• Journal of the Society of Disaster Information
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• v.13 no.3
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• pp.366-375
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• 2017

Internal factors having effects on compressive strength test results of concrete include size, shape, height-diameter ratio(h/d), section processing method, dryness and wetness, etc. of the specimen. As it is difficult to ensure dimensions of core specimen due to rebar cutting from rebar spacing, wall thickness, effects on the structure, etc. when taking core of the concrete structure, correction of dimensions and h/d of the specimen become important for quality control of the concrete. Thus, in order to review effects of specimen size and height-diameter ratio for the concretes with compressive strength within 40~60MPa, this study has experimentally reviewed compressive strength test values by applying correction factors pursuant to KS F 2422 (Method of obtaining and testing drilled cores and sawed beams of concrete), when changing specimen diameter to ${\emptyset}5{\sim}15cm$, and h/d to 2.0~1.25.

• Journal of Korea Foundry Society
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• v.27 no.1
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• pp.36-41
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• 2007

Compressive properties of the open cell 6063 aluminum alloy foams made by the plaster molding process were investigated before and after heat treatment. Loading process was controlled at a displacement rate of 2 mm/min. Compressive strength of 10 PPI foam was the largest of the same density foams. Increase in strength after heat treatment for the bulk material was remark able, however was not for the 6063 aluminum foam. C values were in the range of $0.39{\sim}0.53$ for as cast foams and $0.13{\sim}0.16$ for T6 heat treated foams in the equation of ${sigma}^*_{pl}/{\sigma}_{ys}=C({\rho}/{\rho}_{s})^{1.5}$ and increased with cell size.

• Journal of the Korean Ceramic Society
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• v.45 no.9
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• pp.537-543
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• 2008

Effect of template size ratio on porosity and mechanical properties of porous zirconia ceramics were investigated using two different size (${\sim}8{\mu}m$ and ${\sim}50{\mu}m$ in diameter) of polymethyl methacrylate-coethylene glycol dimethacrylate (PMMA) microbeads as sacrificial templates. Porosity of the porous zirconia ceramics increased with decreasing the template size ratio ($8{\mu}m: 50{\mu}m$) whereas the compressive and flexural strengths of the porous zirconia ceramics increased with increasing the template size ratio. By controlling the template size ratio, sintering temperature and sintering time, it was possible to produce porous zirconia ceramics with porosities ranging from 57% to 69%. Typical flexural and compressive strength values of porous zirconia ceramics with ${\sim}60%$ porosity were ${\sim}37\;MPa$ and ${\sim}85\;MPa$, respectively.

• International Journal of Concrete Structures and Materials
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• v.18 no.2E
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• pp.117-124
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• 2006

Porous concrete has been used recently for the purpose of decreasing the load on the earth environment. It consists solely of cement, water and coarse aggregate of uni form size. Its fundamental properties are considerably affected by the physical properties of aggregate because the aggregate is the main material for the most part in its mix proportion. Because of this reason, this study carried out an investigation of the influence of the size and type of aggregate on the fundamental properties of porous concrete. It is shown that the fundamental properties of porous concrete was seldom affected by the size of aggregate except for the case of using $2.5{\sim}5mm$ aggregate but varied significantly by the type of aggregate. In particular, the compressive strength of porous concrete using $2.5{\sim}5mm$ aggregate was much higher than that using other aggregate, and its void ratio and coefficient of permeability was lower. Moreover, the capacity to maintain the permeability of porous concrete was found to vary by the size and type of aggregate. Of particular notice was that it decreased greatly when $2.5{\sim}5mm$ aggregate was used. Unlike ordinary concrete, porous concrete exhibited very high dynamic modulus of elasticity at early age and continued to increase but slowly afterwards.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.1
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• pp.19-26
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• 2016

This study was performed to evaluate the strength and durability properties of modified epoxy composites with waste tire chip, recycled coarse aggregate, filler and modified epoxy to improve elongation and elasticity of epoxy. Additionally, for comparing to modified epoxy and unsaturated polyester resin as a binder, unsaturated polyester resin composites were developed in the same condition. The mix proportions were determined to satisfy the requirement for the workability and slump according to aggregate size and binder content. Tests for the compressive and flexural strength, freezing and thawing and durability for 20 % sulfuric solution were performed. The compressive and flexural strength of modified epoxy composites were in the range of 34.9~61.6 MPa and 10.2~18.3 MPa at the curing 7 days, respectively. Also, the compressive and flexural strength of unsaturated polyester resin composites were in the range of 44.2~77.8 MPa and 11.3~20.8 MPa at the curing 7 days, respectively. After 300 cycles of freezing and thawing, weight decrease ratio and durability factor of modified epoxy composites were in the range of 0.8~1.9 % and 95~98, respectively. Accordingly, modified epoxy composites will greatly improve the durability of concrete.

