|dc.description.abstract||The most widely used material for civil infrastructure is reinforced concrete. The concrete
deteriorates over time because of several reasons, and therefore, inspection of concrete is
necessary to ensure its compliance with the design requirements. Decision makers often have
insufficient data to implement the appropriate corrective measures in the face of infrastructure
failure. Better assessment methods are essential to obtain comprehensive and reliable
information about the concrete elements. Although, different methods exist to inspect concrete
members, there is no comprehensive technique available for condition assessment of concrete
of shallow foundations. To ensure the integrity of shallow foundations during construction and
during its service life, it is necessary to monitor their conditions periodically. To achieve this
goal a new NDT methodology is developed to reliably evaluate the conditions of new shallow
foundations without changing their future performances.
Recently, there is a trend to overcome coupling issues between the transducers and the object
under investigation, by installing sensor networks in concrete to assess its integrity. Although
many NDT approaches are designed to evaluate the integrity of concrete structural elements,
shallow foundations, which are concrete elements embedded in soil, have received less
attention. The challenging aspect of characterizing shallow foundations is limited accessibility
for in-service foundation inspections because of structural restrictions. Even when accessibility
is possible, the NDT methods (ultrasonic pulse velocity, UPV) used may produce
measurements with high uncertainties because of inconsistent coupling between the transducer
and the surface of the material being tested.
In the current research project, a new NDT procedure is developed based on design of new transducers
embedded at the base of lab-scale concrete foundation models, and these transducers are waterproof and
used as receivers. The transducers consist of radial-mode piezoceramics that can detect waves from
different orientations. The developed methodology relies mainly on two methods to emit the
transmission pulse; either using a direct contact method by gluing the transducer to the concrete surface
or using a plastic tube partially embedded in concrete and filled with water. The first procedure is used
when the accessibility to the top surface of the foundations is possible; otherwise, the second option is
employed to reach the concrete surface of foundations. The new methodology can be used in different
stages: during construction of foundations to monitor the uniformity and quality of the concrete, and
during in-service life to periodically assess the condition of the foundations, specifically after an event
that may cause severe damage in concrete such as earthquake and overloading. To verify the
applicability of the methodology, unreinforced and reinforced shallow foundation lab-scale concretemodels were tested in the laboratory under uniaxial compression loads. In this work, all ultrasonic
measurements are averaged 16 times to ensure the consistency of the results and to eliminate
high frequency noise. The average coefficient of variance obtained is less than 3.5%; which is
considered acceptable in this type of measurements (typical measurement error ~5%). Also,
different tests were repeated more than three times by removing and putting back all the
ultrasonic transducers to enhance the statistical significance of the results.
The main contributions of the research presented in this thesis are:
Characterization of low and high frequency transducers using laser vibrometer to
characterize their responses for better ultrasonic measurements.
Characterization of a single fracture growth in a homogenous material based on wave
velocity and wave attenuation.
Characterization of cement-based materials using ultrasonic pulse velocity and laser
Evaluation of freeze/thaw damage and monitoring progressive damage in concrete
specimens subjected to uniaxial compression load using ultrasonic pulse velocity and
laser vibrometer methods.
Fabrication of thirty-six new radial ultrasonic transducers to embed in concrete models
for quality control purposes and to monitor progressive damage using new transmission