Bhartṛhari—Nītiśatakam. “Knowledge is such a treasure which cannot be stolen” . IS (): Method of non-destructive testing of concret-methods of. “Knowledge is such a treasure which cannot be stolen”. IS (): Method of Non-destructive testing of concret, Part 1: Ultrasonic pulse velocity [ CED 2. IS Part 1 - Download as PDF File .pdf), Text File .txt) or read online. is
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Methods of non-destructive testing of concrete Part 2 Rebound hammer _2 .pdf. Copyright: Download as PDF, TXT or read online from Scribd. Flag for. Rebound Hammer (IS (Part 2): ). ▻ The rebound hammer method could be used for: i) Assessing the likely compressive strength of concrete. IS (Part 1): Indian Standard. NON-DESTRUCTIVE TESTING OF CONCRETE —. METHODS OF TEST. PART 1 ULTRASONIC PULSE VELOCITY.
Relationships between pulse velocity. In most of the cases. In addition. The intrinsic difference between the laboratory test specimens and in-situ concrete. Since such non-destructive tests are at best indirect methods of monitoring the particular characteristic of concrete and the measurements are influenced by materials.
The correlation is valid only within the range of values of pulse velocity. When the quality of concrete is doubtful. The impact energy required for rebound hammers for different applications is given in Table 1. Is Part 2: In view of the limitations of each method of non-destructive testing of concrete.
The rebound hammer method can be used with greater confidence for differentiating between the questionable and acceptable parts of a structure or for relative comparison between two different structures. For testing normal concrete For light-weight concrete or small and impact sensitive parts of concrete For testing mass concrete.
IS No. The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete. The concrete cube specimens are held in a compression testing machine under a fixed load.
The points of impact on the specimen must not be nearer an edge than 20 mm and should be not less than 20 mm from each other. To obtain a correlation between rebound numbers and strength of wet cured and wet tested cubes. IS Part 2: The load should be increased for calibrating rebound hammers of greater impact energy and decreased for calibrating rebound hammers of lesser impact energy.
The same points must not be impacted more than once. Normal aggregates such as gravels and crushed rock aggregates give similar correlations. Open texture concrete typical of masonry blocks. Variations in initial rate of hardening. If loosely adhering scale is present. The test can -thus be conducted horizontally on vertical surfaces or vertically upwards or downwards on horizontal surfaces.
If the situation demands. All correlaticns assume full compactjon. Separate calibration curves are required for different curing regimes but the effect of age can generally be ignored for concrete between 3 days and 3 months old. Trowelled and floated surfaces are harder than moulded surfaces.
In structural concrete. Concretes made with supersulphated cement can give 50 percent lower strength than that with ordinary Portland cement. At least nine readings should be taken on each of the two vertical faces accessible in the compression testing machine when using the rebound hammers. Around each point of observation.
A wet surface will give rise to underestimation of the strength of concrete calibrated under dry conditions. Only the vertical faces of the cube as cast should be tested. Rough surfaces resulting from incomplete compaction. If the specimens are wet cured. The test specimens should be as large a mass as possible in order to minimise the size effect on the test result of a full scale structure.
OF RESULTS rebound hammer method provides a convenient and rapid indication of the compressive strength of concrete by means of establishing a suitable correlation between the rebound index and the compressive strength of concrete. As such.
IS_13311_Part 1__1992__Non destructive test ulta sonic.pdf...
In general. I number is very surface on the rebound significant. Carbonated concrete gives an overestimate of strength which in extreme cases can be up to 50 percent.
It is possible to establish correction factors by removing the carbonated layer and testing the concrete with the rebound hammer on the uncarbonated concrete.
If the concrete in a particular member has internal microcracking. 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.
IS The procedure of obtaining such correlation is given in 5. In personal capacity Univardy of Roorkw. New Delhi Geological Corporation of Ltd. Central Building Research Rese. In this. For example. In most of the cases. The various methods that can be adopted for in-situ assessment of strength properties of concrete depend upon the particular aspect of the strength in question. The correlation is valid only within the range of values of pulse velocity rebound number and compressive strength employed and any extrapolation beyond these is open to question.
