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8
ULTRA SOUNDS
› CONTACT ULTRA-SOUND SURVEYS
(Direct – Indirect – Semi-direct method)
The method is based on the propagation
speed of longitudinal ultra-sonic
waves inside a reinforced concrete
structure. The propagation speeds depends
on the characteristics of the material
such as elasticity, density, presence
of gaps, micro-holes, etc… From
the determination of the following parameters:
reflection, refraction, transit
time (T.O.F.) and mitigation of the vibration
energy, it is possible to obtain information
on:
• Homogeneity of the mix
• Elasto-mechanical characteristics
• Entity, geometry and location of particular
faults or internal defects, variations
in time of the quality parameters
of the concrete
Ultra-sonic tests through which it is
possible to evaluate the transit speed
of the pulses (with known thickness
and time) are particularly important.
The primary goal of the Ultra-sound
survey is to record the time of fly (TOF,
Time of Fly) and the following calculation
of the speed. In order to calculate
the propagation speed of longitudinal
waves (P waves), the arrival of the first
wave-train must be found out with accuracy.
In order to perform this operation
correctly, the instrument must be
equipped with oscilloscope that allows
to visualize the transit wave on the device
display.
The ultra-sound tests can be carried
out with:
• Direct method
When the transmitting and receiving
probes are positioned on the opposite
sides of the element to test.
• Semi-direct method
When the E/R probes are positioned on
adjacent surfaces, usually orthogonal,
of the element to test
• Indirect method
When E/R probes are positioned in the
same side of the structural element to
test.
› CROSS-HOLE ULTRA-SOUND TEST
The cross-hole is a method to analyze
the foundation poles of buildings that,
with the use of ultra-sounds, crosshole,
allow to carry out an accurate
high resolution test. An ultra-sonic
wave is sent from a transmitter to
a receiver, which are convoyed automatically
by the device along the entire
length of the pole inside the pipes
embedded inside of it, during casting.
The speed of the sonic wave and its
energy are strongly influenced by the
quality of the cement. Therefore, it is
possible to assess the characteristics
and give a tomographic representation
in 2D and 3D called diagraphy..