Aug 12, What is the Difference Between Cement and Concrete

What is the difference between cement and concrete? 

First, what is cement?

Cement is a dry powder that’s used as a binding agent, one of the four main ingredients used to make concrete.

Mixing Portland Cement with water forms a paste that hardens and binds or “glues” together whatever it’s mixed with.

Understandably, the terms “concrete and cement” are used interchangeably quite often, but they for sure are not the same!

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.

How is cement made?

How does the cement harden?

When cement gets mixed with water it forms a paste.

As soon as the two materials are mixed together a chemical reaction takes place that produces “heat”. 

The chemical reaction is called HEAT of HYDRATION. As hydration takes place, over time, the paste hardens and gains strength binding together whatever it’s mixed with.

what is concrete?

Besides water, concrete is the most consumed material in the world. No, we don’t eat it, it’s used as a building material.

It’s the most widely used building material on the planet!

You make CONCRETE by using four basic ingredients with CEMENT being one of the four. The others are sand, aggregates, and water.

Combine all four ingredients together in the right proportions and you get concrete.

Mixing the water, cement, and sand together makes a fairly strong paste. Then the aggregates get mixed with the paste making the mixture even stronger.

The strength is determined by the proportions of cement to sand to stone and how much water is used to mix everything together.

A basic concrete mix combines 1 part cement to 2 parts sand to 3 parts stone, then mixed with as little water as necessary to make a workable concrete mix.

A dry, but workable mix, will be stronger than a wet, runny mixture.

characteristics of good concrete

Good quality concrete has a few specific characteristics that you should understand:

1. Strong – when fully cured it has a high compressive strength
2. Durable – can withstand freezing & thawing temperatures as well as very hot weather
3. Workable – when being placed it’s not too wet or too dry. It’s ingredients are proportioned and mixed properly so it consolidates while it’s poured in place.
4. Low shrinkage – Not using too much water to mix and place the concrete

In general, using the least amount of water necessary to mix and place the concrete produces a higher quality concrete. This assumes the concrete is properly placed, consolidated, finished, and cured.

what is a good concrete mix design?

There’s different concrete mix designs for different kinds of projects. All of them can be considered good if the end result turns out as planned.

A concrete mix design for a highway bridge will be different than a mix design for a residential garage floor. Both are good, they just have different proportions of ingredients (and maybe some other additives included).

Basically, a good mix design includes:

• Good workability
• Good strength
• Highly durable
• Fairly dense
• Good finishability

Concrete mixing ratios can be adjusted according to what you’re using the concrete for.

A simple but good concrete mix design is 1 part cement to 2 parts sand to 3 parts stone mixed with as little water an necessary to get the workable mix you need.

See my concrete mixing ratios for 3000 and 4000 psi concrete mix designs.

should i use concrete or cement

Concrete will work the best for most building projects. It’s used for building house foundations and floors, concrete walkways, patios, and pool decks. 

Concrete is used for building roads, bridges and driveways. But it’s also used for making concrete statues, concrete countertops, even concrete canoes.

Cement, on its own, isn’t nearly as strong as concrete and is more likely crack or break if it’s just mixed with water and used for building or repairing something.

There are some concrete repair materials that include cement in their mixture. They look and feel like cement (powdery) but have other ingredients that make them strong and durable. 

Cement could be used to patch small areas of damaged concrete, patch mortar in a brick wall or as a grout for filling small holes.

But honestly, you’re better off just using it to make concrete.

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. 

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

What’s the difference between cement and concrete?

The bag of Portland Cement is a dry “fluffy” powder you can use to MAKE concrete. Just add sand, stone and water.

The bag of concrete already has cement, sand, and stone all mixed together “in the bag”. You just need to add water and mix it to get concrete.

If you making patio blocks, pouring a small slab, or installing a fence post, you’ll want to get the bag of concrete for these type of projects.

Rarely, if ever, will you just use cement to do anything other than make your own concrete from mixing the raw materials (cement, sand, stone, & water).

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