Concrete and Cement: What Is the Difference?
Concrete and cement are both different things – but related. They’re used interchangeably in common conversation. Cement is a much older word used for construction material – hundreds of years old, in fact. Meanwhile, concrete is something that was created relatively recently – the 1830s.
Concrete and Cement: What Is the Difference?
Concrete is the most used material on earth after water. It’s a composite made of multiple materials – one of which is cement.
Cement and concrete (made with cement and a few other materials) are both used in construction all over the world.
What is cement? How is concrete made from cement?
Cement is a limestone-based compound. Here’s how the whole process works:
- Limestone is extracted out of the earth.
- The limestone is then mixed with a source of silica, such as fly ash or industrial byproducts.
- This mixture is fired in a kiln – 2,700 degrees Fahrenheit.
- After this process, we get clinker – solid, round pebble-like pieces.
- Cement plants then grind clinker down until it becomes a fine powder.
- A few additives are mixed in to make it less volatile so that it doesn’t quickly solidify in air. This powder is cement.
- Now, this cement is mixed with water on construction sites, thus creating cement paste.
- Sand is then added into the cement paste – mortar.
- Stone aggregates (or gravel or crushed stone) are added to the mortar. This is the final step in which concrete is created.
In many ways, concrete is an evolution of cement. Cement or mortar itself are both used in construction as well. Concrete, however, has its own identity and a separate use case.
The use of cement vs. concrete
Cement solidifies when it’s mixed with water and kept in the air for a while. For example, two bricks can be attached to each other permanently with mortar between them. This is how brick walls are made.
Cement undergoes a chemical reaction when it mixes with water. A process called hydration dissolves the clinker into basic calcium. This calcium, in the presence of water, combines with water and silica. This ultimately forms a molecule called calcium silica hydrate or CSH. CSH molecules form supertight bonds among them. When sandwiched between two materials, CSH paste will solidify and dry soon to lend them strength and affinity. Solidified cement is surprisingly largely porous – 96% of the pores inside cement are connected. Cement has excellent strength despite its porosity.
Mortar isn’t the only way in which cement is used. Though mortar is used in bricklaying and other construction jobs, concrete is what makes most of the life we see around ourselves (precisely why we call cities concrete jungles). As we know, mortar is mixed with stone aggregates to make the composite we call concrete. These stone aggregates further improve the strength of the composite that mortar is. Concrete is used in larger construction jobs such as buildings, bridges, and entire skyscrapers. The porosity of cement can be reduced further to improve its strength. Research into this field led to the development of “high-performance concrete,” or HPC, in the 1980s.
No cement sidewalks
To the ire of many, cement is used to define concrete more often than not. For example, it’s common to hear terms such as “cement sidewalks”. While in fact, the sidewalk is made of concrete, of which cement is an ingredient. Building something out of cement paste (only cement and water) would be very expensive because you’d need lots of cement. That’s why sand is thrown into the mix, quite literally, which adds additional hardening into the mass.
The cement + water + sand combination, called mortar, is only used for smaller tasks. Large-scale construction work where strength is key to endure storms and extreme weather always uses concrete – mortar mixed with gravel or crushed stone. Concrete is extremely tough when hardened. Concrete is used in the pillars made for the tallest of buildings in the world and the base of the largest of bridges carrying the heaviest of loads.
The next time you mention a sidewalk, say what you mean – a concrete sidewalk and not a cement one!
Additional Reading: 17 Striking Concrete Buildings Around the World
TR Concrete Construction – Omaha Concrete Contractors
This industry takes a lot of heavy machinery and tough labor, but it also requires as much or more planning, critical thinking, and fine touch to get a quality finished product. It is a very rewarding career and keeps you constantly on your toes being that 2 days are never the same. It is a profession that has been around for a long time and is ever-evolving and still remains a very vital staple in today’s economy.
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