Bricks are the primary construction materials that ensure the structural integrity of the building. Since they are an important building component, choosing the right quality bricks becomes mandatory. However, there are numerous defects in bricks, each of which has some impact on the construction. One such defect is blistering and this blog will help you understand what blisters in bricks are, how to identify them, their causes, impact, prevention, usages, and more.
What is a Blister in Bricks?
A blister in bricks refers to a defect that causes raised, bubble-like areas on the surface of the brick, which is usually associated with discoloration and uneven texture. This defect affects the aesthetics and structural quality of the bricks, based on the severity of the defects.
How to Identify Blisters in Bricks?
Blisters in bricks can be identified by visual inspection, touching, and through a sound test. Examine the surface of the bricks for any raised or bubbled areas that look rough and uneven compared to regular bricks.
Sometimes, blisters may be accompanied by cracks or flakes, which can be easily identified. The blisters might cause discoloration, and the appearance will be light in colour.
If visual and tactile inspection cannot identify the blisters, a simple sound test could be useful to identify them. Gently tap the brick with a metal object and listen for the sound; if the sound is dull or hollow, it indicates blisters.
Causes of Blister Formation in Bricks
Poor Compaction
When the clay brick is not completely compacted during the moulding process, it allows air voids to remain trapped within the brick, leading to the formation of blisters when subjected to firing.
Trapped Air or Moisture
During the manufacturing of bricks, air or gases could get trapped inside the brick. When kept under the firing process, the air pockets expand, forming bubbles or creating blisters.
Overhearing During the Firing Process
When the firing temperature is too high or not distributed evenly inside the kiln, the air voids in the brick cause gases and moisture to expand rapidly into the brick, forming a blister.
Impurities in Raw Materials
Any impurities in clay or other raw materials, especially organic matter, could lead to unwanted reactions during the firing process. The gas generated by the decomposition of impurities could lead to gas formation within the brick, resulting in blisters.
Uneven Drying
The blisters are formed when the bricks are not dried consistently under natural weather. This causes the moisture content within the bricks to turn into steam during firing and causes expansion within the structure, causing blisters.
Impact of Blisters on Brick Quality
Aesthetic Damage
The visible raised areas on the surface of the bricks affect the overall appearance of the bricks, making them look less uniform and less visually appealing. The discoloration, rough, and uneven surface affects the overall aesthetic appeal of the bricks. Blistered bricks are not suitable for exposed walls due to their poor visual uniformity.
Structural Weakness
Blisters create weak points in the bricks due to the air voids. This reduces the density and load-bearing capacity, and the pore voids increase the risk of water ingress. These factors make blistered bricks less suitable for construction applications.
Decreased Durability
The blistered bricks can be more vulnerable to environmental conditions, such as rain, freeze, thaw, and more. All these factors could cause degradation over time, thereby reducing the efficiency and resulting in increased maintenance costs.
How to Prevent Blisters in Bricks?
- By proper compaction, the air voids within the bricks can be eliminated, which reduces the occurrence of blisters.
- Proper monitoring and controlling of the moisture content during mixing and drying can help prevent the occurrence of blisters during the firing process.
- Using high-quality clay and other raw materials that are free from impurities could reduce the chances of blistering.
- Maintaining proper temperature during the firing process within the kiln can help avoid overheating, which causes the uneven, rough surface of the brick.
- Protecting freshly moulded bricks from excessive moisture or rain could prevent the chances of blistering.
Can Blistered Bricks Be Used in Construction?
Although blistered bricks are defective, they can still be used for construction for different purposes.
- These bricks can be used for non-structural applications where visibility and stress applications are low, such as in internal or partition walls.
- They can be used for landscaping projects such as gardening walls, paving, or other decorative elements.
- These bricks can also be used as a fill material in places where appearances are not important.
- They can be used for cost-effective construction projects or in temporary structures to save costs.
What Should I Do if I Find Blisters in My Brick Structure?
Access the Severity of the Blisters
If you found blisters in the bricks, determine the spread and severity of the blistering. Small and isolated blisters in bricks can be acceptable; however, large or multiple blisters indicate more serious underlying issues, making it not suitable for construction works.
Determine the Cause
If blistering is found, understand the potential cause behind it. If the blistering occurs soon after the installation, the construction methods can be reviewed to find if it is caused by improper firing or insufficient ventilation. In this case, contact the contractor or brick manufacturer.
In other cases, issues like poor ventilation, high humidity, and improper mortar usage can be addressed to control blistering.
Consider the Type of Structure
Check for the structure where the blistering is found. In the case of non-load-bearing or non-visible walls, the blisters may not be a concern. However, if they appear on load-bearing walls or facing walls, it indicates a problem with the bricks used.
Fix Surface Blisters
If the blisters are small and don’t affect the structural integrity, it don’t need any replacement, and simple cleaning and sealing can prevent blistering. However, if the blistering causes cracks or other structural issues, remove and replace the affected brick carefully.
Address Moisture
If water damages are found to be the major issue for blistering, the structure can be coated with a waterproofing sealant, and necessary surface treatment can be done to prevent further water ingress.
Conclusion
Blistering in bricks is a serious defect that needs to be addressed before or after construction. It affects the shape, strength, durability and aesthetic looks of the bricks, causing damage to the structure. Less severe blistering in non-structural areas may not be a major concern, but severe defects in structural walls could be an indication of a big problem.