Analysis of Spalling Concrete Defect in Reinforced Structures

This report examines spalling concrete, a common defect in reinforced concrete structures, often referred to as concrete cancer. The report identifies the causes of spalling concrete, including water penetration leading to steel reinforcement corrosion and subsequent concrete breakdown. It details a case study of a twenty-year-old residential building in Chatswood, NSW, showcasing spalling concrete defects in various locations. The report reviews the properties of reinforced concrete and the importance of adequate concrete cover and quality materials. Furthermore, it discusses preventive measures such as using water repellents, ensuring proper construction methods, and employing competent workers. Remediation strategies include removing damaged concrete, cleaning and priming steel reinforcement, replacing concrete with high-quality materials, and applying protective coatings. The report concludes that spalling concrete can be prevented and, if it occurs, effectively remedied with proper procedures. Desklib provides more solved assignments and past papers for students.

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MATERIAL SCIENCE IN CONSTRUCTION: MATERIAL DEFECT REPORT
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Table of Contents
1. Introduction.......................................................................................................................................3
2. Description of Material.....................................................................................................................4
3. Description of the Defect...................................................................................................................5
4. Literature Review..............................................................................................................................7
5. Discussion (Prevention and Remediation).......................................................................................8
6. Conclusions........................................................................................................................................8
References..................................................................................................................................................9

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1. Introduction
Defects are very common in construction industry. These defects have numerous effects
on the safety and health of end users of the built structures and facilities (Abisuga, et al., 2016).
The defects are caused by a wide range of factors including faulty design, poor quality of
materials, incompetent workers, inappropriate construction method, defective workmanship,
inadequate supervision, etc. (Ahzahar, et al., 2011); (Ali & Wen, 2011). The aim of this report is
to examine a construction material defect. The defect selected is spalling concrete on a storey
residential building along 327 Mowbray Road, Chatswood NSW. The building is twenty years
old. The location of the building is shown in Figure 1 below.
Figure 1: Location of the building
Figures 2, 3 and 4 below shows spalling concrete on different parts of the building.

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Figure 2: Spalling concrete above the window
Figure 3: Spalling concrete at the edge of slab
Figure 4: Palling concrete on the stairs
2. Description of Material
Reinforced concrete is a composite material comprising of concrete and steel
reinforcement. These materials are used because of their mechanical properties, which contribute
to the structural integrity and soundness of a building. Buildings are exposed to both tensional

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and compressional forces hence they need to be constructed using materials that can withstand
forces in both tension and compression. Concrete has high compressive strength and low tensile
strength. Concrete is a composite material made up of cement, aggregates, admixture and water.
Cement is the material that binds together all other ingredients of concrete. For the concrete to
attain its desired strength, it has to be made up of the correct proportions of good quality
ingredients, mixed using the right method, poured and compacted correctly and cured
adequately. On the other hand, steel reinforcement has high tensile strength and low compressive
strength. When these materials are combined to form reinforced concrete, they complement each
other thus making the structure have high tensile and compressive strength. These materials are
also used because they have almost the same expansion and contraction rates, which reduces
stress fractures. Durability of reinforced concrete is usually increased by use of an appropriate
water repellent on the surface (Tkach, et al., 2015); (Zhang, et al., 2017). The water repellent
inhibits water penetration through concrete surfaces thus preventing concrete spalling (Meier &
Wittman, 2011); (Zhang, et al., 2017). This material is very essential especially for buildings in
coastal regions (Dai, et al., 2010).
3. Description of the Defect
Spalling concrete (also known as concrete cancer) is a failure mode of reinforced
concrete. This defect occur when water (moisture) penetrates through concrete cover and reaches
internal steel reinforcement causing it to corrode, rust and expand significantly. As a result of
this, stresses get created on the surrounding concrete causing it to break away (spall). Once the
concrete starts getting displaced and flaking, more water penetrates into the affected area causing
the steel reinforcement to rust further. This speeds up the process of concrete spalling and
worsens the situation. Spalling concrete is a very major problem in Australia, more so in coastal
areas such as Sydney (Howe, 2015). Buildings that were constructed without using an
appropriate waterproof membrane or water repellent sealer are vulnerable to spalling concrete.
There are numerous causes of spalling concrete. Some of them include: inadequate
concrete cover that allows water to penetrate easily and reach the steel reinforcement; use of
poor quality steel reinforcement; use of poor quality concrete; using incompatible metals too
close to each other; and defective workmanship; among others (Sydney Strata Specialists, 2016).
Concrete has high content of alkali, which is meant to help protect the steel reinforcement

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against corrosion. But once water penetrates through the concrete cover, it neutralizes the alkalis
thus making them ineffective in protecting the steel reinforcement. That is why it is important to
ensure that adequate concrete cover provided, i.e. at least 25.4mm (one inch).
Figures 5, 6, 7 and 8 below shows different spalling concrete defects. The defects are
very similar to the ones identified in the case study analyzed in this report. This shows that
spalling concrete defects are caused by similar factors ad occurs in a similar manner. The defect
is characterized by broken or spalled concrete and exposure of reinforcement, as shown by the
photos.
Figure 5: Example of spalling concrete defect
Figure 6: Example of spalling concrete defect

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Figure 7: Example of spalling concrete defect
Figure 8: Example of spalling concrete defect
4. Literature Review
Reinforced concrete is a very common and widely used material in construction because
of its properties. The main properties of reinforced concrete are: high tensile, high compressive
strength, high shear strength, resistant to fire, durable, high ductility, relatively high modulus of
elasticity, low coefficient of thermal expansion, moderate thermal conductivity and creep
resistance. When plain concrete is combined with steel reinforcement, a thin film develops on the
reinforcement’s surface. This is as a result of the alkaline environment from the lime present in
cement. This makes the steel reinforcement extra-resistant to corrosion since the lime layer
cannot allow easy penetration of moisture (Merlo Construction, 2017). This material is used
because it has properties that are desired for most buildings. The concrete provides compressive
strength whereas the steel reinforcement provides tensile and flexural strength. This enables the
material to resist compressional forces and tensional forces.

