• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.213-221
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• 2016

Uniaxial compression tests for ultra-high performance hybrid steel fiber reinforced concrete (UHPC) were performed to evaluate the compressive behavior of UHPC. The UHPC for testing contains hybrid steel fibers with a predetermined ratio using a length of 19 mm and 16 mm straight typed steel fibers. Test parameter was determined as a fiber volume ratio to investigate the effect of fiber volume ratio on the strength and secant modulus of elasticity. Test results showed that the compressive strength and elastic modulus of UHPC increased with increasing the fiber volume ratio. Based on the test results, the compressive strength and modulus of elasticity equations were proposed as function of the compressive strength of unreinforced and fiber reinforced UHPC, respectively. The simplified equations for predicting the mechanical properties of the UHPC were a good agreement with the test data. The proposed equations are expected to be applied to the SFRC and UHPC with steel fibers.

• 한국터널공학회:학술대회논문집
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• 2005.04a
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• pp.175-186
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• 2005

터널공사에서 숏크리트는 가장 중요한 지보재 이므로 시공중 품질관리를 위한 압축강도시험은 매우 중요하다. 현장 타설 숏크리트의 압축강도는 실험실조건에 비하여 낮은 값을 갖고 있어 현장강도 시험은 필수적이나, 적절한 시험방법의 부재로 인하여 코어채취에 의한 압축강도시험이 적용되고 있다. 이 방법은 적절한 샘플채취와 초기강도 측정에 큰 문제점을 가지고 있다. 따라서, 본 논문에서는 공기압식 핀관입시험법을 고찰하였으며, 압축강도시험의 단점을 해소할 수 있는 점하중강도시험법의 적용성을 검토하였다. 또한, 향후 연구계획으로써, 현장강도시험기법으로 선정된 공기압식 핀관입시험기의 적정성 평가와 숏크리트 압축강도시험을 대체할 수 있는 점하중강도시험의 적용성 분석계획을 제시하였다.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.1-7
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• 2002

The purpose of this research is to obtain a practical expression for the estimation of compressive strength of concrete using non-destructive testing method such as rebound Schmidt hammer and ultrasonic pulse

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.361-367
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• 2011

The uniaxial compressive strength (UCS) is an important factor in the design and construction of surface and underground structures. However, the method employed to measure UCS is time consuming and expensive to apply in the field. Therefore, we developed a model to estimate UCS based on a few properties using linear regression analysis, which is a statistical method. To develop the model, valid factors from the test results were selected from a correlation analysis using a statistical program, and the model was formulated by linear regression based on the relationships among factors. UCS estimates derived from the model were compared with the results of UCS tests, to assess the reliability of the model. The relationship between rock properties and UCS indicates that the factors with the greatest influence on UCS are point load strength and shape facto r. The UCS values obtained using the model are in good agreement with the results of the UCS test. Therefore, the developed model may be used to estimate the UCS of rocks in regions with similar conditions to those of the present study area.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.205-213
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• 2007

Strength relationships are presented through experimental data from the concrete strength tests in this study. Various strength tests such as the compressive, flexural, and splitting tensile strength and the modulus of elasticity are included. An experimental work was performed to determine the various strength characteristics for various mix designs. Three different coarse aggregates such as granite, limestone, sandstone were used and included were fine aggregates such as natural sand, washed sand and crushed sand. Also included was cement amount as experimental variable. It was confirmed that each strength value with respect to curing time is to follow a typical strength development curve. With this somewhat reliable test results various strength relationships such as flexural strength-compressive strength, splitting tensile strength-compressive strength, modulus of elasticity-compressive strength, splitting tensile strength-flexural strength were analyzed through statistics. Experimental data were well fitted to the 0.5-power relationship of flexural strength and compressive strength which has been commonly accepted. The splitting tensile strength is expected to be best in the linear relationship from the flexural strength data. Finally splitting tensile strength was found to be proportional to the 0.87 power of the cylindrical compressive strength.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.217-223
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• 1997

재생콘크리트의 압축강도와 휨강도는 재생골재의 혼입량이 증가할수록 감소하였으며 플라이애쉬를 혼화재로 사용할 때 그 양이 증가할수록 재생콘크리트의 조기 압축강도는 떨어졌다. 골재원에 따른 압축강도는 재생골재의 혼입량이 적을수록, 양생기간이 길어질수록 증가하엿으나, 전반적으로 비슷한 강도변화의 경향을 보여주고 있다. 재생콘크리트의 휨강도 발현은 보통 콘크리트와 비슷하나, 휨강도에 대한 압축강도비는 보통 콘크리트에 비하여 낮았다. 재생콘크리트의 건조수축은 재생골재의 혼입량이 증가할수록 증가하였으며 , 특히 재령2주와3주사이에 건조수축량이 보통 콘크리트에 비해 월등히 높았다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.33-40
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• 2021

