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What Is the Difference Between Concrete and Cement?

Wet concrete being poured.
Dry cement powder.
A man smoothing out a concrete floor.
Cracked concrete.
Concrete is often used in the building of skyscrapers.
Concrete uses cement to bind together different materials, including sand.
Article Details
  • Originally Written By: R. Kayne
  • Revised By: Angela B.
  • Edited By: L. S. Wynn
  • Last Modified Date: 21 July 2014
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The primary difference between concrete and cement is that concrete is a composite material made of water, aggregate, and cement. Cement is a very fine powder made of limestone and other minerals, which absorbs water and acts as a binder to hold the concrete together. While cement is a construction material in its own right, concrete cannot be made without cement. The two terms often are incorrectly used interchangeably, but concrete and cement are distinctly separate products.

Cement

Cement is made from limestone, calcium, silicon, iron, and aluminum, among other ingredients. This mixture is heated in large kilns to about 2,700°F (1,482°C) to form a product known as clinkers, which roughly resemble marbles. These are ground into a powder and gypsum is added, creating the gray flour-like substance known as cement. When water is added to cement, it triggers a chemical process that allows it to harden.

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Portland Cement

There are many different types of cement, but the type most commonly used in construction is Portland cement. Joseph Aspdin of Britain developed the building material in the 1700s, when he found that adding clay to limestone and superheating the mixture allowed the resulting blend to set anywhere. Portland cement is a type of hydraulic cement, which means that when water is added, it starts a chemical reaction that is not dependent on how much water there is. This allows the cement to harden underwater and remain strong even in wet conditions. The different types of hydraulic cement are primarily used in concrete and mortars.

Concrete

Concrete, in contrast, is a masonry material that uses cement to bind together crushed stone, rock, and sand, also called aggregate. Cement makes up from 10% to 15% of the total mass of concrete; the exact proportions vary depending on the type of concrete being made. The aggregate and cement are mixed thoroughly with water, which starts the chemical reaction causing the cement to harden and set. Before this happens, the concrete mix can be poured into a mold so that it will harden in a specific shape, be it a block or a slab.

The amount of time it takes for concrete to set depends in part on how much gypsum is added to the mixture. This time can be accelerated by adding calcium chloride or slowed by adding sugar. These compounds work by affecting the development of the hardening crystals that form as concrete sets. Concrete that is exposed to freezing and thawing conditions may have additional chemicals added to help prevent cracking.

Concrete and Cement Ratios

The properties of concrete depend a great deal on the ratio of aggregate-to-cement-to-water in the mix. The water-to-cement ratio is the most important, as too little water will make the concrete mix difficult to work with, while too much will weaken the final product. This ratio is calculated with the following equation:

r = 8.33 qH2O / Wc

In this calculation, r is the ratio, qH2O is the quantity of water in US gallons, and Wc is the weight of cement in pounds. A ratio of at least 0.25 is required for concrete to harden, while values of 0.35 to 0.4 are typical for most applications.

Aggregate is also important, as it makes up more than 60% of a concrete mix — and up to 80% in some cases. Larger rocks require less concrete, which means less water is needed, and a stronger final product can be made. Aggregate is also less expensive than cement, so a higher percentage can lower the cost. Generally speaking, a good aggregate has a combination of rocks of many different sizes, with a specific average and maximum size; these stones must be clean and durable, and should not contain clay or other minerals that can absorb water.

Concrete's high rock content makes it extremely durable, and it often is used in swimming pool decking, skyscrapers, subways, and lamp posts, as well as sidewalks, driveways, and roads. The ingredients in both concrete and cement are among the most abundant on Earth, and both can be recycled. Cement production does require a large amount of energy, however, because of the high temperatures required and the industry has been criticized for its contributions to carbon dioxide emissions.

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Discuss this Article

anon952090
Post 37

I need more information for a project on both concrete and cement, plus a tiny paragraph about the difference between both of them. I am not asking for much, just a little more information!

anon342099
Post 30

I once worked at a company that made concrete pipes.

anon341425
Post 29

Is pure cement stronger and more durable than concrete? Is concrete used because the aggregates make the finished product stronger or is it because the aggregates reduce the amount of cement used and is hence cheaper?

anon315445
Post 28

A mixture of cement, sand and water is called Mortar. All cement (dry or wet) is dangerous to the health. It is better to take precautions. Simple PPEs do no harm.

anon310736
Post 27

Thanks for the info. Cement is very different.

anon259165
Post 25

So what do you call the mix of cement and sand used to lay bricks? It is clearly not cement or concrete either since it contains no aggregate.

