• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.201-202
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• 2016

Energetically-modified material using reject fly ash was manufactured to investigate the effect of the material on strength characteristic of cement mortar. In order to modify reject fly ash, a vibration mill was used. after grinding process, the defects in the alignment of atom was checked using transmission electron microscope. It was found that the compressive strength values of 28 days-cured specimens using energetically-modified reject fly ash (ERFA) were higher than that of mortar with non-ground reject fly ash.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.205-211
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• 2006

The purpose of this study was to evaluate the effects of fly-ash on strength development and durability of latex-modified concrete (LMC) and ordinary portland cement concrete (OPC). Main experimental variables were latex contents (0%, 10%, 15%) and fly-ash content (0, 10%, 20%, 30%). Air content and slump tests were performed to check the basic properties of fresh concretes, and compressive strength, flexural strength, rapid chloride ion permeability and chemical resistance were measured to analyze the basic properties of hardened concretes. The test results showed that air contents of LMC with fly ash decreased as fly-ash contents increased from 0% to 30%. Compressive and flexural strength developments of LMC with fly ash were quite similar to those of LMC without fly ash. However, the long-term flexural strength development of LMC with fly ash after 90 days were bigger than that of LMC without fly ash. Chloride ion permeability and chemical resistance decreased rapidly as the content of fly ash increased. Thus, fly ash could be used at LMC in order to reduce water permeability.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.234-240
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• 2016

Energetically-modified material using reject fly ash (RFA), generated from thermal power plants, was manufactured to investigate the effect of the material on the physical and chemical characteristics of cement mortar. In order to modify reject fly ash, a vibration mill was used. Particle size, grain shape, and crystal structure of the ash were analyzed. Then, the compressive strength of the mortar using energetically-modified reject fly ash (ERFA) was measured. Microstructure and X-ray diffraction (XRD) patterns were also used in the analysis. As the replacement rate of ERFA increased, the value of the compressive strength tended to decrease. However, it was found that the compressive strength values of 7 and 28 days-cured specimens were higher than those of conventional ordinary Portland cement (OPC) mortar with 10 % replacement rate condition.

• Computers and Concrete
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• v.6 no.1
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• pp.19-40
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• 2009

This paper describes the development of modified heat of hydration and maturity-strength models for concrete containing fly ash and slag. The modified models are developed based on laboratory and literature test results, which include different types of cement, fly ash, and slag. The new models consider cement type, water-to-cementitious material ratio (w/cm), mineral admixture, air content, and curing conditions. The results show that the modified models well predict heat evolution and compressive strength development of concrete made with different cementitious materials. Using the newly developed models, the sensitivity analysis was also performed to study the effect of each parameter on the hydration and strength development. The results illustrate that comparing with other parameters studied, w/cm, air content, fly ash, and slag replacement level have more significantly influence on concrete strength at both early and later age.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.90-91
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• 2020

Utilization of upgraded fine fly ash in cement-based materials has been proved by many researchers as an effective method to improve compressive strength of cement based materials at early ages. The addition of fine fly ash has introduced dilution effect, enhanced pozzolanic reaction effect, nucleation effect and physical filling effect into cement-fly ash system. In this study, an integrated reaction model is adpoted to quantify the contributions from cement hydration and pozzolanic reaction to compressive strength. A modified model related to the physical filling effect is utilized to calculate the compressive strength increment considering the gradual dissolution of fly ash particles. Via combination of these two parts, a numerical model has been proposed to predict the compressive strength development of fine fly ash mortar considering fly ash fineness. The reliability of the model is validated through good agreement with the experimental results from previous articles.

