• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.67-75
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• 2011

The effect of steel-fiber contents on the compressive behavior of ultra high performance cementitious composites (UHPCC) was studied to propose a compressive behavior model for UHPCC. The experiments considered fiber contents of 0~5 vol.% and the results indicated that compressive strength and corresponding strain as well as elastic modulus were improved as the fiber contents increased. Compared to the previous study results obtained from concrete with compressive strength of 100MPa or less, the reinforcement effect on strength showed similar tendency, while the effect on the strain and elastic modulus were much less. Strength, strain, and elastic modulus according to the fiber contents were presented as a linear function of fiber reinforcement index (RI). Fiber reinforcement in UHPCC had no influence on the shape of compressive behavioral curve. Considering its effect on compressive strength, strain, and elastic modulus, a compressive stress-strain relation for UHPCC was proposed.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.501-506
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• 2001

An experimental study was carried out to investigate recycling of an oyster shell, which is disposed in open-dumped way at coastal oyster factory area. For this purpose, the chemical component and reaction of oyster shell with cement paste was examined. And, the characteristics of hardened concrete was quantitatively investigated in terms of fineness modulus and blending rate of the crushed oyster shell. Test results show that interaction between oyster shell and cement paste was not occurred and the crushed oyster shell can be used as the fine aggregate of concrete. And it is found that blending of an oyster shell caused not to reduce the 28 day compressive strength of concrete. Elastic modulus of the concrete blended with crushed oyster shells decreases with increases the blending rate which the modulus reduced about 10% when oyster shells is blended up to the 20% of the sand substitution.

• International Journal of Highway Engineering
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• v.8 no.4 s.30
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• pp.13-24
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• 2006

The stresses in concrete pavement systems are larger when vehicle loads are applied at pavement edges, and these large stresses significantly affect the behavior and performance of pavements. Therefore, in this study, the stress distribution and the critical stresses in concrete pavements were investigated using a finite element model when dual-wheel single-, tandem-, and tridem-axle loads were applied at pavement edges. First, the stress distribution along the longitudinal and transverse directions was analyzed, and then the effects of slab thickness, concrete elastic modulus, and foundation stiffness on the stress distribution were investigated. The effect of the tire contact pressure related to the tire print area was also studied. The location of the critical stress occurrence in concrete pavements was finally investigated. From this study, it was found that the critical concrete stress due to edge loads became larger as the concrete elastic modulus increased, the slab thickness increased, and the foundation stiffness decreased. The effect of the tire contact pressure on the critical stress was clear as the slab thickness became smaller. The critical stress location in the transverse direction was independent of the concrete elastic modulus and the foundation stiffness; however, it moved into the interior as the slab thickness increased. The critical stress location in the longitudinal direction was under the axle for single- and tandem-axle loads, but for tridem-axle loads, it tended to move under the middle axle from the outer axles as the concrete elastic modulus and/or slab thickness increased and the foundation stiffness decreased.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.789-796
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• 2009

The randomness in the strength of a RC member is caused mainly by the variability of the mechanical properties of concrete and steel, the dimensions of concrete cross sections, and the placement of reinforcing bars and so on . Among those variations, the randomness and uncertainty of mechanical properties of concrete, such as compressive strength, tensile strength, and elastic modulus give the most significant influences and show relatively large statistical variations. In Korea, there has been little effort for the construction of its own statistical models for mechanical properties of concrete and steel, thus the foreign data have been utilized till now. In this paper, variability of compressive strength, tensile strength and elastic modulus of normal-weight structural concrete with various specified design compressive strength levels are examined based on the data obtained from a number of published and unpublished sources in this country and additional laboratory tests done by the authors. The inherent probabilistic models for compressive and tensile strength of normal-weight concrete are proposed as Gaussian distribution. Also, the relationships between compressive and splitting tensile strength and between compressive strength and elastic modulus in current KCI Code are verified and new ones are suggested based on local data.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.3
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• pp.225-232
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• 2002

The purpose of this study is to find the mechanical properties of lightweight concrete using expanded clay. Thus, slump, air content, compressive strength, elastic modulus, tensile strength, length change ratio, unitweight change ratio and absorption of lightweight concrete have been investigated. The conclusions of this study are as follows ; 1. The loss of slump and air content of concrete increased as the expanded clay content increased and the size of coarse aggregate decreased. 2. The compressive strength of concrete using 100% expanded clay of 13, 19mm size at 28 days were respectively 282, $252kgf/cm^2$. 3. The elastic modulus and tensile strength of concrete decreased with increase of expanded clay content. 4. The length change ratio of concrete increased with the larger coarse aggregate size, and decreased with the increase of expanded clay content. 5. The unit weight of concrete decreased with the increase of expanded clay content, and the ratio of that was larger at the early age.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.3_4
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• pp.72-81
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• 1995

