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Manual for ZBL-U5 series of Ultrasonic Detector
2.2.2 Ultrasonic-rebound combined method for
testing concrete strength
This combined method adopts two or more than two test methods
to test several physical quantities and establishes relationship between
them and concrete strength. "Ultrasonic pulse speed-rebound value"
combined method is the method with the most research and widest
application at home and abroad.
By adopting low frequency ultrasonic tester and rebound tester
with standard kinetic energy of 2.207J, ultrasonic-rebound combined
method tests acoustic time and rebound value separately in the same
test area of structure or structure member, and calculates the concrete
strength in test area through established strength test formula.
Strong relativity exists among the wave speed, rebound value and
strength of concrete; when strength is stronger and wave speed is
faster, the rebound value is higher; after the relationship curve has
been calibrated, test the acoustic time and rebound value separately in
same test area, then calculate the concrete strength by utilizing
established strength test curve (formula 2-1):
In which: a - coefficient of constant term; b, c - regression
constant; fcu,e - equivalent value of compressive strength; V –
calibrated ultrasonic speed in test area; R – calibrated average rebound
value in test area.
2.2.3 Ultrasonic method for testing
uncompacted area and cavitation
The speed of ultrasonic transmission is directly related to
=
×
b
f
a
V
,
cu
e
×
c
（2-1）
R
20
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