Measuring the compressive strength of concrete is a very important factor in the safety review of concrete structures. Concrete compressive strength measurement methods include destructive and non-destructive methods. The destructive method includes the uniaxial compression failure method, and the non-destructive method includes the rebound hardness method and the elastic wave measurement method. In this study, the type of measurement method and the effect of reinforcing bars inside the concrete were tested to examine the relationship between them. Regardless of the type of specimen, the average compressive strength by the elastic wave measurement method among the three experimental methods was greater than the average compressive strength by the other methods. When the specimen type is the same, the standard deviation of the measured values of the elastic wave measurement method is smaller than that of the other measurement methods, so it can be seen that the elastic wave measurement method does not show large variance in the measured values compared to the other two measurement methods. When the average compressive strength according to the test method for each specimen was compared with the average compressive strength of the compressive failure test method, the average compressive strength was measured to be high in the order of the elastic wave measurement method, the compression failure test, and the rebound hardness method. Since the measured values of the compressive strength of concrete are different depending on the method of measuring the compressive strength of concrete and the presence or absence of reinforcing bars inside the concrete, further research is required considering the effect of various concrete covers.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2003.07a
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• pp.347-352
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• 2003

농산물 포장화물의 경우 농산물의 손상은 겉포장 상자의 파손에 의한 압상이 주요 원인이다. 따라서 농산물 상자의 경우 압축강도를 특히 중요시 여기고 있으며, 한국산업규격을 비롯해 각종 농산물 관련 규정에서는 압축강도에 의한 상자의 품질관리를 규정화 하고 있다. 골판지 상자의 압축강도는 원단인 골판지의 구성 원지들(라이너, 골심지)의 품질과 이들의 구성 형태 및 상자의 외형 치수 비율에 따라 결정되므로, 원지의 링크라쉬(ring crush), 원단의 수직압축강도(edgewise compression strength)를 통해 상자의 압출강도를 관리하는 것이 보통이다. 또한 골판지 상자는 제작 후 유통 과정을 거치면서, 여러 요인에 의해 압축강도가 현격하게 저하되는데, 이중 수분 흡습에 의한 강도저하와 장기 누적하중, 진동 및 충격 등의 피로로 인한 강도 저하가 가장 크다. 여러 산업 분야에서 골판지 상자의 견고성 문제는 물품의 내수 및 수출시 제품에 대한 신뢰성 확보와 기업의 이미지 제고와 직결되는 중요한 사항이다. 특히, 세계 각 국의 농산물 시장이 개방됨에 따라 우리나라 농산물의 수출도 확대될 전망이고 또한 마땅한 대체재가 개발되지 않는 한 골판지 상자의 이용은 날로 증가될 것으로 전망된다. 따라서 골판지 상자의 압축강도와 내구성 향상에 대한 다각적인 연구가 절실하다. (중략)

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.110-118
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• 2010

This research dealt with the effect of steel-fiber reinforcement on the compressive strength of ultra high performance cementitious composites (UHPCC) and compared with that in normal steel-fiber reinforced concrete(SFRC). With wide range of compressive strength of UHPCC, experiments on the fiber reinforcement effect confirmed that the compressive strength in UHPCC is also improved by adding fibers as in normal SFRC. The experimental results were compared with previous researches about reinforcement effect by adding fibers, which are limited within 100MPa compressive strength. The comparison revealed the linear relationship between $f'_{cf}-f'_c$ and RI regardless of the magnitude of compressive strength, from which a general equation to express the effect of fiber reinforcement, applicable to various SFRC's with wide range of compressive strength including UHPCC.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.655-661
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• 2020

In this study, the correlation between concrete core compressive strength and rebound hardness of urban railway underground structures was analyzed. The equations for the range of rebound hardness were derived and compared with the measured concrete core strengths for each range of rebound hardness to confirm the adequacy of the estimated compressive strength. As the result, the linear regression analysis results of the average compressive strength by the Gaussian probability density function (representative compressive strength estimation formula) and the estimation formula by the rebound hardness range were founded to match well within 3% of the experimental concrete core compressive strength test results. Therefore, the stochastic statistical analysis using the rebound hardness measurement results suggested in this study could be help to secure the confidence level of the correlation between the rebound hardness and the concrete compressive strength which are relatively large deviation according to the estimation equations.