Rebound hammer test is a nondestructive testing method of concrete which provide a convenient and rapid indication of the compressive strength of the concrete. Hthe number in parentheses after the colon indicates the page number in. The results of both dt and ndt are presented in tables 2, table 3 and table 4 for concrete cubes of ages 7, 14 and 28 days respectively. Obtaining reliable compressive strength estimations with a. Correlation between schmidt hardness, uniaxial compressive. Due to its importance, schmidt hammer rebound number is. Predicting concrete compressive strength and modulus of.
Generally, rebound number rn and ultrasonic pulse velocity upv as wellknown ndts are combined to obtain a better estimate of concrete strength. Results indicate the existence of two rock groups showing distinct behaviour in. The results show that a higher rebound number result gives high compressive strength value and vice versa. The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete. For reliable results the calibration curve shall be drived from the given set of materials and conditions. The main objective of this study was to establish statistical relationship between schmidt hammer rebound numbers with impact strength index isi, slake durability index sdi and pwave velocity. Correlation between schmidt hammer and destructive. Although there is a high correlation between the surface hardness and the uniaxial compressive strength ucs of intact rocks, the srh provides only a crude estimate for the ucs of rocks. In order to obtain an estimate of insitu compressive strength using a rebound hammer in accordance with major standards, a calibration is necessary. In brazil, the rebound hammer is the most popular nondestructive test, but some researchers question the effectiveness of the method to accurately estimate the concrete strength.
Practically, it is agreed that there is no unique relationship between concrete strength and rebound number. Comparison between the properties of amorphous and. Use of swiss hammer for estimating compressive strength of. Founded in 1904 and headquartered in farmington hills, michigan, usa, the american concrete institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensusbased standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design. Pull off test to evaluate the compressive strength of. In order to establish a relationship between rebound number and concrete strength, inspectors should take a minimum of 2 replicate cores, from 6 or more locations 12 concrete cores in total with different rebound numbers.
Correlation between uniaxial compressive strength and. This method assumes that there is a proportional relation between the rebound number measured by a schmidt rebound hammer and the compressive strength of concrete. Two hundred rock cores were drilled and used for the uniaxial compressive strength and point load index tests. Compressive strength of the concrete can be determined from the relationship between the rebound number and the strength given by the curve. Proper use of the rebound hammer updated to reflect the. Correlation between concrete compressive strength and. Estimating the strength of concrete using surface rebound. The rebound number of concrete sample without additives 24. Standard test method for rebound number of hardened. Rebound number rn for samples in the first and second group is.
The compressive strength is then determined by taking average of rebound reading. Correlation between destructive compressive testing dt. Sole or combined two ndts have discussed in different papers which some of them proposed combined two ndts as accurate prediction models 10, 11, while others, persist on the one ndt to predict the strength of concrete 12. Keywords compressive strength, concrete, rebound hammer, reliability. Schmidt rebound hammer srh test has been used worldwide as an index test for estimating the compressive strength and deformation characteristics of intact rocks. Predicting a mathematical models of some mechanical. Volcanic rocks from the bodrum peninsula have been studied to establish a relationship between the uniaxial compressive strength ucs, youngs modulus e and schmidt hammer rebound number n.
Test results obtained on andesites, basalts and tuffs. These are important properties to characterize a rock mass and are being widely used in geological and geotechnical engineering. Keywords compressive strength, non destructive test, destructive compression test, schmidt rebound hammer. Rebound hammer test graph describes the correlation between the strength of concrete and rebound number. Compressive strength formula for concrete using ultrasonic. The compressive strength can be evaluated directly from the graph provided on the body of the hammer. Nondestructive testing of concrete methods of test. The schmidt rebound hammer test, one of the most popular nondestructive testing methods, is an economical and easy method to evaluate the compressive strength of concrete.
A correlation between schmidt hammer rebound numbers with. How to derive the compressive strength of a component. The strengthrebound number relationship is depended on many factors that are influence on test results which may empirically affect the relationship between compressive strength and rebound number. The rebound hammer is also called as schmidt hammer that consist of a spring controlled mass that slides on a plunger within a tubular housing. Nondestructive testing of concrete by rebound hammer. Schmidt hammer test or rebound hammer test of concrete. This article presents the consideration of relation between compressive strength and rebound number of concrete cooperating with quarry dust as fine aggregate. A correlation between rebound number and strength of concrete structure is established by testing different grades of concrete and this can be used for the. Is there a formula to find the compression strength of. However, the value determined is when the trouble starts, many concrete test hammer models include a graph showing a relationship between hammer orientation, rebound number, and estimated compressive strength. Estimation of compressive strength in an existing structure is established through correlating rebound numbers of structure with the strengths of. Reliability of rebound hammer test in concrete compressive.
