Types of Mortar: Their Uses & Functions Explained

Mortar is an essential construction material used to bind masonry units like bricks, stones, and concrete blocks, ensuring the structural integrity and durability of buildings. In the construction industry, mortar plays a crucial role as a binding agent that holds building components together.

It is vital for binding various building materials like stones and bricks, enhancing the strength and durability of structures. Comprised of cement, lime, sand, and water, mortar acts as both an adhesive and a cushion to distribute loads and absorb structural movements.

This blog explores the importance of mortar, highlighting its role as a mix of a binding agent like cement with water and fine aggregates. Various types of mortars, including cement, lime, gypsum, and epoxy mortars, each serve specific purposes based on their unique properties and applications.

What is Mortar in Civil Engineering?

In civil engineering, mortar is a versatile binding material that holds building blocks like bricks, stones, and concrete blocks together. It is made from cement, lime, sand, and water. Mortar provides structural stability and seals gaps between units, preventing moisture infiltration and enhancing the durability of structures.

Various types of mortar, such as cement, lime, and gypsum mortar, cater to different construction needs, each offering unique properties like flexibility, strength, and water resistance. Understanding mortar’s role and applications is fundamental for ensuring the longevity and safety of masonry works in civil engineering.

Functions of Mortar

Mortar serves several critical functions in construction, contributing to the structural integrity and durability of masonry works. Here are the primary functions of mortar:

Bonding Agent: Mortar acts as a binding material, holding together masonry units such as bricks, stones, and concrete blocks. It ensures these units remain firmly in place, creating a cohesive and stable structure.

Load Distribution: Mortar helps distribute loads evenly across the masonry units, reducing stress concentrations. This uniform distribution of loads enhances the structure’s overall stability and strength.

Sealing Joints: Mortar fills the gaps and joints between masonry units, providing a seal against the ingress of water, air, and other external elements. This helps in preventing moisture penetration, which can lead to structural damage and deterioration.

Accommodating Movements: Mortar allows for slight movements within the masonry units due to thermal expansion, contraction, or other environmental factors. This flexibility helps in preventing cracks and maintaining the integrity of the structure.

Surface Finish: Mortar can be used to provide a smooth and aesthetically pleasing finish to masonry surfaces. It can also be used to fill imperfections and create a uniform appearance.

Insulation: Mortar can contribute to the thermal and acoustic insulation of a building. The type and composition of the mortar can affect its insulating properties, helping to maintain a comfortable indoor environment.

What is Mortar Mix?

Mortar mix is a blend of cement, lime, sand, and water used in masonry construction to bond bricks, stones, and other building units. The proportions of these components can differ depending on the desired properties of the mortar. 

Cement provides strength and durability, lime adds workability and flexibility, and sand serves as an aggregate for the mix. Water activates the cement and lime, creating a workable paste. The resulting mortar mix offers strong adhesion, load distribution, and protection against environmental factors, ensuring the stability and longevity of masonry structures. Properly mixed mortar is essential for effective and durable construction.

Different Types of Mortar

There are various types of mortars such as:

1. Cement Mortar

Cement mortar is a combination of cement, sand, and water. It is widely used in construction for its high strength and durability. Cement mortar is ideal for bonding bricks, blocks, and stones, and is also used for plastering and rendering. Its quick-setting properties make it suitable for various structural applications, providing strong and lasting adhesion.

2. Lime Mortar

Lime mortar consists of lime, sand, and water. The distinction between fat lime and hydraulic lime is crucial; fat lime is particularly suited for dry conditions and is used in a higher ratio of sand, while hydraulic lime is preferred for damp environments or areas with water-logging. It is known for its flexibility and breathability, making it suitable for historic buildings and restoration projects. Lime mortar allows moisture to evaporate, reducing the risk of damage from trapped moisture. It also offers good workability and a longer setting time compared to cement mortar.

