Non-destructive testing (NDT), also known as non-destructive inspection (NDI), is a method used in civil engineering to check buildings for defects in their structure and in the materials used.
The advantage of a non-destructive analysis method is that it is as non-invasive as possible. Some types of testing leave no trace, while others require minor interventions or the removal of some material samples.
Non-destructive testing is also often useful for inspections or digital mapping of infrastructure.
Non-destructive testing (NDT), also known as non-destructive inspection (NDI), is a method used in civil engineering to check buildings for defects in their structure and in the materials used.
The advantage of a non-destructive analysis method is that it is as non-invasive as possible. Some types of testing leave no trace, while others require minor interventions or the removal of some material samples.
Non-destructive testing is also often useful for inspections or digital mapping of infrastructure.
Here is the list of evidence analyzed in this article:
- magnetometer test – MG
- sclerometric test – SC
- ultrasonic testing – UTCiv
- sonic test – SO
- load test – PC
- vibration measurement – MV
- measurements in the static field – MS (structural monitoring)
- georadar – GR
- infrared thermography – TTCiv
visual examination
Visual inspection is the most important non-destructive test, allowing the detection, description, and cataloging of the main problems in structural elements that are visible to the naked eye. The starting point is, in fact, visual inspection, which also determines the investigation plan. In this article (video), we analyze the non-destructive tests that have the least impact on the structure itself.
MAGNETOMETER TEST
Application
Identification of position, depth and diameter of reinforcing bars within concrete castings and detection of plaster-covered ferromagnetic elements
Strengths and limitations
Absolutely nondestructive
Difficult to define bars close together or on multiple levels
Normative reference
BS 1881-204:1988
SCLEROMETRIC TEST
Application
Determination of the rebound index of a beating mass on hardened concrete and estimation of mechanical strength using correlation tables
Strengths and limitations
Absolutely non-destructive, fast, inexpensive
Affects only the surface of the concrete
Normative reference
UNI EN 12504-2
ULTRASONIC TESTING
Application
Measurement of ultrasonic wave propagation velocity and, through correlations, estimation of compressive strength of hardened concrete
Strengths and limitations
Absolutely nondestructive, fast, inexpensive, affects the entire section
Result influenced by the presence of rebar
Normative reference
UNI EN 12504-4
SONIC TESTING
Application
By measuring the propagation velocity of the sonic wave in masonry, considerations can be made about homogeneity and elastic modulus
Strengths and limitations
Assumes only a stonation
Presence of voids or cavities may invalidate the test
Normative reference
ASTM D2845-08
ASTM C597-02
LOAD TESTS
Application
Verification of the actual behavior of structures under operating loads
Strengths and limitations
Depends on the type of evidence
Normative reference
ACI 437.2M-13
ReLUIS Guidelines 2, 2015
VIBRATION MEASUREMENT
Application
Verification of dynamic behavior of structure and validation of theoretical models
Strengths and limitations
Speed in the execution of measurements
Independence of characteristic frequencies from the forcer
Normative reference
UNI 11568
UNI ISO 5348
UNI 9916
UNI 9614
UNI 10985
STRUCTURAL MONITORING
Application
In static monitoring, displacements (e.g., crack opening) are measured; in dynamic monitoring, the magnitude of vibration is measured
Strengths and limitations
Possibility of performing continuous and remote monitoring, setting alarm thresholds, checking the variation of characteristic parameters
Normative reference
UNI/TR 11634:2016
GEORADAR TESTING
Application
The method takes advantage of the reflection of electromagnetic waves and is usually used to search for underground utilities
Strengths and limitations
Absolutely non-destructive; depending on the frequencies of the antennas, different depths can be investigated
The output of the instrument is not intuitive, and the signal is shielded by the presence of ferromagnetic materials and water
Normative reference
RILEM TC 127-MS
ASTM D6432
IEC 306-8
INFRARED THERMOGRAPHY
Application
Taking advantage of the property of any body having T greater than 0 to emit electromagnetic waves, images in the infrared range are acquired
Strengths and limitations
Non-destructive, does not require contact with the surface
Normative reference
UNI EN 16714
UNI EN 13187
