• Computers and Concrete
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• v.33 no.4
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• pp.471-479
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• 2024

In urban areas, appropriate backfilling design is necessary to prevent surface subsidence and subsurface cavities after excavation. Expandable foam grout (EFG), a mixture of cement, water, and an admixture, can be used for cavity filling because of its high flowability and volume expansion. EFG volume expansion induces a porous structure that can be quantified by the entrapped air content. This study observed the unit weight variations in the EFG before and after expansion depending on the various admixture-cement and water-cement ratios. Subsequently, the air content before and after expansion and the gravimetric expansion ratios were estimated from the measured unit weights. The air content before expansion linearly increased with an increase in the admixture-cement ratio, resulting in a decrease in the unit weight. The air content after the expansion and the expansion ratio increased nonlinearly, and the curves stabilized at a relatively high admixture-cement ratio. In particular, a reduced water-cement ratio limits the air content generation and expansion ratio, primarily because of the short setting time, even at a high admixture-cement ratio. Based on the results, the relationship between the maximum expansion ratio of EFG and the mixture ingredients (water-cement and admixture-cement ratios) was introduced.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.75-83
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• 2014

In order to prevent brittle failure of concrete, steel fiber reinforcement is effective composite material. However ductility of steel fiber reinforced concrete may be limited due to shrinkage caused by large content of cement binder. Chemical prestressing for steel fiber reinforcement in cement matrix can be induced through expansive admixture and this can increase reinforcing effect of steel fiber. In this study, mechanical performances in concrete with CSA (Calcium sulfoaluminate) expansive admixture and steel fiber reinforcement are evaluated. For this work, steel fiber reinforcement of 1 and 2% of volume ratio and CSA expansive admixture of 10% weight ratio of cement are added in concrete. Mechanical and fracture properties are evaluated in concrete with steel fiber reinforcement and CSA expansive admixture. CSA concrete with steel fiber reinforcement shows increase in tensile strength, initial cracking load, and ductility performance like enlarged fracture energy after cracking. With appropriate using expansive admixture and optimum ratio of steel fiber reinforcement, their interactive action can effectively improve brittle behavior in concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.9-17
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• 2016

In this study, binary blended concrete mix with fly ash and ground granulated blast furnace slag was prepared according to 3 level of water reduction performance of chemical admixture (0%, 8% and 16%) and 3 level of water-cement ratio (40%, 45% and 50%) for evaluation of quality properties of binary blended concrete according to performance of chemical admixture. concrete mix was carried out repetition test of three times in order to secure the reliability. As a result, compressive strength according to performance of chemical admixture was found that difference of strength was about 20% occurred, chemical admixture was showed that a great influence on qualities of concrete. In addition, reflected the effect of performance of chemiacal admixture, prediction model equations for concrete compressive strength was proposed, it was found that more than 85% of the high correlation.

• Korean Journal of Clinical Pharmacy
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• v.8 no.2
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• pp.147-158
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• 1998

The purpose of this study was to test the stability of TPN basic solutions containing amino acids and dextrose. Test solutions containing $4.25\%$ amino acids in $25\%$ dextrose (central TPN basic solution) or $4.25\%$ amino acids in $10\%$ dextrose (peripheral TPN basic solution) were prepared. Two different amino acids solutions $(Fravasol^{(R)}\;vs\;Freamine^{(R)})$ were tested. The samples were taken from each admixture and stored in the evacuated, sterile containers at $2{\sim}8^{\circ}C$ and ambient room temperature. Each sample was analyzed at 0, 3, 7, 14 and 30 days of storage. Each amino acid was analyzed by amino acid analyzer. Dextrose content was measured by polarimeter. The pH and chromagen formation were also monitored. The decomposition was measured by the changes in concentration of amino acids and dextroser TPN basic $solution-Freamine^{(R)}$ admixture stored at $2\sim8^{\circ}C$ were stable for 30 days. Central and peripheral TPN basic solutions stored at room temperature were stable for 7 days and 14 days, respectively. There were no changes in color for 30 days by naked eye. Amino acid concentrations in TPN basic $solution-Fravasol^{(R)}$ admixture stored at $2\sim8^{\circ}C$ or room temperature were stable for 30 days. But, significant color change was detected according to passing time. In conclusion, Peripheral TPN basic $solution-Fravasol^{(R)}$ admixture stored at room temperature and in refrigerator were stable for 3 days and 7 days, respectively. However, central TPN basic solution-Fravasol admixtures were unstable. Therefore, it is recommended that it should be admixed right before use.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.879-884
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• 2005

