The BrickWood Castable Refractory Guide
Castable Refractory Cement: How to Cast a Pizza Oven Dome, Forge or Fire Pit
What castable refractory is, how much to order, how to mix and place it, and how to cure it without cracking. Written in plain English for first-time builders.
BrickWood Castable Refractory is a dry-mix, hydraulic-setting, high duty refractory castable rated to 2,700°F. You add water, pour or pack it into a form, and it sets hard by chemical reaction in 8 to 10 hours. It's the same castable we use to build our Cortile Barile and Mattone Cupola pizza ovens, and it works just as well for forges, fire pits, kilns and custom refractory shapes.
Building an oven? Download the FREE step-by-step pizza oven plans. They include a full materials list.
Castable Refractory: Quick Answers
- What it is: a dry, hydraulic-setting refractory cement you cast into shapes.
- Rating: 2,700°F maximum service temperature.
- Mixing: 2.5 to 3.5 quarts of clean water per 55 lb bag.
- How much for a pizza oven: 9 bags for a Cortile Barile, 14 bags for a 28-inch Mattone Cupola. See the full chart.
- Other projects: one 55 lb bag casts about 0.44 cubic feet.
- Set time: 8 to 10 hours.
- First heat: after 24 hours, held below 212°F at first so no steam forms.
- Crack control: add stainless steel needles for extra strength.
- Order: 55 lb bags, minimum order of 2.
- Shipping: FREE to the contiguous United States. Non-refundable once shipped.
Inside this guide
What Is Castable Refractory?
Castable refractory is a heat-proof concrete. Instead of laying individual fire bricks, you mix it with water and cast it into a form, so you can build a one-piece oven dome, a forge liner, a fire pit ring or any custom shape you need.
BrickWood Castable Refractory is about 45% alumina and 46% silica with a calcium aluminate binder. It's hydraulic setting, which means it hardens by a chemical reaction with water rather than by drying. That gives it real strength right out of the form and long-lasting durability under repeated heating and cooling.
BrickWood Castable Refractory Specifications
| Type | Dry mix, hydraulic setting, high duty refractory castable |
| Maximum service temperature | 2,700°F |
| Pyrometric cone equivalent (PCE) | 31 to 31½ (melts at about 3,061 to 3,090°F) |
| Water to mix | 2.5 to 3.5 quarts per 55 lb bag (9 to 12% by weight) |
| Coverage | About 0.44 cubic feet per 55 lb bag |
| Set time | 8 to 10 hours |
| First heat | After 24 hours, held below the boiling point of water at first |
| Bulk density (fired) | 125.2 lb per cubic foot |
| Apparent porosity (after 2,500°F) | 25.9% |
| Apparent specific gravity | 2.71 g/cc |
| Reheat change at 2,550°F | 2.2% linear |
| Loss on ignition | 0.68% |
| Chemistry | Silica 46.25%, alumina 44.88%, calcium oxide 4.30%, titanium dioxide 1.90%, iron oxide 1.65% |
| Size | 55 lb bag |
Strength after firing
| Fired to | Modulus of rupture (psi) | Cold crushing strength (psi) |
|---|---|---|
| 200°F | 521 | 1,241 |
| 1,000°F | 266 | 828 |
| 1,500°F | 187 | 1,110 |
| 2,000°F | 189 | 714 |
| 2,500°F | 759 | 2,302 |
Values are typical results from standard ASTM testing and can vary slightly from batch to batch.
How Much Castable Refractory Do I Need?
If you're building a BrickWood oven, order by oven. For anything else, work it out from the volume you're casting.
For a BrickWood pizza oven
| Oven | 55 lb bags | Total weight |
|---|---|---|
| Cortile Barile | 9 bags | 495 lb |
| 28-inch Mattone Cupola | 14 bags | 770 lb |
Your plans include a full materials list for your oven.
For forges, fire pits and other casting projects
Work out the volume of what you're casting in cubic feet, then divide by 0.44. Round up and add a bag for waste. The minimum order is 2 bags.
Example: a 4 ft x 4 ft slab that's 2 inches thick is 4 x 4 x 0.167 = 2.67 cubic feet. 2.67 ÷ 0.44 = 6.1, so order 7 bags.
| Bags | Total weight | Casts about |
|---|---|---|
| 2 bags | 110 lb | 0.88 cubic feet |
| 5 bags | 275 lb | 2.2 cubic feet |
| 10 bags | 550 lb | 4.4 cubic feet |
Since refractory materials are non-refundable once shipped, it's worth checking your numbers before you order.
How to Mix and Place Castable Refractory
- Gear up. Put on a NIOSH-approved dust mask, gloves and safety glasses before you open the bag.
- Stir the dry mix. Blend the dry castable in the bag or mixer so it's even before any water goes in.
- Add the water. Use 2.5 to 3.5 quarts of clean water per 55 lb bag. Start at the low end and add only what you need. Too much water weakens the castable.
