Cracks found in concrete buildings can have various origins, and their severity can range from being merely aesthetic to indicating significant structural issues. The type of structure and the nature of the cracking are both important factors in determining the significance of cracks.
The causes of building cracks can vary widely, and they may be indicative of severe structural problems or a lack of durability. The extent of damage that the cracks display will determine their importance.
To effectively address building cracks, it is essential to identify the underlying causes. Remedies will depend on the specific type of cracking present in the structure.
Causes of Cracks in Concrete Buildings
The principal causes of cracks in a building are as follows:
- Permeability of concrete
- Thermal movement
- Creep movement
- Corrosion of reinforcement
- Moisture movement
- Poor construction practices
- Improper structural design and specifications
- Poor maintenance
- Movement due to chemical reactions
- other factors
1. Permeability of concrete
Concrete durability is greatly influenced by the ability of the material to resist the penetration of harmful substances. Various aggressive agents can initiate the deterioration process and weaken the concrete’s ability to withstand weathering, chemical attacks, and other forms of deterioration. Therefore, low permeability is an essential characteristic of concrete for enhancing its durability.
The permeability of concrete is influenced by several factors, including the water-cement ratio, use of admixtures, curing, air voids resulting from inadequate compaction, micro-cracks due to loading, cyclic exposure to thermal variations, and the age of the concrete. Among these factors, the first three are closely related to the strength of the concrete.
When using high-quality materials and appropriate construction techniques, the permeability of the cement paste is primarily determined by the water-cement ratio. In addition, the permeability of the concrete is influenced by the porosity and connectivity of the pores within the cement paste. By controlling these factors, the permeability of concrete can be reduced, thereby increasing its durability.
Remedial measures
The preceding conversation proposes an appropriate solution to reduce the permeability of concrete, which can ultimately lead to the prevention of cracks.
2. Thermal movement
Cracking in buildings can be caused by thermal movement, which is primarily a result of materials expanding when heated and contracting when cooled. Temperature variations and heat loss of hydration can lead to thermal movement, which can vary depending on factors such as dimensions, coefficient of thermal expansion, and physical properties of materials.
While the internal walls and intermediate floors of a building experience minimal thermal variation, it is the external walls and roof that are most susceptible to cracking due to their exposure to direct solar radiation and substantial thermal fluctuations. Thin walls in particular are at risk of cracking from thermal movement.
To prevent cracking in buildings, it is important to consider the effects of thermal movement and choose materials and construction methods that can accommodate the resulting expansion and contraction. This can include using materials with lower coefficients of thermal expansion, incorporating expansion joints, and designing building systems to minimize thermal stress. By taking these factors into account, it is possible to construct buildings that are more resistant to cracking and other forms of damage from thermal movement.
Remedial Measures
When designing and constructing any structure, it is important to give due consideration to the joints that will be incorporated. Different types of joints serve different purposes and must be constructed properly in order to ensure the longevity and safety of the structure.
One type of joint that must be taken into account is the expansion joint. These are designed to allow for the natural expansion and contraction of the structure as it is exposed to changes in temperature and other environmental factors. Failure to include these joints can lead to cracking and damage to the structure.
Another important joint to consider is the construction joint. This is the point at which two separate concrete pours meet, and it is crucial to ensure that this joint is properly formed and reinforced. If not, it can become a weak point in the structure and may be prone to cracking or failure.
Control joints are also important, as they help to control where cracks will occur in the structure. By placing these joints strategically, it is possible to minimize the visual impact of any cracking that may occur, as well as prevent it from spreading and causing further damage.
Finally, slip joints are used to allow for movement between different parts of the structure. These joints are commonly used in structures that are subject to vibrations or other movements, and they help to prevent damage to the structure as a result of this movement.
Overall, proper consideration and construction of joints is critical to the success of any structure, and should be given careful attention during the design and construction phases.
