal array and four controllable three-level factors was adopted. The test results show that the use of the Taguchi method effectively optimized the composition of high-performance concrete. The slump of the prepared concrete was above 18 cm, and the slump flow was above 50 cm, indicating that it had good workability. On the other hand, the 28-day compressive strength of the hardened concretes was between 31.3-59.8 MPa. Furthermore, the analysis of variance (ANOVA) results showed that the most significant factor affecting the initial setting time of the fresh concretes was the retarder dosage, and its contribution percentage was 62.66%. On the other hand, the ANOVA results show that the most significant factor affecting the 28-day compressive strength of the hardened concretes was the water to binder ratio, and its contribution percentage was 79.05%.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.177-178
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• 2023

In this study, the mass production process was simulated using a 1m³ batcher plant to evaluate the application of high-strength fire resistance concrete. The strength ranges of concrete were set to 50, 60, 70, and 80 MPa, and each concrete mix proportions was selected through preliminary experiments in the laboratory. For the selected concrete mix proportions, after the mixer load value was stabilized in the batcher plant, the slump flow and air content of the fresh concrete were evaluated, and the compressive strength was evaluated up to 56 days. As a result of the experiment, both the slump flow and air content of the fresh concrete satisfied the target performance, and in the case of compressive strength, 50 and 60 MPa satisfied the target performance at 28 days and 70 and 80 MPa at 56 days.

• International Journal of Concrete Structures and Materials
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• 제6권2호
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• pp.65-78
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• 2012

An experimental study was carried out to evaluate fresh properties of a moderately high-strength (high-flowing) self-compacting concrete (SCC) and to investigate shear behavior and performance of deep beams made with SCC. Fresh and hardened properties of normal concrete (NC) and SCC were evaluated. The workability and compacting ability were observed based on casting time and number of surface cavities, respectively. Four-point loading tests on four deep beams (two made with SCC and two with NC) were then conducted to investigate their shear behavior and performance. Shear behavior and performance of beams having two different web reinforcements in shear were systematically investigated in terms of crack pattern, failure mode, and load-deflection response. It was found from the tests that the SCC specimen having a normal shear reinforcement condition exhibited a slightly higher load carrying capacity than the corresponding NC specimen, while the SCC specimen having congested shear reinforcement condition showed a similar load carrying capacity to the corresponding NC specimen. In addition, a comparative study between the present experimental results and theoretical results in accordance with ACI 318 (Building Code Requirements for Reinforced Concrete (ACI 318-89) and Commentary-ACI 318R-89, 1999), Hsu-Mau's explicit method (Hsu, Cem Concr Compos 20:419-435, 1998; Mau and Hsu, Struct J Am Concr Inst 86:516-523, 1989) and strut-and-tie model suggested by Uribe and Alcocer (2002) based on ACI 318 Appendix A (2008) was carried out to assess the applicability of the aforementioned methods to predict the shear strength of SCC specimens.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 봄 학술발표회 논문집
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• pp.16-19
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• 1990

The effect of superplasticizers on the fluidity performance in fresh concrete and physical properties in hardened concrete have been analyzed and investigated under mix proportions of water cement ratio of 0.4, 0.6, crushed stone aggregates, and addition rates of superplasticizers of 0.0, 0.5, 1.0 and 1.5 in the practical range. It is the aim of this study to provide the fundamental data on the workability improvement and engineering properties of crushed stone concrete using superplasticizers comparing with conventional concrete for the practical use and research data accumulation of superplastized concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.79-82
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• 2003

In this study, non-sintering cement is produced by only blending granulate blast furnace slag with phosphogypsum as main materials, and small amounts of hydrate lime or waste lime as activators. This paper was investigated physical properties of fresh concrete and hardened concrete using non-clinker cement according to various mixing ratio. Results obtained from this study have shown that concrete using non-clinker cement could be used for structural concrete and concrete 2th production as binder.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.223-226
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• 2002