- Mix thoroughly. A mortar mixer or a drill with a paddle works best. Mix until every bit is evenly wet.
- Place it right away. Pack or vibrate it into your form to work out air pockets.
- Save what's left. Return any unused dry mix to the bag and close it tight. Store it in a cool, dry place.
Never add anything to it
- Don't mix in sand, Portland cement, lime or accelerators. It's already a complete mix.
- The only add-in we recommend is stainless steel needles for crack control.
Curing and the First Fire
Castable refractory sets in 8 to 10 hours under normal conditions. Heat can usually be applied after 24 hours, but the first fires must stay low and slow. Keep the temperature below the boiling point of water (212°F) at first so trapped moisture leaves as vapor. If it turns to steam too fast, it can crack and spall the castable and lower its strength. Then build the heat up gradually over several fires. Your plans walk you through the curing fires step by step.
Stainless Steel Needles for Crack Control
Every refractory expands and contracts as it heats and cools. Our stainless steel needles mix right into the castable and act like rebar on a tiny scale, holding the castable together and helping to control cracking. We use them in every Cortile Barile and Mattone Cupola oven we build.
Safety and Handling
Like all refractory products, this castable contains crystalline silica. Breathing the dust over time can damage your lungs.
- Wear a NIOSH-approved dust mask or respirator while mixing the dry powder.
- Wear gloves, long sleeves and safety glasses. Wet castable can irritate skin and eyes.
- Mix outdoors or in a well-ventilated area, and don't eat, drink or smoke while you work.
- If castable gets in your eyes, rinse with water. Wash skin with soap and water.
- Store unopened bags in a cool, dry place.
WARNING: This product can expose you to chemicals including crystalline silica, which is known to the State of California to cause cancer. For more information go to www.P65Warnings.ca.gov.
Castable refractory mistakes to avoid
- Too much water. It makes pouring easier but leaves the castable weak.
- Air pockets. Pack or vibrate it into the form.
- Firing too hot, too soon. Steam is the number one cause of cracking and spalling.
- Ordering short. For a BrickWood oven, order 9 bags for a Cortile Barile or 14 for a 28-inch Mattone Cupola. For other projects, calculate your volume and add a bag for waste.
- Damp storage. Keep bags dry so the mix doesn't absorb moisture.
- Skipping the mask. Wear one every time you mix dry powder.
Castable Refractory: Frequently Asked Questions
How hot can castable refractory get?
It's rated to a maximum service temperature of 2,700°F. A wood-fired pizza oven reaches about 1,000°F inside, so it works well below its limit.
How much water do I mix with castable refractory?
Use 2.5 to 3.5 quarts of clean water per 55 lb bag. Start at the low end. Too much water weakens it.
How much castable refractory do I need for a pizza oven?
A Cortile Barile takes 9 bags (495 lb) and a 28-inch Mattone Cupola takes 14 bags (770 lb).
How much does one bag cover?
One 55 lb bag casts about 0.44 cubic feet. For forges, fire pits and other projects, divide the volume of your project in cubic feet by 0.44 to get the number of bags.
How long does castable refractory take to set?
It sets in 8 to 10 hours under normal conditions. Heat can usually be applied after 24 hours, kept below 212°F at first so no steam forms.
Can I use castable refractory outdoors?
Yes. It's hydraulic setting, so it hardens by chemical reaction rather than drying out. It's the castable we use for our own outdoor pizza ovens.
Do I need stainless steel needles?
They're optional, but we recommend them. The needles help control cracking as the castable heats and cools. We use them in every castable oven we build.
Can I add sand or cement to stretch it?
No. It's a complete mix. Adding sand, Portland cement or lime lowers its heat rating and strength.
Is there a minimum order?
Yes, the minimum order is 2 bags.
Can I return castable refractory?
Refractory materials are non-refundable once your order has shipped. If you're not sure how much you need, contact us before you order and we'll help.
How fast does it ship?
It's in stock and ships within 1 to 2 days, with FREE shipping to the contiguous United States.
Please Order Carefully: Refractory Materials Are Non-Refundable Once Shipped
Refractory materials are heavy, costly to ship and can't be resold once they leave our warehouse. For that reason, refractory products can't be cancelled, returned or refunded once your order has shipped.
We're happy to help you get it right the first time. If you're not sure which product or how much you need, contact us before you order and we'll walk you through it.
Shipping
FREE shipping on every refractory product to all locations in the contiguous United States (the lower 48 states). Orders ship by ground carrier or commercial freight, depending on size, and freight carriers will call to schedule delivery. Please leave a phone number we can reach you at in the order notes.
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Cast your oven with the castable we use
55 lb bags at the top of the page. Minimum order of 2, and shipping is FREE.
Not sure how much you need? Our team has helped thousands of backyard builders since 2013, and we're happy to help you get it right before you order.
Specifications are typical values from standard ASTM testing and can vary slightly from batch to batch.