The setting time is a very important factor affecting the quality of tunnel lining and reinforcement of inclined slope etc. Currently, however, the quality criteria of accelerating admixture to improve it is not established well. In this study, evaluation on setting time measuring methods of cement mixed a accelerating admixture (AA) was performed using Gillmore and Vicat needle test methods. For both test methods, the setting time for addition at a time was better than post addition regardless of initial setting and final setting. For Gillmore needle test method, two types of measuring methods were selected and it is noted that setting time with cement type under the same accelerating admixture can be different. Accordingly, manufacturing company shall develop a less sensitive accelerating admixture to cement type. For Vicat needle test method, six types of measuring methods were used and a proper measuring method of the admixture were proposed as follows: (1) the temperature of materials used shall be controlled exactly and (2) to evaluate its properties, an admixture usage of $5\%$ (ratio of cement weight) is recommended.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.267-274
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• 2005

Preparation of cellulose type underwater non-segregation admixture was attempted and the hardening characteristics of underwater concrete according to the addition of this admixture was investigated in order to make underwater concrete with the compressive strength ratio of 0.8 to that of concrete manufactured in common atmosphere. The proposed underwater non-segregation admixture consisted of methyl cellulose of 0.4% by weight, silicon type antifoaming agent of 20% by weight, and sodium aluminate of 0.1% by weight to the amount of cement as setting accelerant, respectively. As the proposed non-segregation admixture was increased, the amount of suspended solid decreased, air content in concrete was increased but the flow loses by elapsed time did not change. The proper amount added of the proposed non-segregation adimixture was 0.8 wt% to the amount of cement. The compressive strength of the test sample underwater concrete manufactured by the addition of the proposed admixture was $325Kg/cm^3$, and the ratio of compressive strength of this sample concrete to that of a concrete manufactured in air was 0.94.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.95-103
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• 2012

In order to improve the dimensional stability and mechanical performance of cement-based composites, the effect of an expansive admixture based on calcium sulphoaluminate (CSA) on the shrinkage and mechanical properties of strain-hardening cement-based composite (SHCC), which exhibits multiple cracks and pseudo strain-hardening behavior in the direct tension, is investigated. Polyethylene fibers reinforced SHCC mixtures with three levels (30, 70, and 100MPa) of compressive strength were compared through free shrinkage, compressive strength, flexural strength, and direct tensile strength measurements. The SHCC mixtures were cast with and without replacing 10% of Portland cement content with CSA admixture. According to test results, CSA admixture is effective in reducing shrinkage of SHCC material. SHCC mixture with CSA admixture exhibited a little higher strength than companion mixture without CSA admixture.

• Magazine of the Korea Concrete Institute
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• v.8 no.2
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• pp.41-56
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• 1996

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.217-226
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• 2005

This study made member specimen for taking specimen, core with the concrete mixing normal concrete, admixture and conducted the same air curing as field conditions. After performing destructive and nondestructive test by age, estimate expression was suggested by analyzing correlations between compressive strength, rebound number and ultrasonic pulse velocity and the results are as follows. As a result of comparing error rate of existing expressions and this estimation expression, error rate of this estimation is reduced compared to existing expressions and has higher reliability. When conventional concrete expression is applied to admixture concrete, error rate occurs and then this study suggests the estimation expressions depending on types of admixture concrete.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.970-976
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• 2002

In this paper, the slump flow of the concrete, suspension, pH, corrosion effect, bleeding and the characteristics of coompressive strength were analyzed using antiwashout underwater admixture and antiwashout underwater agent+corrosion inhibitor mixed admixtures(1type). The results showed that there were no rare difference in physical properties but in the results of rapid corrosion tests there were lots of corrosion inhibitor ratio differences between concrete using only antiwashout underwater admixture and the corrosion inhibitor mixed(1type). In the case of only antiwashout underwater admixture 5.4%, the case corrosion inhibitor mixed(1type) 0.07%, the Antiseawater of the concrete which uses the Corrosion Inibitor Mixed(1type) appeared highly.