A variety of flaws can occur in concrete construction, including scaling, spalling, efflorescence, dusting, curling, crazing, blistering, delamination, and cracking. There are several possible causes or reasons for these flaws.
Reasons for Concrete Structure Flaws
Concrete structural flaws can be roughly classified into the following categories:
1. structural shortcoming brought on by design mistakes, loading requirements, unanticipated overloading, etc.
2. structural shortcoming brought caused by mistakes in the building.
3. Damage from cyclones, earthquakes, floods, and fires, among other events.
4. harm brought on by a chemical assault.
5. harm brought on by maritime habitats.
6. damage brought on by granular material abrasion.
7. Concrete moves as a result of its physical attributes.
Defects in Structure due to Design and Detailing
In such a situation, the design team must thoroughly examine the work and devise corrective actions. After this is completed, the procedures for implementing the corrective actions will resemble those resulting from other flaws.
Defects in Construction Causing Structural Deficiencies
The majority of the problems with the beams are caused by poor construction techniques. These flaws can be roughly categorized as follows:
1. imperfections brought on by low-quality raw materials.
2. refusal to use the intended concrete mix.
3. Concrete is produced, transported, and placed using faulty construction equipment.
4. Poor craftsmanship.
5. Poor quality of detailing.
Selecting the appropriate type of cement is crucial for the concrete that will be used in the proposed structure. The most often used type of cement is regular Portland cement. Ordinary Portland cement often presents no issues when used, as long as the quality of the cement meets the applicable standard criteria. It can be required to utilize special cements, such as low C3A cement, blast furnace slag cement, and sulphate-resistant Portland cement, where the concrete is exposed to harsh environments. It is important to consider the quality of aggregates, especially with regard to the alkali-aggregate reaction. Fortunately, there are very few instances of faults or failures in India that are linked to the alkali aggregate reaction. Another factor that might cause concrete to deteriorate is using salt-containing water when creating concrete. A large range of aggregates can be used to create a concrete mix that is satisfactory. It is important to maintain a fair consistency in the grading of aggregates. The biggest single source of weakness in the concrete mix is the overuse of water. The quality of the weigh batching system that is available has a significant impact on the accuracy of the component weights. The significant variety in the quality of weigh-batched concrete in India can be attributed to the spring-loaded dials of the weigh batchers. Segregation, incorrect placement, excessive or insufficient vibration, mortar leakage through shuttering joints, inadequate concrete cover, insufficient curing, etc. are further contributing causes to poor craftsmanship. A sufficient cover and proper reinforcement detailing are necessary for a successful concrete placement. Even when the concrete is workable, poor detailing causes reinforcement to get so clogged that correct concrete placement and compacting is impossible. A thorough understanding of the methods to be used for concrete placement and compaction should serve as the foundation for detailing reinforcement.
Additional elements causing subpar design details
1. abrupt modifications to the section.
2. Re-entering areas.
3. restrictions on deflection.
4. inadequately detailed joints.
5. scuppers and drips with inadequate detailing.
6. Insufficient or inappropriate drainage.
7. The expansion joints’ detailing is inadequate.
Concrete Defect Types: Causes and Prevention
The following describes the several kinds of flaws that can be found in hardened concrete surfaces as well as how to avoid them:
1. Creaking
Concrete can develop cracks for a variety of reasons, but using a structure made of concrete that has severe fissures is dangerous. A few causes of cracking include using a high slump concrete mix, inadequate curing, leaving out expansion and contraction joints, using the wrong subgrade, and so on. Admixtures containing calcium chloride should be avoided in order to minimize the amount of coarse aggregate in the concrete mix and prevent cracking. It is important to protect the surface from the quick evaporation of moisture content. The concrete surface must only be loaded once it has reached its maximum strength.
2. Crazy
Crazing, sometimes referred to as pattern cracking or map cracking, is the uneven production of shallow cracks that are tightly spaced apart. Crazing happens when the top surface of the concrete hardens too quickly from high temperatures, when there is too much water in the mixture, or when there is not enough curing. By properly curing the concrete, damping the subgrade to prevent water absorption, and shielding the surface from abrupt temperature changes, pattern cracking can be prevented.
3. Spalling and Scaling
Both scaling and spalling cause the surface of the concrete to degrade and cause flaking. Water seeping through the surface of the concrete is the primary cause of these kinds of situations. Steel becomes rusted as a result, and scaling or spalling may happen.
Other contributing factors include the use of low strength concrete, insufficient curing, and non-air entrained concrete mixes. By utilizing properly planned concrete mixes, adding air entrainment admixtures, finishing and curing the work properly, creating a decent slope to drain water that comes to the surface, and other measures, these kinds of faults can be avoided.
4. Blistering
Blistering is the formation of hollow bumps of different sizes on concrete surface due to entrapped air under the finished concrete surface. It may be due to excessive vibration of concrete mix or presence of excess entrapped air in mix or improper finishing. Excessive evaporation of water on the top surface of concrete will also cause blistering. It can be prevented by using good proportion of ingredients in concrete mix, by covering the top surface which reduces evaporation and using appropriate techniques for placing and finishing
5.Efflorescence
The buildup of salt deposits on the surface of concrete is known as efflorescence. Typically, formed salts have a white hue. It is because the water used to make the concrete mix contains soluble salts. These soluble salts are drawn to the top surface of the hardening concrete by hydrostatic pressure, and salt deposits form on the surface once the drying process is finished. It can be avoided by mixing with pure, clean water, utilizing aggregates that are chemically inefficient, etc. Additionally, ensure that no more than 1% of the weight of the cement is made up of alkalis.
6. Delamination
Blistering and delamination are comparable conditions. The top surface of the concrete separates from the underlying concrete in this instance as well. Delamination results from the top layer of concrete hardening before the underlying concrete does. This is because space will form between these two surfaces as a result of water and air leaking from the concrete below striking these surfaces. Similar to blistering, delamination can be avoided by employing appropriate finishing methods. It is preferable to begin finishing after the bleeding process is complete.
7. Dusting Process
The process of dusting, also known as chalking, involves the dissolution of solidified concrete to produce fine, loose powdered concrete. This occurs as a result of concrete containing an excessive amount of water. Because of the water seeping out of the concrete, small particles like sand or cement climb to the top and wear them down, causing dust to accumulate at the top surface. Use a low slump concrete mix to create a firm, wear-resistant surface without creating dust. To get the right amount of slump, use admixtures that reduce water. Additionally, it is advised to start finishing after removing the bleed water from the concrete surface and to utilize better finishing techniques.
