Is Concrete Man-Made or Natural
Concrete is one of the most in-demand materials in our world today, second only to water by some estimates, but despite the pervasiveness of this construction material, few people really know much about it. How concrete cures is one of the most commonly misunderstood aspects of it, but the thing we are concerned within this post is whether or not concrete is a natural product or it is manmade.
Concrete, despite being made from natural substances, is still a manmade product. While it is not beyond the realms of possibility that natural concrete could form in nature, the process involved makes it so unlikely so as to be practically impossible.
So, concrete is manmade, but what does that mean to its place in our society?
What are the Ingredients in Concrete?
There are not many ingredients to the concrete itself; in fact, the basic mix for concrete involves little more than water, sand, cement, and an aggregate. However, the cement is the key ingredient, and that is where things get a little bit more complicated.
The ingredients in cement can vary, but commonly include things like limestone, shale, chalk, clay, sand, and even seashells. This is all ground down to a fine powder and then baked in a kiln to extremely high temperatures, which causes the powder to form nuggets that are known as “clinkers.” These are then ground down into a fine powder once more, and that is what makes up the commonly used Portland Cement that is used in modern concrete.
How Concrete Cures
A common misconception about concrete is how it hardens. The process of making concrete involves mixing it with water until it becomes a pourable liquid, after which it can then be poured into the form that makes up the final desired shape of the concrete. Many people believe the hardening process happens because the concrete “dries out” as the water evaporates. The reality is that cement is a hydraulic compound, and the chemical reactions caused by mixing it with water produce hydrates, which in turn binds the concrete together. Due to this hydraulic nature, water actually makes the concrete stronger.
It is this process that is responsible for the long curing times of concrete. Though concrete may feel hard enough to touch after as little as a single day, it often needs closer to a month to cure to a level of strength that is sufficient for the application it is being used for. Beyond that, concrete can take decades to reach its full strength, with larger structures such as the Hoover Dam potentially taking over a century to cure fully.
It’s worth noting that the engineers and architects behind large projects are fully aware of this aspect of concrete and ensure that the degree of strength reached by the time a structure is used is sufficient, even if it is not the full strength that the concrete will eventually reach. In the case of the Hoover Dam, engineers laced the structure with metal pipes that could then be flooded with water to cool the concrete as its chemical reactions took place. This allowed the concrete to cure much more quickly than it would have done on its own. These pipes were then pumped full of concrete to ensure the structure was as strong as it could be.
The Environmental Impact of Concrete
Further adding to the manmade nature of concrete is its impact on the environment. A truly natural product would likely not be harmful to the environment, but that is not the case for concrete.
The ways in which concrete damages the environment range from the mechanical to the chemical. On the mechanical side of things, we have the physical damage to areas of land caused when extracting the necessary materials for the concrete.
On the chemical side of things, the process of making cement produces carbon dioxide, which is the primary gas responsible for the greenhouse effect and the artificial warming of our planet. It is estimated that concrete production is responsible for around 8% of the world’s carbon dioxide emissions, which, if concrete were a country, would make it the third-largest producer of carbon dioxide after China and the United States.
There is also the fact that making concrete requires a not-insignificant amount of energy. During the process of baking the ingredients for cement, they are fed into a rotating kiln that is heated to around 2,640 degrees Fahrenheit. That kind of heat requires a considerable amount of energy. And, when you factor in that so much of this construction material is being used around the world, it makes for a lot of demand on our largely fossil-fuel-based electricity industries.
Natural Alternatives to Concrete
When you understand the negative impact that concrete has on the environment, it is only natural to wonder if there are less damaging alternatives that could be used instead. The answer to this question is yes, but with a caveat. Though there are alternatives to concrete on small scales, there is nothing that is as economically viable as concrete on the immense scales that it is currently used. In other words, concrete is just too cheap to be beaten at the moment. Still, if you are embarking on a small-scale project and you would like to avoid the use of concrete, there a number of options to choose from;
Though technically still concrete, grasscrete involves pouring the concrete in such a way that patterns are left empty for grass to grow in. This has the advantage of reducing the amount of concrete required while also decreasing the net carbon footprint since the grass will consume carbon dioxide over time.
As the name suggests, this is a type of concrete made by binding lime and hemp fibers to make a strong, lightweight construction material.
A construction material as old as civilization, and perfectly reliable on a small scale (we wouldn’t recommend building skyscrapers out of it). Of course, there are question marks over how much better it is for the environment to chop trees down, but it is far easier to obtain wood in a sustainable manner than it is to reduce the carbon footprint of concrete.