Limestone is hardly the most glamorous material or one we often think of. I know I certainly didn’t think of it as one of the most valuable parts of masonry until I started to learn more about it. After all, on the surface, it seems so simple. A look at the chemical makeup of it gives you an idea of that.
However, once you start to dig into it more, you can find a ton of information about its usefulness. As you can probably guess, I’ll be focusing on its use in stonework and masonry for the most part. However, there are other purposes, so don’t count Lime out!
The Romans, Greeks, and More
If you’re like me and dream about seeing the structures built by the ancient Romans or Greeks, you may be familiar with this already. However, many of us might not realize that many beautiful buildings contain limestone forms. The Romans used two forms of it to create their concrete.
I know concrete might not seem exciting, but it’s good to realize just how much of an advancement it was for the time. It revolutionized how many civilizations built their roads, for example. Sometimes it’s even called the “Concrete Revolution.”
What makes it so valuable for these purposes, though? It’s a bit complicated, but most of it comes down to the properties of it. The main ones are its adhesion, air content, water content, cohesion, spreadability, flowability, and crystal formations.
It also resists most sulfates, is strong, and has sand-carrying abilities. As you can see, it’s a versatile resource. What’s nice is that it is relatively abundant, as well.
The Different Types
Something else you may or may not be aware of is several types of this stone. You can see a bit more on that here, https://www.buildinglime.org/Thomson_TypeS.pdf, which goes into detail about the differences. However, because it has a lot of industry-specific diction, I’ll also try to offer a less technical definition.
First, there is “pure.” Some other ways to refer to it are slaked, slack, air, common, rich, or high calcium. The main chemical compound in it is calcium hydroxide. When it’s exposed to air, it sets pretty slowly. This is primarily due to its low reactivity with oxygen. It’s white in appearance and usually flaky as well.
Water lime, or hydraulic Lime, is different in that it also contains silica and alumina. Thus, it can be set underwater and usually will set with any exposure to the fluid. There are three strength classifications to remember: eminently, feebly, and moderately hydraulic. The difference between them is the clay content percentage.
Poor or weak Lime is usually gray and structurally weak. It’s no longer used, so there is little reason to cover it.
If the stone contains more than five percent of magnesium oxide, it is considered magnesium lime. A subset of this is named after the Dolomite Mountains, part of the Alps in Italy and Austria. It’s called Dolomitic lime.
Finally, there is hydrated lime type S, most commonly used in masonry in the United States. It’s considered “special” because it’s a form of hydrated Lime derived from the dolomitic type I mentioned above. So, the quicklime that we get from it is sandy in texture.
One benefit of this type over the type “N” (standard) is higher elasticity, plasticity, and water retention. Generally, it can develop these attributes quickly, placing it above other types. In the United States, it’s often used to create something called Portland concrete.
Also, note that the particles within it are small and plate-shaped. Thus, the oxide content in this type is limited. When exposed to carbon dioxide, it can even carbonate again.
Type S in Masonry
The typical application for it is in mortars. Mortars need high levels of workability to prevent any slowdowns in the process, after all. So, it’s easier to handle when you have a substance with good water retention and sand-carrying capacity.
Most notably, there is less difficulty when using a trowel, and it can fill joints more effectively. In a single session, you can lay more bricks. Ideally, they won’t need to be retempered, either.
If you are looking for limestone for your construction needs, you might want to consider Type S. While plenty is out there, it’s the most widely used in this country for a reason! Don’t waste time having to retemper your bricks. Slowed progress can also result in low productivity levels on a building site. Just give it a thought!
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