The history and composition of cement

1. Concrete, as a rule, the term associated with modern construction materials mainly used in this century, in fact, also includes composite materials are widely used in ancient times, at least a few centuries before the birth of Christ.
2. The main differences between the two types consist of a conglomerate of different binder used and the concept of the range of inert virtually no production at the old concrete and important, but in today's workplace. The choice of materials, composition and implementation of the concrete used in the Roman Empire, as reported in detail in his 10 Vitruvius books De Architectura. Construction parameters brick or stone, which functioned as the formwork to lose, were filled with cement, which then would be limited to the parties scrap brick and stone (30-50mm), with a sledgehammer pressed iron.
3. In cement binder was only lime or lime and Roman pozzolana.
4. In the first case, very slowly hardening concrete, as a result of the reaction lime, Ca (OH) 2, with the air of carbon dioxide (CO2) and the subsequent production of calcium carbonate (CaCO3).
5. This tightening process, which is largely dependent on the degree of penetration was lower paradoxically, as compactness and impenetrable barrier has been proposed parameters of stone or brick.
   Inside the Pantheon (Rome)
   Concrete old threw on parameters
   Brick (Pompeii).
   The discoverThe discovery of novel pozzolana (the "sand Plague" in the text of Vitruvius) marks a revolutionary progress in the ancient buildings thanks to the ability of a mixture of lime-pozzolana novel, and not just for hardening in the absence of CO2, but also with much greater speed that is required in the process carbonation lime.
6. Today, we know that the Roman pozzolana is a kind of inorganic materials, mainly composed of silica (SiO2) and alumina (Al2O3), or poorly amorfe fully crystallized.
7. It can lead to a hardening of lime and water to make a conglomerate tempered due to the formation of calcium silicate hydrate (CSH) and alluminati football hydrates (CAH) by reaction with lime silicate "aluminum novel pozzolana.
8. The decline in the quality of construction, which began with the fall of the Roman Empire and continued throughout the Middle Ages, it is connected with their detailed recommendations rejected Vitruvius. Only after the fourteenth century.
9. Is the text and translation of Vitruvius again Thus, the art of ancient architects and construction.
10. A true revolution of about 1750 at Smeaton English, an invention of the hydraulic lime random received for firing a limestone that, contrary to the recommendations of Vitruvius for the production of lime, clay contained impurities.
11. The use of hydraulic lime are similar to those characteristic of a mixture of lime-pozzolana novel, with the advantage, however, that you should not use the introduction of novel pozzolana not available in the world.
12. Once understood that the reaction mechanism of hydraulic lime was related to the presence of impurities clay, steel, starting at the beginning of 1800, experiments in cooking artificial mixture of limestone and clay. In 1924, a patent for Aspdin, came to the formulation of Portland cement received fire from the limestone with 40% clay.
13. Since the chemical standpoint, the reaction of Portland cement with water leads to the production of CSH, CAH, and Ca (OH) 2 at a speed much higher than the reaction pozzolanica novel.
14. A key point of the process of production, revealed only in a subsequent patents Johnson of English, firing temperature was well above 850 ° C in order to get the full mix of limestone with lime silica contained in the aluminum "clay. After successes in the field of cement greatly improved the production process by sending members to the presence of these constituents mineralogical (3CaO • SiO2 and 2CaO • SiO2), it is better to contribute to the rapid quenching, without neglecting the importance of ingredients such as • 3CaO on Al2O3 and 4CaO • Al2O3 • Fe2O3 are needed to obtaining clinker at sufficiently low temperatures.
15. Another step forward in the production of modern intuition is due in Germany Michaelis, which proposes to add novel Portland pozzolana cement that, in combination with lime, hydrolysis, improved hydraulic impermeability of concrete through the further production of CSH and CAH. "That awareness must with the subsequent development of novel pozzolana cement pozzolanico use of natural or artificial novel pozzolana (wheel ash, smoke silica), as material from the ground and then add cement clinker.
16. In the same years in which there is progress in the production of Portland cement, is the first publication on the importance of using inert with assorted sizes, to minimize the amount of interstitial voids between the stone elements and, consequently, the volume of cement matrix is necessary to fill them. Achieving this goal has the effect is to reduce the cost of concrete (by reducing the most expensive, cement), as well as restrictions on the technical flaws associated with excess of cement (viscous deformation, cracks, to remove or thermal gradients).
17. It thus formulating equations, which describe the optimal combination of inert to minimize gaps between clusters. Among those further can be used to remind Fuller equation:
    
    100 (d / D) ½-C
    P = 100
    -------------------
    100-C
    In cases where the percentage of inert (maximum diameter D), prior to the opening of passing, or that Bolomey
    
    AC + (100-A) (g / D) 1 / 2
    P = 100
    -----------------------------
    100-C
    When A is a constant, which takes into account the type of inert (natural or crushed), and operating request, C, while that of cement at all solid.
18. That assistance in the fight against inert ground distinguishes modern concrete producers, which, on the other hand, continues to provide specific criteria do not match the original industrial process.