DIY castable refractory

[mikku]

Re: DIY castable refractory

hi, meaning I understand and agree.

[stonecutter]

Re: DIY castable refractory

Hello Stonecutter,
You misinterpreted my comment, it was meant as "when have you ever had to specify "sand as aggregate" when you order concrete?

No, I understood.... My answer was the long way to say why I have never specified sand for a concrete mix.

[mikku]

Re: DIY castable refractory

Earlier this year I worked on a commercial project that used 10,000 cu yards of concrete...does that count?

It's a given that sand is added to a concrete mix.....without it, the concrete would be extremely weak. Think of perlite mixed with portland...same concept. Likewise, if you order a grout mix to pump into the cells of a block wall, you don't have to order sand. It's a component of concrete ( and grout) but still an aggregate. One reason you don't spec sand when ordering concrete is because it's is generally understood that rounded sand is junk, and graded angular sand is what is needed, so you don't make junk concrete. That's what slump tests can help avoid, and what a core sample will confirm. You would be correct in assuming rounded sand makes poor concrete. The same goes for mortar....if anyone else reading this cares to know.

There are reasons different aggregate sizes are used. I'll let this link do the talking.

PCA

Hello Stonecutter,
You misinterpreted my comment, it was meant as "when have you ever had to specify "sand as aggregate" when you order concrete?

I've poured a little concrete in my life as well- had the record for a single day pour while building a taconite plant. We had trucks pulling up to the forms and tailgating straight in--full blast! --trucks were pouring the perimeter, with pumps filling he middle- 8' thick base-40 foot by 120 foot. This was the sub-base for some ball mills in the fine crusher building! Had to put thermal sensors into the slab and use firehoses to spray down the concrete when it started heating up too much!

But I am still not a mason, or a concrete guy---only a carpenter that sometimes does odd forms.

[mikku]

Re: DIY castable refractory

There are standard specifications for the sand used in concrete, grout, and mortar. There are also applicable standards for the larger aggregates, as well as for the cementious components and any additives, as well as the control and testing of the sampling.

Concrete and mortar are not the same, and the specifications reflect this fact. Concrete is generally specified by tensile and compressive strength, while mortar is normally specified by bond and compressive strength, BUT using entirely different methods of specification and testing.

A castable product is an entirely different animal, and adding a refractory requirement adds degrees of complication. It is not practical for an individual to buy the components of a castable refractory mix, as they are not normally sold in small amounts. If you need tons, no problem, if you need a couple hundred pounds, good luck.

That is for materials that are designed to be used at high temperature, as a monolithic cast product, not to be confused with a mortar for refractory units.

You could DIY a refractory castable, but the life-cycle will be short using commonly available materials, and certainly not worth the effort of building a decent mold.

Compare it to a home hot-rod builder deciding to cold mold his own body panels for his '33 ford. It CAN be done, but why why would you when they are already available and will perform better than anything you will produce for 10x the money and effort as a one-off user.

Are you actually agreeing with me? A new day! holy smokes! shucks! wow!

For your car example, I had a friend in Hibbing - (Barney) -a fabulous engineer, really bright guy who could do anything--practically! When I was restoring my 69 XKE, he was working on several 120 and 150's--because some of the parts were difficult to come buy, he built an English Wheel to fabricate the metal parts! Also was machining new suspension parts! His warehouse was full of Jaguars in all different conditions. I do not know if he got any of them completely finished---last time I talked to him, I drove up to his offices with my completed build along with a bunch of trophy's from that summers classic car competitions in the tri-state area. Never got less than third place in the sports car class--even when up against some of the big buck professional restorations!

Love cars! Ovens --something to pass the time and exercise my gray matter once in a while!

[Tscarborough]

Re: DIY castable refractory

There are standard specifications for the sand used in concrete, grout, and mortar. There are also applicable standards for the larger aggregates, as well as for the cementious components and any additives, as well as the control and testing of the sampling.

Concrete and mortar are not the same, and the specifications reflect this fact. Concrete is generally specified by tensile and compressive strength, while mortar is normally specified by bond and compressive strength, BUT using entirely different methods of specification and testing.

A castable product is an entirely different animal, and adding a refractory requirement adds degrees of complication. It is not practical for an individual to buy the components of a castable refractory mix, as they are not normally sold in small amounts. If you need tons, no problem, if you need a couple hundred pounds, good luck.

