Rapid set cement vs Portland?

[RichC]

Just got a materials list of parts required to assemble my oven kit. Can someone explain to me the merits of using rapid set cement vs Portland cement? I think the rapid set stuff is also called cement fondu??? I'm using a kit so it'll be primarily used for making vermicrete insulation. It costs ?8.50 per bag vs ?5 per bag for normal Portland cement. 10 bags total so it doesn't add that much cost, I'm just curious?

Thanks

Richard

[TxTanner]

Re: Rapid set cement vs Portland?

Rapid set conctrete is a mixture or aggregate ,sand and portland cement(portland cement is the"glue"that holds concrete together)that is formulated to set fast and I mean really fast so it's great for setting posts and such but it is concrete just like a side walk so you would not use it to make vermicrete .Just add portland cement to the vemiculit and youll be ok.A good place to use the rapid set concrete is if your dry stacking block for you oven stand. I like to backfill my blocks with it so that I can go right into pouring my slab the oven sits on.I build these proffesionally and this saves me time.I hope this helps.

Bill

[RichC]

Re: Rapid set cement vs Portland?

Thx Bill, ended up buying 2 bags of it anyway. I'm sure ill find a use for it at some point.
Richard

[TxTanner]

Re: Rapid set cement vs Portland?

Go fix that leaning fence your wife's been on your arse about.Just kidding,tell her your not fixing anything until you get that oven fired.Good luck and hope all goes well.


Bill

[RichC]

Re: Rapid set cement vs Portland?

Go fix that leaning fence your wife's been on your arse about.Just kidding,tell her your not fixing anything until you get that oven fired.Good luck and hope all goes well.


Bill

funny you should say that, I've been travelling a bit with work recently and the guilt has helped me make great progress around the house with stuff she's been nagging about for years

[deejayoh]

Re: Rapid set cement vs Portland?

Cement fondu is calcium aluminate cement - used for high-heat applications. Basically refractory cement that you could use to cast an oven. It's not the same as rapid set cement like what you use to set fence posts.

I'd recommend you check your directions again because if they call for cement fondu, you can't substitute portland or rapid set cement - and it's way more expensive than either.

http://en.wikipedia.org/wiki/Calcium_aluminate_cements

[RichC]

Re: Rapid set cement vs Portland?

Hi DJ, from the instructions I have, it appears that the cement fondu is just used to make the vermicrete. They(the refractory who sells the kit), also supply a product they call dinset which is used for sticking down the base and for bonding the fibre blanket to the dome. I assume its refractory mortar.

[deejayoh]

Re: Rapid set cement vs Portland?

Interesting instructions! Yeah, portland is the way to go for vermicrete. Refractory cement is $20 for a small bucket here in the US. You can get 80 lbs of portland for less than $10!

[TxTanner]

Re: Rapid set cement vs Portland?

Check your instructions again Jay if this is a precast oven with multiple sections then more than likely the refactory mortar is used to cover over the joints where the sections join together.To apply this I usally use a rubber grout float to force it in any open gaps and then spread a 6 inch wide 1/4 inch thick cap over the joint.The ideal is not to "butter" the pieces together like bricks but to seal over the joints so to speak.Go build and be happy.

[RichC]

Re: Rapid set cement vs Portland?

Think ill call the supplier for clarification on that before I start assembling the oven.
Thanks guys!

R

[TxTanner]

Re: Rapid set cement vs Portland?

Good ideal Rich just be cautious as we all know clarity comes and goes and usually at the most unfortunate times....
"Damn it I was 100% sure I remembered what I thought he said.'