• Elastomers and Composites
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• v.38 no.1
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• pp.65-71
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• 2003

Influence of low molecular weight styrene-butadiene rubber (liquid SBR) on properties of a silica-filled styrene-butadiene rubber (SBR) compounds was studied. Viscosity of the silica-filled SBR compound decreased by adding the liquid SBR. The crosslink density decreased and the cure rate became slower as the liquid SBR content increased. The modulus and tensile strength decreased while the elongation at break became longer by increasing the liquid SBR content. The abrasion losses were nearly the same irrespective of the liquid SBR content. This might be due to the improvement of silica dispersion by adding the liquid SBR. Considering the experimental results, it was believed that addition of small amount of the liquid SBR (less than 5 phr) was desirable to improve properties of silica-filled SBR compounds.

• Resources Recycling
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• v.27 no.6
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• pp.30-37
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• 2018

A series of experiment was conducted to evaluate basic performances of low-pH, anti-washing grouts incorporating gypsum which applied for reinforcing underwater cavities in limestone- grounds. Various types of mix proportions were designed and the fluidity, strength and environmental impact of these mixtures were evaluated. The flowability was evaluated under two conditions, i.e., flows without and with pressing, respectively. Strength was measured for the hardened mixtures fabricated under conditions of air and water injections. The environmental impacts including the pH of the suspension and the suspended solids concentration for the mixtures were evaluated. The low pH of fresh mixture suspension, below than 10, was achieved by incorporation of gypsum. The mix proportions of cement-quartz powder-gypsum binders and chemical agents resulted in mortar natural flow 7-10 cm and uniaxial compressive strength 4 MPa were derived.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.299-306
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• 2016

In this research, influence of low quality aggregate on engineering properties of concrete was evaluated experimentally. From the experiment, the fresh properties of slump and air content were controlled with unit water and AE dosage and all mixture were designed to have similar fresh properties of slump and air content with various quality of aggregate. Under this conditions, comparing with the mixture with high quality aggregate, the mixture with low quality aggregate showed the unit water and AE dosage were increased about 18 and 98%, respectively, because of poor grading and quantity of fines. For compressive strength, the low quality aggregate, specifically, exploded debris, clay sand, and sea sand contributed on decreasing compressive strength about 20~35%. Additionally, the concrete mixture including low quality fine and coarse aggregate showed adverse quality in not only compressive strength but also durability of freeze-thawing resistance, drying shrinkage, carbonation, and chloride ingression. Therefore, it is considered that for low quality aggregate, extra treatment processes such as washing or controlling gradation, and regulation to limit the use of low quality aggregate are needed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.96-102
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• 2019

When GGBFS(Ground Granulated Blast Furnace Slag) with high blaine is incorporated in concrete, compressive strength in the initial period is improved, but several engineering problems arise such as heat of hydration and quality control. In this paper, compressive strength and durability performance of concrete with 3,000 Grade-low fineness slag are evaluated. Three conditions of concrete mixtures are considered considering workability, and the related durability tests are performed. Although the strength of concrete with 3,000 Grade slag is slightly lower than the OPC(Ordinary Portland Cement) concrete at the age of 28 days, but insignificant difference is observed in long-term compressive strength due to latent hydration activity. The durability performances in concrete with low fineness slag show that the resistances to carbonation and freezing/thawing action are slightly higher than those of concrete with high fineness slag, since reduced unit water content is considered in 3,000 Grade slag mixture. For the long-term age, the chloride diffusion coefficient of the 3000-grade slag mixture is reduced to 20% compared to the OPC mixture, and the excellent chloride resistance are evaluated. Compared with concrete with OPC and high fineness GGBFS, concrete with lower fineness GGBFS can keep reasonable workability and durability performance with reduced water content.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.6
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• pp.127-134
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• 2001

In order to expand agricultural lands in the western and southern coasts of Korean Peninsula, coarse soils excavated from hillsides have been used as fill materials for reclamation. In order to tackle with the problems and to confirm availability, research on soil improvement involve mixing cement to the fine wet soils. Required undrained shear strength$(C_u)$ for fill material was analysed to be 0.34~1.2 $kgf/cm^2$. It has been known that when cement is added to high water content marine clay its unconfined compression strength increased to 2 $kgf/cm^2$. Consolidation results show that pre-consolidation pressure increased to 1.8 $kgf/cm^2$and 3.4 $kgf/cm^2$ with the addition of 3% and 5% of cement respectively. This result shows that low-height embankments could be constructed without significant compression. Since the effectiveness of improvement may be different site by site, the mix design for each site is necessary in order to optimize it. The process is first to determine aimed shear strength and then optimum mix ratio of cement after carrying out a series of tests.

