• Journal of the Korean Chemical Society
• /
• v.21 no.4
• /
• pp.284-292
• /
• 1977

Epoxy-methacrylate prepolymer was synthesized from methacrylic acid and a diglycidyl ether type low molecular weight epoxy resin, and the electron beam curing of the prepolymer was studied using styrene and polyethyleneglycol dimethacrylates as comonomers. The esterification was carried out quantitatively without any side reaction adding more than 250∼300ppm hydroquinone and less than $1{\%}$ (wt) triethanolamine by wt. of methacrylate acid, respectively. In the radiation curing under air atmosphere, the maximum gel fraction was observed at 10∼$30{\%}$ monomer contents. The rate of gel formation was decreased by the presence of unreacted epoxy group and acid in the prepolymer and increased with increasing degree of polymerization of polyethyleneglycol block in the dimethacrylates. Considerable oxygen effect in the curing, particularly when polyethyleneglycol dimethacrylate was used as a comonomer, was recognized through the differences of the product properties, though no remarkable differences were found in the rate of gel formation in air and nitrogen atmosphere.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.21 no.2
• /
• pp.56-62
• /
• 2013

Organic wastes are not disposing object but renewable resources. One of those ways of rendering to resources, composting is environmentally friendly way as to aspect of recycling of resources. Regardless of ways, composting goes through the main processes which are fermentation process and curing process. In the study, mobile composting device was developed with the experiments which were performed to solve the problems of fermentation and curing process. Since reaction vessel is rotated, it does not cease in the middle of agitation because of foreign. In addition, it mixed as well. With maintaining uniform temperature of reaction vessel by controlling amount of air, fermentation and curing are easy to use. Its economic feasibility is better than the existing fermentation equipments. Furthermore, it benefits to reduce the personnel and materiel maintenance cost, and mass produce composting product which use organic waste. Especially, although it needs less space, it has effect to provide transferable composting device with available area to increase by contacting organic waste to air.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.807-812
• /
• 2001

This study is peformed for checking the limitation and application of each curing/heating methods on cold-weathering mat foundation construction, considering temperature control, early strength security and temperature declination range limit, by means of concrete material properties and thermal analysis technique that were published previously. In the result of this analysis, we checked the open air temperature and mat depth that are possible to apply each curing/heating methods on cold-weathering construction and found curing/heating time of each methods that is able to prevent early aged freezing damage and thermal crack

• Proceedings of the Korea Concrete Institute Conference
• /
• 1997.04a
• /
• pp.301-307
• /
• 1997

This paper is evaluated for properties of aggregate and antiwashout admixture not only to minimize segregation and water contamination of underwater concrete but also to meet concrete quality required. Two antiwashout admixtures used in this study were available domestically and slump flow, pH, setting time, and filing property of fresh concrete and the compressive strength, flexural strength under water and in the air under 2 different curing conditions ($10^{\cire}C$ and $20^{\cire}C$ ) were measured. Compressive strength ratio of specimens cured in and water temperature $10^{\cire}C$ /$20^{\cire}C$ added HPEC and HPMC was 64% and 89%, respectively. Relative compressive strength of 2 kinds observed higher concrete added HPEC, 3% at $10^{\cire}C$ curing temperature, 34% at $20^{\cire}C$ . The flexural strength of specimens made under water was 1/4~1/6 of compressive strength similar to the existing data in the literature.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05b
• /
• pp.465-468
• /
• 2005

This Study is concerned workability and the physical properties for practical use of waste concrete powder originated from the manufacturing progress of waste concrete aggregate and it apply to concrete tile. Also because it is important that concrete tile has to ensure the surface moisture stability, for solving the problems aplied curing method is air-dried and autoclave curing. As the result, the physical properties, such as fluent properties, compressive strength, surface hardness and surface glossiness, were decreased with increase of replacement ratio of waste concrete powder, also surface stability was weaked about moisture. But by autoclave curing, it is possible that compressive strength and surface hardness increased, and surface moisture stability is ensured.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.03a
• /
• pp.483-490
• /
• 2002

A massive amount of marine clay produced as dredging of coast and sea bed is often dumped in open sea and filled in pond. The treatment of marine clay demand a large area and make fatal environmental problems for echo system. This research work intend to manufacture a light-weight landfill materials which are produced by mixing the dredged marine clay with various amount cement and foam. An extensive Uniaxial and Triaxial compression test are carried out to investigate the strength characteristics of the light-weight cement mixed marine clay with foam under various test conditions. The results indicated that the required unit weight has been achieved with negligible change after 28days curing time in water. It is also recognized that the compressive strength of light-weight landfill materials linearly decrease with increasing initial water content, and the rate of strength decrease with increasing initial water content in water curing was smaller than that of air curing Futhermore, the rate of strength decreased with increasing initial water content, however, the rate become smaller as cement content increased.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.3
• /
• pp.338-347
• /
• 2021

