What Is Hydraulic Lime and What Is It Used For?

What Is Hydraulic Lime and What Is It Used For?

Hydraulic lime is a type of building material that few people understand unless they work with it. Still, as one of the best materials used for brick and stone masonry today, there’s some important information everyone should know. When it comes to what is hydraulic lime and what is it used for, read this guide to learn the fundamentals.

What Is Hydraulic Lime?

Hydraulic lime is a type of lime carbonate used to make mortar and plaster products. As it heats, calcium carbonate, or lime, mixes with an aggregate, such as sand or gravel. This mixture—often called lime putty— makes up a strong binder for brick and stone masonry. Lime putty is also used for plaster or stucco structures. Lime mixed with clay goes through a kiln at high temperatures, which removes most of the moisture. It also produces mineral byproducts called silicates which combine to form hydraulic lime.

Why Is It Used?

Today, hydraulic lime has many versatile applications. One of the best uses for natural hydraulic lime is historic building restoration. Buildings built before the early 20th century often used brick or stone masonry in their structure. After the early 20th century and the introduction of Portland cement, this changed to cement materials. Still, hydraulic lime has many advantages over cement. Mainly, it’s porous, which allows moisture to escape. It’s also structurally efficient to promote long-lasting durability. That’s why colonial homes in the United States often require hydraulic lime instead of other materials to restructure their foundations.

Considerations To Know

As part of this guide on what is hydraulic lime and what is it used for, keep in mind some of the disadvantages or considerations when using this product. Hydraulic lime sets slower than other materials since it requires moisture to set. As it dries, the pH drops to about 8.6. Hydraulic lime plaster is also weaker than cement, thus requiring multiple layers to fully achieve the desired strength of the mortar.

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