• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2005.05a
• /
• pp.93-98
• /
• 2005

The purpose of this study was to analyze the compression strength research by aerated concrete as mixing ratio This Study used foaming-agent and produced aerated concrete by pre-foam way that is used in construction site. An experiment changes unit cement amount, w/c and the glass fiber mixing rate and 'measured capacity change, unit capacity weight and compressive strength. The results obtained from experimental study are as following; Research to reduce unit capacity weight in condition more than unit cement amount 500kgf is considered should be gone side by side. The highest compressive strength result appeared in aerated concrete that cement amount 600kgf and w/c ratio $45\%$, $50\%$. compressive strength was increased maximum $34%$ when glass fiber $0.7\%$ addition cause by coherence enlargement to enlargement of cement paste and glass fiber addition per unit volume

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.657-660
• /
• 2008

The mechanical properties of concrete such as compressive strength, tensile strength, and modulus of elasticity, are considerably influenced by various factors including locality. The material property prescriptions in national concrete design codes should reflect them. In Korea, they have not been studied systematically yet. A new performance-based design code is being prepared in Korea as a government-supported project and it has a plan to make new material prescriptions adopting domestic research results. As a starting point for the research on material properties, the statistical characteristics of mechanical properties of concrete are studied. In this paper, a probabilistic model of compressive strength, relationship between compressive strength and splitting tensile strength and compressive strength and elastic modulus are proposed based on experimental data.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.3 no.3
• /
• pp.79-85
• /
• 2004

The lightness of components required in automobile and machinery industry is requiring high strength of components. In particular, fatigue failure phenomena, which happen in metal, bring on danger in human life and property. Therefore, antifatigue failure technology takes an important part of current industries. Currently, the shot peening is used for removing the defects from the surface of steel and improving the fatigue strength on surface. Therefore, in this paper the effect of compressive residual stress of spring steel(JISG SUP-9)by shot peening on fatigue crack growth characteristics in stress ratio(R=0 1, R=0 3, R=0 6)was investigated considering fracture mechanics. By using the methods mentioned above, I arrived at the following conclusions: (1) The fatigue crack growth rate(da/dN) of the shot peening material was lower than the unpeening material And in stage I, ${\Delta}K_{th}$, the threshold stress intensity factor, of the shot peening material is high in critical parts unlike the unpeening material. (2) Fatigue life shows more Improvement in the shot peening material than in the unpeening material. And compressive residual stress of surface on the shot peening processed operate the resistance of fatigue crack propagation.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2016.05a
• /
• pp.203-204
• /
• 2016

In this research, it used cement power and reduction slag, which generates high hydration heat in hydration reation without heat cure below -5℃ degree. Purpose of final research is preventing freezing and thawing by making the compressive strength 5MPa in 3days below zero temperature due to own heat of concrete. and it is the result of physical characteristic and thermal property evaluation of reduction slag. Because reduction sag generates high hydration heat, compressive strength development is excellent. By generating highly Hydration heat by C₁₂A₇ and C₃A in reduction slag, compressive strength is developed in low temperature. In case of displacing only reduction slag without SO₃, it is indicated that quick-setting occurs by shortage of SO₃. For preventing quick-setting, gypsum is used essentially. According to this research result, in case of using reduction slag and gypsum as a ternary system, Compressive strength developed 5MPa in 3days below zero temperature. It is identified to prevent early frost damage of concrete below zero temperature.

• Journal of the Korea Furniture Society
• /
• v.12 no.1
• /
• pp.47-55
• /
• 2001

Violin bridge blank cut from maple wood with good quality has typical pattern of the radial direction in the side edge with minimal dispersion. This experimental study was designed and carried out to examine the effect of the physical and macroscopical characteristics on the compressive creep of violin bridge blank which had been imported from European manufacturer. This research arose from the idea that the maple solid wood with heterogeneous wood density and ray direction in the side edge would have uneven rheological property of violin bridge blank which is supposed to be pressed by the tension of strings. Experimentally, the compressive creep of bridge blank became smaller with the higher density of imported maple wood and showed clear density-dependence for the duration of load under the string tension of 5 kgf. Every bridge blank showed the behavior of primary creep stage(stress stabilization) having logarithmic regression creep curve with high correlation coefficient under the designed stress level. Even though the relationship between compressive creep and ray direction on the side edge of bridge was not so clear contrary to expectation, we could conclude that wood density and ray direction should be the quality decisive factors affecting the acoustical characteristics and performance of the bridge, the core member of violin-family bow instruments.

