• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.62-69
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• 2012

This study investigates the engineering properties of the high strength concrete depending on dosages and types of shrinkage reduction agent. Test results showed that for the properties of fresh concrete, the addition of the conventional shrinkage reduction agent (SR) of 0.25% decreased slump flow up to 40% as compared with control concrete, whereas the addition of the emulsified waste cooking oil (EWCO) decreased slump flow of only 5% to 10%. Other properties of fresh concrete with the agents, namely air content, unit weight and setting time, were similar to the results of the control concrete. For the properties of hardened concrete, the compressive strength of the concrete with SR decreased at both early and later stage. However, the compressive strength of the concrete with EWCO was similar to the control concrete at early age, but decreased at later stage (up to 10% reduction at 28 days). For the effect of the agents on autogenous shrinkage of the concretes, the addition of EWCO decreased up to 33%, whereas that of SR decreased up to 29%. Hence, it can be said that the addition of EWCO in high strength concrete has an effect on reducing the autogenous shrinkage as compared with a conventional agent and only slight influence on the slump flow and air content of concrete. By taking all aspects of using EWCO, it is concluded that the optimum content of EWCO will be in the range of between 0.5% and 0.75%.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.34 no.5
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• pp.1-17
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• 2002

The immobilization and consolidation of the model coatings based on the plastic pigment and latex binder of known particle sizes were theoretically Studied in terms of the dense random packing of binary spheres and varying extent of latex film shrinkage. The porosity of the model coatings was calculated based on three proposed latex shrinkage models: Maximum, Minimum, and Linearly Decreasing Latex Shrinkage. The increasing extent of latex shrinkage was calculated up to the critical pigment volume concentration(CPVC) as a function of plastic pigment volume fractions, and the maximum latex shrinkage was estimated from the CPVC. Also, the number of pores and the average equivalent spherical pore diameters were calculated based on those proposed models. The opacity and gloss of the model coatings on polyester films were measured and their porosity was also determined by a simple coat weight-thickness method. As expected, various coating structure-property-composition relationships, such as opacity, gloss, porosity, etc., were shown to exhibit sharp transitions near the CPVC. The CPVC values determined by the opacity, gloss, and porosity vs. PVC relationships, respectively, agreed very well with each other. Especially, the CPVC's determined by the opacity and porosity vs. PVC curves were identical. The comparison between the theoretically calculated and experimental porosity values showed that the intermediate value between the maximum and minimum latex shrinkage would best fit the experimental porosity data. The effect of plastic pigment particle size on the optical properties and porosity of model coatings was also studied and it was observed that the coating opacity and porosity increased with increasing plastic pigment particle size, but the gloss decreased. The ink gloss of the uncalendered model coatings applied onto commercial sheet offset coated papers was shown to be affected by both the coating gloss and porosity: the higher the coating gloss, the higher the ink gloss, but the higher the coating porosity, the lower the ink gloss. Their printability was also studied in terms of the number of passes-to-fail and the rate of ink setting as a function of both plastic pigment volume fractions and plastic pigment particle sizes. A minimum crack-free temperature(MCR) of latex-bound coatings was proposed to better predict the behaviors of latexes as coating binders. The wet state of model coating dispersions, the surfaces of consolidated model coatings, and their internal structure were examined by both electron and atomic force microscopy, and their micrographs were found to be consistent with our immobilization and consolidation models.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.65-66
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• 2012

The cement used in the construction industry of the manufacturing process, large amounts of the greenhouse gas, CO₂ and is currently being studied for cement substitutes that reduce greenhouse gas issue. Therefore, the this study as a replacement for cement industrial by-product of blast furnace slag, red mud, silica fume and alkali-activator, using only inorganic composites without high-temperature calcination process were manufactured. The waste gypsum board micro powder added to compensate for the shrinkage cracks, the compressive strength and flow, and length change characteristics were investigated. Consequently, The setting time was shortened as GB added And liquidity was reduced. GB 2%, 7 days curing the added strength of specimens was the highest. Came out, and change the length of the Plain least.

• Polymer(Korea)
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• v.27 no.3
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• pp.189-194
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• 2003

Interfacial evaluation, damage sensing and cure monitoring of single carbon fiber/thermo setting composite with different curing processes were investigated using electro-micromechanical test. After curing, the residual stress was monitored by measurement of electrical resistance and then compared to various curing processes. In thermal curing case, matrix tensile strength, modulus and interfacial shear strength were higher than those of ultraviolet curing case. The shrinkage measured during thermal curing occurred significantly by matrix shrinkage and residual stress due to the difference in thermal expansion coefficient. The apparent modulus measured in the thermal curing indicated that mechanical and interfacial properties were highly improved. The reaching time to the same stress of thermal curing was faster than that of UV curing case.

• International Journal of Highway Engineering
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• v.14 no.4
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• pp.37-49
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• 2012

PURPOSES : This study is to investigate the fundamental properties of limestone added cement concrete for application of pavement. METHODS : As the production of Portland cement causes environmental problems, engineers have sought more environment-friendly concrete construction materials. Limestone powder can be used for concrete as a partial replacement of Portland cement. One of the great applications of limestone powder added cement concrete might be a cement concrete pavement since the concrete pavement consumes massive quantity of Portland cement. Experimental variables were different replacement level of limestone powder by 0% to 25% with 5% increment. Before hardening of fresh concrete, setting time and plastic shrinkage characteristics were investigated in addition to other basic properties. Properties of hardened concrete included compressive, tensile and flexural strength as well as drying shrinkage. RESULTS : The addition of limestone powder did not significantly affect the properties of fresh concrete. Strength deceased as the replacement ratio increased and when the replacement ratio was greater than 10% decrease rate increased. CONCLUSIONS : It was found that the partial replacement of the limestone powder to cement in pavement materials can be positively considered as its mechanical properties show comparable performance to those normal concrete.

