h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

A scholarly work indeed, G. Congratulations.

Now, a few words on the definition of concrete. Its a moot point as to whether you can use the term 'concrete' for a material not based on cement. But then cement itself is a more general term than the usual (Grey Ordinary Portland Cement) definition. But, does it include Lime. Difficult. The 'concrete' in the Pantheon is, I presume, based on a local Lime, mixed with some type of pozzolanic material.....am I boring you???

A bloke called Trevor!

(Caution to other readers, who may not leave their shadow as a timely reminder - see, I remember some things! - this will mean nothing to you. Please ignore)

I believe, P, that the Romans really did use concrete. Unfortunately, I've just lent my book to someone so I can't check it. It said that in Medieaval Times, the best they could do was mortar which became (not very) strong by drying out. The Romans had an extra ingredient which caused the mixture to cure and harden, even while it was still wet. I believe this is similar to modern cement/concrete, even if it used slightly different ingredients. Unfortunately the secret of Roman concrete was lost for more than 1200 years. This will mean more to you than to me.

Yes, you are sort of right. The Romans used a Lime based concrete, and added pozzolanic material (Like, for example, pumice or volcanic ash) to it to increase the early strength and keep the setting time reasonably short. This 'secret' was not re-discovered - or at least documented - until Smeaton in the 1750's. The pozzolanic material is simply a way of adding silicates. The early (1820) 'Natural Cements' used Limestone with clay - another source of silicaceous material - already within it. These were 'branded' Roman Cements, but actually the manufacture and chemistry was quite different. the early 'Portland' cements duplicated this by mixing limestone and clay. Later (1880) the importance of aluminates was recognised, and the materials heated to higher temperatures, thus changing the chemistry again.

There, wasn't that interesting...

Sirs/Mesdames:

For a great deal more information on Roman concrete, I suggest reference to the following internet site:
[URL removed by moderator]

Regards,

Tom Wukitsch
Rome Italy
[URL removed by moderator]

Thanks your contirbution to the conversations, but, as you see, url's are removed from conversation forums. I suggest that you either put the link in your home page journal, or 'disguise' it before repeating it here. One format might be "If you type the word xxx after www, and follow that with a .it, you can get the info you need"