3. Creep Movement
Creep is a phenomenon where concrete structures deform gradually and slowly over time under sustained loads, which can lead to the development of cracks and generate excessive stress. Various factors can influence the occurrence of creep, including water and cement content, water-cement ratio, and temperature. Admixtures and pozzolans can also increase the likelihood of creep, as can elevated temperatures in steel bars.
Interestingly, the humidity of the surrounding atmosphere and the age of the material at the time of loading can have the opposite effect and decrease the likelihood of creep. As such, it’s important to consider all of these factors when designing and constructing concrete structures to ensure their long-term durability and safety. By doing so, it’s possible to mitigate the risk of creep and prevent potential structural damage down the line.
To improve the quality of concrete, there are several remedial measures that can be taken. One of the most important is to use the minimum possible quantity of water in the mixture. This can help to increase the strength and durability of the concrete, as well as reduce the risk of cracking and shrinkage.
Another important factor is the use of large coarse aggregate in the mix. This can help to improve the workability of the concrete, as well as reduce the amount of water needed. Additionally, providing compression reinforcement, if possible, can help to increase the strength and load-bearing capacity of the concrete.
It is also important to avoid removing formwork at early ages, as this can cause damage to the concrete and reduce its strength. Proper curing is also crucial, as it helps to ensure that the concrete develops its full strength and durability over time. Finally, assigning the proper cross-section for the concrete element can help to ensure that it can support the required loads and maintain its structural integrity over time.
4. Corrosion of Reinforcement
When steel reinforcement corrodes, it creates iron oxide and hydroxide on the surface of the steel bar, causing an increase in its volume. This increase in volume leads to the development of high radial bursting stresses around the reinforcing bars, resulting in localized radial cracks. These splitting cracks then cause longitudinal cracks to form parallel to the bar.
To prevent reinforcement corrosion, it is essential to protect the steel reinforcement properly. This protection can be achieved by providing adequate impervious concrete cover, which prevents the ingress of moisture and other aggressive elements.
Additionally, steel corrosion can be prevented by ensuring that the concrete surrounding the steel is alkaline in nature, with a high pH value. This alkalinity prevents the onset of corrosion by creating an environment that is not conducive to the development of corrosion. By implementing these protective measures, the longevity and durability of reinforced concrete structures can be increased.
Remedial Measures
Low permeable concrete, adequate cover thickness, and good concrete-steel bond are crucial elements to consider in ensuring the durability and safety of reinforced concrete structures.
Using low permeable concrete is essential in preventing harmful substances from penetrating the concrete and corroding the steel reinforcement. Adequate cover thickness also helps in protecting the steel reinforcement from damage by providing a sufficient distance between the reinforcement and the external environment.
Furthermore, ensuring a good bond between the concrete and steel reinforcement is critical in preventing cracking and subsequent corrosion. Concrete is not capable of resisting tensile forces to which it is often subjected, and this can result in cracking that exposes the steel reinforcement to corrosion.
In summary, the use of low permeable concrete, providing adequate cover thickness, and ensuring a good concrete-steel bond are fundamental to the longevity and safety of reinforced concrete structures. By implementing these measures, the risk of corrosion and deterioration of the concrete and steel reinforcement can be significantly reduced, ensuring the structural integrity of the building.
5. Moisture Movement
Many building materials have pores in their structure that create inter-molecular space. These materials tend to expand when they absorb moisture and shrink when they dry out. These movements occur in cycles and are caused by changes in the inter pore pressure due to changes in moisture levels.
There are two types of shrinkage: plastic shrinkage and dry shrinkage. Cement and mortar can experience shrinkage due to various factors, including the use of excessive water and cement quantity. Rich cement mixtures are particularly susceptible to shrinkage.
Remedial measures
To ensure the durability and longevity of concrete structures, it is essential to incorporate movement joints. These joints allow for movement caused by thermal expansion and contraction, which can cause cracking and damage to the concrete. By including movement joints, the concrete can move freely without compromising its structural integrity.
