Mortar: How It's Made and All Its Uses

Overview

The video explains what mortar is, how it is made, its main types and applications, and how it differs from cement and concrete. It also surveys mortar’s history and current efforts to make it more sustainable.

What Mortar Does

• Mortar is a workable paste used to bond bricks, stones, and concrete masonry units.
• It fills the joints between masonry pieces and hardens to help hold them together.
• It is designed to be strong while remaining somewhat softer and more flexible than the materials it joins. This can help it accommodate small movements or stresses without cracking.
• Unlike concrete, mortar is primarily a bonding material rather than one intended to bear heavy structural loads.

Ingredients and Mixing

Mortar typically contains:

• Cement, usually Portland cement, which binds the mixture.
• Sand, which gives it bulk and body.
• Water, which activates the cement and makes the mix workable.
• Lime, sometimes added—particularly in traditional or historic mortars—to improve plasticity and ease of application.

Proportions vary according to the mortar type and the project’s requirements.

Basic Mixing Process

1. Thoroughly blend the dry ingredients.
2. Add water gradually.
3. Stir until the mortar is creamy and spreadable, but still stiff enough to hold its shape.
4. Mix by hand for small batches or use a mechanical mixer for larger jobs.

Common Mortar Types

The video describes five letter-designated types, each with different strengths and uses:

• Type N: Medium strength; common for general interior and exterior work above ground, especially walls without heavy loads.
• Type S: Stronger and more durable; used for applications such as below-grade work, foundations, and retaining walls.
• Type M: The strongest of the common types; used for load-bearing walls and heavy stone structures.
• Type O: Lower strength; used for interior work and some historic restoration.
• Type K: Very low strength; used primarily in the preservation of very old buildings.

Choosing a type depends on the structural demands and the desired appearance of the project.

History and Applications

The video describes mortar’s history as follows:

• Ancient Egyptians used gypsum mortar in pyramid construction.
• The Romans developed an early hydraulic mortar using volcanic ash. It could set underwater and was used in lasting infrastructure such as aqueducts and harbors.
• Lime mortar was widely used for centuries, including in the Parthenon and medieval European castles.
• Portland cement emerged in the 19th century and helped shape modern mortar formulas.

Mortar is used in brick and block laying, stone veneers, chimneys, fireplaces, patios, walkways, retaining walls, and garden features. In historic restoration, mixes may be tailored to match original materials and help preserve old structures. Mortar color and joint finish also affect a wall’s appearance.

Tuckpointing involves replacing deteriorated mortar to help stabilize masonry and restore its appearance. Some specialized mortars include polymers to improve adhesion, water resistance, or setting speed.

Mortar, Concrete, and Cement

• Cement is an ingredient in both mortar and concrete.
• Mortar generally contains cement, sand, and water, sometimes with lime, and is mainly used to bond masonry.
• Concrete contains cement, sand, gravel, and water, and is used for structural elements such as slabs, beams, and columns.

The video emphasizes that these materials are designed for different purposes and that using the wrong one may compromise durability or safety.

Sustainability

Researchers and manufacturers are exploring ways to reduce mortar’s environmental impact, including:

• Using alternative binders such as fly ash or slag to reduce reliance on cement.
• Incorporating recycled materials.
• Developing bio-based mortars, including products described as able to self-heal or absorb carbon dioxide over time.

Speakers and Sources Featured

• Narrator: An unnamed presenter speaking for History of Simple Things; no individual name is given.
• Other speakers or cited sources: None are identified. The video refers to historical peoples and building traditions, including the Egyptians, Romans, and European builders, but does not feature them as speakers or cite specific sources.