1. 10
Introduction
In this modern savvy world, concrete have the big interaction with the
environment and it is significant as you can see without concrete there are no
buildings. According to Robrtson. S (n.d), concrete is a mixture of cement and
water plus the combination of sand and water which harden into an artificial
stone in few minutes but some will takes up to hours or even weeks if some
substances added in the mixing stage. However, there are concrete
degradation and defects.
The meaning of degradation is a turning down process that low in condition,
quality and level. In a simple explanation means the condition of something
getting worse. Moreover, the word ‘defect’ means the lacking of something
essential or can be indicate as an imperfection that causes failure. So the
concrete degradation and defects means that the concrete is undergoing the
damaging stimuli.
Since in this report concrete degradations and defects is the topic discussed
about, all the details about should be briefly explained. First issue is finding
the reasons that can cause concrete degradation and defects, then explaining
the process one by one plus discussing about characteristics of them. Next
level is to find the preventions and solutions for concrete degradation and
defects, how to repair them, and what their effects are, then at the end giving
some examples of structure failure.

2. 11
Types of defects and degradation
There are so many types of concrete degradation and defects, from a minor
cracking to a major structural failure. The examples are cracking, corrosion of
reinforcement bar, concrete spalling, honeycombing, scaling, delamination
and popouts. The followings are the common types of defects that we usually
meet.
1. Honeycombing
Honeycomb is the phenomena that we found a void on the surface of the
concrete slab. This phenomenon is named as concrete honeycomb because
the void looks alike with the honeycomb that made by the honeybees.
"The honeycomb is formed because of the failure of the mortar to effectively
fill the spaces among coarse-aggregate particles” (Honeycomb, 2014). The
failure of filling spaces among coarse-aggregate is due to the ineffective of
vibration. Furthermore, there are few more reasons that lead to this defect
such as poor sampling, incorrect placement of reinforcement bars, and
inaccurate cement to water ratio that causes poor workability (Schultz, 2014).
The honeycomb can be repaired by removing the affected area and then
clean the area thoroughly to remove all the loose materials. Then, the non-
shrink grout should be applied to the affected surface, while a larger affected
area may need the bonding agent.
Honeycombs found on the
surface of concrete. Retrieved
from (Honeycomb, 2014)
Honeycombs found on the surface of
concrete. Source from:
http://www.jfanjoy.com/blog/?p=3885

3. 12
2. Concrete cancer
The correct term for concrete cancer is actually concrete spalling, it is one of
the phenomena of concrete degradation. This phenomenon is the breaking
away of the concrete surface and it will usually happen on top of the slab, slab
edge, soffit and façade.
It happens with the presence of water penetration and salt from the
atmosphere. These two elements will cause the reinforcement bar inside the
concrete to rust and thus the corroded steel will normally expand few times
from its original size. This situation then makes the concrete to spall (break
away). The lack of concrete cover, poor quality of concrete, carbonatation and
Alkali – Silica reaction are also the factors that cause concrete cancer.
Concrete cancer must be treated immediately once it happened. “This is
because the rusting reinforcement bar may cause the concrete around the
steel to become more displaced, and more water penetrates into the steels
thus causing more rusting” (Fitzgerald, 2010).
The areas of concrete that affected by spalling can be repaired if the
damaged top pavement is not more than 1/3 while full-depth repair is needed
if the damage is more than the top 1/3 of the pavement (Concrete Slab
Surface Defects: Causes, Prevention, Repair, 2001). First of all, all the
affected concrete and rust on reinforcement bar must be removed. Then, anti
corrosives should be applied to the steel or waterproofing can be added to
prevent further rusting. And, lastly applying a fresh render on the concrete
surface (Fitzgerald, 2010).
Corroded steel in concrete.
Source from:
http://corrosion.ksc.nasa.gov/corr_
forms.htm
The concrete spalled and left the ugly pits.
Source from:
http://www.concretenetwork.com/fix-spalled-
concrete/fixing-a-spalled-driveway.html

4. 13
3. Cracking
Cracking of concrete is the most frequently defect that happens among all the
concrete defects. The cracking usually happens on the top of surface of
concrete. “Some types of the cracking will not affect the structural stability and
durability of the building, but the use and serviceability of the building will be
affected in some serious cracking and that is why this defect should be
prevented to its minimum” (Cracks in concrete, 2014).
There are so many types of cracking and different type of cracking may be
caused by different factor. Besides, “cracking can be caused by one or a
combination of numerous reasons such as drying shrinkage, thermal
contraction, external or internal restraint, subgrade settlement, and applied
loads” (Concrete cracking, 2005). Other than that, cracking of concrete may
also happen because of the friction between the element and the casting
mould forms during the lifting.
Types of cracking Reasons
Transverse Crack Shrinkage due to low temperature
Longitudinal Crack Poor joint construction
Plastic Shrinkage Crack Quick loss of water (especially during
hot weather) before hardening
Plastic Settlement Crack Ineffective vibration
Shear Crack Structural loading or movement
Craze Crack Improper curing, excessive floating
Table 1: The types of cracking and its causes.
Cracking of concrete is usually unpreventable, but definitely can be reduced.
There are several repair methods that can be applied. But, as normally the
affected area need to be chipped off at first, then sealing and grouting will be
done to the cracks according to its seriousness. On the other hand, the
cracking that caused by corroded steel bar should be treated by removing the

