Manhole and sewer bricks play a crucial role in modern infrastructure, particularly in systems designed to transport sewage, industrial wastes, and storm water. These structures must be durable, resistant to environmental stressors, and built using materials that meet specific engineering standards. In many cases, manhole and sewer bricks are manufactured from natural materials such as clay and shale and must conform to applicable codes like ASTM C 32 to ensure proper performance and longevity.
Manufacturing Process
Sewer and manhole bricks are typically made from naturally occurring materials such as clay or shale . To achieve the desired strength and durability, these raw materials undergo a firing process at elevated temperatures . This thermal treatment ensures a strong bond between the components of the brick, enhancing its structural integrity and resistance to wear and environmental conditions.
The manufacturing process is critical because it directly influences the physical properties of the final product—particularly compressive strength, water absorption, and resistance to abrasion and frost.
Types of Bricks
Sewer and manhole bricks are categorized into different grades based on their intended use and required performance characteristics. Each grade is designed to withstand specific environmental and mechanical stresses.
A. Sewer Bricks
1. Grade SS (Sewer Special)
- Designed for environments where abrasion resistance is critical.
- Suitable for use in high-velocity flows (>2.4 m/s) carrying abrasive materials.
- Commonly used in industrial areas or locations with heavy wastewater flow.
2. Grade SM (Sewer Medium)
- Offers moderate abrasion resistance .
- Appropriate for lower velocity flows (<2.4 m/s) .
- Often found in municipal sewer systems where abrasive loads are less intense.
B. Manhole Bricks
1. Grade MS (Manhole Special)
- Features low abrasive resistance , but high and uniform frost resistance .
- Ideal for use in manholes and catch basins in cold climates.
- Ensures structural integrity under freeze-thaw cycles.
2. Grade MM (Manhole Medium)
- Provides higher abrasion resistance than Grade MS.
- Has moderate and non-uniform frost resistance .
- Used in manholes exposed to abrasive conditions but with less severe freezing effects.
Physical Properties
To ensure functionality and compliance with ASTM standards, manhole and sewer bricks must meet certain physical and dimensional requirements.
Dimensional Requirements:
- Must have a rectangular cross-section .
- Edges and corners should be straight and well-defined .
- Allowable imperfection: up to 5 mm depression or kiln mark on the backside.
- Surface finish :
- Sewer bricks : Smooth and plain surfaces.
- Manhole bricks : Plain surface with a fairly textured finish .
Key Physical Properties (as per ASTM C 32):
| Brick Type | Minimum Compressive Strength (MPa) – Average | Individual | Max Water Absorption (%) – 5-h Boiling – Average | Individual |
|---|---|---|---|---|
| Grade SS Sewer | 55 | 41 | 6 | 9 |
| Grade SM Sewer | 34 | 26 | 12 | 15 |
| Grade MS Manhole | 21 | 17 | 17 | 20 |
| Grade MM Manhole | 17 | 15 | 22 | 25 |
These values indicate the minimum compressive strength and maximum allowable water absorption for each class of brick, ensuring they perform reliably under expected service conditions.
Applications
Manhole and sewer bricks are essential components of underground infrastructure systems. Their primary applications include:
- Drainage Structures : For the conveyance of sewage, industrial waste, and storm water.
- Manholes : Access points for maintenance and inspection of sewer lines.
- Catch Basins : Structures designed to collect runoff and prevent debris from entering the sewer system.
Each application demands a specific type of brick depending on the level of abrasion, moisture exposure, and climatic conditions.
Conclusion
Selecting the appropriate type of manhole or sewer brick is vital for ensuring the long-term performance and safety of underground infrastructure. Whether transporting sewage through high-velocity pipelines or serving as part of a frost-prone manhole structure, these bricks must meet rigorous physical and chemical requirements. By adhering to standards such as ASTM C 32 , engineers and contractors can ensure that the materials used will provide reliable service for decades to come.