Making clay the Afyon way

Clay Technology magazine
11 Dec 2010
Afyon clay deposit, Afyonkarahisar, Turkey

A new deposit of clay from the Afyon province in Western Turkey could be the answer to the country’s growing tile industry.

Researchers at Usak University in Turkey claim the Afyon clay could be substituted where Istanbul clay has traditionally been used.

To assess the feasibility, the team has tested the mineral and chemical properties and plasticity of both clays, using X-ray diffraction and fluorescence techniques. The Atterberg limits method – commonly used to distinguish between silt and clay – was also used to assess plasticity.

Lead researcher Haluk Celik explains, ‘Both clays present a similar plasticity – the plasticity index (PI) of Afyon Clay is 33.1%, and that of Istanbul Clay 31.6%. This PI characterises them as highly plastic. Both clay samples also show high values for plastic limit – 23% for Afyon clay, and 28.7% for Istanbul clay. Istanbul clay has a higher clay fraction (about 77%) than Afyon clay (about 41%)’.

However, Afyon clay shows slightly reduced bending strength compared to Istanbul clay, from 33.3N/mm2 to 35.3N/mm2. Yet Celik adds, ‘This is not a major problem, since it [Afyon clay] provides the bending strength value required for dry-pressed ceramic tiles, corresponding to class BIIa’.

He also notes that, ‘Almost all the technological properties of the Afyon clay deposit demonstrate industrial suitability for use in ceramic tiles and that manufacture [use] of the Afyon clay would only require grinding due to its sand fraction’.

To further demonstrate the potential of this raw material as a substitute, Celik says, ‘Afyon clay presents a wider particle size distribution, with an average particle size of about five micron meters, while the average particle size of Istanbul Clay is about 0.3 micron meters’.

Investigations into the material also show that water absorption is not distinctly changed on partial or full substitution of Istanbul clay with Afyon clay, opening up the possibility of large-scale exploitation of the Afyon deposit.

The next hurdle will be to examine the technological utilisation of Afyon clay for porcelain tile production.