Is Cement Flammable? (A quick guide)

In this, article we will answer the following question: “Is Cement Flammable?”, and other important issues regarding its flammability. We will share some of its properties, curiosities, and safety issues to keep in mind if you plan on constructing using cement.

Is Cement Flammable?

No, cement is not flammable. Cement can’t be set on fire, it won’t melt easily and no toxic vapor will arise from an attempt of burning. Cement is actually made using temperatures above 1400ºC, a heat that can’t be reached unless you have a big furnace.

What is cement?

Cement is a mixture of limestone, clay, and gypsum. It’s an ingredient of concrete, its most common use. Concrete is a thin grey powder that gets hardened once water is added to it.

Each cement ingredient has its own purpose and will supply specific properties in concrete, its most prominent final product.

Cement is normally known as portland cement. Its raw materials are considered cheap worldwide, but at the same time are vital to the world economy.

History and curiosities

The invention of cement is attributed to a British bricklayer named Joseph Aspdin, he obtained a patent for it in 1824. He made it by burning powdered limestone on his own kitchen stove.

He called it Portland Cement because of its resemblances with Portland Stone.

Nowadays, four billion tonnes of cement are produced every year, and almost half of them are made in China.

Cement production alone is responsible for 8% of the global carbon dioxide emissions in the atmosphere, a huge contribution to climate change.

Cement properties

Cement is considered to be chemically inert. Its constituents are essentially solid minerals

The basic cement function is to bind materials together, but it also sets them, hardens, and adheres to them.

Hydraulic cement is the most common type. Its adhesiveness arises from a chemical reaction between water and its ingredients

What is it made of?

Portland cement is made out of calcium (Ca), silicon (Si), aluminum (Al), iron (Fe), and other ingredients. Each suffers a series of chemical reactions to form what we call cement.

When heated under extreme temperatures, these ingredients form a rock-like substance that is later shattered to become a fine powder.

The most common form of cement is called hydraulic cement, and portland cement is the most familiar example. The less common is known as non-hydraulic cement, it uses calcium hydroxide instead of calcium oxide (its usability is very different).

Here’s a list of major sources for the two most important cement components:

Calcium SourceSilicon source
LimestoneClay
ChalkShale
Coral LimestoneCalcareous Marl
MarbleMarl
Lime-sandMarly clay
ShellsGlass
Lime SludgeSand

Portland cement production and chemistry

At first, limestone (CaCO3) is burned (oxidized) to remove the carbon from its structure, resulting in calcium oxide (lime). This process is known as calcination. 

This simple chemical reaction alone is responsible for up to 4% of global carbon dioxide emissions and is only the first step in the production of cement.

This pollution happens because temperatures must reach about 1000ºC continuously, which requires a lot of heat that is normally obtained by the combustion of fossil fuels. Also, tons of limestone must be burned every day.

Lime (CaO) is the basic ingredient for 3 other chemical reactions. 

All 3 happen inside and through the kiln, in temperatures near 1500°C. The diameter of the kiln is big as a car.

One of them is the formation of calcium silicates (2CaO • SiO2 and 3CaO • SiO2) when lime reacts with silicon (SiO2).

Another is when lime reacts with aluminum oxide to form tricalcium aluminate (CaO • Al2O3).

Lastly, Lime reacts with both aluminum oxide (Al2O3) and ferric oxide (Fe2O3) to produce a  more complex molecule called tetracalcium aluminoferrite (CaO • Al2O3 • Fe2O3).

These strange dots “ • ” indicates that we are talking about a solid inorganic structure that’s strongly bonded. Such structures often acquire a crystal formation (crystalline network), something that will be very important in the formation of concrete.

After the reactions are done, the products unite in a rock-like amalgam which is called: clinker. A few more things are added to the clinker, and after crushing the cement is ready to be packed.

You can have some more insight into cement production by watching this video.

 Flammability

As stated before, the process to manufacture cement requires up to 1500°C, so it’s not a flammable compound.

If cement is around a source of fire, intense heat, or any form of ignition, nothing will happen.

Also, standard cement present no toxicity to humans but the powder could irritate our respiratory system if inhaled. In such cases, the person should be moved into the fresh air and other first-aid measures should be followed according to the fabricant.

Cement is composed basically of minerals, inorganic compounds which, in essence, can’t be burned since they’re not combustible.

Cement also has a low rate of heat transference, which is also true for concrete, so it can act as a fire retardant substance. 

If a room is set on fire in a concrete house or apartment, the fire will take a much longer time to spread when compared with a home with wood walls.

Also, this fire retardancy may be enough so the firefighters could arrive on time, and before more damage is caused.

During the terrorist attacks of 2011 in the USA, the materials and architecture of the Twin Towers allowed thousands of people to escape before the building collapsed, after the planes crashed, even under extreme heat and pressure. 

This happened because concrete can contain the heat, as a consequence of the high thermal insulation, because it’s a bad heat conductor.

Cement and concrete cannot react with oxygen, even under extreme conditions. They can still react with strong oxidizing agents like chlorine trifluoride but, if you do have something like this at home, handling the substance alone be your biggest concern.

Conclusion

Cement is a nonflammable substance that can’t light up a fire, and can hardly be heated. During an eventual fire misfortune, having a concrete home will definitely be safer than owning a wood-based home.

Frequently Asked Questions (FAQS): “Is cement flammable?”

Is concrete flammable?

No. The concrete in a home is not flammable unless something that can be burned is added to it, like flammable paint or varnish. In fact, concrete helps prevent the fire from spreading because it can contain the heating.

What is the concrete melting point?

It is around 1000ºC. It’s really hard to obtain such temperature outside an industrial furnace.

Is wood cladding flammable?

Yes. Wood cladding won’t sustain 1h of intense heat from an eventual fire. Fire retardant substances can be applied to prevent this hazard but it’s not even close to the safety concrete has.

How is cement made?

It is made in big kilns that reach up to 1500°C, where minerals like limestone, clay, and gypsum are used. Several chemical reactions take place, and the result is a compound named clink that’s crushed until gets powdered.

Is concrete biodegradable?

No. It’s inert to the environment since it’s not reactive, but it’s not easily degradable. Since it’s not organic, decomposing microbes can’t really eat it, so it’s up to the weathering to slowly break the concrete blocks. 

Also, it’s not very useful for recycling yet. The biggest ecological concern is the CO2 produced due to the calcination process.

Citations

TAYLOR, Harry FW et al. Cement chemistry. London: Thomas Telford, 1997.

BULLARD, Jeffrey W. et al. Mechanisms of cement hydration. Cement and concrete research, v. 41, n. 12, p. 1208-1223, 2011.

https://en.wikipedia.org/wiki/Cement

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