Concrete compressive strength prediction using non. However, no relationship exists between the number indicated and. If the relationship between rebound index and compressive strength can be checked by tests on core samples obtained from the structure or standard specimens made with the same concrete materials and mix proportion, then the accuracy of results and confidence thereon are greatly increased. The correlation between rebound number and compressive strength is very much dependent on the concrete mixture under test. Materials free fulltext characteristic curve and its. The rebound hammer is also called as schmidt hammer that consist of a spring controlled mass.
Application of rebound hammer method for estimating. Rebound hammer test on concrete principle, procedure. Test results obtained on andesites, basalts and tuffs have been assessed statistically and the parameters obtained correlated. This paper presents some models for correlation between rebound number and compressive strength of bricks. Relationship between compressive strength and rebound number. Assessment of characteristic compressive strength in. Although there is no unique relation between hardness and strength of concrete, experi mental data relationships can be. Correlation between concrete compressive strength and rebound. However, the value determined is when the trouble starts, many concrete test hammer models include a graph showing a relationship between hammer orientation, rebound. The rebound number is then crossreferenced to an actual compressive strength value. The relationship shall be established for a given concrete mixture and given apparatus. Although past investigations showed that there is a general relationship between compressive strength of concrete and the rebound number, there is a wide range of disagreement among various research workers regarding the accuracy of estimation of strength from schmidt hammer. Predicting concrete compressive strength using ultrasonic.
The most satisfactory way of establishing a correlation between compressive strength of concrete and rebound number is to test the concrete cubes using compression testing machine as well as using rebound. Correlation between actual compressive strength of. Such correlations will be valid for that particular type of rebound hammer and it will as well be influenced by size, shape and characteristics of brick to be tested. This is the reason behind the development of data relating rebound numbers to the compressive strength of the concrete mixture or cores from the structure. Different methods have been proposed to establish a relationship between rebound number and compressive strength.
The rebound hammer test is basically a surface hardness test to find out the compressive strength of concrete by using rebound hammer as per the second part of is 311 1992 21 with little apparent theoretical relationship between the strength of concrete and the rebound number of the hammer. The relationship shall be established over the range of concrete strength that is of interest. Although several previous studies 15 concluded that, for concrete with a particular mixture proportion, there is a good correlation between upv and the compressive strength. Sanita rubene, obtained the relationship between compressive strength of concrete cubes and rebound number of the concrete cubes using rebound hammer. Correlation between schmidt hammer and destructive academic. Rebound hammer test procedure for concrete hardness. Rebound hammer test, on the other hand, can give an estimated magnitude of compressive strength of brick if a fair correlation is established between rebound number and compressive strength of brick. The model is therefore designed as a median curve plotted through the experimental data. Inaccurate compressive strength estimations from rebound hammers can then. The surface hardness and both the properties simultaneously on concrete therefore the rebound is taken to be related to cubes. When the plunger of rebound hammer is pressed against the surface of the concrete, the spring controlled mass rebounds and the extent of such rebound depends upon the surface hardness of concrete. Correlation between compressive strength of concrete and rebound. Correlation between compressive strength of concrete and rebound number.
For the sonreb combined method, the differences between the actual compressive strength and compressive strength obtained from nondestructive tests lie in the interval. Rebound hammer data show a direct relationship between the compressive strength results and the rebound number. These three reports, discussed above, show a very general and simpl ified rule that the strength increases. Is there a formula to find the compression strength of concrete from. Non destructive testing for determining the strength of. The operation of schmidt hammer is depicted in the following diagram and you can also refer the above figure 1 for clear understanding. Review of the rebound hammer method estimating concrete. Determine the compressive strength of calcium silicate.
Relation between rebound strength and upv of cores u cor 0. Evaluation of the relationships between schmidt hardness. Evaluation of the relationships between schmidt hardness rebound number and other engineering properties of rocks a. The curve for the relation between rebound readings and compressive strength for the gravel concrete corresponds very closely to that furnished by the manufacturer and shown in figure 2. After impact, the rebound number should be recorded by taking at least 10 readings from each tested area ts 3260, 1978. A statistical interpretation of the two alternatives provided by the standard for the establishment of the relationship between the insitu strength and the rebound number is presented, and some relevant aspects related to the regression analysis not mentioned by the standard, such as the precision of the rebound number and the confidence level. Estimate concrete strength using rebound hammer fprimec. Rebound number of river bed and crusher run coarse. Investigation of the rebound number and compressive strength of. Most previously published models of the relationship between the rebound number and compressive strength are designed to estimate the median value of compressive strength. Evaluation of the ratio between uniaxial compressive. The test hammer rebound hammer is intended to measure the surface hardness of concrete and there is an empirical relationship between the compressive strength of concrete and the rebound index which is a code consisting of a letter giving an indication of the quality of the concrete and a. The concrete cube specimens are held in a compression testing machine under a fixed load, measurements of rebound number taken and then the compressive strength determined as per is 516. Correlation between nondestructive testing ndt and.
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