Home brew concrete and cast-in-place concrete.

[stonecutter]

Re: Home brew concrete and cast-in-place concrete.

Actually pasted the stone and the hearth locations with the sandless portland/lime mix--sucked in like painting latex on a hot day.

Common effect...even if you pre-wet the stone. This will still help with a good bond...you need to make sure that you have enough solids in your slurry though.

[mikku]

Re: Home brew concrete and cast-in-place concrete.

Stonecutter,
Thank you for the wealth of information. I'm going to print out your post so I don't have to check into the forum to reference the information. I failed to mention that I did use a latex bonding agent on the surface of my concrete base prior to painting the slurry.

The 15 minute wait period was just to look at things, looked under the edge and saw voids in places, actually attempted to force some additional mortar beneath.. I just decided, if I leave this sit too long--I will get an initial bond and make it difficult to remove, longer yet and I would have to destroy the stone to get it off. That is why the operation was aborted.

I will keep in mind all the things you said. I should have considered this stone just a big piece of tile (unglazed) in the first place. It is a challenge working with something as porous as this is. So far no damage done, and some good experience gained.

Thank you for taking the time to explain technique as well as setting conditions for working with this stone. Many professionals tend to keep what they have learned by experience as a guarded secret --so amateurs will fail! They don't realize that the amateur must learn by experiencing the same things --and words are only guides, doing is where they learn---and that takes a lot of time!
Being good at it takes a lifetime.

[stonecutter]

Re: Home brew concrete and cast-in-place concrete.

Many professionals tend to keep what they have learned by experience as a guarded secret --so amateurs will fail! They don't realize that the amateur must learn by experiencing the same things --and words are only guides, doing is where they learn---and that takes a lot of time!
Being good at it takes a lifetime.

I don't think pro's hold back so others fail...well, maybe a few of the petty ones do. But then, if that's the case, they aren't much of a pro anyway. And it's up to the amateur to pursue the knowledge they are seeking, not the job of the pro to give it all away. If you want it bad enough, all the information you need is out there.

when you are trying to learn about something in masonry, it's no different than anything else in this world. Look for consistency, when in doubt, stick to proven methods and never,ever be afraid to fail..it's the best teacher. And remember that nobody in the trade/craft owes you even one word of information about technique, methods or anything else.

I'm not trying to imply you feel this way, but I guess this was my time to vent this out. It's also my perspective on a point I have seen before, so take it with a grain of salt....it's just my opinion.

Moving on......

[david s]

Re: Home brew concrete and cast-in-place concrete.

I'm too old to benefit from keeping secrets and prefer to share anything I've learned from experience. This oven building thing is fraught with hurdles and pitfalls. Might as well share to help others to the glorious path of a good functioning oven. There are so many ways to get there it makes the subject fascinating. Might not always be right, but if it promotes healthy discussion then surely that advances knowledge.

[Tscarborough]

Re: Home brew concrete and cast-in-place concrete.

Secrets don't mean much, none of it is really secret, the difference is manual skill, and the obstacle is repeating the same thing over and over, when a good search will generally suffice.


I answer any question, but do not offer technique.

[stonecutter]

Re: Home brew concrete and cast-in-place concrete.

Let's bring this thread back to concrete.....

Im planning to do some cast pieces on my oven using a hand pressed method. Anyone do this before? I've done a couple pieces, and I'll put some pics up later.

[mikku]

Re: Home brew concrete and cast-in-place concrete.

I just want to say something about this, because similar expressions have been made on other forums and blogs I have read. Indulge me while I jump on my soapbox.....

You have to realize, guys like me depend on the knowledge we have to earn a living...and not in the obvious sense of that statement either. Not all professionals take the time to learn proper technique or educate themselves in the particular trade or craft they practice. For the ones that do, much of what is learned has come at a cost...not just financially, but mentally and physically. A good tradesman keeps striving to learn, succeeding and failing, while assuming all the responsibility and cost of acquiring this knowledge. Professionals do realize amateurs must learn by experience..that's why some don't want to give away what they had to earn...paying your dues, so to speak.

You have to take this into account. It may be difficult for some to just put hard earned knowledge out there, for anyone to take and get no return on it, other than personal satisfaction that you are helping somebody out. For some, that may be why they only lurk or the comments are limited...and that is not wrong. That doesn't make them bad or selfish. I'm speaking from both sides...I never commented much in the past either, but I have come to enjoy helping out and offering advise if I think I can. Have I benefited financially? Nope...not a cent. But who knows? That's not why I participate anyway. I just really enjoy doing my trade and talking about it with others too.

I don't think pro's hold back so others fail...well, maybe a few of the petty ones do. But then, if that's the case, they aren't much of a pro anyway. And it's up to the amateur to pursue the knowledge they are seeking, not the job of the pro to give it all away. If you want it bad enough, all the information you need is out there.

I'll say this in conclusion...when you are trying to learn about something in masonry, it's no different than anything else in this world. Look for consistency, when in doubt, stick to proven methods and never,ever be afraid to fail..it's the best teacher. And remember that nobody in the trade/craft owes you even one word of information about technique, methods or anything else.

I'm not trying to imply you feel this way, but I guess this was my time to vent this out. It's also my perspective on a point I have seen before, so take it with a grain of salt....it's just my opinion.

Moving on......

I agree, with what you say!
I know where you are coming from! Been there!

[david s]

Re: Home brew concrete and cast-in-place concrete.

Let's bring this thread back to concrete.....

Im planning to do some cast pieces on my oven using a hand pressed method. Anyone do this before? I've done a couple pieces, and I'll put some pics up later.

