As long ago as 50 BC Diodorus Siculus wrote in his book Bibliotheca Historica about the Nabataeans, "They are conspicuously lovers of freedom and flee into the desert, using this as a stronghold. They fill cisterns and caves with rainwater, making them flush with the rest of the land. They leave signals there which are known to themselves and not understood by anyone else. They water their herds every third day, so that they do not constantly need water in waterless regions, if they have to flee." The information that Diodorus gathered was already common knowledge in the Middle East. The Nabataeans had been building hidden water cisterns for years.
As with the Romans, the Nabataeans secret to waterproof cement was the material known as pozzolan. Where the Romans used volcanic ash to create their waterproof cement, the Nabataeans had a much easier source. In the Hisma desert near Wadi Rumm are major surface deposits of silica, which geologists today claim is nearly 100% silicone.
B. Mason, in his book Principles of Geochemistry provides a technical discussion of research into geology to explain rock composition. For instance, he explains how a pozzolan material can be created by ground water seeping through silica. While the Romans had to search for this key component of ancient waterproof concrete, the Nabataeans simply had to locate places where water had seeped through the silica and scoop it up and add it to their lime plaster. (B. Mason, Principles of Geochemistry. John Wiley and Sons, New York, 1966, p. 160)
Natural pozzolanas are abundant in certain locations and are extensively used as an addition to Portland cement in countries such as Italy, Germany, Greece and China. Volcanic ashes and pumices largely composed of volcanic glass are commonly used, as are deposits in which the volcanic glass has been altered to zeolites by interaction with alkaline waters. Deposits of sedimentary origin are less common. Diatomaceous earths, formed by the accumulation of siliceous diatom microskeletons, are a prominent source material here.
Ashes of organic origin. Coal cinders generally have an acceptable balance of silica and alumina, and have been used historically as a pozzolanic additive, but their physical structure tends to weaken the mortar and to absorb excessive water. Coal ash is widely used, in the form of PFA (pulverised fuel ash) as an additive to cementitious mortars and in lime-based grouts. The use of coal-based products carries a risk of sulphate contamination and the materials should always be selected from low sulphate coals. The residue of fuels from lime burning, whether from coal-, coke-, or wood-fired kilns, known as lime-ash, is well known historically as a pozzolan and is still available.(8) Other vegetable ashes, such as rice husk ash, are used as pozzolans in other parts of the world. Bone ash is also known to have been used.
http://www.buildingconservation.com/art ... /pozzo.htm
Sarsen stones are also known as Grey Wethers, as from a distance, they can resemble flocks of sheep (a wether is a castrated ram).
They are blocks of hard sandstone and may be the remains of the Reading Beds.
Although their formation is not well understood, it is thought they formed when evaporation from the surface drew groundwater up through the Reading Bed sands, depositing silica around the sand grains to form a strong cement.
Over the past 40 years, material scientists have conducted tests on the Egyptian pyramid stones and the scientific consensus is that the outer casing stones were in fact created from a man-made limestone-concrete mixture, known as a geopolymer. The claim, although underpinned by scientific research, is unsurprisingly not accepted by Egyptologists. Watch the video to learn more.
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