Natural pozzolan is one of the main components of the historical mortars together with lime and Ceramic flour (Kourasani). It was used in the construction of monuments in ancient Greece, in Rome's Pantheon, in Byzantine monuments, but also in classical 19th century building and gave them considerable resistance to wear of time and on earthquakes and maintained by the centuries until nowadays.
Nowadays, natural pozzolan mainly used in the Greek market by the cement industry as a main ingredient for the production of cement and as a raw material from the archaeological services for the restoration of important monuments such as the archaeological site of Nikopolis, National Library in Athens, many monasteries of Athos Mountain, the Benaki Museum, the Panathenaic Stadium etc.
It is also used in the exterior and interior decoration of modern constructions, but also as a building material providing in constructions durability and an aesthetic effect that is in harmony with the natural environment.
The 2 licensed pozzolana quarries in Pella prefecture, that owned and exploited by the Olympus company, they produce an excellent quality pozzolan. Note that the pozzolana quarries in Pella are operating without interruptions from 1971 until today and they fulfill the needs of TITAN S.A. cement industry in Thessaloniki.
The quarried materials were transferred to the company's processing plant in Assiro, Thessaloniki. The process can be divided in two faces.
In the first one the material is fractured.
Then, it is dried, sieved and milled in an iron-free mill in order to avoid the mixing of iron and chromium oxides with the final product.
Pozzolan - 45μ
The Olympus S.A. pozzolan is produced by volcanic tuff which is an amorphous aluminosilicate.
According research that have been done by the Aristotle University, the specific surface of the-45μ. pozzolan of our company is 8.920cm2/g (the maximum percentage of the grains is between 2-40mm) and the content of the reactive silica is greater than 50%.
The exceptional pozzolanic properties the Olympus S.A. pozzolan has, were confirmed by the research that have been done by Professor Papagianni in the laboratory of building materials in the department of Civil Engineers of Aristotle University according the ASTM C593-06 standards (Standard Specification for Fly Ash and Other Pozzolans for Use With Lime for Soil Stabilization).
|Bending resistance||Compressive resistance||Active porosity||Specific weight|
|4,21 MPa||12,58 MPa||21,88 %||1,842|
The mineralogical structure of the Olympus pozzolan is amorphous by more than 95% (XRD analysis by the laboratory "Mineral Lab Inc." in Colorado, USA).
The chemical structure of our product is fulfill the requirements of ASTM 618-05 standards. The following table depicts the XRF analysis that made by the CTL laboratories in Illinois, USA :
|XRF||ASTM 618-5 standards|
|L.O.I||3,72%||L.O.I < 10%|
The available alkali metals of pozzolan according the ASTM C311 standards, expressed in Na2O are 0.94%.
The effectiveness in the control of Alkali reaction measured with specimens expansion rated in 14 days, according the ASTM C311 standard is 38%, significantly lower than the maximum allowed of 100% (CTL Illinois, USA).
The drying shrinkage according ASTM C618-05 / C311 is zero (CTL Illinois, USA).
Advantages of using pozzolan
- In fresh mortars: The fresh mortars which tend to exudate or segregate, it is widely known that addition of fine particles, improves the workability by reducing the size and the volume of voids. As thinner the granulometry of the added material is, the less percentage required to improve the consistency and workability of fresh mortar.
- In hardened form: The use of pozzolan as mortars ingredient or cement-lime mortars, helps to capture the released calcium oxide during the hydration of cement, reduces the porosity, prevents the release of water and the destruction of the mortar from frost, contributing to the long life of the mortar, which is confirmed by the surviving constructions of antiquity.
The slow pozzolanic reaction enables the reduction of the temperature rise rate of the hardened mortar (the maximum temperature of a construction is achieved in 3 days after the molding thereof) in proportion to the addition of the pozzolan and makes it highly resistant to cracking (due to thermal expansion).
As it mentioned before, the pozzolanic reaction causes in a reduction of porosity, with a significant improvement of the chemical resistance. The permeability plays a key role in determining the rate of destruction of these chemical actions such as expansion due Alkali reaction and attack by acidic and sulfate environments.
Superfine Pozzolan -10 μm
The Olympus Superfine pozzolan from -10μm to -20 μm (q.v. LASER grain size analysis - compared with the known Super-pozz) It is suitable for specialized uses such as special mortars, for precision seals and repairs of dams, tunnels, sewage systems and generally seals microcracks for soil sealing (www.usgrout.com). The pozzolanic properties (the ability to capture the Ca(OH)2 increases in proportional to the specific surface area and inversely proportional to the grain size.
The usage of superfine pozzolan is indicated for preventing cracks in cement due to non commitment of the released Ca(OH)2 during the hydration of cement and contraction. Also, the usage of superfine pozzolan is indicated at the self-leveling floor screeds and the self-compacting concretes.
The monitoring of the grain size for the superfine products with a LASER is carried out by CERTH (National Technology and Development Center) in Thermi, Thessaloniki.
It is noted that while there are several plants in the country that producing superfine soft minerals (calcium carbonate, etc.) the Olympus Minerals plant is the only capable plant of producing superfine products of hard mineral (> 6 Mohs).