In view of the limitations of the methods for predicting the strength of concrete in the structure it is preferable that both ultrasonic pulse velocity and rebound hammer methods given in Part 2 of the standard are used in combination to alleviate the errors arising out of influence of material. A complex system of stress waves is developed which includes longitudinal compressional.
If there is a crack.
Density and modulus of elasticity of aggregate also significantly affect the puise velocity. In view of the limitations of each method of non-destructive testing of concrete. The receiving detects the onset of the longitudinal waves. Table 1 Natural Frequency of Transducers for Different Path Lengths Path Length Because the velocity of the pulses is almost independent of the geometry of the material through which they pass and depends only on its elastic properties.
IS 13311-1: Method of Non-destructive testing of concret, Part 1: Ultrasonic pulse velocity
In case of poorer quality. Piezoelectric and magneto-strictive types of transducers may be used. When the pulse is induced into the concrete from a transducer. The actual pulse velocity obtained depends primarily upon the materials and mix proportions of concrete. Typical couplants are petroleum jelly. In such cases. Transducers with a frequency of 50 to 60 kHz are useful for most all-round applications.
The shorter of the reference specimens should be used to set the zero for the apparatus and the longer one should be used to check the accuracy of transit time measurement of the apparatus.
If it is necessary to work on concrete surfaces formed by other means. The two reference specimens usually steel bars should have pulse transit times of about 25 microseconds to microseconds respectively. This difference may vary from 5 to 20 percent depending largely on the quality of the concrete under test. If there is very rough concrete surface.
For good quality concrete. For this. If both the forms of timing apparatus are available. This is to ensure a sharp pulse onset. The pulse velocity V is given by: It shall be capable of measuring the time interval elapsing between the onset of a pulse generated at the transmitting transducer and the onset of its arrival at the receiving transducer.
A minimum path length of mm is recommended for the direct transmission method involving one unmoulded surface and a minimum of mm for the surface probing method along an unmoulded surface. After traversing a known path length Q in the concrete. TWO forms of the electronic timing apparatus are possible. The indirect velocity is invariably lower than the direct velocity on the same concrete element. Surface probing is not so e5cient as cross probing. Each junction point of the grid becomes a point of observation.
The pulse velocity of saturated concrete may be up to 2 percent higher than that of similar dry concrete. For most concrete surfaces.
Shape and Size of the Concrete Member As concrete is inherently heterogeneous.
When the concrete surface is rough and uneven. In general. The apparent increase in pulse velocity depends upon the proximity of the measurements to the reinforcing bar. Below freezing temperature. IS Part 1: This in turn. When concrete is subjected to a stress which is abnormally high for the quality of the concrete. If one of the faces is not. This influence is likely to be the greatest when the pulse path is normal to the predominent direction of the planes of such micro-cracks.
Transducers are held on corresponding points of observation on opposite faces of a structural element to measure the ultrasonic pulse velocity by direct transmission. In field work. This is because. The shape and size of the concrete member do not influence the pulse velocity unless the least lateral dimension is less than a certain minimum value.
Table 1 gives the guidance on the choice of the transducer natural frequency for different path lengths and minimum transverse dimensions of the concrete members. This occurs when the pulse path is perpendicular to the direction of a uniaxial compressive stress in a member. This influence is more for low strength concrete than high strength concrete. This influence is generally insignificant unless the stress is greater than about 60 percent of the ultimate strength of the concrete.
The correlation so obtained may not be applicable for concrete of another grade or made with different types of materials.
The estimated strength may vary from the actual strength by f 20 percent. From these measurements. The reason is that a large number of parameters are involved. Designs and Railways.
There may be some reduction in the accuracy of path length measurement, still it is found to be sufficiently accurate. This arrangement is otherwise similar to direct transmission. Indirect transmission should be used when only one face of the concrete is accessible when other two arrangements are not possible. It is the least sensitive out of the three arrangements.
A pulse of longitudinal vibration is produced by an electro acoustical transducer, which is held in contact with one surface of the concrete member under test 2.
After traversing a known path length L in the concrete, the pulse of vibration is converted into an electrical signal by a second electro-acoustical transducer and electronic timing circuit enable the transit time T of the pulse to be measured.
