Refractory Castables
Castable Refractory – High-Performance Monolithic Linings
Refractory castables are advanced materials used to form monolithic linings in furnaces, kilns, incinerators, and other high-temperature industrial units. Due to their outstanding thermal performance, mechanical strength, and adaptability, castable refractories play a critical role in the construction and maintenance of high-temperature installations. Castables can be categorised into several types based on their composition and application method: conventional, low iron, low cement, and insulating. They may be installed via gunning, casting, or manual application, depending on project requirements. Refractory castables are formulated from a wide range of raw materials, including chamotte, andalusite, bauxite, mullite, corundum, tabular alumina, and silicon carbide. For insulation purposes, lightweight aggregates such as perlite and vermiculite are incorporated.

What Are Refractory Castables?
Refractory castables are unshaped refractory materials that can be mixed on-site with water and cast into virtually any form. They consist of carefully graded refractory aggregates, hydraulic or chemical binders, and performance-enhancing additives.
Their formability and durability make them suitable for both new installations and repairs in furnaces, kilns, incinerators, and similar thermal equipment. Castables are valued for their versatile application, thermal shock resistance, and ability to accommodate complex geometries, reducing the number of joints and potential failure points.
Conventional Dense Refractories
Conventional dense castables are based on high-alumina cement and are designed for service temperatures ranging from 1300°C (2370°F) to 1800°C (3270°F). These materials are suitable for a wide range of furnace applications, including burner blocks, muffle furnaces, and boiler linings.
Performance characteristics such as abrasion resistance, thermal shock resistance, and slag corrosion resistance are determined by the formulation and raw materials used. Installation methods include casting and gunning. In gunning applications, the material is mixed with water at the nozzle, providing an efficient solution where traditional formwork is impractical or time-consuming. Selection of the installation method depends on site conditions and budget considerations.
Gunning Refractory Castables
Gunning mixes are a specialised type of refractory castable designed for installation via pneumatic gunning, a method that allows for fast, efficient application without the need for formwork. These materials are particularly advantageous for repairs or relining of furnaces and kilns where downtime must be minimised. Formulated with controlled grain size distribution and bonding systems suitable for dry or semi-wet application, gunning castables provide excellent adhesion to existing linings, resistance to rebound loss, and durability under thermal shock and abrasion. They are ideal for spot repairs, overhead work, and hard-to-reach areas where conventional casting is impractical. The gunning method ensures uniform material placement and rapid turnaround in high-temperature environments.
Insulating Castables (Low Thermal Conductivity)
Insulating refractory castables are low-density materials formulated to offer minimal thermal conductivity. They are used either as hot-face linings in lower-load applications or as backup insulation behind dense refractory linings or brickwork.
By reducing cold face temperatures and overall lining weight, insulating castables help improve energy efficiency and reduce thermal losses. While their mechanical strength ranges from low to medium, their primary function is insulation. They are not intended for high-abrasion environments and are best suited for areas with limited mechanical wear.
Low Cement Refractory Castables
Low cement castables (LCCs) contain significantly less calcium aluminate cement than conventional castables, resulting in lower porosity, higher strength, and improved abrasion resistance.
These castables offer excellent performance in high-temperature environments and are ideal for gas or oil burner surrounds, heat exchangers, and forced-air systems. Many low cement castables are self-flowing and can be pumped or cast without vibration, allowing for faster and more efficient installation under controlled conditions.
Advantages of Refractory Castables
Compared to traditional refractory bricks, castable refractories offer several key benefits:
- Form flexibility - Easily poured into complex shapes and tight spaces
- Fewer joints - Reduced risk of heat loss or air leakage
- Thermal shock resistance - Suitable for cyclic temperature environments
- On-site mixing - Adaptable to specific project requirements
- Cost and time efficiency - Faster installation with fewer cuts and adjustments
These advantages make castables an excellent choice for diverse applications across high-temperature industries.