This paper aims to evaluating the interlayer strength of 3D-printed concrete with interlayer reinforcement. According to lap splices, two reinforcement methods were considered. One method did not include lap splices of interlayer reinforcement, but the other method included lap splices with length of 40mm. In addition, two different curing conditions were applied: air curing conditions and water curing conditions. The compressive, splitting tensile, and flexural tensile strengths of 3D-printed concrete specimens were measured in three loading directions with different reinforcement methods and curing conditions. Splitting and flexural tensile strengths decreased considerably when tensile stresses acted over the interlayers of 3D-printed concrete specimens. However, the flexural tensile strength or interlayer bonding strength of the printed specimens increased significantly at the interlayers when the longitudinal interlayer reinforcement penetrated printed layers. Interlayer bonding strength of printed concrete decreased after air curing treatment was applied because interlayers of printed concrete with more pores formed by the air cu ring conditions are more vulnerable to the load.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.1
• /
• pp.139-146
• /
• 2015

The amount of by-product from sulphur increases in domestic industrial facilities. However, the amount of its consumption is limited so that the amount of unused sulphur continues to increase. Therefore, in this study, the use sulfur polymer as the concrete surface protecting material was conducted. The compressive strength showed that as the substitution ratio of filler increased up to 40%, the compressive strength also increased. A high compressive strength was shown at the curing temperature of $40^{\circ}C$ (SS, FA) and $60^{\circ}C$ (OPC) according to the type of filler. The difference of compressive strength between air dry curing and water curing was insignificant so that there was no significant influence of moisture during curing process. The evaluation result of bond strength showed that the highest bond strength was shown at the air-dry condition of $40^{\circ}C$ regardless of type of filler. Bonding didn't occur properly during water curing in comparison to air dry curing. Also, in case of the specimen cured at $60^{\circ}C$, discoloration and hair cracks appeared due to the influence of temperature, and the highest bond strength was shown at the substitution ratio of 20% (SS, FA) and 30% (OPC) according to the type of filler. The releasing test result of harmful substance showed that no harmful substance was released, so there is no harmfulness in the surface protecting material using sulfur polymer. As a conclusion drawn in this study, it is most appropriate to substitute silica by approximately 20%, mix and cure at the air-dry condition of $40^{\circ}C$ in order to use sulfur polymer as the surface protecting material.

• Geomechanics and Engineering
• /
• v.2 no.4
• /
• pp.321-335
• /
• 2010

This article describes a laboratory research on stabilizing tropical peat using ordinary Portland cement (OPC) as a binding agent, and polypropylene and steel fibres as chemically inert additives. California bearing ratio (CBR) and unconfined compressive strength (UCS) tests were carried out to evaluate the increase in the strength of the stabilized samples compacted at their optimum moisture contents and air cured for up to 90 days. The results show that the UCS values of stabilized peat samples increased by as high as 748.8% by using OPC (5%), polypropylene fibres (0.15%), and steel fibres (2%). The CBR values of the samples stabilized with OPC (5%), polypropylene fibres (0.15%), and steel fibres (4%) showed an increase of as high as 122.7%. The stabilized samples showed a shrinkage in volume upon air curing and this shrinkage was measured by an index called, volume shrinkage index (VSI). The highest VSI recorded was 36.19% for peat without any additives; and the minimum was 0% for the sample containing 30% OPC, 0.15% polypropylene fibres and 2% steel fibres. The technique of stabilizing peat with OPC, polypropylene and fibres, coupled with air curing, appears to be cost-effective compared with other frequently used techniques.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2002.10a
• /
• pp.177-180
• /
• 2002

This study is performed to properties of ready mixed concrete (RMC) in site. The unit weight of the B company's RMC is range from $2,308kg/m^3\;to\;2,355kg/m^3$ and that of the J company's RMC is range from $2,288kg/m^3\;to\;2,310kg/m^3$. The compressive strength of B company's RMC of curing age of 7 days is range from $191kgf/cm^2-232kgf/cm^2$ and that of curing age of 28days is $273kgf/cm^2{\sim}306kg/cm^2$. The compressive strength of J company's RMC of curing age of 7 days is range from $151kgf/cm^2{\sim}177kgf/cm^2$ and that curing age of 28 days is range from $215kgf/cm^2{\sim}234kgf/cm^2$. The B and J company's air content is range of $3.2{\sim}5.2%$. The content of Chloride of the Band J company's is range from each $0.026kg/m^3{\sim}0.046kg/m^3\;and\; 0.034kg/m^3{\sim}0.069kg/m^3$, respectively.