• 한국유체기계학회 논문집
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• 제19권3호
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• pp.25-28
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• 2016

The Schmidt hammer test is one of the best nondestructive tests to measure the strength without breaking structures, which has been used to measure the strength of concrete structures in a simple way at construction sites. However, the future research is needed to apply Schmidt hammer in cold regions. This study is intended to investigate the correlation between unconfined compression test result of the oil storage facilities foundation taken at the King Sejong Antarctic Station and Schmidt hammer test result at the sample-taking site. Also, the equation for uniaxial compression strength using Schmidt hammer rebound value is proposed.

• 한국지반공학회논문집
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• 제22권10호
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• pp.139-150
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• 2006

울산분지 퇴적암을 대상으로 Schmidt hammer 타격시험을 시행하여 일축 압축강도, 압열 인장강도, 탄성계수, 흡수율 및 간극율과의 상호 관계를 구명하였다. 기 연구된 결과는 여러 암종이 혼합된 결과로 실용적 적용에 어려움이 있어 지질학적 생성배경의 차이로 인한 원인을 배제하고 실용적 적용에 유용하도록 울산분지 퇴적암만을 대상으로 하여 연구를 시행하였다. Schmidt 햄머 반발지수와 각 실험결과상호간에 높은 상관성이 있으며 본 연구 결과 값으로 상호 교차검정을 한 결과도 만족할 수 있는 결과가 도출되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.239-242
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• 2002

This study is intended to investigate the relationship between rebound value of P type schmidt hammer and the compressive strength with various aggregates, and a series of experiments about early strength quality control by P type schmidt hammer was performed. According to the results, the compressive strength of concrete using basalt and limestone aggregate is higher by 3% and lower by 4% than that of concrete using granite aggregate respectively. Concrete using basalt and lime stone aggregate show high rebound value in vertical strike. Estimation of the compressive strength does not show differences in horizontal strike, but the compressive strength is estimated high in order of granite, basalt and limestone aggregate in vertical strike. A good correlation between the rebound value of schmidt hammer and the compressive strength is confirmed regardless of aggregate types, so it could be possible to control the quality of concrete by P type schmidt hammer test when basalt and limestone aggregates are used at the same time.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.615-618
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• 2005

This study concerns the equation of high strength concrete by schmidt hammer test. There are not only few prediction strength equations of concrete by schmidt hammer test, but also many problems to apply them because of time, cost, easiness, structural damage, reliability and so on. For this study, there performed a series of schmidt hammer test with in existing 1,095days' concrete structures and proposed equations as follows ; Linear: ${\Large f}_{ck}=-45.35+2.44R(r^2=72.7\%)$ Quadratic: ${\Large f}_{ck}=-502.08+24.0R-0.25R^2(r^2=82.4\%)$ here, $f_{ck}$ : Estimated compressive strength of concrete by MPa, R : Rebound index of concrete

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.133-136
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• 2004

This study concerns the. new equation of concrete strength by schmidt hammer test. There are not only few estimate strength equations of concrete by schmidt hammer test, but also many problems to apply them because of time, cost, easiness, structural damage, reliability and so on. For this study, there performed a series of schmidt hammer test with in existing 730days' concrete structures and proposed equations as follows; $$Linear\;:\;f_{ck}=2.18R-40.54\;(r^2=77.7\%)$$ $$Quadratic\;:\;f_{ck}=0.076R^2-2.92R+40.04\;(R^2= 85.5\%)$$ here, fck : Estimated compressive strength of concrete by MPa, R : Rebound index of concrete.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술.기술논문발표회
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• pp.11-15
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• 2002

This study is intended to analyze the relationship between the rebound value of P type schmidt hammer and the compressive strength for a quality control of concrete. According to the results, the compressive strength of standard curing specimen increases in proportion to age, but that of air curing specimen hardly increases after 28 days. The rebound value of P type schmidt hammer, however, increases due to carbonation of concrete in air curing specimen. The correlativity between the rebound value and the compressive strength is very favorable in the case of standard curing specimen, but drops remarkably in the case of air curing specimen. Thus, as application of age coefficient is required for exact estimation of the compressive strength, the age coefficient is derived from this study. The age coefficient of P type schmidt hammer is higher at the age of 3 and 7days, and drops significantly, compared with the age of 28days. And it is lower before 28days than that of N type schmidt hammer suggested in Japan, and shows the similar tendency after 28days.

