Refractory cement is a specially designed and mixed cement product that will withstand extremely high temperatures while maintaining its structural integrity. Popular uses for castable refractory cement include fireplace inserts and linings, stone ovens, kilns and foundries.

By combining mineral and chemical mixes within the refractory cement, moisture is purged from the concrete during the curing process. When applied and cast properly, this greatly reduces the chance of degradation and cracking due to rapid changes in temperature. Standard cement maintains a high level of moisture after curing. When rapidly heated, this can turn to steam very quickly. The result is cracks, in minor cases, and explosions in more extreme cases.

Refractory cement is available from a variety of online retailers and home improvement stores. It can often be found in departments that feature fireplaces or heating solutions. As with most things, when it comes to refractory cement, you often get what you pay for. Heavier grade cements will be resistant to higher temperatures, while lower grade castable refractory cement will be more fragile and tolerate much lower temperatures.

While it is often easy to find refractory cement in a variety of stores, mixing your own refractory cement recipe provides ultimate customization options. This is great way to tailor the characteristics of your castable refractory cement to meet your needs. Keep in mind, however, that this can be pricey and will require a bit of work. To know how to mix cement, the procedures and techniques are available online.

How To Make Refractory Cement

• You will need:
  • 1.5 parts river run or crushed firebrick
  • 1 part sand
  • 1 part calcium aluminate cement
  • One-quarter part lime
  • 3-3.5 liters of water

• Gather materials needed and find an open, easy to clean space to mix your concrete.
• Spread gravel and sand
• Add cement and lime
• Add water and mix with a shovel

When using refractory cement, proper technique is vital to successful and long-lasting function as the concrete ages. While specific instructions might vary, in general the process is similar for most types.

1.       Work with your pre-mixed refractory cement quickly. This will ensure a solid and dense finished product. Always work on a surface that is easy to clean. Sheet metal or wooden surfaces can be ideal if you need to cast multiple pieces.
2.       Create your pieces using rigid forms. Wood, cardboard or plexiglass make affordable and easy to work with form solutions.
3.       Allow your forms to sit and cure. Keep the surface of the cement damp during curing to prevent cracking. Cover the cement forms with a damp cloth as it dries. Curing takes approximately 24 hours. However, more time might be required depending on your mix and environmental conditions
4.       After the form has set, assemble your final product using refractory mortar.
5.       Slowly bring the temperature of your refractory cement from room temperature to the maximum operating temperature intended. This should be performed slowly to allow all moisture to escape from the refractory concrete safely. Rapid heating can result in cracking.
6.       After curing and firing, apply a castable refractory cement sealant.
7.       Enjoy the benefits of your new stove, kiln, furnace, hearth or fireplace insert.