Jake's In Mass (Started July 3, 2011)

[PizzaIdiot]

Re: Jake's In Mass (Started July 3, 2011)

When I checked the density, it's about 198#/cubic foot.
The bags are also about the same size the 80# concrete mix, which is about 0.59 cubic feet.

So how many bags of cement did you wind up using?
In any case, it looks great.

I hope a few other people will weigh in on this.

-jeff

[rodeair]

Re: Jake's In Mass (Started July 3, 2011)

I did an insulation layer of vermicrete 4.5 inches thick. The calculations showed I would need 8.5 cuft. I ended up needing 10 cuft of vermiculite and (2) 94# bags of portland which gave me a 5:1 mix.

Leigh

[PizzaIdiot]

Re: Jake's In Mass (Started July 3, 2011)

Leigh
Thanks for the timely input. Maybe I'm being too technical in my thinking, but I would have thought yours was a 10:1 (assuming 1 94# bag is 0.5 cubic feet).
-jeff

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

So, I also took a 94# bag of portland to be 1 cuft. A 80lb bag of ready mix is .66cuft, the 94 lb bag is slightly larger.

So, for each 20# bag of vermiculite, about 4.4 CUFT each, I use a little less than 1 bag of portland cement. That gave me somewhere between 4:1 and 5:1 at 5" thick.

Overall the mix looked just about right, it is strong, but airy.

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

Also googling around, Dan the brick Man says....
"a bag of portland cement is exactly 1 cu. ft. ...to this you would add 2 cu. ft. of sand and 3 cu. ft. of gravel... a six bag mix of concrete (3500 psi mix) would contain 6 bags of portland...so roughly 1/6th of a cu yd..."

[Hank10746]

Re: Jake's In Mass (Started July 3, 2011)

HI
Found this at Portland Cement Association.

Example: Assume that the proportions will be made based on one part being a cubic foot (this is convenient since a 94 lb. bag of cement is 1 cubic foot of bulk material). For a 3/4" maximum coarse aggregate, the mixture would be 1 part Portland cement, 2 1/2 parts sand, 2 1/2 parts coarse aggregate, and 1/2 part water. The sum of the parts is 6 ?. In general the final volume of concrete produced will be approximately 2/3 of the sum of all the volumes included in the mixture. Therefore the approximate volume of this concrete mixture is 4.3 cubic feet. There are 27 cubic feet in a cubic yard so we divide 27 by 4.3 giving 6.2 batches for a cubic yard. Plan on making 7 batches to assure that you will have more than enough material at the start of the job.

Hope it helps in your calculations.

One thing they are not talking weight but volume. So I know that I can get more volume of cement on a shovel than I can get aggregate depending on how wet it is sand can be equal or more than the first two. So it would probably be best to use a small bucket to mix equal parts especially the water as I can get very little on the shovel. In my case it will probably be a measuring cup.

[PizzaIdiot]

Re: Jake's In Mass (Started July 3, 2011)

Thanks Hank and Jake. I did some googling too. It's not that I don't believe people here, I just try to understand the differences I'm finding.

I found this at Concrete Technology | Frequently Asked Questions (FAQs): Unit Weights | Portland Cement Association (PCA)and this http://www.adhf.co.uk/portland.pdf and they addressed all the concerns I've run up against. It covers the range of density values I've found and what people are saying here.

Q: What are the unit weights (densities) of cement and concrete?

A: Cement: Cement (finely ground gray or white powder used to bind concrete mixtures) weighs between 830 kg/m3 and 1650 kg/m3 (52 lbs/ft3 and 103 lbs/ft3) depending on its handling. The weight of cement that has been pneumatically loaded into a cement silo may be as low as 830 kg/m3 (52 lbs/ft3), while cement that has been stored for a period of time exposed to vibration may be as heavy as 1650 kg/m3 (103 lbs/ft3). It is standard practice to consider a 94 lb bag of cement to be one cubic foot when freshly packed.

Why can't they just put 1 cu ft on the bag ? ! ? UPDATE: They did - I just didn't see it -ARG

I've spent the past week trying to make sure I get my next step right. So with everyone's input I can finally feel good about mixing my 12 cf of perlite with 2 93# bags of cement (in 4 batches!).

Thanks for y'all's patience.

-jeff

[rodeair]

Re: Jake's In Mass (Started July 3, 2011)

Jeff, not to beat a dead horse, density is not necessarily the same as weight. If you use the homebrew, you'll find hydrated lime is very light compared to sand. A cubic foot of each would be very different as far as weight. Your mix will turn out to be a 6:1 ratio. You'll find it's easier to moisten the perlite before you add the premixed slurry of portland, at least it was for me. Good luck!
Leigh

[PizzaIdiot]

Re: Jake's In Mass (Started July 3, 2011)

Leigh - Since Density = Mass / Volume, I thought if I had the mass and the density, I could calculate the volume. Seemed simple enough when I bought the cement - LOL.

Well I'm off to create the forms for the perlcrete and if all goes well, I'll get that poured today too.

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

Good luck.

[Hank10746]

Re: Jake's In Mass (Started July 3, 2011)

Thanks Hank and Jake. I did some googling too. It's not that I don't believe people here, I just try to understand the differences I'm finding.