There are a few things to consider.
1. The stuff is expensive so you don't want to waste it.
2. It goes off fast (particularly in hot weather- use chilled water) so don't mix up too much in one batch.
3. Add stainless steel needles, at least 2% by weight, for reinforcing.
4. Much stronger and stable under firing if you can fire the casting to 1000 C if practicable.
5. Excess water in the mix weakens it. Water reducers easily create separation.
6.the stuff is very thixotrpic.
7. Use vibration when placing, or mash it in, to reduce voids.
8. Does not require extended curing, should be covered but 24 hrs is sufficient.
9. There are many types of castable refractories available, seek advice from your supplier.
10. Oil your moulds.

[stonecutter]

Re: Home brew concrete and cast-in-place concrete.

There are a few things to consider.
1. The stuff is expensive so you don't want to waste it.

2. It goes off fast (particularly in hot weather- use chilled water) so don't mix up too much in one batch.
3. Add stainless steel needles, at least 2% by weight, for reinforcing.
4. Much stronger and stable under firing if you can fire the casting to 1000 C if practicable.
5. Excess water in the mix weakens it. Water reducers easily create separation.
6.the stuff is very thixotrpic.
7. Use vibration when placing, or mash it in, to reduce voids.
8. Does not require extended curing, should be covered but 24 hrs is sufficient.
9. There are many types of castable refractories available, seek advice from your supplier.
10. Oil your moulds.

1.Tell me about it. but I use a local company if I use a bagged mix or I just make my own, which is much, much cheaper. When I mix bagged concrete, I only mix what I need.
2.The product I use behaves pretty close to standard concrete. Cold water, yeah..just like making mortar in hot weather too. Clean water is just as important too.
3. SS needles not necessary when I use the bagged mixes...highly engineered with polymers and fibers. When I make my own I used galvanized wire screen and polymer/acrylic additives.
4. This concrete is not for the oven chamber or anywhere near the heat...it is for capping the dry stone base I built.
5. Excess water is bad for any mortar or concrete mix. Only add enough to hydrate the cement or mortar accordingly.
6. Doesn't really apply to this application.
7. Voids are the point with the hand pressed technique, it is how you create the veining effect. Only about a third-half the form is pressed, the rest is filled with a flowable mixture ( at least this is how I have seen it done and the way I have done it myself.)
8. Any concrete should be covered when slow curing is needed or to prevent excessive evaporation of water.
9. I would be interested in doing a cast refractory dome sometime in the future!
10. I always use melemine or pvc trim for my forms and I always use a release agent...though simply cleaning these types of materials is usually enough to prevent sticking.

I think your list was good, but you might be thinking I am talking about cast refractory...I'm not. Pics coming soon.

[david s]

Re: Home brew concrete and cast-in-place concrete.

Sorry, when you said you wanted to make a casting for your oven I assumed it was for the hot part. Forget everything On my list except 7 and 10. If you don't have a vibrator probe an orbital sander without the paper, held to the outside of the mould works reasonably well.With normal concrete remove from the mould after 24hrs and keep wet, wrap in plastic for a week.

[stonecutter]

Re: Home brew concrete and cast-in-place concrete.

Forget everything On my list except 7 and 10. If you don't have a vibrator probe an orbital sander without the paper, held to the outside of the mould works reasonably well.

Well... like I said, a release agent applied to my forms, even though it doesn't need it if the form is clean. But you don't vibrate the form when you do this technique. If you did, it would defeat the whole purpose of hand pressing the concrete into the form..and that is to create voids that are later filled with a contrasting colored slurry.

Incidentally, I have tried the orbital sander trick before, but I prefer a sawzall (reciprocating saw) with the blade removed. It is a little more aggressive and did the job better than the sander .( IMO)

[david s]

Re: Home brew concrete and cast-in-place concrete.

If you want voids then remember that they weaken the casting. Try making the mix fairly stiff and do a thin layer, then fill the rest with normal consistency. Thanks for the vibrating reciprocating saw idea, I shall try it.

[stonecutter]

Re: Home brew concrete and cast-in-place concrete.

If you want voids then remember that they weaken the casting. Try making the mix fairly stiff and do a thin layer, then fill the rest with normal consistency. Thanks for the vibrating reciprocating saw idea, I shall try it.

1.Tell me about it. but I use a local company if I use a bagged mix or I just make my own, which is much, much cheaper. When I mix bagged concrete, I only mix what I need.
2.The product I use behaves pretty close to standard concrete. Cold water, yeah..just like making mortar in hot weather too. Clean water is just as important too.
3. SS needles not necessary when I use the bagged mixes...highly engineered with polymers and fibers. When I make my own I used galvanized wire screen and polymer/acrylic additives.
4. This concrete is not for the oven chamber or anywhere near the heat...it is for capping the dry stone base I built.
5. Excess water is bad for any mortar or concrete mix. Only add enough to hydrate the cement or mortar accordingly.
6. Doesn't really apply to this application.
7. Voids are the point with the hand pressed technique, it is how you create the veining effect. Only about a third-half the form is pressed, the rest is filled with a flowable mixture ( at least this is how I have seen it done and the way I have done it myself.)
8. Any concrete should be covered when slow curing is needed or to prevent excessive evaporation of water.
9. I would be interested in doing a cast refractory dome sometime in the future!
10. I always use melemine or pvc trim for my forms and I always use a release agent...though simply cleaning these types of materials is usually enough to prevent sticking.

I think your list was good, but you might be thinking I am talking about cast refractory...I'm not. Pics coming soon.

Voids are fine, check #8 for the method....it's done with success everywhere.

[stonecutter]

Re: Home brew concrete and cast-in-place concrete.

Make that #7..stupid phone

[david s]

Re: Home brew concrete and cast-in-place concrete.

Stonecutter,
I think Gulf has done this technique, and it is well documented with pics. Try his thread
Mississippi 44"
Dave