Assessment of Concrete Elements of A Collapsed Building Using Ultrasonic Pulse Velocity Test

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SSRG International Journal of Recent Engineering Science Volume 8 Issue 2, 16-19, Mar-April, 2021
ISSN: 2349 – 7157 /doi:10.14445/23497157/IJRES-V8I2P103 © 2021 Seventh Sense Research Group®
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Assessment of Concrete Elements of A Collapsed
Building Using Ultrasonic Pulse Velocity Test
Timothy Danjuma1, Aliyuda Yohanna Adamu2, Mbimda Ali Mbishida3*, Benjamin Yusuf Mailafiya4
1,2,3,4 Nigerian Building & Road Research Institute (NBRRI) North Central Zonal Office Jos, Plateau State
(Federal Ministry of Science & Technology, Nigeria)
Abstract
Some ugly trends have bedeviled the construction industry
in Nigeria for about a decade now that includes building
collapse. One of these incidences that occurred in 2018 is
the catastrophic collapse of the hall/office complex of the
Nigerian Medical Association. This research present the
findings from the Ultrasonic Pulse Velocity Test (UPVT)
carried out on the concrete elements of the collapsed
building with the sole purpose for prognosis, diagnosis and
quality control by the Nigerian Building and Road
Research Institute (NBRRI) and other relevant stake
holders in the construction industry. The results of the
UPVT on all the beams and slabs showed that the quality
of the concrete is quite below the recommended standard
of 3.0km/s. The UPVT performed on the selected ground
floor columns were found to be good as the Pulse Velocity
(PVs) were averagely more than 3.5 km/s. However, the
part of the column below the ground floor level is doubtful
(PV<3.0 km/s). These clearly shows that the columns
above the ground floor level are good, but those below are
the suspected cause of the collapse.
Keywords - Building Collapse, Concrete Quality,
Ultrasonic Pulse Velocity
I. INTRODUCTION
A building is a roofed and walled structure built
for permanent use. A building can serve as living quarters,
for storage, an office or a factory. A building is a human
aesthetically and artistically created space that provide
habitat for humans and other living things for their comfort
to prevent the adverse effects of the natural and artificial
environmental conditions for their survival. A building is
an enclosure for spaces designed for specific use, example
religious activities, control local climate, distribute
services and evacuate waste [1].
There are two main components to a building,
namely, the structural components and the non-structural
components. The structural components bear the entire
weight of the building structure and transmit that weight to
the ground effectively. Examples of these include columns,
beams, slabs, etc. Non-structural components carry only
their own weight and they transmit that weight to the
structural components. Examples of these include doors,
windows, partition walls, etc. The primary supporting
structure of a building can be made with different
materials; the most frequent materials used include steel,
timber and reinforced concrete. However, the use of
reinforced concrete is most common [2], [3].
It has been concluded by [4], [5] that more than
90% of storey buildings in Nigeria have been made from
reinforced concrete, therefore, the study of the concrete
used is important to know the quality of buildings
constructed in Nigeria. According to [6], studies were
carried out in Nigeria which revealed the effects and
showed low level of awareness of the applications of
cement strength class in concrete production. In
construction work, buildings are made to stand firm and
strong, a building is held primarily by its structural
components, once there is a problem with the structural
components of a building, then failure of that building is
inevitable. In Nigeria, most of the structural building
components are made of concrete, then it can be concluded
that the highest percentage of building structural failure is
as a result of concrete failure. The concrete could fail due
to the production of lower concrete quality below the
capacity to effectively resist its imposed load, service
factors that deteriorate a good concrete to a quality
decrease below the service requirement like the ingress of
nitrates in concrete service conditions [7] and once the
concrete structure is loaded beyond its service limits like in
upward building adaptations.
Collapse refers to an instant of a structure falling
down as a result of being weak. In architecture and
construction, collapse is considered to be a mechanical
failure of a building. Globally, building collapse is
considered to be caused by one of the two major factors:
the natural or man-made factor [8], [9]. Building collapse
has gradually made the headlines in most developing
countries today, and this has become rampant and
devastating. The effects of each building collapse is felt
and not forgotten especially by its victims. These include
loss of lives, huge loss of money spent on investment, or
property, jobs, trust in building professionals and
increasing uncertainty among stakeholders and
environmental disaster [2].
