Iron-silicate fines (Fayalite)

Iron-silicate fines, also called fayalite, is a by-product produced by Aurubis Bulgaria, with universal application in variety of areas in construction. Received by complicated metallurgical process after cooling down, crushing, grilling, flotating, thickening and filtration of copper slags it has stable physical and chemical characteristics.

Properties of iron-silicate fines make it compatible with various materials like limestone, soil, clay, clinker, cement, sand, gravel, chemicals, etc. Its’ application transfer building materials to those with lower environmental impact and reduced utilization of natural resources.

This product has non-hazardous status and can be applied in various areas in the construction process: starting from the soil embankments, through structural elements and brick walls till finishing works like plasters and coatings for buildings and facilities.

Iron-silicate fines is a universal source of raw materials applied in variety of applications, making final products with better performance.

Basic characteristics:

Particle shape




Bulk density

1800 kg/m^3

Specific density

3700 kg/m^3

Moisture content

Two types: 12 % & 1%

Loss of ignition


Friction angel

At moisture 12 % – 70% lower than 1 % – 45%




Typical range

Fe elem.

46% (as Fe2O3>60 %)















Cement clinker with iron-silicate fines (ISF)
Cement clinker with iron-silicate fines (ISF)

Portland cement clinker production consumes large amounts of natural resources, mostly limestone and clay, but also sand and iron additives. Nowadays, the cement industry is facing the challenge of protecting the environment by decreasing the consumption of natural raw materials.

Various industrial solid wastes have been utilized as alternative raw materials in Portland cement clinker production. Iron-silicate fines (ISF) are such alternative material, which can be used as a substitute of the commonly used iron ores. According to the mineral composition of the main raw materials (clay and limestone), ISF could be used as silica and iron corrective material or as a source of iron.

There are several benefits of ISF valorisation in the cement industry:

  • Ready-to-use source of iron;
  • No need for additional crushing and grinding;
  • Suitable for both dry and wet clinker production lines;
  • Good mixing properties;
  • Promote lower calcination temperature;
  • Eliminate the need for mineralizers.

The chemical composition of the material includes the minerals fayalite, magnetite, pyroxene and quartz, basically in the form of ferrous and silica dioxide, which give the name of the material – iron-silicate.


Typical value



46,0% (Fe2O3>60 %)























ISF contractors are: Heidelberg Cement, Lafarge Holcim, Titan, American Cement, etc.

Variety of ISF concretes
ISF heavy concrete

Heavy concrete containing ISF is applied in civil and industrial structures, where there is a need for high density and heavy weight facilities. With a proper mix design and chemical admixtures, heavy concrete containing ISF can have a good workability. Aurubis provides a blend for the production high density concrete.

There are many applications of ISF heavy concrete:

  • Heavy foundations for structures and facilities;
  • Underground and tunnelling;
  • Marine structures (coast protection, retaining walls, tetrapods, etc.);
  • Bridges;
  • Anchorages;
  • Coatings for pipelines;
  • Lego Blocks.

There are several benefits of ISF valorization in heavy concrete:

  • Approved as a concrete aggregate according to EN 12620;
  • Increased strength and density of concrete (about 2,8kg/m3);
  • Improved durability, especially waterproofing (Cw0,8 & Cd50 (BNS EN 206:2013 & NA.N)) and protection against the aggressive impact of chlorides, sulphates and salts
  • Concrete volume stability (no shrinkage, no swelling);
  • Reduced heat of hydration;
  • Increased abrasion resistance (18±0,2cm3/50cm2 (BNS EN 13892-3:2015));
  • Significantly increased frost resistance (∆m=0,2% & ∆f=2,3% (BNS EN 206:2013+A1:2016)).
ISF shielding concrete

ISF shielding concrete is a building material used for the construction of protection shields. These shields guarantee the work safety of the people inside, subjected to different radiations and attacks.

This type of concrete is used for:

  • walls, ceilings and floors against ionizing radiation;
  • multi-threat protection from electromagnetic radiation;
  • radiation protection in hospitals, laboratories, oncology clinics and waste treatment facilities;
  • protection against the hazard of nuclear radiation leakage;
  • protection against terrorist attacks;
  • protection against extreme natural disasters.

There are several benefits of ISF valorization in shielding concrete:

  • Combines structure and shielding system;
  • Increases strength and density of concrete (about 2,8kg/m3);
  • Decreases maintenance and increase durability of structures;
  • Reduction of size while maintaining high protection capacity;
  • Thermal insulation capacity;
  • Sustainable and cost effective.
ISF ultra high performance concrete

Ultra High Performance Concrete (UHPC) is characterized by a very high compressive strength (above 150 MPa) and extreme durability, even when exposed to high aggressive environmental impacts. All these characteristics make it an alternative to other construction materials (e.g. steel) for the construction of transport and hydraulic facilities, high-rise buildings, as well as for special mine structures, structures for military application and high aesthetic architectural elements and details. At the same time, UHPC is a material, which complies with the policy of sustainable development by reducing the need for maintenance and rehabilitation of the facilities.

Iron-silicate fines (ISF) are one of the best materials for making UHPC, which bring plenty of benefits in the structures and elements:

  • Compact the macro- and microstructure due to the small grain size;
  • Increase the density by additional interaction with other ingredients;
  • Increase the workability of the fresh mixtures;
  • Reduce natural raw material utilization;
  • Create long-term life products;
  • Make sustainable final products.

Standard ISF UHPC mix design includes:

  1. ISF = 1150kg/m3;
  2. Cement = 820kg/m3;
  3. Fly ash = 380kg/m3;
  4. Water/Cement =0,3

The density of ISF UHPC is about 2,4 kg/m3 and the compressive strength exceeds 100MPa. In case thermal treatment is applied, the mechanical properties of concrete could increase by 30%. For application in thin structural elements subjected to flexture, it is recommended to use short (6 to 8 mm) steel fibres – 2% by volume.