5. 14
rusts from the corroded steel and then apply anti corrosives on the steel. And,
finally sealing and grouting will be done to the affected area.
Longitudinal cracking from poor longitudinal
joint construction.
Retrieved from (Longitudinal Cracking, 2008)
Small transverse crack
Retrieved from (Transverse Cracking, 2006)

6. 15
Preventions and Solutions
Concrete is kind of different from other materials used in construction and it is
because at the same it is one of the strongest, however it is relatively fragile
material. One of the hardest parts in construction is to know how to prevent
concrete defects and finding solutions. For this reason solutions can be
divided into two types of concrete degradation including chemical and
physical.
There are some solutions for concrete chemical degradation such as using
fibers in concrete composition to remove the concrete tends to crack and also
reducing corrosion and rust. However acids penetrating inside the concrete
and concrete efflorescence can be prevented too, just by adding concrete
densifires. Furthermore many measures can control corrosion in concrete
such as:
 Using a high quality concrete with adequate coverage. There must be a
minimum of 2 inches of concrete covering the metal
 Coating the steel with epoxy
 Using a corrosion inhibitor in the concrete
 Employing a cathodic protection system
 Keeping the concrete dry
Physical degradation is understood to mean all the causes of concrete spall
and can be prevented during mixing process by adding air entertaining agents
for creating microscopic air bubbles in the concrete so penetrate water can
expand in these bubble instead of concrete material. Also adding concrete
densifires can prevent further infiltration.
Sulfate attack is a chemical and physical reaction between sulfates usually in
soil or ground water and concrete or mortar, primarily with calcium aluminate
hydrates in the cement-paste matrix, often causing deterioration. There are
factors that can affect concrete sulfate attack so can be prevented by
considering some factors:
 Cement type and content
 Fly ash addition

7. 16
 Sulfate type and concentration
 Chloride ions

8. 17
Effects of Concrete Degradation and Defects
Different types of concrete degradation have different effects on
infrastructures such as concrete cracks and rusts, which can cause many
problems, troubles, and at the end disasters may occur, but some of them
happens more common.
One of the most dangerous effects of concrete degradation is on bridges
which in this case they usually start deteriorating within 5 to 10 years of
construction which is because of corrosion in reinforcement steels resulting
cracks and crumbles. The other case happens for structures built in contact
with water such as in rivers or marine environments when salt water can
directly contact with reinforcement concrete plus reinforcing steel corrodes
resulting in cracks and crumbles. However failure attributed to corrosion is not
common in buildings, but because of inaccurate or incomplete site
investigation, poor design, and poor workmanship they have occurred causing
problems and structural failures.
All of this failures can result in falling piece of concrete and probably hit
people underneath or larger disasters such as collapsion of buildings, bridges,
and etc., which can put many people life in danger plus loss of huge amount
of money.
Bangladesh's Rana Plaza factory
collapsed on April, 2013 (source from:
http://news.nationalgeographic.com/new
s/2013/13/130425-bangladesh-dhaka-
building-collapse-world/)
6-storey building collapse on October,
2011 in Maryland, Lagos, Nigeria (source
from: http://nigeriatrends.com/why-
buildings-in-nigeria-collapse/)

9. 18
Examples of Structure Failures
Example 1: Terminal 2E at Charles de Gaulle Airport
On 23rd of May 2004, the concrete roof of Terminal 2E at Charles de Gaulle
airport in Paris, France caused a structure failure leading to collapse. The
stretch of the roof because of cyclical loads is one of the mai n reasons, but
reports say that wrong position of reinforcements or lack of enough
reinforcements in concrete blocks are the most effective reasons of this
damage. However rapid thermal expansion is an important factor too.
.
Example 2: Dolphin Tower
A huge crack observed in Dolphin towers convoyed by bucking walls plus
some floor tiles, which were broken, forced all the residences, an emergency
evacuation on 1st of July 2010. This 15 stories residential building, including
116 units was built in 1974 in Sarasota, Florida, United States. Due to wrong
movements and high pressure of concrete members and slabs the strength of
them became lower and also the live loads are much lower than dead loads
on the transfer slabs and columns. Furthermore the most possible reason of
failure of the transfer blocks is use of low strengthening concrete where high
resist concrete is required.
In 2004 part of the roof of terminal 2E of Charles de Gaulle airport
in Paris collapsed (source from:
http://www.dailymail.co.uk/news/article-1341419/Chaos-European-
airports-Charles-Gaulle-roof-risk-collapse-heavy-snow-mass-
cancellations-continue.html)

10. 19
Example 3: Seabrook Nuclear Power Plant
In Seabrook, New Hampshire, United States, 2009, due to entering moisture,
concrete degradation observed by specialists on section walls of Seabrook
nuclear power plant which could be very dangerous. They found the main
reason high chemistry activities on the structure of this nuclear power plant,
which is always in contact with soil and ground water (Special NRC Oversight
at Seabrook Nuclear Power Plant: Concrete Degradation, 2014).
Dolphin tower condominium, built in
1974, Florida United States (source from:
http://www.buysarasota.com/dolphin-
tower-sarasota.html)
Stands for keeping the building
(Dolphin tower) away from
collapsing while repairing (source
from
https://failures.wikispaces.com/Dol
phin+Towers+Condominiums+-
+Transfer+Slab+Failure)
Seabrook nuclear power plant, New Hampshire, United States
(source from: http://www.nrc.gov/info-
finder/reactor/seabrook/concrete-degradation.html)