Other meanings of Mortar (weapon)
Construction & Materials
Mortar is a workable paste used to bind building blocks such as stone, brick, and concrete masonry units together, fill and seal the irregular gaps between them, and sometimes add decorative color or pattern to masonry walls. It is a mixture of fine aggregate (sand), a binder (such as lime or cement), and water, which hardens over time to form a rigid, durable joint. Mortar has been used in construction for thousands of years, with ancient examples surviving in structures like the pyramids of Egypt and the Great Wall of China.
Mortar consists of a binder, fine aggregate, and water. The binder can be lime, cement, or a combination (lime-cement mortar). Sand is the most common aggregate, providing bulk and reducing shrinkage. Modern mortars are classified by their compressive strength and composition, with types M, S, N, O, and K specified by ASTM C270. Type N is a general-purpose mortar with moderate strength, while Type S is stronger and used for load-bearing walls. Type M is high-strength for heavy loads, and Type O is low-strength for interior non-load-bearing work. Lime mortars are more flexible and breathable, making them suitable for historic restoration.
Mortar has been used since ancient times. The earliest mortars were mud or clay, used in Neolithic structures. The Egyptians used gypsum mortar in the pyramids around 2600 BC. The Romans developed lime mortar and later added volcanic ash (pozzolana) to create hydraulic mortar that could set underwater, enabling the construction of harbors and aqueducts. After the Roman Empire, the knowledge of hydraulic mortar was largely lost in Europe until the 18th century, when engineers like John Smeaton rediscovered it using hydraulic lime. Portland cement, patented in 1824, eventually replaced lime in most modern mortars due to its faster setting and higher strength.
Key properties of mortar include workability, water retention, compressive strength, and durability. Workability is crucial for bricklaying, as it affects the ease of spreading and the bond with the units. Water retention prevents premature drying and ensures proper hydration of the cement. Compressive strength is important for structural integrity, but mortar must also be softer than the masonry units to accommodate minor movements and prevent cracking. The porosity of mortar allows moisture to escape, which is essential for the longevity of walls. The choice of mortar type depends on the application, with softer mortars used for historic buildings to avoid damaging softer bricks.
Mortar is used in a wide range of construction applications, from simple garden walls to high-rise buildings. It is applied with a trowel, and the technique of laying bricks or blocks involves spreading a bed of mortar, placing the unit, and then filling the vertical joints. Pointing is the process of finishing the joints, either flush, raked, or struck. Mortar is also used for plastering and rendering, where it is applied to walls to provide a smooth or textured finish. In restoration, repointing involves removing deteriorated mortar and replacing it with a compatible mix to preserve the structure's integrity.
Beyond its basic role, mortar has niche applications and historical curiosities. For instance, 'limecrete' is a type of concrete using lime as the binder, used in eco-friendly construction. In some regions, mud mortar is still used for traditional earthen buildings. The ancient Romans used mortar in the construction of the Pantheon's dome, which remains the world's largest unreinforced concrete dome. A lesser-known fact is that mortar can be used as a medium for fresco painting, where pigments are applied to wet lime plaster. Additionally, the term 'mortar' is also used in artillery, but the masonry sense is unrelated. The strength of mortar can be tested using a mortar cube test, which is a standard quality control procedure.
This article focuses on mortar as a construction material, distinct from the weapon of the same name.
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