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Microsilica for castable refractory products

Improving high temperature and mechanical resistance for cast refractories

Refractories: Mastering a versatile and complex process

Castable refractories are either used as-delivered or after adding one (or several) liquids or additives. They must meet several, sometimes contradictory, specifications:

  • Protecting the integrity of the kiln or furnace shell from elevated temperatures, while maintaining continuous high temperature and reducing heat loss when possible
  • Preventing unwanted reactions, such as abrasion or chemical reactions, between the shell, the raw material and the end-product
  • Resisting chemical attacks as well as mechanical stress due to extreme heat or periodical heating/cooling cycles.


Elkem for refractories: lets make a castable

Microsilica, which has become the generic term for silica fume, is a key ingredient in finding solutions in these complex processing challenges. It adds several beneficial properties to a refractory product thanks to its sub-micron particles, which contribute to efficient particle packing in concrete and refractory mixes, facilitate production of self-flowing castables with a minimum of water addition, and provide high temperature and mechanical resistance.

Refractories: main industrial applications

Making the right decision for castable refractory materials

Elkem Silicon Products is the global leader in microsilica technology since the 1980s, having been at the forefront in the development of refractory technology. Elkem MICROSILICA® powders, a co-product of silicon or ferrosilicon manufacturing mainly consist of ultrafine, amorphous spheres of silicon dioxide (SiO2). They feature high-purity properties, which can have a strong impact on the performance of refractory castables, particularly in the bonding phase of refractory at temperatures above 1250 °C.

Elkem MICROSILICA® also features control of particle size distribution (PSD), an important factor in developing dense refractory castables. It also provides the specific properties and benefits in all types of refractory materials, including low cement castables (LCC), ultra-low cement castables (ULCC) and no cement (NC) castables.

The benefits of Elkem MICROSILICA® refractory castable products include:

  • Improved flow, particle packing and adjusted levels of densification, facilitating casting
  • Reactivity during sintering, contributing to improved ceramic bonding at reduced firing temperatures
  • Lower gas formation
  • Versatility in application, including gunning mixes, shotcrete, etc.
  • Gel bonding
  • Improved hot-strength properties and guaranteed stability

Here is a non-exhaustive list of our product offering for castable refractory processing. Elkem experts, technicians and sales staff are available to explore the right solutions for your specific applications:

Silicon based materials for refractories​

Elkem Microsilica® 971

The ELKEM MICROSILICA® 971 product, a high quality, purpose-made, low-impurity grade, for versatile applications in refractories, available in densified (D) or undensified (U) form, to be used in advanced refractory products such as self-flowing, low, ultra-low and no-cement castables.
Product data sheet

Elkem Microsilica® HQ

The Elkem Microsilica® HQ product is a cost-effective alternative for low cement castables, with controlled and stable chemical composition, based on low alkalis and higher reactivity.

Product data sheet

Elkem Microsilica® 968

The ELKEM MICROSILICA® 968 product, a cost-effective alternative for low cement castables, featuring a controlled and stable chemical composition.
Product data sheet

Elkem Microsilica® 955

The Elkem Microsilica® 955 product, a medium-quality grade silica fume with tight specification limits based on in-process control, resulting in higher silica content and reduced impurities.
Product data sheet


Designed for microsilica-containing LCC and ULCC, based on Al2O3 - SiO2 system with quick wet-out and low water demand.

Product data sheet


Designed to act as an accelerator in undispersed aluminosilicate systems like dry gunning LCC and ULCC mixes without clay.

Product data sheet



 Designed for microsilica-gel bonded systems (NCC) to control the working and demoulding time and to develop high green-strength at room temperature.

Product data sheet


Designed to work as a multi-functional microsilica dispersant, for aluminosilicate LCC, ULCC and NCC, giving customers freedom to fine-tune their products with other additives (accelerators, retarders, etc.). It enhances the rheological properties, reduces the water demand and increases the flow. Suitable also for shotcreting.

By combining both SioxX®-Flow and SioxX®-Set products, setting can be controlled. SioxX®-Flow product will also work in combination with Silica-Sol (colloidal silica) in NCC to control flow, working and setting time.When used in silica-sol systems a separate gelling agent needs to be added.

Product data sheet


Designed for undispersed systems mainly for NC gunning mixes. Can also be used for LC and ULC gunning. In castables and shotcrete (dispersed systems) SioxX®-Set can be used as accelerating agent.

Product data sheet


SioxX®-Ten / SioxX®-Ten PLUS

SioxX®- Ten and SioxX®- Ten PLUS are primarily designed for ultra low cement alumina-based or microsilica-gel bonded no-cement castables.
SioxX®- Ten mainly works at the range of 800-1100ºC, while SioxX®- Ten PLUS is recommended to work at the range of 600-900ºC.
Both of them enhance the rheological properties, reduce the water demand, increase the flow, control the working and de-moulding time, help develop high green strength as well as high strength at the indicated working range of temperature.

Product data sheet

SioxX® Mag

Designed for basic (MgO-based) refractory castables, to help avoid inherent problems of crack formation and poor workability. For advice how to best use our Specialties, contact our competent technical staff.

Product data sheet

BOCAREPS™ (Boron carbide)

Boron carbide (B4C) is a dark grey–black material comprising 76.5–78 wt% boron, with an exceptional hardness that is only exceeded by diamond and cubic boron nitride.

Product Data Sheet

Safety data sheet and technical data sheet

Product Data Sheet center

If you are looking for our product safety datasheets, you can also go to our product safety datasheet center

Refractory technology: Maintaining Elkem’s leadership through sustainable technology

Refractory technologies are constantly evolving, using alternative materials and product formulations, such as increasing development of raw materials and more enhanced and synthetic minerals. Changes are driven by a need for greater heat efficiency, cost-effectiveness and sustainability requirements, such as the use of recycled metals and less energy, a move to more low-carbon and renewable fuels, including the use of new technologies such as hydrogen and electric arc furnaces (EAFs) in metallurgy, etc. In R&D, Elkem refractory product design is also focusing on longer in-service life and greater safety for people and factories.

Discover the different silicon based materials for refractory applications, each with unique properties that are specifically crafted to meet the demands of high-temperature environments.

Silica Fume / Microsilica

Silica fume is a byproduct of the production of silicon metal or ferrosilicon alloys, and is a highly reactive pozzolanic material that is used as a supplementary cementitious material in concrete to improve its properties.

Read more about silica fume

Silicon powder / micronized silicon

Silicon powder is a finely ground, micronized form of elemental silicon that is used in a wide range of industrial applications, including metallurgy, ceramics, electronics, and more.

Read more about silicon powder

Specialties for Refractories

Specialties for refractories are various types of silicon products specifically designed for use in high-temperature applications. 

Read more about specialties for refractories


Elkem Materials Mixture Analyser

Elkem Materials Mixture Analyser

Get the best out of Elkem's Silica fume / Microsilica material by leveraging upon our world reknown software to optimize your mixture.


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