• Computers and Concrete
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• 제21권5호
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• pp.525-530
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• 2018

As a nondestructive testing method, the Schmidt rebound hammer is widely used for structural health monitoring. During application, a Schmidt hammer hits the surface of a concrete mass. According to the principle of rebound, concrete strength depends on the hardness of the concrete energy surface. Study aims to identify the main variables affecting the results of Schmidt rebound hammer reading and consequently the results of structural health monitoring of concrete structures using adaptive neuro-fuzzy inference system (ANFIS). The ANFIS process for variable selection was applied for this purpose. This procedure comprises some methods that determine a subsection of the entire set of detailed factors, which present analytical capability. ANFIS was applied to complete a flexible search. Afterward, this method was applied to conclude how the five main factors (namely, age, silica fume, fine aggregate, coarse aggregate, and water) used in designing concrete mixture influence the Schmidt rebound hammer reading and consequently the structural health monitoring accuracy. Results show that water is considered the most significant parameter of the Schmidt rebound hammer reading. The details of this study are discussed thoroughly.

• Computers and Concrete
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• 제15권3호
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• pp.473-484
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• 2015

In this study, the availability of Schmidt hammer has been investigated as a reliable method to determine the quality of concrete in irrigation networks. For this purpose, the 28-day compressive strength of concrete material used in the construction irrigation channel of Bafra lowland, which is one of the most fertile plains in Turkey was examined by means of concrete compression and as well as concrete Schmidt hammer in laboratory conditions. This study was carried out on cylindrical samples to represent the everyday concrete party ($150m^3$) produced by contractor firm as 3 replications. The statistical analysis of experimental data showed that the correlations between the values of 28-day compressive strength of Schmidt hammer and the rebound number was found to be 0.98. Differences of the compressive strength between compression testing and Schmidt hammer were statistically significant at P<0.01. In this context, it was found that the reliability of compressive strength of the concrete compression test are excellent, also the reliability of compressive strength of Schmidt hammer are fair in assessing the quality of concrete irrigation channels.

• Structural Engineering and Mechanics
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• 제65권5호
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• pp.601-609
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• 2018

Steel bolts are used in the construction industry for a large variety of applications that range from fixing permanent installations to temporary fixtures. In the past much research has been focused on developing destructive testing techniques to estimate their pull-out load carrying capacity with very little attention to develop non-destructive techniques. In this regards the presented research work details the combined use of ultrasonic pulse velocity and Schmidt hammer tests to identify anchor bolts with faculty installation and to estimate their pull-out strength by relating it to the Schmidt hammer rebound value. From experimentation, it was observed that the load capacity of bolt depends on its embedment length, diameter, bond quality/concrete strength and alignment. Ultrasonic pulse velocity test is used to judge the quality of bond of embedded anchor bolt by relating the increase in ultrasonic pulse transit time to the presence of internal pours and cracks in the vicinity of steel bolt and the surrounding concrete. This information combined with the Schmidt hammer rebound number, R, can be used to accurately identify defective bolts which resulted in lower pull-out strength. 12 mm diameter bolts with embedment length of 70 mm and 50 mm were investigated using constant strength concrete. Pull-out load capacity versus the Schmidt hammer rebound number for each embedment length is presented.

• 터널과지하공간
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• 제19권5호
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• pp.421-431
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• 2009

본 연구에서는 Schmidt hammer 시험법을 적용하여 국내 공사현장에서 출현 빈도가 높은 화성암, 변성암 및 퇴적암 11종을 대상으로 일축압축강도와 타격값의 상관성 해석을 시도하였다. 암종에 따라 타격거동이 각각 다르게 나타난 암석의 상관성 해석을 거동별로 시행하여 6개의 경험식을 제안하였다. 이 식들의 신뢰성 분석을 교차검정으로 시행한 바 새로이 제안된 시험방법은 국내 암석을 대상으로 시행한 결과의 신뢰도가 높아 활용가치가 높다고 할 수 있다.