• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.313-322
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• 2005

Recently, as the remodeling market gradually substitute for new construction market and safety diagnosis for reconstruction apartment become a matter of principal Interest, it is demanded that scientific diagnosis and evaluation for existing concrete structure state. And it is increasing that the significance for reliability of data which is used for estimating the concrete compressive strength by nondestructive test. As a result, it is found that different proposal to material age and hitting angle is good to improving the reliability of presumption of concrete compressive strength in the linear hitting rebound test hammer. And for the reason that mutual relation between the compressive strength and rebound degree is highest in linear hitting rebound test hammer 25mm in all portion according to early md middle material age and hitting angle except the early material age $-45^{\circ}$, analysis showed that linear hitting rebound test hammer is more reliable than existing schmidt hammer in presumption of concrete compressive strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.783-786
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• 1999

The compressive strength of concrete is one of the most important properties in concrete structures. There are, two methods for the testing of concrete compressive strength in structure ; coring and nondestructive testing. The latter is more often used than the former in a view of time and expenses. The Nondestructive test methods used nowadays include Rebound Hammer test and Ultrasonic Pulse Velocity test. Carbonation through aging makes changes of the interior structure and the properties of concrete. It is well-known fact that the surface hardness of concrete is increased by its carbonation. This fact makes it difficult in estimating the compressive strength of concrete using Rebound Hammer test. This study aimed to quantitatively analyzed the effects of carbonation on results of the Rebound Hammer test.

• 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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• 2002.10a
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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.

• 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.

• 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.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.77-79
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• 2012

This paper intends to review possible application in the high strength area through compressive strength estimation of the simulated high strength concrete member using Rock Test Hammer and suggest it as a reference data for the strength estimation technique of the ultra high strength concrete in the future. From the results of our test, in the low strength area less than 15MPa and normal strength area in 15~60MPa, as shown on the existing studies, it is indicated that P Type Schmidt Hammer in the low strength area and N Type Schmidt Hammer in the normal strength area have high correlation of rebound-compressive strength. As the Rock Test Hammer indicated more or less reduced accuracy in the low strength area and the normal strength area but high correlation on the high strength area (50~100MPa) defined on this test, it is determined that it would be possible to make the fastest and simplest compressive strength estimation on the site where the high strength concrete is applied.

• 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.

• Journal of the Korean Geosynthetics Society
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• v.7 no.1
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• pp.13-21
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• 2008

To investigate the engineering properties of basalt in Cheju Island, rock samples of Pyosenri basalt, trachy-basalt and scoria were taken from Seoguipo-Si Seongsan-Eup area. The laboratory tests such as absorption test, specific gravity test, permeability test, Schmidt hammer test, elastic wave test and uniaxial compressive testwere carried out for the collected rock samples. The absorption, the specific gravity, the permeability, the elastic wave velocity and uniaxial compressive strengthwere investigated and analyzed as the results of these tests. As the result of regression analysis for the relationship between the rebound values from Schmidt hammer test and the uniaxial compressive strengths from uniaxial compressive test, especially, estimation equations were proposed using the rebound values from Schmidt hammer test. Therefore, the simple method to estimate the uniaxial compressive strength was provided.