When mixing cement concrete or cement mortar, it is crucial to use the minimum possible quantity of water. This is because excess water weakens the concrete and increases the risk of cracking and shrinkage. By using the correct water-to-cement ratio, the mixture will have the right consistency and strength to withstand the stresses placed upon it.
Proper compaction of concrete is also essential for reducing shrinkage. Vibrated concrete is less prone to shrinkage compared to manually compacted concrete. Therefore, it is essential to ensure that the concrete is thoroughly and uniformly compacted to minimize shrinkage.
Finally, the excessive use of cement should be avoided as it can cause cracking and shrinkage in the concrete. It is important to use the correct amount of cement necessary to achieve the desired strength and durability of the concrete. By following these guidelines, concrete structures can maintain their structural integrity and resist damage over time.
6. Poor Construction practices
Concrete cracking is a prevalent issue in the construction industry, and it can result from a variety of improper construction practices. These practices are often the result of ignorance, carelessness, greed, or negligence. The primary causes of poor construction practices are the selection of inadequate or poor quality materials, and improper proportioning of mix constituents for concrete and mortar. Additionally, inadequate control over various steps of concrete production such as batching, mixing, transporting, placing, finishing, and curing can contribute to these problems.
Construction overloads during the construction process can be even more serious than those imposed during service. Inadequate quality control and supervision can cause large voids (honeycombs) and cracks, leading to leakages and ultimately causing the concrete to deteriorate more quickly. Improper construction joints between subsequent concrete pours or between concrete framework and masonry can also be a contributing factor. The addition of excess water to concrete and mortar mixes is another common mistake that can result in cracking.
Lastly, poor quality plumbing and sanitation materials and practices can also play a role in the deterioration of concrete. It is essential to address these issues to ensure that construction practices result in high-quality, durable concrete structures that can withstand the test of time. By taking steps to prevent these mistakes, builders can create long-lasting and reliable concrete structures.
Remedial measure
The key to ensuring proper monitoring of the construction process is to utilize high-quality materials during the construction phase. By doing so, the construction project can be closely monitored to ensure that all aspects of the process are being executed properly. It is important to keep an eye on the project from start to finish and make any necessary adjustments along the way to ensure that the project is completed to the highest standards possible. Ultimately, the use of quality materials and close monitoring will help to ensure the successful completion of any construction project.
7. Improper Structural Design and Specifications
Structural design, detailing, and specifications are critical aspects of any construction project. Incorrectly designed and specified structures can lead to a range of problems. For instance, the thickness of the structure may be inadequate, the reinforcement may be insufficient, the geometry may be incorrect, materials may not be used appropriately, and detailing may be incorrect. These errors can lead to several problems that can compromise the safety and stability of the structure.
One of the issues that can arise due to design errors is cracking, which can occur when the reinforcement is insufficient. Improper foundation design can also cause excessive differential movement, which can cause the structure to become unstable. Moreover, poorly designed re-entrant can result in an increased concentration of stresses that can lead to the failure of the structure.
It is essential for designers to take into account the environmental conditions that exist around the building site. The surrounding environment can significantly impact the structural integrity of the building. Factors such as wind loads, seismic activity, temperature variations, and soil conditions can all affect the stability of the structure. Therefore, designers must consider these factors when designing the structure to ensure that it can withstand the environmental conditions of the site.
In conclusion, structural design, detailing, and specifications are crucial components of any construction project. Errors in these areas can lead to a range of problems, compromising the safety and stability of the structure. By taking into account the surrounding environmental conditions, designers can create structures that are better equipped to withstand external pressures, ensuring the safety and longevity of the building.
Remedial measures
To prevent the cracking and eventual deterioration of structures, Architects, Structural Consultants, and Specifiers must take several measures into consideration. One of the primary measures is to specify concrete materials and concrete properly. Additionally, they must make proper specifications to address environmental and sub-soil conditions that may impact the structure’s integrity.
