• Computers and Concrete
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• 제24권2호
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• pp.137-150
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• 2019

In this paper, surrogate models such as multivariate adaptive regression splines (MARS) and M5P model tree (M5P MT) methods have been investigated in order to propose a new formulation for the 28-days compressive strength of self-compacting concrete (SCC) incorporating metakaolin as a supplementary cementitious materials. A database comprising experimental data has been assembled from several published papers in the literature and the data have been used for training and testing. In particular, the data are arranged in a format of seven input parameters covering contents of cement, coarse aggregate to fine aggregate ratio, water, metakaolin, super plasticizer, largest maximum size and binder as well as one output parameter, which is the 28-days compressive strength. The efficiency of the proposed techniques has been demonstrated by means of certain statistical criteria. The findings have been compared to experimental results and their comparisons shows that the MARS and M5P MT approaches predict the compressive strength of SCC incorporating metakaolin with great precision. The performed sensitivity analysis to assign effective parameters on 28-days compressive strength indicates that cementitious binder content is the most effective variable in the mixture.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.369-372
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• 2008

This study analysis fundamental properties of high-strength concrete corresponding to W/B ratio for suggested table of high strength concrete, mixed with premixed cement. As a result of this study, the amount of using air entraining and high-range water reducing agent for intended slump flow and air content decreased as W/B increased, and the setting time corresponding to the W/B ratio delayed as W/B ratio increased except 20% W/B ratio. The compressive strength according to W/B ratio decreased as W/B ratio increased, and there was no great deferent as the intended slump flow. Also it could possible to use this study at work as the correlation coefficient is high enough as 0.9646 substituting B/W and compressive strength for the regression formula.

• Journal of the Korea institute for structural maintenance and inspection
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• 제11권6호
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• pp.143-151
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• 2007

This study presents the experimental results of frost durability including resistance to freezing-thawing and surface scaling of concrete. Mixing design was proportioned with the various water-binder ratio between 0.37 and 0.47 and three different binder compositions corresponding to Type I cement without any supplementary cementitious materials(OPC), Type II cement with 50% blast-furnace slag replacement(BFS50), and ternary cement with Type III cement, 15% fly ash, and 35% slag replacement (BFS35%+FA15%). Test results showed that the mixing design with BFS50% and BFS35%+FA15% exhibited higher durability factor than that made with OPC only. Finally, the use of blend cement containing slag can be used effectively in terms of frost durability of the concrete exposed to severe condition under coastal environment like as flying salt, sea water spray, etc.

• Journal of the Korea Concrete Institute
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• 제14권3호
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• pp.402-408
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• 2002

The permeable polymer-modified concrete has a lot of internal voids, which has more excellent performance in permeability and durability than asphalt and cement concrete. Therefore, the purpose of this study is to ascertain the strength properties of water-permeable polymer concretes with SBR latex and redispersible polymer powder. The water-permeable polymer concretes using SBR latex and redispersible polymer powder with water-binder ratio of 29 ％, polymer-cement ratios of 0, 5, 10, 15 and 20 ％ are prepared, and tested for compressive strength, splitting tensile strength, flexural strength, water permeablility. From the test results, improvements in the strength properties of the water-permeable polymer concretes due to the addition of the SBR latex and redispersible polymer powder are discussed.

• Computers and Concrete
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• 제3권4호
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• pp.249-260
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• 2006

Self-consolidating concrete (SCC) in the fresh state is known for its excellent deformability, high resistance to segregation, and use, without applying vibration, in congested reinforced concrete structures characterized by difficult casting conditions. Such a concrete can be obtained by incorporating either mineral or chemical admixtures. This paper presents the results of an investigation to asses the applicability of Abram's law in predicting the compressive strength of SCC to any given age. Abram's law is based on the assumption that the strength of concrete with a specific type of aggregate at given age cured at a prescribed temperature depends primarily on the water-to-cement ratio (W/C). It is doubtful that such W/C law is applicable to concrete mixes with mineral or chemical admixtures as is the case for SCC where water to binder ratio (W/B) is used instead of W/C as the basis for mix design. Strength data of various types of SCC mixtures is collected from different sources to check the performance of Abram's law. An attempt has been made to generalize Abram's law by using various optimization methodologies on collected strength data of various SCC mixtures. A set of generalized equations is developed for the prediction of SCC strength at various ages. The performance of generalized equations is found better than original Abram's equations.