• International Journal of Concrete Structures and Materials
• /
• v.3 no.1
• /
• pp.25-32
• /
• 2009

A non-destructive testing (NDT) method for evaluating physical properties of concrete including the compressive strength is highly desirable. This paper presents such an NDT method based on measurement of electromagnetic (EM) properties of the material. Experiments are carried out on cement mortar with different water/cement (W/C) ratios. Their EM properties including the conductivity and the dielectric constant are measured at different exposure conditions and curing periods over a wide frequency range of the EM wave. The compressive strength of these specimens is also tested. It is found that both the conductivity and the dielectric constant increase as the W/C ratio decreases and the curing period increases, which lead strength development in the specimens. A linear correlation is observed between the averaged EM properties over the 5 to 20 GHz frequency range and the measured compressive strength, demonstrating the effectiveness of the EM property-based NDT method in evaluating strength of OPC mortar.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.54 no.5
• /
• pp.43-47
• /
• 2012

A evaluation for the strength of rock includes a lot of uncertainty due to existence of discontinuity surface and weakness plain in the rock mass, so essential test results and other data for the resonable strength analysis are absolutely insufficient. Therefore, a analytical technique to reduce such uncertainty can be required. A probabilistic analysis technique has mainly to make up for the uncertainty to investigate the strength of rock mass. Recently, a artificial neural networks, as a more newly analysis method to solve several problems in the existing analysis methodology, trends to apply to study on the rock strength. In this study the unconfined compressive strength from basic physical property values of sedimentary rock, black shale and red shale, distributed in Daegu metropolitan area is estimated, using the artificial neural networks. And the applicability of the analysis method is investigated. From the results, it is confirmed that the unconfined compressive strength of the sedimentary rock can be easily and efficiently predicted by the analysis technique with the artificial neural networks.

• Geomechanics and Engineering
• /
• v.19 no.4
• /
• pp.307-314
• /
• 2019

Light construction waste (LCW) particles are pieces of light concrete or insulation wall with light quality and certain strength, containing rich isolated and disconnected pores. Mixing LCW particles with soil can be one of the alternative lightweight soils. It can lighten and stabilize the deep-thick soft soil in-situ. In this study, the unconfined compressive strength (UCS) and its mechanism of Construction Waste Stabilized Lightweight Soil (CWSLS) are investigated. According to the prescription design, totally 35 sets of specimens are tested for the index of dry density (DD) and unconfined compressive strength (UCS). The results show that the DD of CWSLS is mainly affected by LCW content, and it decreases obviously with the increase of LCW content, while increases slightly with the increase of cement content. The UCS of CWSLS first increases and then decreases with the increase of LCW content, existing a peak value. The UCS increases linearly with the increase of cement content, while the strength growth rate is dramatically affected by the different LCW contents. The UCS of CWSLS mainly comes from the skeleton impaction of LCW particles and the gelation of soil-cement composite slurry. According to the distribution of LCW particles and soil-cement composite slurry, CWSLS specimens are divided into three structures: "suspend-dense" structure, "framework-dense" structure and "framework-pore" structure.

• Journal of Ceramic Processing Research
• /
• v.19 no.5
• /
• pp.407-412
• /
• 2018

In this study, we have made a cement based inorganic insulation material and added CSA (Hauyne Clinker) to reduce the demolding time and enhance the handling workability. CSA contents were varied by 0%, 1%, 3%, 5% and the atmospheric steam curing was tried for enhancing the compressive strength. As the CSA contents are increased to 5%, a rapid reaction of hydration caused the sinking of the slurry. So, the setting-retarder was added to control the reaction of hydration. By this, the sinking of the slurry was controlled but the height of the green body after expansions was a little bit lowered. In the CSA-added slurry, it was possible to demold within 24 hours and in case of CSA 5%-added, the sufficient workability was secured. Atmospheric steam curing (temperatures $-40{\sim}80^{\circ}C$, for 6~10 hrs.) was attempted to improve the compressive strength and found that an excellent strength of 0.25 MPa was achieved at $80^{\circ}C$ for 8 hrs. Specific gravity was about $0.12{\sim}0.13g/cm^3$ and heat conductivity was about 0.045 W/mK in all specimens. This strategy significantly improves the compressive strength of CSA 5%-added specimen up to 25% compared to without CSA added specimen.

• Composites Research
• /
• v.31 no.6
• /
• pp.421-428
• /
• 2018

In order to optimize the prepreg compression molding (PCM) process, the forming simulation is required to cope with any problems that may be raised during the process. For the improvement of simulation accuracy, the input data of material property should be measured accurately. However, most studies assume that the compressive properties of the prepreg are identical to the tensile properties without quantifying them separately. Therefore, in this study, the in - plane compressive properties of the prepreg are presented to improve the accuracy of the forming simulation. As a result, the compressive modulus of the fibers was measured to be about $10^{-2}$ times lower than the tensile modulus. Also we designed a square-cup mold with a tilting angle of $110^{\circ}$ to simulate the prepreg formability during the high temperature compression mold process. Shear angles were measured at each corner, which were compared with the simulation results. It was observed that the simulation results using the accurate compressive properties of the prepreg showed a similar trend with the experimental results. It was confirmed that the measured data of the in-plane compression property improved the accuracy of the forming simulation results.