Pozzolan

Natural Pozzolan is one of the main components of the historical mortars together with lime and tile flour. It was used in the construction of monuments in Ancient Greece, in Rome’s Pantheon, in Byzantine monuments, but also in neoclassic buildings of 19th century and gave them considerable resistance to wear of time, resistance to earthquakes and maintained in the centuries until nowadays.

Today natural pozzolan is mainly used in the Greek area primarily by the cement industry as a main ingredient for the production of cement and as for the archaeological services for the restoration of important monuments, such as the archeological site of Nikopolis, National Library of Athens, many monasteries in the Holy Mountain of Athos, the Benaki Museum, the Panathenaic Stadium and others.

It is also used in the external and internal decoration of modern constructions, but also as building material providing constructions time durability and an aesthetic effect that is harmonious with natural environment.

The licensed pozzolan quarry owned and exploited by the company OLYMPUS SA in Pella Prefecture, is providing an excellent quality of pozzolan. We have to notice that quarries of pozzolan in the prefecture of Pella is operating without interruption from 1971 until today and is fulfilling the needs of TITAN Cement SA Thessaloniki factory.

The quarried material is transferred to the company’s processing plant in Assiros Thessaloniki where is handled in two sectors. In the first sector, the material is crushed. Then, in the second sector, the material is dried, sieved and milled in an iron-free stone-mill in order to avoid material contamination from iron and primarily chromium oxides in the final product that can differentiate the final product in color and other characteristics.

Advantages of pozzolan use

  • In fresh mortars: The fresh mortars which tend to exudate or segregate, it is well known that the introduction 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 the workability of the fresh mortar..
  • In the 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 porosity, prevents the release of water and the destruction of the mortar from the frost, contributing to the long life of the mortar, which is confirmed by the surviving constructions of the antiquity.
    The slow pozzolanic reaction enables the reduction of the temperature rise rate of the hardened mortar (the maximum temperature of a massive construction is achieved in 3 days after the molding thereof) in proportion to the addition of pozzolan and makes it highly resistant to cracking (due to thermal expansion)..

    As mentioned before, the pozzolanic reaction causes a reduction of the porosity, with significant improvement of the chemical resistance. The permeability plays a key role in determining the rate of destruction, due to chemical actions, such as expansion due to alkali-silica reaction and attack by acidic and sulfate environments.

Pozzolan – 45μ

The Pozzolan of OLYMPUS SA is a volcanic tuff, which is an amorphous aluminosilicate material.

According to research made by Aristoteles University of Thessaloniki, Pozzolan -45μ. has a specific surface 8920cm2/g (with maximum percentage of the grains rated between 2-40μm) and the content of reactive silica is greater than 50%.

The pozzolanicity (the reaction between reactive silica and calcium hydroxide) increase proportionally with the percentage of active silica and the finess. The pozzolanicity of our product is 50% active silica.

The exceptional pozzolanic properties of OLYMPUS SA were confirmed more by the research done by professor Papayianni I. in the Laboratory of Building Materials in the Department of Civil Engineers of Aristoteles University of Thessaloniki according to the Standard ASTM C593-06 (Control of pozzolan material):

Bending Resistance Compressive Resistance Active Porosity Specific weight
4,21 MPa 12,58 MPa 21,88 % 1,842

 

The mineralogical structure of the OLYMPUS SA Pozzolan is amorphous by more than 95% (XRD analysis from “Mineral Lab Inc” Colorado USA, Laboratory.

The chemical structure fulfils completely the requirements of ASTM618-05 for natural pozzolans and their use in concrete that is evident in the following table in the XRF analysis made by CTL Laboratories in Illinois, USA for control in cement and mortars:

Ποζολάνη-45μ
XRF Analysis ASTM 618-5 Requirements
SiO2 70,20%
Al2O3 14,40% SiO2+Al2O3 +Fe2O3>70%
Fe2O3 1,99%
CaO 1,09%
MgO 0,52%
SO3 0,04% SO3 <4%
Na2O 2,71%
K2O 4,82%
TiO2 0,21%
P2O5 0,11%
Mn2O3 0,10%
SrO 0,05%
Cr2O3 0,01%
ZnO 0,02%
L.O.I 3,72% L.O.I < 10%
Humidity <1% Humidity <3%

The available alkali metals of pozzolan according to ASTM C311 Standards, expressed in Na2O are 0.94%.

The effectiveness in the control of alkali-silica reaction measured with specimens expansion rated 14 days, according to the ASTM C311 standard, is 38% significantly lower than the maximum allowed of 100% (CTL Illinois, USA).

The drying shrinkage according to the ASTM C618-05/C311 is zero (CTL Illinois, USA).

Superfine Pozzolan -10μm

The OLYMPUS SA Superfine Pozzolan from -10μm up to -20μm (q.v Laser particle size analysis-compared to the known Super-pozz)is suitable to specialized uses such as special mortars, for precision seals and repairs for dams, tunnels, sewage systems and generally microcracks seals for soil sealing (www.usgrout.com). The pozzolanic properties (the ability to capture Ca(OH)2) increases in proportional to the specific surface area and inversely proportional to the particle size.

The usage of superfine pozzolan is indicated for preventing cracks in cement due to not binding of the released Ca(OH)2, during the hydration of cement and contraction. Also, the use of superfine pozzolan is indicated at the self-leveling floor screeds and the self-compacting concretes.

The monitoring of the particle size for the superfine products by LASER is carried out by CERTH (Centre for Researsh and Technology Hellas) 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 SA is the only capable plant of producing superfine products of hard minerals (>6 Mohs).

Agricultural Application of Pozzolan

The use of mineral powders to enhance the trace elements in the cultivated area is continuously developed especially in North America.

The intensive crops are lowering continuously the soil content in trace elements to the minimum necessary.

The replacement is done with technical preparations having trace elements, but this it was applicable only to a small extend due to high cost.

Today rock extraction is done-primarily in volcanic rocks- having sufficient content in trace elements, according to the recommendations to the area to be improved.

The extracted rocks are grinded in 50-100μ, bulk transported and mixed with the surface soil of the fields.

Among the projected materials for this use are also pozzolan with the following potential characteristics:

  • Water retention 100%
  • Bio-Fertilization of the soil with increased efficiency
  • Soil Ventilation
  • Neutralization of aridity and frost results
  • Neutralization of nitrogen excess in the soil to avoid water contamination

Many information can be extracted in Google with the use of words “rock dust agriculture”.