It’s the fifth most abundant element on earth – and the world’s building block. Do we fully appreciate the value of calcium?

Most of us are familiar with the idea that our bodies need calcium. I remember being told to drink up my milk because the calcium in it would make my bones strong.

And calcium is indeed the key element in our bones. In fact, it is the most abundant metal in the human body – and in those of most other animals too.

Many organisms use calcium to build the structures that house and support them – skeletons, egg shells, mollusc shells, coral reefs and the exoskeletons of krill and other marine organisms.

And calcium is also the key ingredient in man’s most important structural material – cement.

These days virtually all our architecture, all our great building and engineering projects start with calcium, because cement is the basis of the most widely used man-made substance on earth – concrete.

Fortunately there’s a lot of calcium about – the soft grey metal is the fifth most abundant element in the earth’s crust.

There is plenty dissolved in the sea. For millennia, marine organisms have been combining it with carbon dioxide they fix from the atmosphere to make shells of calcium carbonate.

Bath stone is made from oolitic limestone, which consists of a large number of calcium carbonate fossils

When they die, their shells and skeletons sink down to the bottom of the sea and collect in great drifts. Over millions of years they have been compacted to form limestone, chalk and marble.

 

When you get the chance, take a close look at a piece of limestone. You’ll probably see the tiny fossils of the ancient marine creatures of which it is composed.

Some 10% of all sedimentary rock is limestone, which is pretty extraordinary when you consider that it represents the concentrated bodily remains of living creatures.

So how do we get from limestone to concrete?

Read  more

Read more

 

Advertisements