In Nigeria, building collapse occurs either by
natural elements or by the negligence of man. The
frequency of building collapse in the construction industry
has become worrisome to the extent that research has
begun in order to fined lasting solutions. The recorded
incident of building collapse has occurred in buildings
under construction, buildings undergoing renovation as
well as buildings in service [10]. There has been several

Mbimda Ali Mbishida et al. / IJRES, 8(2), 16-19, 2021
17
building collapse in Nigeria which have had a negative
impact on the socio-economic status of the citizens. [11]
have shown that no loss of life occurred in 20.3% in the
occurrence of building collapse, while in 44.4% of the
recorded incident, between 1 and 5 lives were lost, while
the worst-case condition was the death of more than 21
people in 9.3% of the incidents. [12] carried out analysis
and evaluated the death rate involved in 47 reported cases
of building collapses verified between 2000 and 2010, over
300 death rates were recorded for Lagos, Abuja and port
Harcourt which are the three major areas with high rate of
casualties. According to [1], increase in population in
cities as a result of migration created the specific problem
of inadequate building structures. This resulted into an
increase of building projects from various contracting
firms of doubtful competence. [13] pointed to the fact that
building collapse has cast a stain on the competence of the
nation’s building community of professionals responsible
for designing and monitoring construction work at building
sites. Experts in the field of building construction have
suggested the blame should not be on the professionals
alone. This is due to the following reasons:
i. It has been proven that owners of buildings under
construction derail from their approved plans.
ii. The authorities that are supposed to monitor the
implementation and compliance of the
approved plans also fail in doing their job.
iii. Some building owners shun professionals in order
to cut cost.
iv. Some greedy contractors do not go for the high
cost standard building materials, but rather
patronize the substandard building materials.
All these factors contribute to the failure and collapse of
buildings in Nigeria.
A. Ultrasonic Pulse Velocity Test (UPVT)
Ultrasonic Pulse Velocity Test is a non-
destructive test employed for compressive strength
estimation and quality assessments of the concrete
samples. It is used for the testing of the homogeneity and
integrity of the concrete. The UPVT detects some
imperfections in homogeneous materials and its results are
reliable. Total control of a structure can be obtained, when
the properties variation with the time is used. When the
analysis of the propagation variations of ultrasonic velocity
wave is used, it is possible to detect heterogeneous regions
in the concrete [14]. The UPVT results can be used for
prognosis, diagnosis and quality control.
The following can be accessed on the concrete using the
ultrasonic pulse velocity test.
a. Quality assessment of strength of concrete, its
gradation in different locations of structural
members and the plotting the same.
b. Any discontinuity in cross section like cracks,
cover concrete delamination etc.
c. Depth of the surface crack.
d. To check the uniformity of concrete
e. To control the quality of concrete and concrete
products by comparing results to a similar made
concrete.
According to [15] and [14], the UPVT method is
based on the propagation of high frequency sound wave
which passes through the material. The wave’s speed
varies in function of the density of the material, making it
possible to estimate the porosity and the detection of
discontinuity. The idea is to transmit sound inside a
material and measure the time necessary for the wave to
propagate through it. Having known the distance, the pulse
velocity can be determined, which is a function of several
factors such as nature of the material, the presence of water
in the pores, e.t.c. Though there is no clearly defined
relationship between compressive strength and pulse
velocity, however it can be used to determine the
homogeneity and the integrity of the concrete [15].
Table 1: Concrete Quality based on Ultrasonic Pulse
Velocity Test
S/N
PULSE
VELOCITY
CONCRETE
QUALITY
1
>4.0km/s
Excellence
2
3.5-4.0km/s
Good
3
3.0-3.5km/s
Medium
4
<3.0km/s
Poor
Quality of concrete in terms of strength, homogeneity,
trapped air, internal flaws, cracks, segregation,
honeycombing, compaction, workmanship and durability
can be conducted from this test (ASTM C597-09 Standard
Test Method for Pulse Velocity through Concrete-
astm.org)
B. The NMA Collapsed Building
The Collapsed building in question belongs to the
Nigerian Medical Association sited at Gura-Zot B, Kwang,
Jos South Local Government Area of Plateau State,
Nigeria. The site lies in the savanna vegetation belt of
Northern Nigeria with coordinates of 9.878°N and
8.918°E. It is an on-going 2-storey building plan of which
the work was taken up to the 1st floor. The building was
reported to have collapsed on Thursday 6th September,
2018.
The aim of carrying the Ultrasonic Pulse Velocity
Test (UPVT) on the different concrete structure of the
collapsed building is for the purpose of prognosis,
diagnosis and quality control by the Nigerian Building and
Road Research Institute (NBRRI) and other relevant stake
holders in the construction industry.
II. MATERIALS AND METHOD
A. Materials and equipment
The materials used for the purpose of this test are the
concrete slabs and columns of the collapsed structure.

Mbimda Ali Mbishida et al. / IJRES, 8(2), 16-19, 2021
18
While the equipment used was the Ultrasonic Pulse
Velocity Tester.
