Limestone is hardly the most glamorous material, or one that we think of all that often. I know I certainly didn’t think of it as one of the most useful 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 how useful it is. 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 as well, 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, what a lot of us might not realize is that many of these beautiful buildings actually contained forms of limestone. In fact, the Romans ended up using 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, spread ability, flowability, and crystal formations.
It also resists most sulfates, is strong, has sand-carrying abilities, and more. As you can see, it’s a versatile resource. What’s nice is that it is fairly abundant, as well.
The Different Types
Something else you may or may not be aware of is that there are 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’s got a lot of industry-specific diction, I’ll try to offer a less technical definition of them as well.
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 quite slowly. This is mostly 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/or alumina. Thus, it can set under water and usually will set with any exposure to the fluid. There are three strength classifications to keep in mind, those being eminently, feebly, and moderately hydraulic. The difference between them is the clay content percentage.
Poor or weak lime is usually gray in color and is structurally weak. It’s not used much anymore, so there is not much 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 actually named after the Dolomite Mountains, which are part of the Alps in Italy and Austria. It’s called Dolomitic lime.
Finally, there is hydrated lime type S, which is most commonly used in masonry in the United States. It’s considered “special” because it’s a form of hydrated lime that is derived from the dolomitic type that I mentioned above. So, the quicklime that we get from it is sandy in texture.
Some of the benefits of this type over the type “N” (normal) is higher levels of 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 usual application for it is in mortars. Mortars need high levels of workability to prevent any slowdowns in the process, after all. So, when you have a substance with good water retention and sand carrying capacity, it’s easier to handle.
Most notably, there is less difficulty when using a trowel and it can fill any 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 there are plenty 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 result in low productivity levels on a build site, too. Just give it a thought!