• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.31 no.1
• /
• pp.53-61
• /
• 2018

Ballast track requires constant maintenance work due to progress of track irregularity. Fast Hardening Track(FHT) has been developed to reduce the maintenance effort done by injecting fast hardening mortar in aged ballast to convert slab track. For the application of FHT to a railway bridge, post-installed anchors should be placed at center of the track segment to fix it on bridge. This paper presents track-bridge interaction analysis results with FHT considering stiffness and strength of post-installed anchor, age of FHT concrete and friction between FHT and bridge deck surface. Based on the analysis results, this study suggests when is good to install the anchors and allow normal operation of passing train.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1993.04a
• /
• pp.22-25
• /
• 1993

The study of recycled aggregate concrete in which demolition waste is utilized to produce aggregate for new concrete, can contribute to the solution of two problems, The first is the shortage of aggregate from river, and the second is the waste disposal problem. In comparison with natural aggregate concrete, recycled aggregate concrete shows reductions in compressive strength , tensile strength, vending strength , shear strength and increases in drying shrinkage and creep. Recycled aggregate concrete may also be less durable due to increase in porosity and permeability. The purpose of this study is to investigate and analyze the variation of engineering properties according to replacement proportion of recycled aggregates and applicability of non-destructive test in the gardened recycled concrete.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1994.10a
• /
• pp.127-132
• /
• 1994

This study attemps to investigate the influence of heat of hydration occured during hardening on the strength development of high strength concrete. The concrete design strengths of 500kg/$\textrm{cm}^2$ and 700kg/$\textrm{cm}^2$ were considered to simulated the square columns having $80\times80cm$ and $100\times100cm$, respectively. Both standard curing and field curing specimen were prepared at the specified ages, and the cores were drilled out from the structure. The thermal sensors were installed into the specimen to measure the heat of hydration process occurred during the hardening. This paper tries to uncover the relationship between the temperature history of the concrete and strength development. The correlation of core strength and specimen strength with curing condition is also discussed. Further research is desired to enlight the relationship between strength and heat of hydration of high strength concrete.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1995.04a
• /
• pp.84-87
• /
• 1995

Production of high strength concrete requires a low water-cement ratio and this leads to the high cement content. Mineral admixture like fly ash(FA) is often cheaper than ordinary portland cement(OPC) and this factor in combination with possible improvement in workability and moderation of the heat evolution of the cement-rich mixes tends to encourage its use. The other mineral admisture that its use has been widly advocated is silica fume that increases compressive strength due to its pozzolanic reaction. The objective of this study is to assess the contribution of mineral admixtures(FA, SF) to the workability and the strength of concrete with low water-binder ratios. In this experimental study that investigates and analyzes the properties of fresh concrete. it is presented that using admixtures like flyash and silica fume as binding material increases properties of high strength flowing concrete having very low water cementitious ratios of 0.25 and 0.30.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1989.10a
• /
• pp.21-24
• /
• 1989

The effect of superplasticizing agents on the mechanical properties in hardened concrete have been analyzed and investigated under various mix proportions of water cement ratio of 0.40, 0.50, 0.60 and 0.70, Superplasticizing agents of NL-4000, and Rheobuild-716, and addition rate of sp. agents of 0.0, 0.5, 1.0, 1.5 and 2.0 in the practical range. It is the aim of this study to provide the fundamental data on the compressive strength, dynamic and static modulus of elasticity, stress and strain curve of hardened concrete comparing with base concrete and conventional concrete for the practical use and research data accumulation of superplasticized concrete in the side of development of concrete construction technology and management.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1993.10a
• /
• pp.35-38
• /
• 1993

Although bonding material content of the high strength flowing concrete is very important in engineering properties, in rich mix concrete increasing the bonding material content may not follow more good properties. This study is to investigate the influence of the bonding material content affecting on the engineering properties of high strength flowing concrete, and this paper is to analyze the properties of hardened concrete. The results reveal that the strength of concrete having loss bonding material content is higher than that of concrete having more bonding material content, and that in proportion to increasing of concrete strength brittleness factors decrease, and that the static modulus of elasticity in this study is less than that in specification.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1995.10a
• /
• pp.256-261
• /
• 1995

Large-scaling recycling of demolished concrete will concrete will contribute not only to the solution of a growing waste disposal problem, it will also help to consweve natural resoures of sand and gravel and to secure future supply of reasonly priced aggregates for building and other construction purposes within large urban areas. Because recycled aggregate particles consits of substantial amount of relatively soft cement paste component, it is less resistant to mechanical actions. With this view in mind, to obtain a reference data for the development of recycling system and to a basic data the guiedline of recycled aggregate concrete construction and engineering properties of recycled aggregate concrete according to the factors, such as blending ratio of recyced aggregete with the natural aggregate, addition to the factors, such as blending ratio of recycled aggregete with the natural aggregate, addition of flyash, water coment ratio.

• Applied Chemistry for Engineering
• /
• v.21 no.4
• /
• pp.457-462
• /
• 2010

In this research, the effects of the concrete superplastizers on the wettability of cement particle and concrete strength were studied. The wettability of the cement particles strongly depended on the type of the superplastizer. When the superplastizer had a higher wettability with the cement particles, it revealed a good fluidity of the concrete mortar and a higher concrete strength. Non-ionic superplastizers (polycarboxylic type) had a relatively good performance on the mortar fluidity and concrete strength properties compared to anionic superplastizers (lignosulfate, sulfonated naphthalene formaldehyde, sulfonated melamin formaldehyde). It was observed that the blending of the polycarboxylic and the lignosulfate type concrete superplastizers resulted in synergistic effects on the concrete mortar fluidity and concrete strength properties.

• Journal of the Korea Concrete Institute
• /
• v.28 no.3
• /
• pp.309-316
• /
• 2016

In this study, performance of hardening accelerator types which promote setting and hardening of cement has been reviewed in order to develop early age strength of concrete with compressive strength of 21~27 MPa after examination of strength development of the concrete at early age according to curing temperature and unit cement(binder) content. As results, soluble mineral salt showed better hardening acceleration effect than organic salt in the scope of this study. Also, hydration reaction accelerating effect of $C_3S$ by Soluble mineral salt is effective on development of early age compressive strength and it was shown that the Pt's hydration reaction accelerating effect was the best. Construction duration reduction can be expected by securing compressive strength for prevention of early aged freezing damage in 25hour-curing time under curing temperature at $15^{\circ}C$. Also, it was shown that compressive strength of specimen cured at $5^{\circ}C$ was similar with plain specimen cured at $10^{\circ}C$. Therefore, it is expected that fuel costs and carbon dioxide can be reduced when the same construction duration is considered.

• Magazine of the Korea Concrete Institute
• /
• v.17 no.2 s.85
• /
• pp.48-55
• /
• 2005