• Journal of Korean Society of Steel Construction
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• v.12 no.2 s.45
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• pp.133-142
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• 2000

This study deals with behavior of steel box girder bridges according to the concrete slab casting sequences and sectional types. The time dependent behavior of bridges caused by the differential setting of slab concrete resulting from time gap for each part of slab deck in a sequential placing method produces is analyzed. In correlation studies between girder section types and placing sequences, time dependent effects of concrete creep and shrinkage are implemented in the analytical model proposed in the previous study. Finally, field recommendations in terms of concrete slump and relative humidity are suggested to prevent early transverse cracking of concrete slabs.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.246-252
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• 2021

The basic properties and volume stability of the ultra-rapid setting cement mortar containing low-quality recycled aggregate with a higher water absorption and lower specific gravity than relavent Korea Standard were experimentally confirmed. The mix proportion without recycled aggregate followed that of the general repair mortar used in the fields. 15% and 30% of the fine aggregate was substituted by the recycled aggregate in the mixtures with and without latex emulsion, and properties and characteristics of the mortar including mortar flow, setting time, compressive and flexural strength, and linear deformation under sealed and unsealed conditions were evaluated. It was confirmed that when low-quality recycled aggregate was used by 30%, there were risks of decrease in the early-age strength by up to 50% within 24h and increases in drying shrinkage by up to 2 times for 2 weeks compared to the the mixtures without the recycled aggregate.

• Journal of the Korean Society of Clothing and Textiles
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• v.30 no.2 s.150
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• pp.255-265
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• 2006

The purpose of this study was to examine the dyeing properties of four kinds of composite yams that were twisted in different processes. The composite yarns consist of acetate and functional polyester in ratio of 70 : 30. The composite yams were dyed at 100$^{circ}C$ and 125$^{circ}C$ using three types of dyes, disperse dyes for acetate fiber, PET fiber and PET-acetate blended fiber, in the three primary colors. The exhaustion($\%$) and K/S value were observed for each case. Also the effects of four different twisting processes to dyeing properties and physical properties were examined. Regardless of twisting methods, the composite yarns that were dyed at 125$^{circ}C$ had higher exhaustion($\%$) than those were dyed at 100$^{circ}C$ with all three types of dyes; However, tendency of the K/S value after reduction cleaning process was measured at 100$^{circ}C$ and the value measured 125$^{circ}C$ had a great difference with disperse dyes for acetate and dyes for PET. The difference of the K/S values of composite yarns, when dyed at 100$^{circ}C$ and 125$^{circ}C$ with disperse dyes for PET-acetate blended fiber, was almost negligible. According to twisting methods K/S values were in the following order: AP1 > AP3 > AP4> AP2. This means that AP1, treated at 220$^{circ}C$, had the highest K/S value and K/S value becomes higher as the yam is higher twisted and becomes lower as lower twisted. On the other hand, the dry shrinkage and wet shrinkage showed low shrinkage rate when the twist was high and steam setting temperature was high.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.62-68
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• 2009

This research examined engineering properties of high performance concrete, when substitution rate of BS increases. A summary of the test result is as follows. The fluidity of unset concrete increases as the substitution rate of BS increases. The amount of air is reduced more or less, but it seems that enough amount of air can be secured by using more air-entraining agent. Setting time is dramatically delayed as the substitution rate of BS increases. The compressive strength of hardening concrete was weaker than OPC before 28 days passes, due to latent hydraulic property of BS. However, after 28 days, it shows same or better property, which is exceptional for the practical uses of hyper strength concrete. Changes in drying shrinkage rate is quite much, because when hydration happens, the amount of free water in concrete increased as W/B gets larger. The amount of drying shrinkage increases as BS substitution rate increases, but every composition shows less than $-500{\times}10^{-6}$, which is relatively fine.

• Journal of the Korea Institute of Building Construction
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• v.18 no.6
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• pp.551-558
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• 2018

This study evaluate the fluidity and hardening properties of mortar by replacement ratio of ferronickel slag powder to estimate the applicability of ferronickel slag powder for cement replacement materials. Ferronickel slag powder was replaced by 0, 5, 10, 15 and 20% of the cement weight. In addition, blast furnace slag powder and fly ash were also used for comparing with the mixtures using ferronickel slag powder. As the test results, the micro-hydration heat of the mixture containing the ferronickel slag powder was lower than that of the mixtures containing the same amount of blast furnace slag powder and fly ash. The flow of the sample with ferronickel slag powder was relatively higher than the other mixtures. In all ages, the compressive strength of the mixture with ferronickel slag powder and fly ash was similar to that of the mix containing only fly ash. In case of drying shrinkage, the mixture containing ferronickel slag powder exhibited lower drying shrinkage than the mixture using blast furnace slag powder, and similar to the mixture containing fly ash.