That is for materials that are designed to be used at high temperature, as a monolithic cast product, not to be confused with a mortar for refractory units.

You could DIY a refractory castable, but the life-cycle will be short using commonly available materials, and certainly not worth the effort of building a decent mold.

Compare it to a home hot-rod builder deciding to cold mold his own body panels for his '33 ford. It CAN be done, but why why would you when they are already available and will perform better than anything you will produce for 10x the money and effort as a one-off user.

[stonecutter]

Re: DIY castable refractory

When is the last time you ordered ready mix concrete? Usually when you call in the order, you will tell them the location of your jobsite, your name, when you need it, the slump, which PSI mixture you want, temperature conditions, sometimes test cones, and the aggregate size.

In this instance, they are asking if you want: pea stone, possibly 3/4 rock, or larger. Rarely will anyone ask which kind of sand you need. Around here, there are two different sands usually in the mixture- one is "yama tsuna" or mountain sand; the other is "kawa tsuna" or river sand. I would imagine the difference being that the river sand has rounded particles, compared to the mountain sand being produced by some crushing and multiple screenings.

Not being a mason, I have never thought of sand as aggregate. Thank you for making this point clear.

Earlier this year I worked on a commercial project that used 10,000 cu yards of concrete...does that count?

It's a given that sand is added to a concrete mix.....without it, the concrete would be extremely weak. Think of perlite mixed with portland...same concept. Likewise, if you order a grout mix to pump into the cells of a block wall, you don't have to order sand. It's a component of concrete ( and grout) but still an aggregate. One reason you don't spec sand when ordering concrete is because it's is generally understood that rounded sand is junk, and graded angular sand is what is needed, so you don't make junk concrete. That's what slump tests can help avoid, and what a core sample will confirm. You would be correct in assuming rounded sand makes poor concrete. The same goes for mortar....if anyone else reading this cares to know.

There are reasons different aggregate sizes are used. I'll let this link do the talking.

PCA

[mikku]

Re: DIY castable refractory

It's not only government opinion (only one of those links had gov affiliation), classifying sand as an aggregate is accepted and understood by masons and builders using cementitous materials.

When is the last time you ordered ready mix concrete? Usually when you call in the order, you will tell them the location of your jobsite, your name, when you need it, the slump, which PSI mixture you want, temperature conditions, sometimes test cones, and the aggregate size.

In this instance, they are asking if you want: pea stone, possibly 3/4 rock, or larger. Rarely will anyone ask which kind of sand you need. Around here, there are two different sands usually in the mixture- one is "yama tsuna" or mountain sand; the other is "kawa tsuna" or river sand. I would imagine the difference being that the river sand has rounded particles, compared to the mountain sand being produced by some crushing and multiple screenings.

Not being a mason, I have never thought of sand as aggregate. Thank you for making this point clear.

[stonecutter]

Re: DIY castable refractory

My belief is your first attempt at a build
whether its a pizza oven, wooden box, or oil painting isn't going to be as good
as your second or 10th attempt.

If you want perfection hire someone who has done it many times and has chosen to make a career from it. They say it takes 1000 hours to become proficient at anything.

Bridges are mission critical. If you screw it up people die and millions of dollars are wasted.
If a pizza oven is screwed up, whats the worse that can happen? The oven that takes too long to heat up, heats up unevenly, cools too quickly, or structurally fails. All bad things, but relatively not in the grand scheme of things. Its not a bridge.

Just making light of what seems is turning out to be a silly internet squabble.

Still unsure why people don't think that the homebrew stuff wouldnt work for a castable. It is afterall what is used to mortor the firebricks in a firebrick oven. If it didnt work all
firebrick ovens using the homebrew for mortaring bricks would have failed.

I personally don't view this as a squabble, unless people get over sensitive over certain comments and start lashing out....discussion is a way to get information, good or bad IMO. That way, anyone that is considering a cast oven can make a better decision when researching different products. I for one, would like to see this stay productive...I am considering making a cast oven just for haha's. To the point......

There is a big difference between using fire mortar as a castable vs using it as a binder for masonry units. For one, the portland has poor refractory qualities, which effect the longevity when it is continually subjected to thermal shock.