I found this at Concrete Technology | Frequently Asked Questions (FAQs): Unit Weights | Portland Cement Association (PCA)and this http://www.adhf.co.uk/portland.pdf and they addressed all the concerns I've run up against. It covers the range of density values I've found and what people are saying here.

Q: What are the unit weights (densities) of cement and concrete?

A: Cement: Cement (finely ground gray or white powder used to bind concrete mixtures) weighs between 830 kg/m3 and 1650 kg/m3 (52 lbs/ft3 and 103 lbs/ft3) depending on its handling. The weight of cement that has been pneumatically loaded into a cement silo may be as low as 830 kg/m3 (52 lbs/ft3), while cement that has been stored for a period of time exposed to vibration may be as heavy as 1650 kg/m3 (103 lbs/ft3). It is standard practice to consider a 94 lb bag of cement to be one cubic foot when freshly packed.

Why can't they just put 1 cu ft on the bag ? ! ? UPDATE: They did - I just didn't see it -ARG

I've spent the past week trying to make sure I get my next step right. So with everyone's input I can finally feel good about mixing my 12 cf of perlite with 2 93# bags of cement (in 4 batches!).

Thanks for y'all's patience.

-jeff

HI
No problem. The best way to go about it is to use a equal volume if it calls for 5 to 1 use a 1 gallon container and use 1 gallon cement to 5 gallons of perlite. If you use 1 quart do the same but use the same size for both. Weight is not the problem volume is. a shovel is not accurate. It will not be exact but close enough for government work

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

Jeff, how did it go this weekend? Hope your insulation layer worked out for you.

I was not able to do much this weekend, it was my son's 10th birthday. However the kids did want a fire....

I have my wife picking up final refractory brick samples from the two local suppliers I have near me. Both are within 10 minutes of the house. I'll post some photos of the choices I have soon.

[PizzaIdiot]

Re: Jake's In Mass (Started July 3, 2011)

Jake, thanks for asking.
Your grass is soooo green - I'm jealous. It's been soooo hot and dry here.

I got the 5" perlite layer taken care of. Thanks to someone on here that recommended the 10:x:3 ratio of perlite, portland cement and water. Knowing how much water was key in getting it done quickly (2h for 10 cu.ft.).

Here's a link to the pix.

http://www.fornobravo.com/forum/8/je...r-16011-2.html

I was reading Dino's build and he used 1/3 cut bricks. I really like that option even though it means more cuts. It will get the right vertical angle and minimize the homebrew needed. Have you looked at/thought about this?
I'm trying to find out how one determines when to move from 1/2 bricks to third bricks.

I've also decided not to do the soldier course. I'm going to do a sailor's course, where the first course is flat and level with the floor and go up from there. If, and that's a big if, if it will crack at the soldier course, this seems less likely to do so with a sailor's course. From the inside, they both look the same.

-jeff

[jatsrt]

Re: Jake's In Mass (Started July 3, 2011)

So, I too have looked at many, many, many different variations on the "standard" design. From cutting each brick to a specific angle, to making a "soccer ball". In all of that I have determined to KISS. So, I will be doing a single cut 1/2 brick, no extra angles. Normal soldier row, etc. I know I may regret this, if so, I know I can always knock down the oven and rebuild it. In the grand scheme of things the actual oven part isn't that expensive :-)

[PizzaIdiot]

Re: Jake's In Mass (Started July 3, 2011)

Hi Jake,
I started out with the KISS principle. My mind wanders and then reality kicks me and I'm back in KISS-land. So I'm trying to stay with it. I don't have the time, money or skill to much more than that. I try to live vicariously through the works of others - LOL.
I spent an hour trying to figure out the angles for each course. But first I wanted to go back and look at parabolic and elliptic arch profiles - blah, blah, blah. Here's a picture. It doesn't help that i have my PhD in engineering.
Parabolic should do a better job of focusing the radiant heat, but this oven will be so hot, I don't think it will matter much. Plus I like the elliptic (Neapolitan) look better. Then again, the hemispherical shape (Tuscan) is the easier to build - just set the indispensible tool and go - LOL. Decisions, decisions...

From everything I've found here, it really won't matter - just have sufficient thermal mass, insulation in the right places, stagger the joints and a have good attitude (or at least a bottle of red wine -preferably a good one) and everyone will enjoy the pizza. It's not rocket science, but it is something that I want to build myself (with the kids' help, as offered).

Jake, you are right about the cost of the dome - 300 bricks and some home brew. If I screw it up, I can re-use the bricks and redo it. I'll be afraid to close it up until I'm sure it's not going to crack (at least not too much). That's still a month or two away.

My neighbor loaned his 10" brick saw to someone who's not using it, so I'm hoping I can get it from him later this week. He does tile work and when the blade dulls, it's relegated to brick work. I haven't seen it yet. i hope I'm not disappointed, but the price is right!

I'm not going to worry about the heat break between the dome and arch/entry; part of the KISS principle! I'll leave a small gap 1/8" between the entry and my granite landing.

I can't wait to get to the fun part!

-jeff