• Elastomers and Composites
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• v.37 no.3
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• pp.177-182
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• 2002

For low-smoke-type polyolefin compound, LDPE, EVA, and EEA as base resin, magnesium trihydrate, alumina trihydrate, and red phosphorous as flame retardant and MAH type compatibilizer were applied. The amount of each component was changed to find out optimum composition. Mechanical properties were obtained by tensile test and residual stress after aging and flame retardancy was evaluated by smoke density, LOI(Limit Oxygen Index), and UL-94 test. SEM was used for the investigation or morphology and halogen contents were obtained by measuring the amount of HCI. Two kinds of halogen free compositions for flame retardant and low smote resin were found and it is expected to be applied for various purposes.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2008.11a
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• pp.559-561
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• 2008

본 연구는 저토심 저관리를 목적으로 한 옥상녹화시스템에 각시둥글레와 흰줄무늬사사를 식재한 후, 식물생육과 토양수분함량의 평가를 통해 적정 토양배합비와 토심을 추출하고자 실시하였다. 흰줄무늬사사의 경우, 적은 개체로도 높은 피복율을 나타냈으며, 7cm 실험구를 제외한 모든 실험 구에서 양호한 생장량을 보였다. 특히, 배합비율 6:2:2 실험구에서 초장, 근원직경, 엽폭, 엽길이, 엽병길이, 착엽수 모두 가장 높게 나타났다. 각시둥글레는 높은 고사율을 보여 옥상녹화에는 적합하지 않은 것으로 나타났다.

• Korean Journal of Poultry Science
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• v.32 no.1
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• pp.67-72
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• 2005

Forty-wk-old 480 ISA Brown layers were used in a 10-wk feeding trial to investigate the effects of additional various levels of limestone to a low calcium diet without any calcium additives on the performance of laying hens. There were significant differences in average egg weight (P<0.05) without any specific trend among treatments and hen-day egg production was not influenced by the dietary treatments. Daily intake and conversion per kg egg of feed excluded the calcium supplement were significantly reduced (p<0.05) as the level of additional calcium supplement increased in both types of layer diet, while those of feed included the calcium source were significantly increased (P<0.05) as the level of additional calcium supplement increased. Egg specific gravity, eggshell breaking strength and thickness were increased as the level of additional calcium supplement increased, however the significant differences were found only in egg specific gravity It would be possible to reduce the daily feed intake and feed conversion and to improve the eggshell quality by feed the low calcium diet devoid of calcium supplement from the conventional laying hen diet and by supply the additional calcium source at 3 to 4 p.m. instead of the continuous feeding of conventional high calcium diet.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.1-7
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• 2018

This study examined the effect of binder-to-soil ratio(B/S) and water-to-binder ratio(W/B) on the flow and compressive strength development of soil concrete using high-volume supplementary cementitious materials. As a partial replacement of ordinary portland cement, 10% by-pass dust, 40% ground granulated blast-furnace slag, and 25% circulating fluidized bed combustion fly ash were determined in the preliminary tests. Using the low-cement binder incorporated with clay soil or sandy soil, a total of 18 soil concrete mixtures was prepared. The flow of the soil concrete tended to increase with the increase in W/B and B/S, regardless of the type of soils. The compressive strength was commonly higher in sandy soil concrete than in clay soil concrete with the same mixture condition. Considering the high-workability and compressive strength development, it could be recommended for low-cement soil concrete to be mixed under the following condition: B/S of 0.35 and W/B of 175%.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.1
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• pp.17-24
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• 2024

The characteristics of low-heat concrete, mixed with ground blast furnace slag and ferronickel slag aggregate, were analyzed. Moreover, the applicability of this concrete for mass concrete in LNG storage tanks was examined. Initially, the study investigated the characteristics of fresh and hardened concrete. Subsequently, the temperature rising curve was obtained. Utilizing the obtained parameters from the curves, a series of thermal stress analyses for the LNG storage tank were conducted to assess the risk of cracking. The results confirmed that concrete mixtures incorporating ground blast furnace slag and ferronickel slag aggregate not only exhibited sufficient workability but also achieved a compressive strength of approximately 40 MPa within 28 days. Furthermore, the concrete demonstrated a lower terminal heat rise and a faster heat generation rate compared to low-heat Portland cement concrete. An analysis of thermal stress in various sections of the LNG tank validated a low risk of cracking.