• Environmental Engineering Research
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• v.10 no.6
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• pp.294-305
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• 2005

The effectiveness of fly ash-, quicklime-, and quicklime-fly ash-based stabilization/solidification(S/S) in chromium(Cr) contaminated soils was investigated using modified semi-dynamic leaching tests. Artificial soil samples composed of kaolinite or montmorillonite contaminated with chromium nitrate(4000 mg $Cr^{3+}\;kg^{-1}$ of solid) were prepared and then subjected to S/S treatment using quicklime, fly ash, or quick lime-fly ash. The effectiveness of the treatment was evaluated by assessing the cumulative fraction of leached $Cr^{3+}$ as well as, by computing the effective diffusivity ($D_e$) and the leachability index (LX) of the treated samples. The reduction in $Cr^{3+}$ release for the untreated samples was more pronounced in the presence of montmorillonite, which was attributed to sorption. Treatment with quicklime, fly ash, or quick lime-fly ash was significantly effective in reducing $Cr^{3+}$ release most probably due to the formation of pozzolanic reaction products and $Cr(OH)_3$ precipitation. The most effective treatment was observed in montmorillonite-sand soil samples treated with quicklime-fly ash (99.8% removal). The mean $D_e$ decreased significantly and the mean LX was greater than 9 for all treated samples, indicating that the treated soils were acceptable for "controlled utilization". The mechanism controlling $Cr^{3+}$ leaching from all treated samples during the first 5 days appeared to be diffusion.

• KCI Concrete Journal
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• v.14 no.2
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• pp.76-80
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• 2002

The role of high volume Class F fly ash in reducing expansion due to Alkali-Silica Reaction (ASR) was investigated. A series of modified ASTM C 1260 tests were performed under three different levels of NaOH normality, extending the test period to 28 days, using high- or low alkali cement, and Class F fly ash up to 58 ％ by mass of cement. A reactive siliceous fine aggregate was used. The test results confirm that HVFA replacement in a cementitious system significantly helps in controlling expansion caused by ASR.

• Geomechanics and Engineering
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• v.9 no.2
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• pp.261-273
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• 2015

In the present investigation, a series of laboratory compaction and unconfined compressive strength laboratory tests has been performed. To determine the effect of compaction energy, type of sand, and fly ash content, compaction tests have been performed with varying compaction energy ($2700kJ/m^3-300kJ/m^3$), types of sand, and fly ash content (0% to 40%) respectively. From the experimental results, it has been found that the optimum value of unconfined compressive strength obtained for a sand-fly ash mixture comprised of 65% sand and 35% fly ash. Based on the data obtained in the present investigation, a linear mathematical model has been developed to predict the OMC of sand-fly ash mixture.

• Computers and Concrete
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• v.8 no.5
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• pp.583-595
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• 2011

This paper studied the cement efficiency factor (k factor) of high calcium Class F fly ash. This k factor represents a unit of fly ash with efficiency equivalent to k unit of cement. The high calcium Class F fly ash was used to replace cement in concrete. The modified Bolomey's law with linear relationship was used for the analysis of the result of compressive strength, cement to water ratio (c/w) and fly ash to water ratio (f/w) by using the multi-linear regression to determine the k factor and other constants in the equations. The results of analysis were compared with the results from other researcher and showed that the k factor of high calcium Class F fly ash depends on the fineness of fly ash, replacement level and curing age. While the amount of CaO content in Class F fly ash not evident. Furthermore, necessary criteria and variables for the determination of the k factor including the use of the k factor in concrete mix design containing fly ash were proposed.

• Computers and Concrete
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• v.9 no.5
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• pp.375-387
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• 2012

The objective of this investigation was to develop rules for automatic categorization of concrete quality using selected artificial intelligence methods based on machine learning. The range of tested materials included concrete containing a new waste material - solid residue from coal combustion in fluidized bed boilers (CFBC fly ash) used as additive. The rapid chloride permeability test - Nordtest Method BUILD 492 method was used for determining chloride ions penetration in concrete. Performed experimental tests on obtained chloride migration provided data for learning and testing of rules discovered by machine learning techniques. It has been found that machine learning is a tool which can be applied to determine concrete durability. The rules generated by computer programs AQ21 and WEKA using J48 algorithm provided means for adequate categorization of plain concrete and concrete modified with CFBC fly ash as materials of good and acceptable resistance to chloride penetration.