Constructible and adequate structural design is another critical factor that must be considered. It is important to ensure that the design is both achievable and sufficient to support the intended load. Another key consideration is the quality and thickness of concrete cover around the reinforcement steel. This must be carefully specified to prevent corrosion and other forms of deterioration.
In slender structures, proper reinforcement layout planning and detailing is essential to facilitate proper placement of concrete without segregation. This is important because segregation can lead to voids or weak spots in the structure, which can weaken it over time.
Finally, Architects, Structural Consultants, and Specifiers should be careful in selecting the construction agency responsible for building their designs. It is crucial to choose a reputable and reliable agency that has the necessary experience and expertise to construct the structure according to the specified design and materials.
8. Poor Maintenance
Maintaining the condition of a structure is crucial after a certain period from its construction completion. Some structures may require early attention to their deterioration problems, while others can sustain themselves for many years based on the quality of their design and construction.
Regular external painting of a building can provide some protection against moisture and chemical attacks. However, waterproofing and protective coating on reinforcement steel or concrete are additional lines of defense. The effectiveness of these measures depends greatly on the quality of the concrete used in construction.
Leaks should be addressed as soon as possible to prevent the corrosion of steel inside concrete, which can lead to spalling of the concrete. When concrete spalls, it loses its strength and stiffness, and the rate of corrosion increases as rusted steel is fully exposed to the aggressive environment.
It is essential not only to repair deteriorated concrete but also to prevent moisture and aggressive chemicals from entering the concrete to prevent further deterioration.
9. Movement due to Chemical Reactions
When active silica is present in the aggregate and comes into contact with the alkaline produced by cement hydration, it can lead to expansive reactions that cause concrete to crack. Specifically, the reaction between the alkali and silica in the aggregate generates a swelling gel. This gel has the ability to draw water from surrounding areas of the concrete, leading to localized expansion and ultimately the formation of cracks in the structure. Therefore, the alkali silica reaction can be a significant factor in the degradation and deterioration of concrete over time.
Remedial measures
To improve the quality of concrete, several measures can be taken during its production. One such measure is to use low alkali cement. This type of cement has a lower percentage of alkali compounds, which can cause a harmful reaction known as alkali-aggregate reaction. By using low alkali cement, the risk of this reaction occurring is reduced, resulting in a stronger and more durable concrete.
Another way to enhance the quality of concrete is to employ pozzolana. Pozzolana is a type of volcanic ash that can be mixed with cement to create a more sustainable and resilient concrete. When mixed with cement, pozzolana reacts chemically to form a gel-like substance, which fills in the gaps between the cement particles, resulting in a stronger bond.
Lastly, selecting proper aggregates is also important to ensure the quality of concrete. Aggregates are the materials used in concrete that provide its bulk and texture. Using high-quality aggregates that are strong and durable can significantly improve the strength and durability of concrete. Additionally, the size, shape, and texture of the aggregates can also affect the workability and finish of concrete, so it’s important to choose aggregates that are appropriate for the desired end-use.
10. Others factors
The decoration employed in a certain space can sometimes be excessively harsh or rough, resulting in undesirable consequences. For instance, the use of harsh or brutal decoration might lead to the removal of load-bearing walls or the creation of holes that can cause cracking in the structure. Such damage can be costly and challenging to fix, and it can put the safety of the occupants at risk.
In addition, accidents such as fires can occur in any setting, and they can cause significant damage to the property and put lives in danger. These fires can arise due to a range of factors, including electrical faults, gas leaks, or human error. In the worst-case scenario, fires can spread rapidly and become uncontrollable, causing extensive damage to the property and putting the lives of those inside at risk.
Furthermore, even mild earthquakes can cause damage to a building that has been poorly designed or constructed. This can be particularly true if the building has not been adequately reinforced or lacks essential safety features. In some cases, a poorly constructed building may even collapse or sustain significant damage during an earthquake, resulting in loss of life and property damage. Therefore, it is essential to ensure that buildings are constructed to meet safety standards and regulations to minimize the risk of damage from earthquakes.