Now about the strongest knitting - cement. Its history as it was already told, leaves in depth of centuries. Much it underwent transformations while became such what we know it today.
From Ancient Rome we will be transferred to a XVIII-th century. In 1756 to English engineer Smitonu have charged to construct a beacon in such place where the sea almost never was quiet. Smiton was for the time the person vysokoobrazovannym. He read also ancient authors, whence knew about special characteristics of volcanic sand. Than they are caused? The engineer was accepted to researches. Also has found out that here the important role play clay and izvest.
As they say, ice has got under way. In total in 40 years after Smitona its other compatriot, Parker who too was engaged in research ancient Roman knitting, has exclaimed: "Грёхь to resort to use of consequences of volcanic eruptions? It is enough to mix clay with izvestju and to burn this mix. Business even is easier: after all in the nature such mix ёѕЁхё=тѕх=".
Really, any geologist names to you it, is a marl.
Parker said that it managed to open, at last, up to the end secret of Romans. He named received by it knitting Romance cement.
In 1824 has appeared portlendsky cement. This name has reached up to now, having changed only one letter, and today on buildings well know and widely use portlandtsement. Its mason Joseph Espidin who lived near to the city of Portlenda has invented. Here long since for building needs used a local stone. Here from it Espidin also has received a grayish powder. The solution from it has appeared excellent.
And one more legend about "шчюсЁх=хэшш" cement. Tell that at clearing to exhaust-kipelki (at clearing to exhaust-kipelkn an incomplete quantity of water - 600... 700 l on 1 m 3 kipelki - receive a thin powder - izvest-pushonku, at clearing by a full quantity of water - 3000... 4000 l on 1 m 3 - receive limy milk) came across such "эхяюёыѕ°э№х" blocks which in any way in what did not wish to turn. Them simply threw out, while to someone has not come to mind to shatter them in a powder and to get mixed up on it a solution. And - about a miracle! - this solution has appeared many times better limy, received in the usual way. Having hardened, it gave much stronger artificial stone.
Have reflected, in what here business? Perhaps, these lumps somehow not so burnt? Began to experiment. It has appeared, if limestones to heat up before sintering and a firm body (it named klinkerom), and then to crush, it turns out excellent knitting - cement.
Have soon learnt to make cements of various properties. For this purpose limestone burnt in furnaces, added to it various minerals. The set of these minerals defines properties of cement. Not to repeat a long line of making additives, it has been decided to name a certain set them under the first letters of the Latin alphabet: alit, bleaches, aims. Alit in klinkere gives to cement durability and fast tverdenie, bleaches - average durability and slowed down tverdenie, etc.
But with selection of the necessary structure klinkera definition of properties of the future cement yet does not come to an end. Last word will tell a grinding. The it is more thin, the better quality will be knitting. Cements of marks 200, 250, 300 need a sieve where on 1 sm 2 4900 apertures are necessary and through it passes not less than 85% of the taken sample. Marks 500, 600 pass through a sieve from 9000 apertures. It is difficult even to imagine such fine dust.
We have told above: cement mark. And what it means? Durability of the future artificial stone received with participation of the given knitting. In other words, strength size in kgs/sm 2 which will show a cube from a structure cement mortal 1:3 (cement: sand) at the age of 28 days at its compression.