This study was performed to evaluate the mechanical properties of high performance lightweight polymer concrete using fillers and synthetic lightweight coarse aggregate. The following conclusions were drawn. 1. The unit weight of the G3, G4 and G5 concrete was 1.500t/m$^3$, 1.506t/m$^3$ and 1.535t/m$^3$, respectively. Specially, the unit weights of those concrete were decreased 33~35% than that of the normal cement concrete. 2. The highest strength was achieved by heavy calcium carbonate, it was increased 27% by compressive, 95% by tensile and 195% by bending strength than that of the normal cement concrete, respectively. 3. The elastic modulus was in the range of 8.0 x 104~ 10.4 x lO4kg/cm2, which was approximately 35~42% of that of the normal cement concrete. Normal cement concrete was showed relatively higher elastic modulus. 4. The ultrasonic pulse velocity of fillers was in the range of 2, 900m/sec, which was showed about the same compared to that of the normal cement concrete. Heavy calcium carbonate was showed higher pulse velocity. 5. The compressive, tensile, bending strength and ultrasonic pulse velocity were largely showed with the increase of unit weight.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.41-44
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• 2008

The purposes of this study are to estimate thestrength of concrete and quantify the deterioration of concrete by a unique X-ray technique with a contrast medium. In order to estimate the strength of concrete, specimens with different water-cement ratios were fabricated using non-air-entrained concrete, air-entrained concrete and mortar to determine the relationship between their compressive strength and the transit dose obtained by the X-ray technique. Also, an experiment to quantify deterioration was carried out on specimens that were subjected to freezing and thawing action to different levels of dynamic elastic modulus. As a result of this experiment, estimation of the strength and relative dynamic elastic modulus of deteriorated mortar, concrete and air-entrained concrete was found feasible by measuring the transit dose by the X-ray technique.

• Structural Engineering and Mechanics
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• v.69 no.1
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• pp.33-42
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• 2019

Thermal cracks are cracks that commonly form at early ages in mass concrete. During the concrete pouring process, the elastic modulus changes continuously. This requires the time domain to be divided into several steps in order to solve for the temperature, stress, and displacement of the concrete. Numerical simulations of thermal crack propagation in concrete are more difficult at early ages. To solve this problem, this study divides crack propagation in concrete at early ages into two cases: the case in which cracks do not propagate but the elastic modulus of the concrete changes and the case in which cracks propagate at a certain time. This paper provides computational models for these two cases by integrating the characteristics of the extended finite element algorithm, compiles the corresponding computational programs, and verifies the accuracy of the proposed model using numerical comparisons. The model presented in this paper has the advantages of high computational accuracy and stable results in resolving thermal cracking and its propagation in concrete at early ages.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.5
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• pp.95-105
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• 1996

This study was performed to evaluate the mechanical properties of permeable polymer concrete using fillers and unsaturated polyester resin. The following conclusions were drawn; 1. The unit weight was in the range of 1, 663~ l, 892kg/$cm^3$, the weights of those concrete were decreased 18~28% than that of the normal cement concrete. 2. The highest strength was achieved by fly ash filled permeable polymer concrete, it was increased 22% by compressive strength, 190% by tensile strength and 192% by bending strength than that of the normal cement concrete, respectively. 3. The external strength of permeable pipe was in the range of 3, 083~3, 793kg/m, the external strengths of those concrete were increased 2~26% than that of the normal cement concrete. Accordingly, these permeable polymer concrete pipe can be used to the members and structures which need external strength. 4. The static modulus of elasticity was in the range of $5.7{\times} 10^4 ~ 15.4{\times} 10{^4}kg/cm^2 $, which was approximately 35~64% of that of the normal cement concrete. Fly ash filled permeable polymer concrete was showed relatively higher elastic modulus. The poisson's number of permeable polymer concrete was less than that of the normal cement concrete. 5. The dynamic modulus of elasticity was in the range of $83{\times} 10^3 ~ 211{\times} 10{^3}kg/cm^2 $, which was approximately Ins compared to that of the normal cement concrete. Fly ash filled permeable polymer concrete was showed higher dynamic modulus. The dynamic modulus of elasticity were increased approximately 22~45% than that of the static modulus. 6. The ultrasonic pulse velocity was in the range of 2, 584 ~ 3, 587m/sec, . which was showed about the same compared to that of the normal cement concrete. Fly ash filled permeable polymer concrete was in the range of$0.58~8.88 {\ell}/cm^2/hr$, , and it was larglely dependent upon the mixing ratio. These concrete can be used to the structures which need water permeability.

• Korean Journal of Agricultural Science
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• v.23 no.1
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• pp.61-69
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• 1996

This study was performed to evaluate the engineering properties of permeable polymer concrete with fillers and unsaturated polyester resin. The following conclusions were drawn. 1. The highest strength was achieved by stone dust filled permeable polymer concrete, it was increased 17% by compressive, 148% by tensile and 188% by bending strength than that of the normal cement concrete, respectively. 2. The static modulus of elasticity was in the range of $1.17{\times}10^5{\sim}1.32{\times}10^5kg/cm^2$, which was approximately 53~56% of that of the normal cement concrete. Stone dust filled permeable polymer concrete was showed relatively higher elastic modulus. The poisson's number of permeable polymer concrete was less than that of the normal cement concrete. 3. The dynamic modulus of elasticity was in the range of $1.3{\times}10^5{\sim}1.5{\times}10^5kg/cm^2$, which was approximately less compared to that of the normal cement concrete. Stone dust filled permeable polymer concrete was showed higher dynamic modulus. The dynamic modulus of elasticity were increased approximately 10~13% than that of the static modulus. 4. The water permeability was in the range of $3.076{\sim}4.390{\ell}/cm^2/h$, and it was largely dependent upon the mix design. These concrete can be used to the structures which need water permeability. 5. The compressive strength, tensile strength, bending strength and elastic modulus were largely showed with the decrease of water permeability.