Artificial hydraulic lime

Over the centuries, other pozzolanic substances were blended with slaked lime to produce what are now called synthetic (or artificial) hydraulic limes. Both naturally occurring pozzolans (such as trass, found in Germany), and synthetic pozzolans (such as ground blast furnace slag) have been, and still are used. It was also found that some impure limestones, containing silica and alumina, produced slaked limes with a range of hydraulic properties. Such natural hydraulic limes were widely used in construction and building for mortar and concrete. 

Natural and artificial hydraulic limes offered faster setting and hardening rates than lime. Their hydraulic properties enabled them to set, even under water, by the formation/hydration of calcium silicates and aluminates. The disadvantages of such limes were that the raw materials were not widely available and were often variable in quality (modern hydraulic limes are generally much more consistent and are widely used in some countries). 

It will be noted that the compressive strength requirements of the three classes of hydraulic limes overlap. This is to accommodate variations caused by changes in the composition of the limestone and in the calcining process (in the case of natural hydraulic limes) and by variations in the components of artificial hydraulic limes. 

Artificial hydraulic limes consist mainly of calcium hydroxide, calcium silicates and calcium aluminates. They are produced by blending suitable powdered materials, such as natural hydraulic limes, fully hydrated air limes and dolom-itic limes, pulverised fuel ash, volcanic ash, trass, ordinary Portland cement and blast furnace slag. 

Hydraulic limes have the property of setting and hardening under water — see natural hydraulic limes, special natural hydraulic limes and artificial hydraulic limes. The term is also used to describe eminently hydraulic and Roman limes. 

The author of artificial hydraulic lime, produced by the burning of the interground mixture of choc and clay was L.J. Vicat, which published his results in 1818. He can be recognised as the predecessor of the technology of Portland cement production. 

There ate proofs that already in buildings in Create the cmshed ceramic potsherds (minoyen culture) were added to lime to give it the hydrauhc properties [1]. On this basis the assumption was developed that Romans used firstiy artificial pozzolanic materials, before they check the natural pozzolanas. Jaworski stats that in twelveth century before Christ Phoenician used hydraulic lime to mortar building the temple in Cypms [2]. Already about tenth century before Christ they used the bricks flour as the admixture giving to hme mortar hydraulic properties [2]. 

Galal, A.F. et al. (1990) Hydraulic reactivity and microstructure of artificial pozzolana-lime pastes, iaProceedings 12th International Conference on Cement Microscopy, Vancouver, pp. 135-153. 

It is uncertain where it was first discovered that a combination of hydrated non-hydraulic lime and a pozzolan produces a hydraulic mixture (see also Pozzolanic reaction), but concrete made Irom such mixtures was first used by the Ancient Macedonians and three centuries later on a large scale by Roman engineers. They used both natural pozzolans (trass or pumice) and artificial pozzolans (groimd brick or pottery) in these concretes. Many excellent examples of structures made from these concretes are still standing, notably the huge... 

Gilmore s book explains that although stones to make hydraulic lime were found extensively in the United States, it was not manufactured. He comments on the reported successes of lime-pozzolan mortars in France, reporting that repeated inspections of French port facilities almost always led to observed failures. His view of the controversies surrounding the hydraulic hmes used in France concluded The American engineer can congratulate himself that the supply of hydraulic cement in this country affords a more rehable source of hydraulic mortars than either natural or artificial pozzuolana. ... 

Pozzolana. A material that, when ground and mixed with lime and water, will react with the former to produce compounds having hydraulic properties. There are both natural and artificial pozzolanas. The original Natural Pozzolana was a volcanic tuff worked at Pozzoli (or Pozzuoli), Italy, in Roman times. One of the principal types of Artificial Pozzolanas is produced by firing clay or shale at 6fJtt-1000°C. 

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