• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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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.

• Computers and Concrete
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• v.21 no.5
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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.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.11a
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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.

• Journal of the Korean Geotechnical Society
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• v.22 no.10
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• pp.139-150
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• 2006

A study has been made of the Schmidt hammer rebound test for the estimation of engineering and physical characteristics of sedimentary rocks. As there is no universal formular for the estimation of rock strength due to geological conditions, in this study only sedimentary rocks are adopted to testing. The aim of study is to make the information more meaningful and useful for engineers and contractors by providing rapid, cheap and easy method. The obtained parameters were correlated and regression equations were established among Schmidt hammer rebound number, uniaxial compressive strength, tangent Young's modulus, indirect tensile stress, water absorption and porosity of rocks with high coefficients of correlation with each other.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.909-912
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• 2001

This paper presents the validities of the removal time of side forms considering the relationship between rebound number of P type schmidt hammer and compressive strength. According to test results, compressive strength of 40% of W/C at 12 hours shows 16kgf/$cm^{2}$ and 50% of W/C at 15 hours, 13kgf/$cm^{2}$. Rebound number at 9 hours after casting shows 13 and 9 (W/C 40% and W/C 50%). According to the regression analysis, rebound number of P type schmidt hammer to gain 50kgf/$cm^{2}$ of is estimated 20.1. It is thought that desirable rebound number of P type schmidt hammer to gain 50kgf/$cm^{2}$ is determined 25 considering safety factor.

• Structural Engineering and Mechanics
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• v.65 no.5
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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.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.157-162
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• 2002

This study is intended to present a reference data for effective quality control of concrete through comparing the rebound value of P type schmidt hammer with the compressive strength with variation of mix proportion and curing condition. According to the results, the air-curing specimen shows the higher rebound value than standard specimen except high strength in the whole. Also the vertical stroke shows higher rebound value than horizontal stroke in standard specimen, however, the rebound value of the two does not show prominent difference in air-curing specimen. The estimation equation of compressive strength derived from this experiment estimates the compressive strength more largely than the estimation equation in P type schmidt hammer manual. Therefore it is thought that the new estimation equation that fits our condition will have to be presented.

• Computers and Concrete
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• v.15 no.3
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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.

• The KSFM Journal of Fluid Machinery
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• v.19 no.3
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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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.199-207
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• 2008

As infrastructures are being deteriorated, nondestructive evaluation of existing structures and construction quality control are increasingly demanded. The importance of predicting compressive strength of concrete structure is also gradually increasing in construction industry. The estimation of concrete compressive strength is a critical factor of the construction management and quality control. This study has been conducted using Schmidt hammer test and Impact echo method, which are nondestructive test methods for the comparison of the concrete compressive strength. It is focusing to examine the relationship between compressive strength of concrete and rebound number by Schmidt hammer test result by Impact echo method. It was found that concrete compressive strength and rebound number have a close correlation.