What's the difference between concrete and cement?

concrete vs cement

The answer to that question is simple; cement is a powder and one of the four ingredients used to make concrete.

Concrete is made from combining the cement with water, sand, and stone. When the cement mixes with water it forms a paste that binds all the materials together.

The surfaces of the stone and sand get coated with the cement paste during the mixing process.

Once the paste sets and hardens, it forms a rock hard mass known as concrete.

How does the cement harden?

When the cement gets mixed with water it forms a paste.

As soon as the two materials are mixed together a chemical reaction takes place that causes "heat". 

The chemical reaction is called HYDRATION. As hydration takes place, over time, the paste hardens and gains strength.

A lot of people use the term "cement" when they're really referring to "concrete".

When talking to my customers, they'll say things like cement floor, cement truck, or cement driveway.

Or... people will ask me "Do you pour cement?"

When this happens, I have to politely explain to them the difference between concrete vs cement and for most people, I don't think they really care that much.

Is cement stronger than concrete?

No, cement isn't stronger than concrete. The aggregate's (stone) and sand is what make concrete strong.

Cement, when mixed with water, will form a paste that will harden. It's called mortar, but on its own, it's not very strong.

Sometimes sand is mixed with the cement and water to form a stronger mixture of mortar, but it's still not stronger than concrete.

What makes concrete so strong?

It's the carefully designed portions of each ingredient that make up different concrete strengths.

In it's most basic form, concrete is proportioned at about 15% cement, 70% sand and stone, and 15% water. 

It's the ratios of these ingredients when they're all mixed together that make the concrete strong.

The quality and strength of the paste is determined by how much water is mixed with it. 

This is called the "water-cement-ratio". The higher the w-c-r, the lower the concrete strength. The lower the w-c-r, the stronger the concrete mix is.

You want the concrete to be workable so it can be properly consolidated and placed. But not too wet or soupy which would produce a lower quality concrete. 

How is cement made?

Cement is a mixture of materials like limestone, silica, shale, clay, slate, and iron ore.

After being mined from the ground, they get heated to extremely high temperatures in a rotating kiln.

The kiln looks like a large rotating pipe about 10 - 15 feet in diameter and about 300 feet long.

One end of the kiln is raised, this is where the raw materials are placed. As the kiln rotates, the materials move slowly to the lower end.

Jetted flames at the lower end heat all the materials to temperatures between 2700 and 3000 degrees Fahrenheit.

When the materials are exposed to these extremely high temperatures, they form marble sized balls called "clinker".

The clinker is very finely ground into a powder called Portland Cement.

After it's ground into the fine powder, the cement is mixed with small amounts of limestone and gypsum. 

This mixture is the cement that's transported to ready-mix concrete plants and used to make concrete.

There's different types of cement

Did you know there's different types of cement? 

Here they are:

  • TYPE I - A general purpose cement that can be used for most applications
  • TYPE II - Moderate sulfate resistance
  • TYPE III - High early strength
  • TYPE IV - low heat of hydration, slower reacting
  • TYPE V - High sulfate resistance, develops strength slower than other types

Here's a good video description of the difference between concrete and cement

Should I use cement or concrete? 
And where can I get it?

To learn more about concrete

This book will teach you all about concrete.

What it is, how it's made, and how it behaves.

It's a great learning guide for people that need to become more knowledgeable in the field of concrete and inspection practices.

It also explains what self-consolidating concrete and pervious concrete are all about.

This book explains all you need to know about concrete. It's like the concrete bible.

It talks about cement, mixing water, admixtures, aggregates, set time, mix designs.

It explains how to pour in hot weather, cold weather, and slump. It talks about reinforcement in concrete.

And a whole lot more!

This is a great book that shows and teaches you all about building foundations and slabs.

It shows you how to do forming, block work, poured foundations and setting up and pouring a small slab.

It covers all the basic fundamentals you need to know about doing concrete work.

Learn my concrete mixing ratio for strong concrete.

Discover how old concrete really is.

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