anon199739
Post 22

Thank you for your explanation. It quickly and easily made sense of concrete and cement!

anon143057
Post 21

For the person who said breathing concrete dust won't kill you may wish to consult a doctor - always wear breathing protection.

anon131365
Post 20

I'm so smart, I didn't even know there was a difference. Thanks for a very nicely done, informative page.

anon109460
Post 19

I form, prep, pour, finish, strip and cut concrete without masks and i still have nostrils. the only deal that will affect you is dropping it on your hand foot or whatever. I have breathed concrete dust had wet concrete in my eye. it's really no big deal and you won't die from it.

anon105741
Post 18

Can you tell me what are the mechanical construction materials.

anon100188
Post 17

cement is binding material only, but cement only plays the vital role in concrete. it gives the good bonding to the fine aggregate and coarse aggregate.

concrete takes the maximum compressive strength in the structural members. T.T. Vinothkumar -- project engineer

maxhouse17
Post 16

Look, concrete gets hard. It gets rock hard, whereas cement only gets hard -- not rock hard. If you get dust in your airways that will also succumb to your secretions and become hard. It will eat away at the core of you nostrils until you no longer have nostrils. At 3 in the morning you will wake to find you have no nostrils. Either way, concrete or cement - in the end no nostrils. Have a good day.

anon62198
Post 14

We always wear eye protection with wet cement.

If it splashes in your eye then five minutes could mean very permanent sight damage. Breathing the dust can lead to a sensitization reaction making you allergic to the chrome vi content.

COSHH Manager

anon53838
Post 13

I went out in the garage. I'm no expert on concrete or cement, but there are warnings to wear a mask. lung disease and cancer were among the warnings. I always wear a mask when handling the stuff, eye protection wouldn't be a bad idea either. better safe than sorry. I would figure it would take prolonged exposure to cause any real damage though.

as for 2700 degrees, I made a gingery furnace out of concrete and a 5 gallon bucket and a plastic coffee can for the center with a 1/2 steel pipe for an air hole. with that and a leaf blower and some charcoal it got hot enough to melt aluminum. it also melted the bottom out of a mild steel pipe I was using to hold the aluminum one day. :) It shot 3-5 foot lazy flames out without the air and blasted less than 1 foot flames with. It was like a jet engine.

anon51594
Post 12

Thanks for the clarification on how cement cures. Is that why they sprinkle newly cemented highway with water?

anon45248
Post 11

i didn't know the iron was in concrete. that's really helpful. Thank you!

mmcmenus
Post 10

The romans probably used pitch, coal, or charcoal for fuel. 2700 degrees is not really hard to come by with any carbon based fuel and good air flow.

anon24037
Post 9

How did the Romans heat the compound to 2700° F? There were no old tires back then. (...And any follow-up on whether they used the same recipe as we do today (per kentfx's question)?)

mmcmenus
Post 8

Cement does not dry, it hydrates. The process of making the cement bakes all of the water of hydration out of the crystalline structure of the components. When water is added it rehydrates the this crystalline structure that is what allows the cement or concrete to harden or cure. This is why cement can cure under water.

As far as being environmentally friendly, after transportation and power generation, cement manufacture is the 3rd largest producer of anthropogenic CO2.

seadog
Post 7

Although Concrete may last for years and can be reconstituted. The massive amounts of energy used to produce cement clinker is a cause for concern.

Cement factories often burn old tires to reach the extreme heat required for the process.

anon23736
Post 6

Are you kidding Celaire? A single exposure to concrete dust won't do a thing. He'll be fine. Some people spend their whole lives around it on a daily basis without so much as a mask. I don't recommend that, but really, one time? Come on.

mwalsh
Post 5

Hi there, this may sound trivial but concrete is "placed" not poured. Happy New year all!

kentfx
Post 4

I read some time ago that the concrete made during the Roman mid-empire period has not been successfully duplicated -- the method and formulation aren't known. Is that true?

anon21679
Post 3

This was great help! Thank you!!!

Celaire
Post 2

Hello, a question for you. Not a very important one but thought I'd ask anyway. A friend of mine was drilling a hole in a concrete ceiling to input some alarms. He was directly underneath drilling the hole not wearing a mask or goggles which obviously meant him being covered in the substances etc causing red eyes, sneezing and so forth. He has since learnt to wear protection. But, will this cause any problems to his health...???

mendocino
Post 1

Concrete can also be painted. Back in the day this was a popular "aesthetic" enhancement.

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