hakkında şirket haberleri How to solve the efflorescence problem on the exterior walls of ceramic bricks in an automated brick factory? Causes and solutions.

How to solve the efflorescence problem on the exterior walls of ceramic bricks in an automated brick factory? Causes and solutions.

1. What is efflorescence?

Efflorescence is a common surface defect of buildings. Depending on its different causes and manifestations, it has various names such as efflorescence, whitening, efflorescence, frosting, and erosion of walls and decorative surfaces. It is a defect caused by the physical and chemical changes that occur in building materials such as soil, adobe, brick, cement, mortar, concrete, masonry, tiles, and paint due to changes in external environment such as temperature and humidity, as well as the absorption, migration, and evaporation of moisture. The degree of erosion and damage varies greatly, and common phenomena include dampness, blistering, powdering, bulging, hollowing, cracking, peeling, mold, and crystallization.

Efflorescence can form on any type of rammed earth, terracotta brick, concrete, stone, and mortar. It is particularly common in new construction, appearing to varying degrees within days, weeks, or months after completion. Currently, the academic community generally believes it is primarily caused by water-soluble salts within the material. This occurs when these salts migrate to the surface and crystallize as moisture evaporates. However, for exposed brick walls, in addition to water-soluble salts, there is also the issue of lime and gypsum leaching. Therefore, chemically speaking, efflorescence is mainly composed of gypsum, lime, and salts (sodium sulfate, potassium sulfate, or potassium carbonate). These substances are present in building materials and water. When water passes through the bricks or mortar and then evaporates on the surface, these substances are left behind. It is worth noting that while efflorescence does not necessarily harm structural integrity, its appearance significantly impacts the aesthetics of the building. Furthermore, it is often accompanied by underlying moisture problems and further structural cracking.

2. What causes efflorescence?

a. The material contains a large amount of free crystals such as calcium sulfate (gypsum), calcium hydroxide (lime), and water-soluble salts;

b. These free crystals have channels (capillaries) that allow them to move outward;

c. Moisture acts as a carrier and driving force to facilitate their dissolution, forming free crystals and migrating.

3. Solutions to efflorescence

     We can start with the three conditions mentioned above:

 1) Free crystals such as water-soluble salts

Source:

a. Manufacturing process: The bricks and mortar may contain raw materials from clay or used in the production process.

b. Groundwater: Salt can dissolve in groundwater and be transported to the bricks through capillary action.

c. Chemical reaction: The interaction between water and cementitious materials (such as cement-based mortar) forms gypsum, which is then carried to the surface of the bricks by water.

Countermeasures:

a. from penetrating into the bricks. Use small-sized dry-hanging ceramic bricks to avoid the possibility of water accumulation in the system.

b. Groundwater: Structurally isolated from groundwater.

c. Chemical reaction: Minimize the use of cement-based mortar. Due to the effect of carbon dioxide on mortar, excessive gypsum will be released from the cement. Gypsum is insoluble in water or acid and is the most difficult form of efflorescence to deal with.

 2) Water source:

Source:

a. Rainwater: The moisture and water from rain inevitably seep into the bricks.

b. Groundwater : Moisture rising from underground capillaries will introduce moisture and salt into the brick.

c. Condensation: Water vapor accumulates inside walls, leading to condensation under certain conditions.

Countermeasures:

a. Rainwater: Use a protective agent to increase the water-repellent effect of the terracotta bricks.

b. Groundwater: Install a damp-proof layer at the bottom of the brick wall during construction; avoid contact with the ground as much as possible during dry hanging , and if it cannot be avoided, install a damp-proof layer at the bottom.

c. Condensation: Ventilation structures should be installed between decorative walls and interior walls, and the thickness of the ventilation layer should be at least 2cm.

3. Capillary channels

1. Ceramic bricks: During the high-temperature firing process, internal capillaries are formed inside the material, giving ceramic bricks certain water absorption and air permeability .

2. Mortar: Lime-based mortar used for masonry and joint filling also has porous characteristics, maintaining the same air permeability as ceramic brick materials . Although cement-based mortar has significantly fewer capillary channels, it alters the migration path of moisture, causing greater problems.

Countermeasures:

1. Earthenware bricks: Earthenware bricks made with low water absorption materials are used. Low water absorption means the material is denser and has fewer capillary channels. However, it is important to avoid using coating-type waterproofing agents and to maintain the breathability of the earthenware bricks.
2. Mortar: Use mortar materials with similar breathability to ceramic bricks to avoid the poor breathability of cement-based mortar, which hinders moisture migration and leads to the accumulation and damage of efflorescence on ceramic bricks. The use of hydraulic, low-alkalinity lime-based mortar in traditional architecture can be adopted as a reference.

 4. Summarize

a. Dry-hanging ceramic bricks use fewer materials and auxiliary materials (mortar) compared to wet-laid ceramic bricks , reducing the possibility of efflorescence.

b. When choosing mortar, try to avoid using cement-based mortar, as the gypsum precipitated from cement-based mortar is the most difficult form of efflorescence to treat.

c. When conditions permit, use a surface protectant for ceramic tiles to increase the surface hydrophobicity of the ceramic tiles.

d. Lime-based mortar maintains the same air permeability as ceramic bricks, which can effectively alleviate the problem of efflorescence and improve the durability of ceramic bricks.