What is cement?
Cement is a binding substance which sets and hardens independently. Cement on its own is a very dry and powdery substance. When mixed with water most cements produce a fast-setting slurry which can range in consistency from almost liquid to virtually solid.
The most common variety of cement is “Portland Cement”. This is made by heating limestone
to 1450°C, to produce quicklime, or calcium oxide. Quicklime is then mixed with the small amounts of other materials, to produce a hard substance called 'clinker'. Clinker is then crushed with a small amount of gypsum to produce powdered Portland cement.
Cement is usually characterised as either hydraulic or non-hydraulic. Hydraulic cements (such as Portland Cement) harden because of their exposure to water, and can harden in bad weather and even under water. Non-hydraulic cements require dry conditions in order to set correctly.
How is cement used?
The most important use of cement is in the production of concrete and mortar.
Mortar is produced by mixing roughly 1 part cement with 3 parts sand in as little water as necessary to produce a usable slurry. Mortar mixes are the binding agent in brick walls. Finer mixes are also used in rendering both internal and external walls.
Concrete is used in almost every modern building. It is used to make bricks of any shape or size, or to build massive reinforced walls like those which dam our rivers. Transport infrastructure such as roads, pathways, bridges and tunnels are often constructed with concrete. It is also the primary building materials for piers, docks, wharfs and canals.
Concrete reinforced with steel is used in the world’s tallest buildings, including the “Burj Khalifa” in Dubai, United Arab Emirates, standing 828m high. Over 110,000 tonnes of reinforced concrete were used in the foundations of this building alone.
Who uses cement?
Total global cement consumption for 2010 was roughly 3.29 billion tonnes. This was dominated by China who consumed 54% or roughly 1.8 billion tonnes. India was the next biggest consumer with 212 million tonnes, roughly 6.4% of the global total. The third largest consumer was the USA who consumed roughly 70 million tonnes.
Where does cement come from?
World cement production is roughly 3 billion tonnes as of 2009, the latest year for which statistics are available. China is by far the leading producer, accounting for more than 1.6 billion tonnes, roughly 53% of the global total.
Other top 10 producers across the globe in 2009 were:
- India 205 million tonnes
- United States 64 million tonnes
- Japan 55 million tonnes
- Turkey 54 million tonnes
- Brazil 52 million tonnes
- Korea 50 million tonnes
- Iran 50 million tonnes
- Vietnam 48 million tonnes
- Egypt 46 million tonnes
Australia produced 8.5 million tonnes.
Interesting facts about cement:
The word ‘cement’ comes from the Roman term 'opus caementicium' describing masonry resembling modern concrete, made by mixing crushed rock with burnt lime.
New cements derived from talc (magnesium silicate) require less energy input to create and absorb carbon as they harden, making them environmentally friendly.
All images sourced from wikipedia.
Top image: Portland cement in bags.
Left image: Blue Circle Southern Cement works in Berrima, NSW, Australia.
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