3. Gypsum Mortar

Gypsum mortar, also known as plaster of Paris, is made from gypsum and water. It sets quickly and is primarily used for interior plastering and decorative work. Gypsum mortar provides a smooth finish and can be moulded into intricate shapes, making it ideal for ornamental plasterwork and wall finishes.

4. Gauged Mortar

Gauged mortar is a combination of cement and lime with sand and water. This type of mortar combines the strength of cement with the flexibility and workability of lime. It is used for general masonry work, offering a balance of stability and ease of application, and is suitable for various construction projects.

5. Surkhi Mortar

It includes surkhi (brick dust), lime, and sand. Surkhi acts as a pozzolanic material, enhancing the mortar’s strength and durability. This type of mortar is often used in historical restoration and construction where a traditional approach is required. It is suitable for use in humid conditions due to its improved resistance to moisture.

6. Aerated Cement Mortar

Aerated cement mortar contains cement, sand, water, and a foaming agent to create a lightweight, air-entrained mixture. This type of mortar has excellent insulation properties and is used for thermal insulation, soundproofing, and lightweight construction applications. It provides a higher yield and reduces the overall weight of the structure.

7. Mud Mortar

Mud mortar is made from clay, sand, and water. It is one of the oldest types of mortar, traditionally used in rural and low-cost construction. Mud mortar is eco-friendly and offers good thermal insulation. It is easy to work with but has lower strength and durability compared to modern mortars, making it suitable for non-load-bearing walls.

8. Heavy and Lightweight Mortar

Heavy-weight mortar includes high-density aggregates like barytes or iron ore, used in radiation shielding and other specialised applications. Lightweight mortar, on the other hand, uses lightweight aggregates such as pumice, vermiculite, or perlite. It is used for thermal insulation, soundproofing, and reducing the load on structures.

9. Thin-set Mortar

Thin-set mortar is a cement-based adhesive used to bond tiles to surfaces. It is made from cement, fine sand, and a water-retaining agent. Thin-set mortar is ideal for tile installations on floors and walls due to its strong adhesive properties, water resistance, and thin application layer, which ensures a smooth finish.

10. Epoxy Mortar

Chemical resistant mortar, such as epoxy mortar, is a blend of epoxy resins, hardeners, and aggregates. It offers exceptional strength, chemical resistance, and durability, making it suitable for industrial flooring, repair work, and areas exposed to harsh chemicals. Epoxy mortar sets quickly and forms a robust, impermeable bond, ideal for high-stress environments.

11. Fire-resistant Mortar

Fire-resistant mortar is designed to withstand high temperatures and prevent the spread of fire. It typically contains refractory materials such as calcium aluminate, fire clay, or ceramic fibres. This type of mortar is used in fire-rated walls, chimneys, and furnaces, providing thermal protection and structural stability during fires.

12. Packing Mortar

Packing mortar is used for packing spaces between structural elements, such as between beams and walls or around pipes. It ensures a tight, secure fit and can accommodate slight movements. This type of mortar is often made with a high proportion of sand and may include additives to enhance its performance.

13. Other Variants

Other mortar variants include polymer-modified mortars, which incorporate polymers to enhance properties like adhesion, flexibility, and water resistance. Type S mortar is a medium-strength mortar with high bonding capabilities, suitable for grade-level applications. Waterproof mortars are formulated to prevent water penetration in damp conditions. Self-healing mortars contain additives that enable them to repair cracks autonomously. Each variant serves specific purposes, offering tailored solutions for unique construction challenges.