This study is performed to investigate the influence of aggregate factor on the estimation of water content in fresh concrete. According to the results, water content is estimated higher in the case of basalt and granite aggregate than in the case of limestone because absorption water ratio of basalt and granite is large. As the replacement ratio of recycled aggregate increases, water content is estimated higher. But, after correcting absorption water ratio of aggregate, estimated water content is similar to mixture water content. Therefore, it is important to know the absorption water ratio of aggregates accurately, to estimate water content.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.141-142
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• 2023

In this study, the correlation between the properties of concrete in the fresh state and the compressive strength of hardened concrete was analyzed. It was found that the compressive strength increased as the values of T500 and plastic viscosity increased. However, there is a relationship between T500, which is a qualitative method, and compressive strength, but it seems difficult to predict through this. However, the correlation between plastic viscosity and compressive strength appears to be high, and it is believed that compressive strength can be predicted, but more data will be collected in the future for additional analysis. I think this will be necessary.

• Advances in concrete construction
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• 제6권2호
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• pp.145-157
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• 2018

This paper presents a review on the use of Silica Fume (SF) as a mineral admixture in the concrete. Distinctive outcome from several researches have been demonstrated here, particularly emphasizing on the fresh and hardened properties of concrete when blended with Silica Fume (Micro-silica or Nano-silica). The results showed a substantial enhancement in the mechanical properties of concrete when replaced with SF. The review also presented a brief idea of percentage replacement of SF in case of normal and high-strength concrete. A decreasing trend in workability (slump value) has been identified when there is a increase in percentage replacement of SF. It can be concluded that the optimize percentage of replacement with SF lies in the range of 8-10% particularly for compressive strength. However the variation of blending goes up to 12-15% in case of split tensile and flexure strength of concrete. The study also demonstrates the effect of silica fume on durability parameters like water absorption, permeability, sulphate attack and chloride attack.

• Steel and Composite Structures
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• 제23권5호
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• pp.517-527
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• 2017

In this paper, the effect of active confinement on the compressive behaviour of circular steel tube-confined concrete (STCC) and concrete-filled steel tube (CFST) columns is investigated. In STCC columns the axial load is only applied to the concrete core, while in CFST columns the load is carried by the whole composite section. A new method is introduced to apply confining pressure on fresh concrete by laterally prestressing steel tubes. In order to achieve different prestressing levels, short-term and long-term pressures are applied to the fresh concrete. Three groups of STCC and CFST specimens (passive, S-active and L-active groups) are tested under axial loads. The results including stress-strain relationships of composite column components, secant modulus of elasticity, and volumetric strain are presented and discussed. Based on the elastic-plastic theory, the behaviour of the steel tube is also analyzed during elastic, yielding, and strain hardening stages. The results show that using the proposed prestressing method can considerably improve the compressive behaviour of both STCC and CFST specimens, while increasing the prestressing level has insignificant effects. By applying prestressing, the linear range in the stress-strain curve of STCC specimens increases by almost twice as much, while the improvement is negligible in CFST specimens.

• 한국도로학회논문집
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• 제14권4호
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• pp.51-61
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• 2012

PURPOSES : This study deals with the working life of polymer concrete, which is typically used as a repair or overlay material for portland cement concrete pavements. METHODS : In the scope of this study, laboratory testing was conducted on fresh MMA modified UP polymer concrete, which uses an MMA monomer for viscosity adjustment and strength improvement of UP resin. The experimental variables were temperature (-20 to $+20^{\circ}C$) and binder components (MMA, MEKPO, and DMA). RESULTS : The result showed that the optimum binder ratios for polymer concrete production were 12, 11, and 10 wt.% when the MMA contents were 20, 30, and 40 wt.%, respectively. The working life of polymer concrete depending on temperature and binder components could be expressed by a logarithmic functional formula. The coefficient of variation for each binder component was the highest for DMA content while the lowest for MEKPO content. Also, the contents of each binder component for ensuring the working life of 60 minutes were proposed. CONCLUSIONS : Ultimately, the present study derived a linear regression equation estimating 60 minutes working life based on the setting times of each binder component.