• Magazine of the Korea Concrete Institute
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• 제8권2호
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• pp.109-117
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• 1996

Recently, High-Workable Concrete has been developed and began to be used to a great extent in foreign countries, but it is not familiar with and fully Introduced in Korea yet. Therefore the aim of this paper is to suggest a reference data. for the development of High-Workable Concrete according to the comparative analysis which were done on the effects of mix proportion(water-binder ratio, sand-aggregate ratio, unit water, a kind of superplasticizer) on the flowing characteristics. And also this paper aims to examine the compactability and segregation resistance of High-Workable Concrete in a mock-up test and in a field test. From the result, we concluded that it is possible to produce and to use the High-Workable Concrete at the construction site.

• Journal of the Korea Concrete Institute
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• 제27권5호
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• pp.511-519
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• 2015

Methods such table flow, slump and outflow time have used to be as a main evaluation criteria regards to fluidity of concrete. Since those methods mentioned above have some inaccuracies which are up to its condition of test. Studies that evaluate fluidity applying the rheology has increased its portion in this field. Meanwhile, demands for AAS binder have been increased in accordance with its demand for this market, studies for rheology of AAS binder are little though. Therefore, this paper mainly deals a rheological peculiarity of AAS binder according to its condition of W/B ratio and alkali activators. The fluidity of AAS paste was evaluated with the index of table flow and outflow time. And shear stress following its shear rate was analyzed through rheological test. Rheological parameters were deduced through this rheological test of Bingham model and analyzed its interrelation with fluidity test. As the final outcome, it proposed the interrelation among table flow, yield stress, viscosity and outflow time. In basis of this study, we would like to suggest a reference for mixing AAS mortars and concretes.

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2016년도 추계 학술논문 발표대회
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• pp.79-80
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• 2016

In this study, we measured the relative density and the compressive strength in order to select the appropriate W/ B for the ultra-high strength concrete development. If W/B is lowered than the W/B of highest relative density, it was confirmed that the strength is lowered. However, if water is increased than the W/B of highest relative density, the relative density is decreased compressive strength was similar. The selection of the W/B of the lower than the highest relative density is not appropriate. Appropriate W/B is selected to be more than the maximum relative density of W/B.

• Steel and Composite Structures
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• 제23권5호
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• pp.543-555
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• 2017

The mechanical properties of steel fiber reinforced high strength concrete (SFRHSC) made with binary and ternary blends of metakaolin (MK) and ground pumice (GP) are investigated in this study. The investigated properties are ultrasonic pulse velocity ($U_{pv}$), compressive strength ($f_c$), flexural strength ($f_f$) and splitting tensile strength ($f_{st}$) of SFRHSC. A total of 16 steel fiber reinforced concrete mixtures were produced by a total binder content of $500kg/m^3$ for determining the effects of MK and GP on the mechanical properties. The design $f_c$ was acquired from 70 to 100 MPa by using a low water-binder ratio of 0.2. The test results exhibit that high strength concrete can be obtained by replacing the cement with MK and GP. Besides, correlations between these results are executed for comprehending the relationship between mechanical properties of SFRHSC and the strong correlations are observed between these properties. Moreover, two models in the gene expression programming (GEP) for predicting the $f_c$ of SFRHSC made with binary and ternary blends of MK and GP have been developed. The results obtained from these models are compared with the experimental results. These comparisons proved that the results of equations obtained from these models seem to agree with the experimental results.

• Journal of the Korean Institute of Rural Architecture
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• 제21권2호
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• pp.35-42
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• 2019

There are 17,427 reservoirs in Korea, of which about 96% were built before the mid 1980s. Therefore, aging is severe and reinforcement are necessary. In addition, aged reservoirs, which are more than 50 years old, account for 70% of the total. Therefore, there is a problem such as the collapse of the reservoir and the decrease of the storage capacity due to progress of aging with time. The grouting method using cement is mainly used as maintenance and reinforcement method of old reservoir. However, the grouting method using cement has engineering and environmental problems. In order to solve the engineering and environmental problems of cement grouting method, an eco-friendly grouting material was developed that mixes circular resource grouting binder, high molar ratio sodium silicate and colloidal silica. The engineering and environmental properties of the developed injection materials were evaluated by conducting gel time, homo-gel strength, sea water resistance test and environmental stability evaluation. Also, examined the possibility of replacing OPC existing aged reservoir reinforcement methods. As a result, it was found out that it was better than the conventional cement method in terms of engineering and environment. However, since this study is the result of laboratory test, it is necessary of verify the application at field of aged reservoir.