This article explains the basic composition and role of concrete, specifically the properties of reinforced concrete, and explores why reinforced concrete is so important in architecture and why it has been called a godsend, given that rebar and concrete have nearly identical coefficients of thermal expansion.
We’ve all seen ready-mixed concrete on the road – the gray, cylindrical trucks slowly turning and delivering concrete is a common sight everywhere in the city. Have you ever watched a concrete truck go to a construction site and wondered what’s inside? I remember growing up and hearing my parents tell me that concrete contains important materials used to build houses. At the time, I was just curious about the big spinning vats, but over time I learned how important concrete is as a building material.
Before I explain the benefits of concrete and why it’s such a miracle, let’s first understand what concrete is. Concrete is a building material made from coarse aggregates like gravel and fine aggregates like sand, mixed with water and cement. Concrete has been around for thousands of years, but it has become increasingly important in modern times. The reason for using different types of aggregates is that different sizes and types of aggregates produce different types of concrete, with varying strengths and densities. Research has been done to improve the cement by mixing it with other substances, and as a result, concrete has become an essential building material in modern cities. Take a walk down any city street and you’ll notice that most large buildings are made of concrete, especially reinforced concrete.
This might raise a question. How were buildings in the past built without concrete? In fact, even in ancient Rome, concrete-like materials were used. For example, the Pantheon in Rome is the largest dome structure ever built using the construction techniques of the time, and it was constructed using a special type of concrete mixed with volcanic ash. With this historical background, it’s clear that concrete has been a staple of construction for a long time. However, modern concrete is far more advanced than its predecessors, and its strength and durability have been greatly improved through a technique called reinforced concrete.
So, let’s take a look at the benefits of reinforced concrete. The most basic principle of concrete is adhesion. When water and cement are mixed together, they form a very strong bond. They seep between the materials and slowly harden and solidify, which is why normal concrete is very resistant to pressing forces, or compressive forces. But it’s much weaker than you might think when it comes to tensile forces, which are pulling forces, because the water and cement mixture seeps further into the material. What compensates for this weakness is the reinforcing steel in reinforced concrete. The rebar takes up the tensile force and makes the concrete stronger to withstand any force. The downside is that rebar is a fairly expensive material, so reinforced concrete is usually only used in areas that are likely to be subjected to high tensile forces. For example, rebar is essential for important structures, such as the foundations of skyscrapers or the main structure of bridges.
Reinforced concrete also excels in terms of durability. It deforms less over time and is relatively safe from natural disasters like fires and earthquakes. This is why many modern buildings are choosing reinforced concrete as their primary material of choice. These benefits make concrete more than just a building material; they’re critical to the safety of our lives.
So, let’s take a look at the reasons why this reinforced concrete is not just a great human discovery or invention, but a gift from God. To understand this, we first need to understand the concept of thermal expansion, which literally means that a substance stretches when heat is applied to it. This happens because the application of heat, or energy, increases the kinetic energy of the molecules that make up a substance. Just as people move more when they have more energy, molecules move more when they have more energy, causing objects to increase in length, width, and volume. You can see this when a ping-pong ball is dented, and you put it in hot water and see the dents return to their original shape. The formulas for finding the amount by which these three physical quantities increase are all different. But what they all have in common is that they’re proportional to a constant called the coefficient of thermal expansion, which is unique to the object. Just like people have different levels of energy, and different levels of energy after resting, molecules have different levels of thermal expansion depending on what molecules are around them and the situation they’re in. So different types of objects will have different coefficients of thermal expansion.
This explains why reinforced concrete is said to be a godsend: the coefficient of thermal expansion of rebar and concrete is almost identical. Consider what would happen if rebar and concrete did not have nearly the same coefficient of thermal expansion. What happens if you stack two objects on top of each other, but the inner object has a higher coefficient of thermal expansion, making it more sensitive to temperature changes? As the temperature rises, the inner object will increase in volume more rapidly, causing the outer object to buckle under the force and break. Conversely, as the temperature drops, the outer object will shrink more rapidly, causing the inner object to buckle under the force and break. In either case, the objects’ different coefficients of thermal expansion will cause problems when the temperature changes. In the case of building materials, temperature changes are inevitable. This is not true in every country, but as the seasons change, the temperature usually changes. So if we were making reinforced concrete and the rebar and concrete didn’t have the same coefficient of thermal expansion, we wouldn’t be able to build houses with it.
In the end, the fact that reinforced concrete and concrete have the same coefficient of thermal expansion is not a coincidence, but rather a miracle of nature. Thanks to this fact, which scientists discovered after a long period of research, we are able to construct tall buildings and strong bridges today. As such, reinforced concrete is a great example of the importance of harmonizing human technology and nature.
We’ve explained the benefits of reinforced concrete and why it’s such a fascinating technology using the concepts of force and thermal expansion, and you can see how something you might not think much about is so important to our lives. The next time you see a ready-mixed concrete truck, take a moment to think about the greatness of the technology behind it and the miraculous way it came together. I’ll close by saying that I hope you’ve been reminded of the benefits of concrete.
