Concrete delamination refers to the detachment of thin layers of concrete from the concrete surface, which can weaken the structure by exposing it to abrasives in the atmosphere. To prevent further damage, it is crucial to identify and address the affected area promptly. A common indicator of concrete delamination is the emergence of a hollow sound when the concrete surface is struck with a hammer.
The detachment of concrete layers can occur due to various factors, such as poor surface preparation, improper mixing, or curing of the concrete. Additionally, environmental factors like extreme temperatures or exposure to moisture can contribute to concrete delamination.
The effects of concrete delamination can be severe and may lead to structural failure if left unaddressed. The weakened surface can result in further damage and may also create safety hazards for people in the vicinity.
To prevent concrete delamination, proper measures must be taken during the construction phase. This includes ensuring adequate surface preparation, proper mixing and curing, and careful monitoring of environmental factors. Additionally, regular inspections and maintenance can help identify and address any delamination issues before they worsen.
In summary, concrete delamination is a serious issue that can weaken the structure and create safety hazards. It is important to identify and address the affected area promptly, and take appropriate measures to prevent it from occurring in the first place.
Causes of Delamination
Delamination of the concrete surface is often caused by improper timing of final trowelling operations. To avoid this issue, it is crucial to start the finishing operations, such as trowelling, only after the initial setting time of the concrete has passed. If trowelling is carried out too early, before the concrete has properly set, delamination issues may arise, leading to separation or detachment of the concrete surface. Therefore, it is recommended to adhere to the appropriate timing for trowelling to ensure a durable and well-bonded concrete surface.
Trowelling operation conducted before the initial setting time can lead to the formation of blisters due to bleeding water or air underneath. These blisters can delaminate when the surface is subjected to load, causing subsurface voids and weakening the concrete zone. Delamination can also occur due to factors such as using a sticky mortar mix with excessive fines, high rate of evaporation, and hastily performed finishing works. When finishing is done hastily, delamination can be widespread, affecting larger areas of the concrete surface. The detachment layers may be around 3 to 6mm thick, and delamination is commonly observed in concrete slabs.
Effect of Delamination on Concrete Performance
Delamination can occur on a single spot of a concrete surface, which may not necessarily cause any significant issue. However, when this problem starts spreading, it can adversely impact the performance of the concrete surface. Delamination causes the separation of the flooring material from the top surface of the concrete, leading to the splitting up of any top coat. This creates pathways for moisture intrusion, which can propagate cracks and ultimately affect the overall performance of the structure.
Moisture intrusion resulting from delamination can be particularly problematic. It can seep into the concrete through the gaps created by the delamination, causing cracks and further spreading the problem. As a result, the performance of the structure is severely compromised. The pathways created by delamination also facilitate the penetration of other external elements that can cause further damage to the concrete surface. Thus, it is essential to address delamination at the earliest stages to avoid any long-term structural damage.
Precautions for Concrete Delamination
Delamination is a common issue faced in concrete construction which can be avoided by controlling certain factors. The uniformity of the concrete placement, the rate of bleeding, the setting time of the concrete surface, the rate of surface evaporation, and the process of finishing are the main factors that need to be controlled. Premature finishing process is the major cause of delamination. To avoid this, enough time should be given for the bleeding water to rise up and evaporate prior to the finishing process. This time is mainly the initial setting time of the concrete.
There are several dos and don’ts to avoid concrete delamination. For instance, the sealing of the concrete surface before the completion of the bleeding process must be avoided. Concrete mix with high cement or high sand content tends to bleed more easily. If the concrete contains air-entrained admixtures, the finishing process must be carried out lightly with care. If the concrete surface is made over an impervious surface, it is recommended not to perform the finishing process too early. The temperature of the ground subgrade is also a crucial factor. If it is less than 40 degree Celsius, it is recommended not to place the concrete.
Accelerators can be used to obtain a uniform concrete setting and increase the final setting time of the concrete. If the site has a rapid evaporation rate due to hot temperatures, lower humidity, and high wind rate, special ways are adopted to decrease the evaporating rate. The wind can be reduced by the use of windbreaks and an evaporative retardant can be used to reduce the rate of evaporation.
If a concrete area is affected by delamination, the remedy is to remove the defective concrete layer until a sound concrete layer is observed. The unsound concrete can be removed by shotblasting, hydrodemolition, or grinding. After the removal of the affected surface, a new layer is placed. The whole area can be then ground and smoothened to obtain a final smooth and sealed finish.