B. Method
The test was performed in accordance with the
provision of BS 1881: Part 203 (1986) on the concrete
specimen of the collapsed building. The equipment used is
called “Ultrasonic Pulse Velocity Tester”. Ultrasonic
testing equipment includes a pulse generator circuit,
consisting of electronic circuit for generating electronic
pulse into mechanical pulse having an oscillation
frequency in the range of 40 KHz to 50 KHz and a pulse
reception circuit that receives the signals. The transducer,
clock, oscillation circuit and power source are assembled
for use. After calibration to a standard sample of material
with known properties, the transducers are placed on the
opposite sides of the material. The pulse is obtained by
applying a rapid change of potential from a transmitting
transducer to the receiving transducer. The path of the
travel of the emitting pulse between the specimens (path
length) by the two transducers were noted and fed into the
Tester [16]. The Pulse velocity was then read-out and
recorded accordingly.
Pulse velocity is measured by a simple formula:
……..……1
III. RESULT AND DISCUSSION
A. Concrete Beams
Table 2 shows the test performed on the un-
collapsed beams samples collected from the collapsed
building site.
Table 2: Beams Ultrasonic Pulse Velocity (UPV) Test
Result
Element ID
Path
Length
(mm)
Transit
Time
(μs)
Pulse
Velocity
(km/s)
Beam 9
(main beam)
230
85.1
2.7
Beam 6
(secondary
beam)
230
99.5
2.3
The results of the Ultrasonic Pulse Velocity test on the
beam samples as shown in Table 1 attest to the poor nature
of the beam of the collapsed building as the Pulse Velocity
(PV) recorded were less than 3.0 km/s as it should have
been (See Table 1). This indicated a poor quality of
workmanship and concrete were doubtful. It is pertinent to
note that these tests were performed on the un-collapsed
beams that were yet to be loaded at the second floor.
B. Concrete Slab
Table 3 shows the test performed on the slap sample
collected from the collapsed building site.
Table 3: Slab Ultrasonic Pulse Velocity Test Result
Element
ID
Path
Length
(mm)
Transit
Time (μs)
Pulse
Velocity
(km/s)
Slab
(150mm)
150
59.9
2.5
Due to the insignificant rebound number obtained the
compressive strength cannot be read from the graph. This
further shows that the concrete is of poor quality and
strength, despite the use of machine crushed granite
aggregate and well graded fine aggregate for the
construction. Cement content in the concrete mix may be
grossly inadequate in content since the mix was not
designed according to any known standard.
C. Concrete Columns
Table 4 below shows the results of different concrete
columns collected from the site of the collapsed building.
A remark on each was made after comparing the result of
each column with a standard as shown in Table 1.
Table 4: Columns Ultrasonic Pulse Velocity Test Result
Element ID
Path
Lengt
h
(mm)
Trans
it
Time
(μs)
Pulse
Velocit
y
(km/s)
Remar
k
Colum
n P2
Ground
Floor
230
66.6
3.5
Good
Colum
n 08
Ground
Floor
240
64.2
3.7
Good
Colum
n B8
Foundati
on
Concrete
230
91.8
2.5
Doubtf
ul
Ground
Floor
240
61.9
3.9
Good
Colum
n G1
Ground
Floor
230
65.9
3.5
Good
Colum
n K1
Ground
Floor
240
73.8
3.3
Mediu
m
Colum
n F8
Ground
Floor
400
103
3.9
Good
From the UPV test performed on all the ground floor
Columns as shown in Table 4, they were found to be good

Mbimda Ali Mbishida et al. / IJRES, 8(2), 16-19, 2021
19
as the PVs were on average more than 3.5 km/s as
suggested in Table 1. The part of column below the
Ground floor level is doubtful (PV<3.0). It shows that the
Columns above the ground floor level were good but
below it was suspect for failure
IV. CONCLUSION
From the results obtained, the building may have
collapsed due to the following reasons:
a. Poor workmanship as evident by the poor quality
and strength of the concrete.
b. The cement content in the concrete mix may be
grossly inadequate in content since the mix was
not designed according to any known standard.
c. There may be compromise in the foundation
depth and thickness as the ultrasonic pulse
velocity test shows that the columns above the
ground floor were very good, but below it was
suspect for failure.
RECOMMENDATION
a. Subsequent construction and use of the same
building should be stopped by the relevant
government authority as the un-collapsed part of
the building is liable to total failure.
b. The relevant Government authorities and building
owners should ensure that relevant construction
professionals are actively engaged during design
and construction process of buildings.
c. Relevant Government authorities and regulatory
bodies responsible for the approval and
supervision of the project at any point should do
that with all diligence.
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