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5. Discussion (Prevention and Remediation)
Preventive measures for spalling concrete are: providing adequate concrete cover (based
on AS 3600-2009 standard recommendation); using good quality concrete materials (cement,
coarse and fine aggregates, admixtures and water); use of good quality steel reinforcement; use
of suitable construction method to ensure good quality workmanship (to ensure that the steel
reinforcement is properly installed and the concrete is correctly mixed, poured, vibrated or
compacted and cured); employing competent workers to do the concreting job; ensuring
adequate supervision of concrete works; and applying a suitable water repellent on finished
concrete surfaces. These measures will help in preventing voids in the concrete and penetration
of moisture into the steel reinforcement.
But if this defect occurs, it can be remedied. First is to remove the cracked, broken or
spalled concrete from the affected area, using small chipping guns, until reaching the
reinforcement. This is so as to allow inspecting the level to which the steel reinforcement has
corroded, to enable easy cleaning of the reinforcement and to ensure a good bond between the
new patching material and the steel reinforcement. Care must be taken to avoid cutting the
existing steel reinforcement. Second is to sandblast and clean the steel reinforcement using a
hard brush and applying a suitable priming material (such as epoxy coating) on it. This will help
to protect the steel reinforcement against further corrosion. Third is to replace the removed
concrete with good quality concrete. Fourth, is to apply a cement mortar on the surface so as to
achieve the desired finish. Last but not least is to apply a suitable water repellent on the finished
surface (Pestine, 2014). The remediation work should be done by a qualified and certified
contractor so as to ensure good workmanship. The reinstated area should also be cured for at
least seven consecutive days.
6. Conclusions
Reinforced concrete is a common and widely used construction material. This material
has desirable properties that makes structure strong and durable. However, reinforced concrete is
exposed to numerous defects due to faulty design, use of poor quality materials, poor
workmanship, incorrect construction method, environmental factors, etc. This report analyzed
spalling concrete defect on a residential building in Chatswood, one of the Sydney suburbs. This
defect can be prevented by considering the factors or conditions that cause them when designing

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or constructing a reinforced concrete building. In the event that the defect occurs, it can be
remedied by following a procedure that has been discussed in this report. Therefore spalling
concrete is a defect that can be prevented, but if it occurs it can still be remedied.
References
Abisuga, A., Famakin, I. & Oshodi, O., 2016. Educational building conditions and the health of users.
Construction Economics and Building, 16(4), pp. 19-34.
Ahzahar, N., Karim, N., Hassan, S. & Eman, J., 2011. A Study of Contribution Factors to Building Failures
and Defects in Construction Industry. Procedia Engineering, Volume 20, pp. 249-255.
Ali, A. & Wen, K., 2011. Building Defects: Possible Solution for Poor Construction Workmanship. Journal
of Building Performance, 2(1), pp. 59-69.
Dai, J. et al., 2010. Water repellent surface impregnation for extension of service life of reinforced
concrete structures in marine environments: The role of cracks. Cement and Concrete Composites, 32(2),
pp. 101-109.
Howe, M., 2015. Peak Strata Body Warns of Concrete Cancer. [Online]
Available at: https://sourceable.net/peak-strata-body-warns-of-concrete-cancer/
[Accessed 23 May 2018].
Meier, S. & Wittman, ,. F., 2011. Recommendations for water repellent surface impregnation of
concrete. Restoration of Buildings and Monuments, 17(6), pp. 347-358.
Merlo Construction, 2017. Properties of Reinforced Concrete. [Online]
Available at: https://www.merloconstructionmi.com/properties-reinforced-concrete/
[Accessed 23 May 2018].
Pestine, G., 2014. Concrete Spalling - Expert Article. [Online]
Available at: https://www.robsonforensic.com/articles/concrete-spalling-expert-article
[Accessed 23 May 2018].
Sydney Strata Specialists, 2016. Spalling in Strata Buildings. [Online]
Available at: http://sydneystrataspecialists.com.au/tips/spalling-in-strata-buildings/
[Accessed 23 May 2018].
Tkach, E., Semenov, V., Tkach, S. & Rozovskaya, T., 2015. High Effective Water-Repellent Concrete with
Improved Physical and Technical Properties. Procedia Engineering, Volume 111, pp. 763-769.
Zhang, P., Liu, S. & Han, S., 2017. Visualization of rapid penetration of water into cracked cement mortar
using neutron radiography. Materials Letters, Volume 195, pp. 1-4.
Zhang, P. et al., 2017. The Effect of Water Repellent Surface Impregnation on Durability of Cement-
Based Materials. Advances in Materials Science and Engineering, Volume 2017, pp. 1-9.

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