Masonry construction relies heavily on mortar, a workable paste created by mixing a binding material with fine aggregates and water. Mortar serves as the adhesive that holds together building materials such as bricks and stones, ensuring structural integrity and aesthetic appeal. This article explores the various types of mortars used in masonry construction, categorized by application, binding materials, density, strength, and specific purposes.
Types of Mortar in Masonry Construction
I. Based on Application
1. Bricklaying or Stone Laying Mortar
Bricklaying or stone laying mortar is primarily used to bind bricks and stones in masonry structures. The proportions of the ingredients depend on the type of binding material utilized. This mortar provides the essential adhesion needed for durable and stable masonry work.
2. Finishing Mortar
Finishing mortar is employed for tasks such as pointing, plastering, and creating aesthetic finishes on buildings. This type of mortar requires high strength, mobility, and resistance to environmental factors like rain and wind. Its primary function is to enhance the appearance and longevity of the masonry work.
II. Based on Binding Material
3. Cement Mortar
Cement mortar is made by mixing cement as the binding material with sand as the aggregate. The ratio of cement to sand typically ranges from 1:2 to 1:6, depending on the desired durability and working conditions. This type of mortar is renowned for its high strength and excellent water resistance.
4. Lime Mortar
Lime mortar utilizes lime as the binding material and can be categorized into two types: fat lime and hydraulic lime. Fat lime requires two to three times the amount of sand and is suitable for dry work. Hydraulic lime, when mixed in a 1:2 ratio with sand, performs well in damp conditions. Lime mortar is known for its high plasticity, making it easy to work with. Notably, the pyramids at Giza were constructed using lime mortar.
5. Gypsum Mortar
Gypsum mortar consists of plaster and soft sand as the binding material and fine aggregate. While it is useful for various applications, it generally has low durability in damp conditions.
6. Gauged Mortar
Gauged mortar is a blend of lime and cement, combining the benefits of both materials. This mixture enhances the strength of traditional lime mortar while maintaining its plasticity. The typical ratio of cement to lime ranges from 1:6 to 1:9, making gauged mortar a cost-effective option.
7. Surkhi Mortar
Surkhi mortar incorporates lime as the binder and surkhi, or finely powdered burnt clay, as the fine aggregate. Surkhi provides greater strength than traditional sand and is readily available, making this type of mortar both effective and economical.
8. Aerated Cement Mortar
Aerated cement mortar is essentially cement mortar that includes an air-entraining agent to improve plasticity and workability. This mortar is particularly useful in applications requiring enhanced performance.
9. Mud Mortar
Mud mortar, composed of mud as the binding material and aggregates like sawdust, rice husk, or cow dung, is often used in regions where cement or lime is unavailable. Its historical use is well-documented in the Middle East, Central Asia, and southwestern USA cultures.
III. Based on Bulk Density
10. Heavy Mortar
Heavy mortar is defined as having a bulk density of 15 KN/m³ or more. It typically uses heavy quartz as fine aggregate, providing durability and structural integrity.
11. Lightweight Mortar
Lightweight mortar has a bulk density of less than 15 KN/m³. It is made by mixing lime or cement with aggregates such as sawdust, rice husk, or jute fibers. Lightweight mortar is particularly valuable in soundproof and heatproof constructions.
IV. Based on Strength (ASTM C270)
12. Type M Mortar
Type M mortar is the highest strength mortar, with a minimum compressive strength of 17.2 MPa (2500 psi). It is designed for exterior masonry applications and below-grade uses where significant loads are expected, such as load-bearing walls and footings.
13. Type S Mortar
Type S mortar is a medium-strength mortar with a minimum strength of 12.4 MPa (1800 psi). It is suitable for grade-level applications with normal to moderate loading and is often used in areas where masonry is in contact with the ground.
14. Type N Mortar
Type N mortar is a versatile, medium-strength mortar with a minimum compressive strength of 5.2 MPa (750 psi). It is the most commonly used mortar for reinforced interior and above-grade exterior load-bearing walls.
15. Type O Mortar
Type O mortar is characterized by its low strength, with a minimum compressive strength of 2.5 MPa (350 psi). It is typically employed for interior non-load-bearing applications and repointing where the structural integrity of the wall remains intact.
V. Based on Special Purpose
16. Fire Resistant Mortar
Fire resistant mortar is made by mixing aluminous cement with fine powder from fire bricks. It is crucial in areas with fire hazards, providing a protective layer against high temperatures.
17. Packing Mortar
Packing mortar consists of cement-sand, cement-loam, or a mixture of both. This mortar is used to pack oil wells and requires high homogeneity, water resistance, and strength.
18. Sound Absorbing Mortar
Sound absorbing mortar utilizes binding materials like cement, lime, gypsum, or slag combined with fine aggregates such as pumice or cinders. This type of mortar effectively reduces noise levels, making it valuable for soundproofing applications.
19. X-ray Shielding Mortar
X-ray shielding mortar is a heavy type of mortar with a bulk density of around 22 KN/m³. It is used to line walls and ceilings in X-ray rooms, providing protection from radiation.
20. Chemical Resistant Mortar
Chemical resistant mortar is formulated to withstand potential chemical attacks on structures. The specific type of mortar is chosen based on the anticipated chemical exposure, and various additives can enhance its resistance.
Conclusion
Selecting the appropriate type of mortar is crucial in masonry construction, as it affects the strength, durability, and performance of the structure. Understanding the various types of mortars based on application, binding materials, density, strength, and specific purposes ensures that builders can make informed choices that meet their project’s requirements.