Strength assessment beyond coring.
Applications:
Estimation of compressive strength of concrete / Mapping of concrete uniformity / Estimation of compressive strength of high strength concrete / Control of concrete curing for formwork removal
Variants: Please select a product variant to add to cart.
The legendary and the Original Schmidt rebound hammer and its Swiss-made accuracy is now even more flexible and connected. Measure, evaluate and fully report even the most extensive inspection projects within just minutes.
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Standards
Guidelines
The formulae used in the compressive strength correlation curves in the OS8000 and OS8200 rebound hammers can be found in the Schmidt Hammer Conversion Curve Database below:
1. Original Schmidt OS8000 Type N
Curve
Min R
Max R
Unit
Form factor
Equation
Proceq B (14 - 56 day mean)
15
55
N/mm2
150 mm cube
Fck = 1.05 x ( 0.01078R2 + 0.904R - 12.91)
Proceq A (7 days mean)
Fck = 1.05 x ( 0.012516R2 + 0.706R - 7.49)
Portland Cement J
kg/cm2
Fck = 1.05 x ( 0.133R2 +8.82R - 122)
Early strength J
Fck = 1.05 x ( -0.0803R2 + 20R - 253)
Blast Furnace J
Fck =1.05 x ( 0.2R2 + 1.83R + 22.4)
Averag Curve J
Fck = 1.05 x ( 0.0485R2 + 12.3R - 146)
Characteristic strength R
10
95
Step function (see below)
The characteristic strength curve is based on the reference table for the screening test provided in the Annex to EN13791. This curve provides a safe estimate with <5% probability of over-estimating the strength.
R value - Strength (N/mm2) 20 to 29 - <10 30 to 32 - 10 33 to 34 - 15 35 to 37 - 20 38 to 39 - 25 40 to 42 - 30 43 to 46 - 37 47 to 48 - 45 49 to 50 - 50 51 to 52 - 55 53 to 56 - 60 57 to 59 - 67 60 to 64 - 75 65 to 68 - 85 69 to 75 - 95
Impact angle conversion is applied to the measured R value before calculation of the compressive strength according to these curves. The impact angle correction is based on this formula:
Rcorr=R +(-a0+R*a1)*sin(angle)
a1+
0.08
a0+
7.1
a1-
0.043
a0-
4.3
Take a0+ and a1+ for angles >= 0°, a0- and a1- for angles < 0°
Min Q
Max Q
< 10% (old)
22
75
fck = 2.77e^0.048Q
Ref EU (old)
21
62
fck = 1.8943e^0.064Q
Ref CN
20
fck = 0.0244Q^2-0.6129Q+10
Ref RUS
77
fck = 0.03Q^2-0.86Q+9.5
Mean strength
fck = 3.6473e^0.0475Q
Characteristic strength Q
No angle correction is required for measurements with the Silver Schmidt.
Note! The Ref EU curve was determined with very high quality concrete and gives very high strengths.
Q value - Strength (N/mm2) 10 to 33 - <10 34 to 39 - 10 40 to 44 - 15 45 to 48 - 20 49 to 51 - 25 52 to 55 - 30 56 to 59 - 37 60 to 61 - 45 62 to 63 - 50 64 to 65 - 55 66 to 67 - 60 68 to 70 - 67 71 to 72 - 75 73 to 74 - 85 75 to 80 - 95
Here it is necessary to differentiate between classical rebound hammers (R-value) and the Silver Schmidt hammers (Q-value). Classical rebound hammers require an impact angle correction when the impact is not carried out...
Here it is necessary to differentiate between classical rebound hammers (R-value) and the Silver Schmidt hammers (Q-value). Classical rebound hammers require an impact angle correction when the impact is not carried out horizontally. For the Original Schmidt, the correction can be found in the manual for vertically up and vertically down measurements. The Original Schmidt OS8000 applies a more advanced impact angle correction automatically for any angle. On the app, the user can see both the uncorrected and the corrected values. The Silver Schmidt hammers are intrinsically impact angle independent so no correction is necessary.
There is no simple answer to this question. The answer depends on the region you are in and the standards you are working to. In China for example there are standardized correlation curves, which may be selected in the...
There is no simple answer to this question. The answer depends on the region you are in and the standards you are working to. In China for example there are standardized correlation curves, which may be selected in the Original Schmidt Live app. Other regions such as Korea and Japan have nationally accepted correlation curves that are widely used. These may also be programmed directly into the Schmidt Live app and used. However, unless the standard you are using provides a method to use standardized curves then you should always calibrate your hammer to the concrete under test using a custom materials curve. If this is not possible we recommend using the lower 10th percentile curve with the Silver Schmidt OS8200 hammer to give a conservative estimate. This is a safer option with a smaller chance of overestimating the strength. Another option is to use the EN13791 screening test with either Original Schmidt OS8000 or Silver Schmidt OS8200 which again gives a conservative estimate. The use of custom material curves is fully explained in the tutorial "12. Custom materials" included in the Original Schmidt Live app.
In order to create a custom materials curve, it is necessary to record rebound values at a number of locations in the structure where cores will be taken. Alternatively, rebound measurements can be made on standard cubes...
In order to create a custom materials curve, it is necessary to record rebound values at a number of locations in the structure where cores will be taken. Alternatively, rebound measurements can be made on standard cubes or cylinders which are then crushed in the press to determine the actual compressive strength. This data is then used to create a custom material curve using a simple spreadsheet function. The complete procedure is explained in the tutorial video "12. Custom materials" included in the Original Schmidt Live app.
No, it is not possible. The mushroom plunger was specifically designed or use with the Silver Schmidt OS8200 type L. It extends the range of the hammer down to approximately 5 MPa and is typically used for the...
No, it is not possible. The mushroom plunger was specifically designed or use with the Silver Schmidt OS8200 type L. It extends the range of the hammer down to approximately 5 MPa and is typically used for the determination of the early strength of concrete. e.g. for formwork removal in tunnel applications.
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