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Grey Firebricks

Code: Grey Firebricks
Category: Firebricks

Grey Firebricks
The production of refractory bricks has always been our company’s core activity. With a production capacity of 200.000 tones per annum and three production units, RO.KA Refractories is one of Europe’s largest players. Our bricks belong to the category of “fireclay refractory bricks”.
Our first production, back in 2011, comprised only red firebricks. However, a few years later we responded successfully to the global demand for the yellow firebricks. With the pass of time, we managed to deploy the accumulation of knowledge, offering products of highest quality at competitive prices.
Our cause is primarily the production of shaped refractories, namely fireclay bricks.
In order to fulfil the best possible quality standards, we cooperate with the National Center of Scientific Research “Demokritos” in the field of Research and Development and as an eco-friendly company we invest in new, cleaner ceramic technologies such as geopolymerism.
With more than 2.000 clients worldwide and by exporting in more than 35 countries, we are the only company of its kind that focuses on special refractories for appliances that call for elevated aesthetics such as barbecues, fireplaces, stoves, pizza ovens. 
We manufacture uniquely silicoaluminate products, taking advantage of our own private resources. 
This Category of firebricks refers to Eco-Friendly solutions
As an eco friendly company, by over passing all the difficulties, we succeeded in developing ‘’greener’’ firebricks.  Geopolymer bricks are special refractory clay bricks whose heat resistance exceeds 1200°C. They differ from common firebricks in basic physical, mechanical and thermal properties as they are designed to resist to higher stress – strain conditions. Roka Refractories’ geopolymer bricks constitute an innovation with mentionable environmental saving. Using calcium – based binders and availing of the reaction of calcium with silica and alumina to generate Calcium Silicoaluminate Hydrates, semi-dry pressed bricks are stabilized without further pyroprocessing requirement. C-S-H and C-A-H are “green” compounds that act as glass to keep the structure robust and durable.
What ‘’firebricks’’ terms mean:
Refractories are products with minimum heat resistance of 1000°C.  They may be shaped, in predetermined form, or unshaped, in dry mixes that need some activator such as water.
Firebricks may be silicoaluminate or basic. Silicoaluminate refractory bricks are made from minerals such as kaolinite, quartz, andalusite and bauxite. Basic refractory bricks are made of magnesite.
Shaped refractories are classified as insulating and dense, depending on their porosity. The main technical feature that indicates their insulation capacity is the thermal conductivity index «λ».
 Silicoaluminate firebricks distinguished as silica, semi-silica, low duty, medium duty, high duty, super duty firebricks, depending on their Alumina (Al2O3) content and their refractoriness.
Roka Refractories Firebricks:

  • are mainly made of kaolinite, quartz and some chamotte. 
  • are fire-resistant up to 1200°C.
  • are formed through semi-dry compression.
  • are thermally balanced, namely neither highly insulating, nor highly heat accumulating.
  • belong to the shaped, silicoaluminate, dense, semi-silica and low-duty subcategory of refractories.

Why to choose Roka Refracotries Firebricks:
Color stability:
Most refractories manufacturers address their products to industrial users. Hence, little or no attention is paid to the uniformity of the products.  Often, there are noticeable color variations within a lot, a batch, or even a single palette.  Given that barbecues and fireplaces are considered vital equipment for internal and external decoration in a house owner’s eyes, the constancy of the color of the construction is, without doubt, very important. ROKA Refractories considers the appearance of its firebricks fundamental, seeking to satisfy even the most demanding decorators.
Finest Finishing’s :
Appearance is not just a matter of color. The edges of the bricks are equally significant, as a mismatch could end up “destroying” the lineage of a construction.  Similarly, finishing’s form part of what a client perceives as quality. ROKA Refractories accomplishes sharp, linear edges for its bricks by investing in the quality of the metal of the molds used to form the bricks.  In addition, the company holds a long-term relationship with a specific manufacturer of molds to secure a high level in the supplied services.
Mentionable frost resistance:
Given that firebricks are used in exterior furniture such as barbecues and pizza ovens, they are exposed to low temperatures for several months. Firebrick barbeques are also known as “Mediterranean” barbeques since firebricks crack in northern countries when they freeze.  What causes the bricks to crack is the freezing of the water absorbed inside their body and the shrinkage-expansion that ice generates. ROKA Refractories’ firebricks have very low water absorption rate, close to 7% per weight, being able to withstand extreme environmental conditions.
Higher Strength Properties :
Shaped refractories are not famous for their mechanical performances. Generally, firebricks are of lower compressive and flexural strength than other types of ceramics. Yet, firebricks are subject to quite severe load, especially in fireplaces, where wood is combusted.  In addition, builders prefer “stronger” bricks as they do not break easily during construction. ASTM sets a minimum of 3 MPa for the Modulus of Rupture of firebox bricks. This value is indicative of the average strength of firebricks. ROKA Refractories’ fireclay bricks carry a MOR index greater than 8 MPa, being among the strongest in the global market.

  • Aristotle University of Thessaloniki for Refractoriness
  • CE.RE.CO for Refractoriness
  • Istituto di Ricerche Agrindustia for Food Contact Suitability
  • Democritos Institute for Absence of Asbestos
  • T.U.V. Austria-Hellas for Quality Management System (ISO 9001:2008)


SiO2 72,40% 40-75%  
AI2O3 17,50% 15-45%  
CaO 0,29% 0-0,7%  
Fe2O3 1,32% 0-6%  
K2O 3,43% 0-4%  
MgO 0,53% 0-0,7%  
Na2O 1,07% 0-2%  
TIO2 0,95% 0-2,8%  


Shapes and Dimenssions 165kgf/cm2=16,18MPa  
Bending strength 8,81MPa  
Cold crushing strength 62,82Mpa=640,76kgf/cm2  
Porosity 7,2% p.w.  
Specific weight 2,12gr/cm3  
P.C.E. >1100oC  
Thermal expansion <1%