ISF deicing concrete

De-icing concrete is a special mixture containing ingredients, which are electrically conductive. Ordinary concrete does not have this property. The composition of de-icing concrete consists of high quantities of iron-silicate fines (ISF) in combination with other geological materials with high iron content and a cocktail of building materials. When de-icing concrete is connected to a power source its ingredients are heated and prevent ice formation on concrete surface. This special type of concrete is used on several US bridges and sidewalks and is invented by Prof. Christopher Tuan and assigned by the University of Nebraska with Patent No.: US 6,825,444 B1. The concrete surface is heated up to +20°Celsius above the ambient temperature.  

There are several benefits of ISF valorization in de-icing concrete:

  • Source of electrically conductive components;
  • Improves the mechanical and durability properties of concrete;
  • Certified building material according to EN 12620;
  • Sustainable building material.
ISF paving concrete products

Vibro-pressed concrete products are widely distributed in urban areas. The technology of their production requires a concrete mix design with specific workability and flowability of the fresh concrete mix and at the same time high mechanical properties and durability of the hardened products. Alternative materials, which in general improve the properties of hardened concrete, could be effectively utilized in paving products, if they cover the requirements for low water-cement ratio and formability of elements. Iron-silicate fines (ISF) improve the compaction rate of the products thanks to their small grain size, which leads to improved appearance and durability. ISF can be used for a wide range of concrete products like tiles, blocks, panels, curbs, etc.

There are several benefits of ISF valorization in paving products:

  • Improved mechanical properties (up to 25%);
  • Better durability due to compacted structure and possible pozzolanic activity of ISF with cement;
  • Improved abrasion resistance (14±0,2cm3/50cm2 (BNS EN 1338:2005, app. H));
  • Volume stability, no risk of alkali-silica reaction;
  • Certified building material according to EN 12620;
  • Sustainable building material.


ISF anti-skid surface coatings
ISF anti-skid surface coatings

Anti-skid coatings (ASC) refer to a surface treatment of roads by providing improved top surface skid resistance. Normally the thickness of the coating is about 3-5 mm and helps drivers brake under emergency conditions at hazardous locations. Ordinary ASC contains natural bauxite as an aggregate for surfaces subjected to high friction.

Although there is an increasing interest in ASC, natural bauxite stops the development of such coatings, because of its very high price and rarity. Iron-silicate fines (ISF) can substitute natural bauxite in ASC and make geopolymer concrete with better properties.

The Polished Stone Value (PSV) is a coefficient which defines road resistance to skidding. ISF improve the PSV value and the abrasion resistance of synthetic geopolymer in general. University of Ulster, Northern Ireland are responsible for current research and development of ISF ASC, according to EN and ASTM standards.

There are several benefits of ISF valorization in anti-skid surface coating:

  • Improved abrasion resistance;
  • Improved compressive strength;
  • Certified building material according to EN 12620;
  • Sustainable building material.
ISF dry mixtures
ISF dry mixtures

Dry mortars or dry-mixed mortars are made of cement, sand, mineral and chemical additives, mixing together proportionally. They are often in powder or granule form pre-mixed in special factory and transported to construction site in paper sacks or by cement trucks. After stirring with certain amount of water, it can be used directly. Fine structure of iron-silicate fines is a benefit for dry mortars, because it improves workability of mortars and keeps the consistency in time.

There are usually two kinds of dry mortars- normal type and purposed type. Normal type includes masonry mortar, plastering mortar and ground mortar. Special purposed ones like tile adhesive, interface dry powder, insulating mortar, self-leveling, water-proof mortar, repair mortar, wall putty, etc.

There are several benefits of ISF valorization in dry mortars:

  • Improves fresh properties;
  • Improves mechanical characteristics in hardened state; 
  • Absent of linear deformations;
  • Reduced shrinkage.
ISF ceramic products
ISF ceramic products

Ceramic is one of the most ancient building materials on our planet, dating from earlier than 10 000 years BC. Once humans found that clay mixed with water could be moulded and then fired, they started experimenting with different shapes, colours and mix designs.

Nowadays, scientists and the industry have been testing a wide range of alternative materials for ceramic production, which improve the properties of the final products on the one hand and reduce the extraction of natural resources on the other.

Iron-silicate fines (ISF) is such a material, which utilization leads to several benefits in different types of ceramic products (bricks, ceramic and clinker tiles & plates, roof tiles, etc.):

  • Increase mechanical properties;
  • Increase volume stability;
  • Decrease plasticity during drying;
  • Decrease linear shrinkage;
  • Sustainable and cost effective.
Coal flotation with ISF
Coal flotation with ISF

Coal mines are using beneficiation processes based on the principle of gravity separation – jigging, heavy media bath and cyclone, and flotation. Iron-silicate fines (ISF) are very efficient in the flotation of fine coal particles (0-0,5) mm in size.

The suspension is stable, easy to prepare, easy to recover from the process and to reutilize. In fact, the most widely used material is magnetite, but this it is not uniformly distributed.

ISF are a very good alternative material due to several benefits:

  • High specific density;
  • Lower viscosity;
  • Easy preparation in suspension;
  • High stability in suspension;
  • Local source, easily available than magnetite;
  • Fine and effective material;
  • Sustainable utilization.

Our ISF contractors are several local coal mines and heat power plants.

Detailed reference on material specification, material safety data sheet, logistics and shipping options, can be obtained in our PDF brochures here.

Emanuela Manolova
Emanuela Manolova

Iron-silicate Business Development Manager

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Alexander Blazhev
Alexander Blazhev

Commercial Director

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