Uspv Test On Specimens Six cubes samples were cast, targeting at different mean strengths. Further, the cubes samples were cured for different number of days to ensure availability of a wide range of compressive strength attained by these cubes. Then the cubes were then loaded up to their ultimate stress and the Breaking Load was obtained. This graph can now also be used to approximately predict the Compressive Strength of Concrete. Those who have establish the correlation between ultra sonic pulse velocity results with reference to the variation of the reinforcement present in the structural elements.
The results were used for assessing the quality of the concrete of the newly under construction office building. Two Beams were casted of the following dimensions: 1. Grade of concrete used: M20 and M25 The points where the reinforcements existed were known so the testing was done in two stages: 1.
By avoiding the impact of reinforcements or by trying to minimize its impact. By undertaking the effect of reinforcements or by maximizing its impact. A comparative analysis given in table 5 is then made to know the effect of reinforcement. The observations and remarks have been given in tables 6 and 7. The assessment of compressive strength of concrete from ultrasonic pulse velocity values is not accurate because the correlation between ultrasonic pulse velocity and compressive strength of concrete is not very clear.
Because there are large number of parameters involved which influence the pulse velocity and compressive strength of concrete to different extents. However, if details of material and mix proportions adopted in the particular structure are available, then estimate of concrete strength can be made by establishing suitable correlation between the pulse velocity and the compressive strength of concrete specimens made with such material and mix proportions, under environmental conditions similar to that in the structure.
The correlation so obtained may not be applicable for concrete of another grade or made with different types of material. At some places in columns USPV gave no results or indicated that the velocity was out of range. This place gave a unique sound on striking softly with a hard material like iron which clearly indicated a void in between the concrete. A general trend was obtained in the columns. The trend was such that towards the base of the column the tests always showed a higher quality of concrete i.
The compressive strength went on decreasing as we go up towards the roof. A graph has been plotted with increasing height against the predicted compressive strength obtained on the basis of the USPV evaluation.
It is evident from the graph that the compressive strength goes on decreasing with increase in height of column Figure 2. The reason for this variation is better compaction at the base.
Since all the weight of the column acts at the base higher compaction is achieved and also better compaction facilities are available near the base and process compaction becomes difficult as we go up. No such regular trend was observed for beams. Conclusions The main conclusions drawn from investigation performed are as follow: 1.
The poor quality concrete allows the ingress of moisture and oxygen to the reinforcing bars, and hence corrosion occurs. Presently the system is limited to penetration depths of 1 ft. Research is ongoing to develop a system that can penetrate to a depth of 10 ft or more.
The pulse velocity method is an ideal tool for establishing whether concrete is uniform. It can be used on both existing structures and those under construction 3. Usually, if large differences in pulse velocity are found within a structure for no apparent reason, there is strong reason to presume that defective or deteriorated concrete is present.
Fairly good correlation can be obtained between cube compressive strength and pulse velocity. Ultrasonic pulse velocity tests have a great potential for concrete control, particularly for establishing uniformity and detecting cracks or defects. Its use for predicting strength is much more limited, owing to the large number of variables affecting the relation between strength and pulse velocity.
The deviation between actual results and predicted results may be attributed to the fact that a sample from existing structures was obtained by using various corrections introduced in the specifications. The method presented is simple, quick, reliable, and covers wide ranges of concrete strengths..
The method can be easily applied to concrete specimens as well as existing concrete structures by taking direct measurements on concrete elements.
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The final results were compared with previous ones from literature and also with actual results obtained from samples collected from existing structures.
The correlation curves established in the study can be useful for the assessment of the quality of the concrete in an existing nearby structures made with the similar grade of the concrete and the similar sources of the DOI: Unlike other work, the research ended with important and useful charts that require no previous knowledge of the constituents of the tested concrete.Sivamurugan Perumal. Once the velocity is determined, an idea about quality, uniformity, condition and strength of the concrete tested can be attained.
Standards are also reviewed periodically. This in turn. This Indian Standard has been developed from Dot: The correlation is valid only within the range of values of pulse velocity.
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