• The Journal of the Korea Contents Association
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• v.20 no.12
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• pp.529-536
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• 2020

This paper presents experimental investigations about compressive strength and durability of reinforced concrete compressive members repaired using ductile fiber reinforced cementitious composite (DFRCC) and carbon fiber sheet through freezing and thawing test. Total 24 RC specimens of 100x100x400mm size were tested by compressive strength test and freezing and thawing test by KS F 2456. The specimens were reinforced using 4D10 steels and repaired on 4 sides expect on top cycle. Test results showed that the specimens repaired using fiber carbon sheet revealed about 5% higher values of the compressive strength compared than the cases of DFRCC motar. On the other hand, the resurts did not showed meaningful differences in the aspect of durability. For further research, considerations of the steel interference effect and real old specimens such as taken from real deteriorated structures are needed to be tested after repairing with DFRCC and carbon fiber sheet.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.169-176
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• 2015

Since the size effect law announced currently has been based on the normal weight concrete, for light weight concrete having different fracture characteristics, its application is questionable. Accordingly, in this study, a model equation to predict the effect of dried unit weight of the concrete on size effect of its compressive strength was developed and a database using existing research results was created. After determining the experimental constants of prediction models of Ba${\check{z}}$ant based on nonlinear fracture mechanics, Kim and Eo, and this study using the database, their results are mutually compared. Finally, it was found that the prediction model of this study considered dried unit weight of concrete predicted well the test results for light weight concrete than that of the models of Ba${\check{z}}$ant and Kim and Eo.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.514-522
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• 2022

In this study, as part of a study to improve the self-healing performance of concrete structures by applying self-healing capsules made of cementitious materials to cement composite materials, the engineering characteristics of mortars according to PCC(Powder Compacted Capsule) size and mixing ratio were compared and analyzed. For this, fluidity, compressive strength, reload test, carbonation, ultrasonic velocity, and water permeability characteristics were measured according to PCC size and mixing ratio of mortar. As a result of the measurement, the fluidity and compressive strength increased as the mixing ratio of PCC increased, and in the case of the load reload test, the healing ratio increased as the mixing ratio of PCC increased in the 03PC formulation. In the case of water permeability test, it was found that when PCC was used, the reduction ratio of water flow was up to 35 % higher than that of Plain, and when PCC with a size of 0.3 to 0.6 mm was mixed with 15 %, it was found to be effective in improving the crack healing ratio of the mortar.

• Journal of the Korean Ceramic Society
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• v.12 no.4
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• pp.9-18
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• 1975

Polymer emulsion was used as the admixture for the purpose of increasing the mechanical properties of cement mortar. The effect of polymer emulsion admixture on compressive strength and tensile strength and chemical resistance, relative humidity on compressive and tensile strength, sand particles on water absorption were studied. The results were as follows. 1. Polymer emulson modified mortar cured under 95% of realative humidity showed lower strength than the mortar cured at dry condition. 2. The maximum strength was attained at 10~20% of polystyrene and polyacrylic acid ester polymer-cement mortar. 3. The modified mortar (sand size rate (-9＋35)mech:(-35＋60)mech=4 : 1) was 1.5 times lower than the modified mortar (1 : 1) in water absorption. 4. Compared with the ordinary mortar, the modified mortar showed 2~3 times greater chemical resistance for 5% HCl or 5% H2SO4.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.215-225
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• 2011

Metakaolin is a dehydroxylated form of the clay mineral kaolinite. Rocks that are rich in kaolinite are known as china clay or kaolin, traditionally used in the manufacture of porcelain. The particle size of metakaolin is smaller than cement particles, but not as fine as silica fume. This paper investigates the effect of the concrete containing metakaolin as a mineral admixture on the compressive strength and resistance properties to chloride ion penetration. In this study, the experiment was carried out to investigate and analyze the influence of replacement ratio of metakaolin and micro silica fume on the compressive strength and chlorine ion penetration resistance of concrete. All levels were water/binder ratio 30%, replacement ratio of metakaolin and silica fume were 0, 5, 10, 15, 20% respectively. The compressive strength of concrete using metakaolin tends to increase, as the replacement ratio increases but the chlorine ion penetration resistance was not so as lager as silica fume concrete. Therefore, the optimum mixing ratio of metakaoline to satisfy a properties of compressive strength and chlorine ion penetration resistance was was approximately10%.