Properties of Good Mortar

A good mortar must possess several key properties to ensure the structural integrity and durability of masonry work. Here are the essential properties of a good mortar:

1. Adequate Strength: Mortar must have sufficient compressive and tensile strength to support the loads imposed on it by the masonry units and any additional structural loads.
2. Workability: Good mortar should be easily workable, allowing for smooth application and spreading. This ensures proper bonding between masonry units and ease of use during construction.
3. Durability: Mortar must withstand various environmental conditions, such as moisture, temperature fluctuations, and weathering, without degrading over time. Durability ensures the long-term stability of the structure.
4. Adhesion: Mortar should have strong adhesive properties to ensure a firm bond between the masonry units, preventing any displacement or loosening over time.
5. Consistency: The consistency of mortar should be such that it can be easily spread and applied to surfaces while maintaining its shape and stability.
6. Setting Time: Mortar should have an appropriate setting time, allowing sufficient working time for application but also ensuring that it sets and hardens within a reasonable period to maintain construction efficiency.

Advantages of Mortars in Civil Engineering

Mortars play a crucial role in civil engineering, providing numerous advantages that contribute to the strength, durability, and functionality of masonry structures. Here are the key advantages of using mortars in civil engineering:

Enhanced Structural Integrity:

Mortar binds masonry units such as bricks, stones, and blocks together, creating a cohesive and stable structure. This bonding capability ensures that the individual units act as a single, unified element, improving the overall structural integrity.

Load Distribution:

Mortar helps to distribute loads evenly across the masonry units, reducing stress concentrations and preventing structural failure. This uniform distribution of loads enhances the stability and strength of the structure.

Sealing and Waterproofing:

Mortar fills the gaps and joints between masonry units, providing a seal against water penetration, air infiltration, and other environmental elements. This sealing property protects the internal structure from moisture damage and improves the durability of the building.

Thermal and Acoustic Insulation:

Mortar contributes to the thermal and acoustic insulation of a building. By filling the spaces between masonry units, mortar reduces heat transfer and dampens sound transmission, enhancing the comfort and energy efficiency of the structure.

Aesthetic Appeal:

Mortar can be used to create smooth and aesthetically pleasing finishes on masonry surfaces. It can also be colored and textured to match or complement the building’s design, enhancing its visual appeal.

Flexibility and Adaptability:

Mortar can accommodate slight movements within the masonry units due to thermal expansion, contraction, or settling. This flexibility helps prevent cracking and maintains the structure’s integrity over time.

Disadvantages of Mortars in Civil Engineering

While mortar is an essential material in construction, it does have certain disadvantages that can impact its performance and application in civil engineering. Here are the key disadvantages of using mortars:

Limited Tensile Strength:

Mortar generally has low tensile strength compared to its compressive strength. This limitation can lead to cracking under tension or flexural stress, requiring additional reinforcement in structural applications.

Susceptibility to Weathering:

Mortar can deteriorate over time due to risk to harsh weather conditions like  freeze-thaw cycles, rain, and UV radiation. This weathering can reduce the mortar’s effectiveness and longevity.

Shrinkage and Cracking:

Mortar tends to shrink as it dries and cures, leading to cracking if not properly managed. Cracks can compromise the structural integrity and aesthetic appearance of the masonry work.

Maintenance Requirements:

Mortar joints require regular maintenance and repointing to ensure they remain intact and functional. This ongoing maintenance can increase a structure’s long-term costs.

Setting Time Variability:

Environmental conditions like humidity and temperature can affect mortar’s setting time. This variability leads to inconsistencies in the curing process, affecting the overall quality of the masonry.

Mixing and Application Challenges:

Achieving the correct proportions and consistency of mortar mix can be challenging and require skilled labor. Improper mixing or application can result in weak or ineffective mortar joints.

Conclusion

Mortar is indispensable for constructing robust and durable masonry structures. Comprising various mixes like cement, lime, gypsum, and epoxy, each types of mortar offers unique properties tailored to specific construction needs. While mortars enhance structural integrity, load distribution, and aesthetic appeal, they also present challenges, such as susceptibility to weathering and shrinkage. Understanding different mortars’ functions, advantages, and potential drawbacks is crucial for selecting the appropriate type for each project. Proper selection and application of mortar ensure the longevity and safety of masonry works, ultimately contributing to the success of construction projects.