Also, an oven built with refractory units is not as dependent on the material used to bind the courses, as a cast oven made of the same material. I hold the view that the mortar in a brick oven functions as a network of gaskets and a web of masonry that assists in strengthening the structure, rather than 'glue' holding the structure together. This is a principle of all forms of unit masonry building.

To put it simply, a dome cast with fire mortar will not last that long compared to refractory material....will it work? Yes...you can even make an oven out of an elephant flop or clay or a trashcan which will function just fine. How long will it last? Depends on the how it is built, used, the exposure...infinite variables. Is that good enough for everyone that wants to cast an oven? Well.......


What that comes down too, is what the individual builder or user wants as a final product, and the variables that are unique to them. What is right for some, isn't for others. Material availability will also effect what to use for the build....as seen many times on this forum.

Certain material make a better oven....I feel this is the root of the discussion, not if something will work or not.

Oh, and while I agree that every attempt will help a person improve their skill, building something to perfection will never be achieved by anyone in this lifetime. Likewise, with the bridge comparison...building an oven isn't like launching a man to the moon, or defusing a bomb, or jumping the grand canyon on a motorcycle...apples and oranges. Unless I missed something and there is a bridge building thread...which is fine with me, I do that with masonry too.

[michelevit]

Re: DIY castable refractory

My belief is your first attempt at a build
whether its a pizza oven, wooden box, or oil painting isn't going to be as good
as your second or 10th attempt.

If you want perfection hire someone who has done it many times and has chosen to make a career from it. They say it takes 1000 hours to become proficient at anything.

Bridges are mission critical. If you screw it up people die and millions of dollars are wasted.
If a pizza oven is screwed up, whats the worse that can happen? The oven that takes too long to heat up, heats up unevenly, cools too quickly, or structurally fails. All bad things, but relatively not in the grand scheme of things. Its not a bridge.

Just making light of what seems is turning out to be a silly internet squabble.

Still unsure why people don't think that the homebrew stuff wouldnt work for a castable. It is afterall what is used to mortor the firebricks in a firebrick oven. If it didnt work all
firebrick ovens using the homebrew for mortaring bricks would have failed.

[stonecutter]

Re: DIY castable refractory

We're not building a bridge- we're building an oven.

Anyone can build an oven...and do it with all kinds of material. I think the discussion is about the quality of the material used.

And as simple as oven building is, it's very easy to screw it up. I'm not implying you did in anyway, just making an observation.

[stonecutter]

Re: DIY castable refractory

Stonecutter,
If you were doing a project that required a castable refractory, would you use this homebrew recipe or buy the real stuff?

I have never given it much thought, mainly because I think unit masonry makes a superior oven.

But to answer your question, I would say it depends on who the oven is for.

For myself, I would definitely use a material I could make at home. My ratios wouldn't be quite the same as the ones posted here, for one, I would reduce the amount of Portland. I would probably make several different mixes before I moulded a dome.

For a client, I would use a bagged refractory product, something with a good reputation for quality. Unless they insisted on using a home made fire mortar to save a buck...then they would get a disclaimer and explanations of the differences, with pros & cons. And, I would only use it if I had a successful ratio and had tested it myself.

I would probably try to convince them to build with brick in either scenario anyway.

[stonecutter]

Re: DIY castable refractory

I guess you proved the point. What a person "me" perceives as aggregate and what the government describes as aggregate are not the same. I guess the government is right. Sounds like a wise ass answer, but it isn't meant to be. Thanks for taking the time to present information that is more than someone's opinion.

It's not only government opinion (only one of those links had gov affiliation), classifying sand as an aggregate is accepted and understood by masons and builders using cementitous materials.

[mikku]

Re: DIY castable refractory

Cobblerdave,
If you were doing a project that required castable refractory would you use this recipe or would you buy the real stuff?

[mikku]

Re: DIY castable refractory

Stonecutter,
If you were doing a project that required a castable refractory, would you use this homebrew recipe or buy the real stuff?

[mikku]

Re: DIY castable refractory

Some useful links

pg 11 Aggregate Specifications
and Requirements

Construction aggregate

Pg 8Carbonating and Hydraulic Mortars

I guess you proved the point. What a person "me" perceives as aggregate and what the government describes as aggregate are not the same. I guess the government is right. Sounds like a wise ass answer, but it isn't meant to be. Thanks for taking the time to present information that is more than someone's opinion.