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• Advanced research & development services for ultrasonic testing of concrete.
• Collaboration opportunities.
• Newsletters.

Benefits of the I2L-225-CIR transducer

• Probe through thicker concrete than conventional metal-body transducers - works when other transducers fail.
• Uses new solid coupling agent - transducer conveniently held in place during test.
• Transducer can be permanently attached - ideal for in-service monitoring.
• Works on surfaces of almost any roughness.
• Exceptional performance - for research applications.
• High sensitivity typically +10db to +20dB greater than conventional metal-body transducers.
• Can be used in arrays - application to research.
• Impulse response data file available - research applications.

Development history

The I2L-225-CIR is an ultrasonic transducer developed by Cambridge Ultrasonics for testing concrete and is the product of several years of research and development. It was developed as part of a project promoted by the German Concrete Association and managed by the Institut fur Massivbau, Darmstadt.

The transducer has excellent coupling to concrete due to the use of a solid coupling agent which also allows the transducer to work on surfaces of virtually any roughness. It has high efficiency and a wide frequency range - again due to the use of an almost ideal ultrasonic coupling agent.

Applications

The transducer is recommended for:

• Research, for example in developing novel pulse-echo inspection systems to detect corrosion in tendons.
• Civil Engineering universities and institutes, when modern methods must be demonstrated.
• Transmission applications on-site, where long range is needed.
• Applications requiring transducers to be attached permanently (a special permanent bonding mortar can be supplied).

The solid coupling agent is a specially formulated fast-setting mortar that takes a few minutes to reach full working hardness at room temperature (see graph). A modified formulation is available for lower temperatures. A thin metal blade is driven into the mortar to detach the transducer - the mortar is brittle and falls away from both the transducer and test surface, a scratch brush can be used to remove the final residues. The transducer can be reused indefinitely provided no leverage force is applied to the body when trying to break the mortar bond. A modified mortar is available for permanently attaching transducers for in-service monitoring - the transducers cannot be re-used in this case.

It takes longer to attach the I2L-225-CIR but the transducer usually allows a test to be made when other transducers do not work.

The I2L-225-CIR is sealed against moisture and dust and it has no serviceable parts. Output is via a screened 50 ohm cable (2 m long) terminated in a bnc 50 ohm plug.

Performance

The transducer offers state-of-the-art performance for testing concrete. Its good bandwidth makes it ideal for use with chirp signals as well as pulses. Chirps give better performance than sharp spikes in heterogeneous scattering materials like concrete.

After signal processing chirp durations are compressed from typically 100 us to give sharp pulses of typically 10 us - an equivalent axial resolution of approximately 40 mm. This resolution is close to the size of the largest aggregate particles used for making concrete and, we believe, this sets the limit of what is physically possible.

Range in pulse-echo depends on concrete type but in tests ranges of 1.5 m have been achieved (using arrays). The limiting range in transmission has not yet been measured but 2 m has been achieved without difficulty and this is not thought to be the maximum. All range figures depend upon concrete mix; generally, the larger the maximum aggregate size the shorter the range. Values for ranges given above refer to maximum aggregate sizes of approximately 16 to 25 mm.

In pulse-echo mode - where two or more transducers are used from a single surface - performance can be improved very substantially by using arrays of 7 or 19 transducers. This requires the use of additional equipment.

Specification

Power bandwidth (-6 dB): 210 kHz to 288 kHz
Useful bandwidth: 85 kHz to 292 kHz
Sensitivity: +10dB to +30dB
Signal/noise ratio: +50dB
Waterproofing: IP67
Dimensions: 53 mm diam x 100 mm
Weight: 500 gm
Beam profile (semi-angle): 20 deg (300 kHz)
80deg (100 kHz)
Near field range: 13 mm (300 kHz)
40 mm (100 kHz)
Calibration: Impulse response
Calibration option order: CAL-I2L-225-CIR

Specification is subject to change as part of a policy of improving the quality and performance of products.

Publications

• "A novel ultrasonic transducer for inspecting concrete" D.R.Andrews, A.M.Hughes. IEEE Symp Ultrasonics & Ferroelectrics Dec(1991), Orlando, Florida.
• "Non-destructive evaluation of concrete materials and structures" D.R.Andrews, C.W.Turner, B. Twycross. HM Publication OTH 90 320 (1990) 243-51.
• "Development of equipment and assessment procedures to locate the position and determine the condition of steel reinforcement in concrete" Report to the Transport Research Laboratory and Shell Exploration & Production (UK) Ltd. (1992).