The stuff in between bricks is called mortar, a fundamental building material essential for the structural integrity and aesthetic appeal of brickwork.
Mortar serves as the adhesive that binds individual bricks or other masonry units together, creating a solid and durable structure. Beyond its primary role as a bonding agent, it also fills the gaps between units, helps to distribute loads evenly, and provides a barrier against weather elements.
Understanding Mortar: Composition and Purpose
At its core, mortar is a mixture of sand and various types of cements, combined with water. This blend creates a workable paste that hardens over time, forming strong joints that hold the masonry together.
- Cement: Acts as the binder, undergoing a chemical reaction with water to solidify and gain strength. Different types of cement offer varying properties suited for specific applications.
- Sand: Serves as an aggregate, providing bulk, stability, and compressive strength to the mortar mix. The fineness and shape of the sand particles are crucial for workability and final strength.
- Water: Activates the cement, initiating the hydration process, and also helps achieve the desired consistency for application.
Why Mortar is Essential for Masonry
Mortar is far more than just "filler" between bricks. Its essential functions include:
- Bonding: It creates a strong, durable bond between bricks, preventing them from shifting or separating.
- Load Distribution: Mortar joints help to evenly distribute the weight and stresses from the structure above, preventing concentrated pressure points on individual bricks that could lead to cracking.
- Weather Resistance: It seals the gaps between bricks, protecting the interior of the wall from moisture penetration, wind, and temperature fluctuations.
- Leveling and Alignment: During construction, mortar allows masons to adjust and level bricks, ensuring a plumb and true wall.
- Aesthetics: The color, texture, and joint style of mortar significantly contribute to the overall appearance of the finished brickwork.
Mortar vs. Concrete: Key Differences
While mortar and concrete share similar ingredients (sand, cement, and water), they are fundamentally different materials designed for distinct purposes and should not be used interchangeably. The primary difference lies in their aggregate composition and resulting strength and application.
| Feature | Mortar | Concrete |
|---|---|---|
| Primary Role | Binds masonry units (bricks, blocks, stones) | Structural element (foundations, slabs, columns, beams, pavements) |
| Aggregates | Fine aggregates (sand only), creating a smooth, paste-like mix | Coarse aggregates (gravel, crushed stone) in addition to sand |
| Strength | Lower compressive strength, designed for adhesion and flexibility | Much higher compressive strength, designed to bear heavy loads |
| Consistency | Thicker, more plastic, allowing for easy placement between units | More fluid, designed to be poured or cast into forms |
| Application | Joining individual building blocks, pointing, and repointing repairs | Forming monolithic structures, pavements, and other large structural components |
The intentional differences in their formulations mean that each material is optimized for its specific construction role. Using concrete as a substitute for mortar in brickwork, for instance, could lead to a less flexible and weaker bond, ultimately compromising the wall's integrity.
Types of Mortar
Mortar is available in various types, categorized by their compressive strength and specific applications. Common types include:
- Type M: Very high strength, suitable for severe weather exposures and below-grade masonry.
- Type S: High strength, good for structural applications and where high lateral strength is needed.
- Type N: Medium strength, the most common type for general-purpose masonry above grade.
- Type O: Low strength, typically used for non-load-bearing walls and historic restoration where softer mortar is required.
- Type K: Very low strength, used exclusively for delicate historic restoration work to match existing weak mortars.
The selection of the appropriate mortar type is critical for the durability and performance of any masonry structure, depending on factors like structural loads, exposure to weather, and the type of masonry units being used.
