Leaky Rayleigh wave investigation on mortar samples.

Area of Science:

• Materials Science
• Civil Engineering
• Geotechnical Engineering

Background:

• Aggressive groundwater poses a significant risk to the durability of concrete in tunnels and underground structures.
• Sulfate interactions within concrete can lead to material degradation and compromise structural integrity.
• Accelerated laboratory experiments are crucial for understanding long-term material behavior under harsh conditions.

Purpose of the Study:

• To develop and validate a nondestructive testing (NDT) method for assessing the surface layer of mortar samples.
• To investigate the effects of sulfate interaction on mortar using accelerated laboratory testing.
• To establish a reliable diagnostic tool for evaluating concrete cover integrity in underground constructions.

Main Methods:

• Utilized ultrasonic surface waves, specifically leaky Rayleigh waves, for material analysis.
• Employed a pitch and catch transducer arrangement in an immersion technique.
• Measured the propagation velocity of ultrasonic waves to infer material properties.

Main Results:

• Successfully verified the ultrasonic technique on reference materials: aluminum, copper, and stainless steel.
• Demonstrated the applicability of the developed NDT method on mortar specimens.
• Obtained initial measurements indicating the technique's potential for diagnosing concrete degradation.

Conclusions:

• The developed ultrasonic surface wave method is a viable NDT tool for investigating the topmost layer of mortar.
• This technique offers a promising approach for early detection of concrete damage caused by aggressive environments.
• Further application on actual underground constructions is warranted to confirm field performance.