How to make High-Temperature Mortar with a low-cost 4 material blend (Silica Sand, Portland Cement, Fireclay and Lime)

Construction Materials Needed to Build a BrickWood
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High-Temperature Mortar – Low-Cost 4 Material Blend

High-Temp Mortar is basically the glue that holds all the brick and block together on all wood-fired ovens (and fireplaces). This simple and inexpensive high-temperature mortar recipe is used the world over. From Australia to Zimbabwe… we all make it the same way.

In a clean wheelbarrow or mixing tub, thoroughly dry-mix the (4) materials listed below in a 3:1:1:1 ratio.

  • 3 Parts Silica Sand
  • 1 Part Hydrated Lime
  • 1 Part Fireclay
  • 1 Part Portland Cement

Silica Sand –

Silicon is the 2nd most abundant element in the earth’s crust – so it should be easy to find bags of Silica Sand near you - right? Well, not so much. Pure Silica Sand (which is almost like powder) can be elusive. Some Landscape Supply Stores carry this item – some don’t. But almost EVERY Pool Supply store does (it’s pool filter sand) Google Maps

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ONLY USE THESE TYPES OF SAND
Pool Filter Sand
Fine Sand
Fine Silica Sand (All mesh sizes)
(The Finer the Grain the Better)

DO NOT USE -
All-Purpose Sand
Concrete Sand
Course Sand
Mason Sand
Medium Sand
Mortar Sand
Multi-Purpose Sand
Natural Sand
Play Sand
Sand / Topping

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Fire Clay / Mortar Clay / Bricklayers Clay -

Pure Fire Clay, Mortar Clay and/or Bricklayers Clay is an organic material that has been dried and turned into a powder form. It is usually a brackish red / brown in color or it could be white / grey. The texture is like baking flour or baking soda.

These powdered clays can be found at most Masonry and Landscape Supply Stores for about $10 - $15 a bag. You may find a bag at a Big Box store, but it’s unlikely. And you will never find fire clay at a Refractory Materials dealer.

If you can’t find a bag near you, be sure to check with your local Ceramic Supply Google Maps and they can order a bag of Fire clay for you.

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Hydrated Lime / Powdered Lime / Construction Lime -

This is the product that confuses some of our customers. It is NOT granulated Lime that is sold in the plant section at Home Depot or Lowes but a white and fluffy material that looks and feels like powdered sugar. It is used in the masonry and landscape industry – but it also used in the Plant Nursery industry in 50lb bags.

If you are unable to find this product at your Landscape Supply, call a local Plant Nursery and they can order lime for you - Google Maps

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Portland Cement -

Portland Cement is sold at EVERY Big Box and most Mom & Pop hardware and lumber stores. It’s a staple in the construction industry… and it’s cheap! Just make sure you buy pure Portland Cement – NOT PORTLAND CEMENT WITH LIME PRE-MIXED INTO IT. That will throw-off the mixture of the high-temp blend.

PLEASE NOTE - THIS IS A SCRATCH RECIPE FOR HIGH-TEMPERATURE MORTAR. NO MATTER WHAT YOU READ ONLINE OR WATCH ON YOUTUBE, THIS BLEND CAN NOT, AGAIN, CAN NOT BE USED AS A HOMEMADE CASTABLE REFRACTORY. THIS RECIPE IS TO BE USED AS A MORTAR ONLY.

Be sure to Download & Print this High-Temperature Mortar Recipe!
BrickWood Ovens Installation Instructions

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How is the High-Temp mortar (Factory Blend) different from the 4 Ingredient High-Temp mortar I can make myself?
Can I use Pre-Mixed High-Temp Mortar on a Mattone Barile Grande fire brick pizza oven kit?
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Is the 3-1-1-1 by weight or volume?

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Volume.

I like to use empty Costco coffee cans as a good way to measure.

The leftover 100% Columbian coffee grounds are good for STRONG mortar!

How To Make High Temperature Mortar
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By volume. (Though my mind also goes to the object of this exercise and I do my pizza dough by weight.) Unlike flour, these are all fairly stable materials that will settle out the same way no matter how many times you scoop up a measure. That’s versus flour, which compresses or expands depending on how much air you mix into it.

How much material do you need?

Your oven’s installation instructions will tell you how much premixed dry high-temp mortar you need. If you are planning to use the 4-material blend, and are thinking “How much of each of these materials do I need?” (like I was), here’s a cheat sheet to figure it out:

Take the total quantity of dry premix specified for your build and divide it by 6 (which is the total number of parts you need in the mix ratio).

Then, multiply the result by the number of parts needed for each ingredient. (Which requires only one multiple, for the sand, because every other ingredient is just one part!)

For my build, the Mattone Barile Grande, the instructions specfiy about 400 pounds of dry pre-mix. So:

400 ÷ 6 = 66⅓ (or 66.667) pounds

So the approximate quantities of dry ingredients I need are:

Silica Sand: 3 [parts] X 66.67 = 200 pounds
Fireclay, Lime, and Portland Cement: 1 [part] X 66.67 = 66.67 pounds of each ingredient

Of course you’ll need to round up to the closest bag size they sell, but this should also account for any differences in volume among the different materials.

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Hi, person, and welcome to the BrickWood forums.

This question kinda takes us beyond the purpose for these forums, but I can address it in general terms.

The discussion about high-temp mortar is in relation to ovens that are expected to reach temperatures of up to 1,000°F and retain that heat for a long time.

Your fire pit project needs concrete, not refractory materials. In my humble opinion, those would be 9 times of overkill for what you are planning.

The key to a successful fire pit is digging and replacing the subsoil with aggregate materials (for both safety and stability). Your goal is to produce immediate direct heat for grilling and the very satisfying look of an open flame. High-temp concrete should be more than enough for that purpose.

Again IMHO, you’d be better off redirecting your $$$ toward making sure you have a safe area under the bowl and a really nice, stable grate for any grilling you plan to do on it.

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Here’s a quick read (which you may already have seen) from Bob Vila’s web site. It’s focused on safety and durability, and some materials to avoid. (Compressed concrete blocks, for example, are on a list of materials not to use because they can trap steam and eventually explode.)

If you are building a raised structure, you can use standard concrete blocks and apply a decorative veneer to them. If you are concerned about heat damage, it would be fine to use the high-temp mortar recipe for those blocks, but I don’t think it will add much to your build.

The big difference between a fire pit and a wood-fired oven is that the fire pit radiates most of its heat immediately. Infrared energy warms the inner walls, and the pit itself will absorb heat from direct contact with the fuel. The oven is designed to retain and concentrate heat energy rather than radiating it. It has to withstand much higher temperatures, and ideally it would do that indefinitely. Ordinary brick and concrete would deteriorate and crumble through the heating and cooling cycles of an oven, so that’s why the firebrick and special mortar are used.

I do wish you the very best with your project, and hope you’ll let us know how it turned out!

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