Refractory cement not drying

[valleyman]

Why isn't the refractory cement not drying? It should have set up within 24hrs. Its been several days. I didnt think I put it on overly thick.

Over the weekend I re designed my stack in the block evaporator. I motored in a 6" diam. section of flue pipe into the back wall. I then fit a 6" black stove pipe elbow into the flue pipe. There was a little play so I used the refractory cement to secure it. While wet, gravity was working against the elbow and dropping it so the elbow couldnt keep the 90 degree angle. I was hoping that the cement would hold it up for when I add the 8-10' stack. Seems like the weight is going to stress that area too much.

Guess I have to reinforce it somehow. Any thoughts on my situation?:confused: :mad:

[Haynes Forest Products]

Well lets see there are two differant typs of cement. One is premixed and then the type that you mix. The type you mix sets up from a chemical reaction and the other is air dry. The air dry gets its strengh when its fired. Did you mix it to thin? Yes I would support it during the setting prosess and if its the premix I would speed up the drying with a heat lamp/halogen type lamp to get it dry.

[valleyman]

I used pre mixed. I actually lit a very small fire last night to get the stack heated up. I dont think it got too hot. It did get pretty hot to the touch but only briefly. Hope it wasnt too much too quick.

Since working on the flue the temps in my area have been maxing out around 50 and 30 for low. I''m sure that's not hastening the drying either. As long as it will eventually harden.

[red maples]

I am cementing mine in next sunday, monday, and tues. because it is suppose to be warmer. On the container (pre-mixed) I have is says to not have a layer more than 1/8 inch think and to let it set up for 24 hrs. and temps over 60 degrees. then start a fire slowly so boiling doesn't occur and allow the bricks to heat up slowly then fire it up to 500 degrees for I think it said 1 hr have to double check. and don't let that pre mixed stuff freeze. like haynes said lights to keep it warm!!!

I'll let you know how mine comes out next week!!!

[RileySugarbush]

You shouldn't expect the elbow to hold up your stack anyway. When that black pipe turns red, the stack will start falling over.

Here is a suggestion:

Now, before the ground is frozen, dig a hole and plant a 2x4 or 4x4 about 18 inches behind your stack. That is far enough it shouldn't scorch from the stack heat. It doesn't need to be the full height of the stack. Use heavy galvanized wire or perforated strapping to connect your stack to the support post in three or four places. If you use wire, you may need to put a block under the elbow to keep it from sagging down

I did this and it was still good when I abandoned the block arch after many years.

[valleyman]

Thanks Guys,

John. That's exactly what I will do to support the stack. I didt think it would hold without some type of support no matter how good the cement works. I like your suggestion.

About not letting the pre mix freeze. I sure hope you mean while working with it until it cures. I have my block evaporator set up exposed to the elements and it'll surely go below freezing during the season.

[Haynes Forest Products]

Its like clay that you make pots out of its water soluble until you fire it and thats only after it dries. Then it will withstand anything except gravity.

[peacemaker]

did u let it freeze in the pail?

[valleyman]

Hey peacemaker,

No it didnt freeze in the container but I probably could have mixed it better. I think the problem is I put it too thick. If it becomes a real problem when I boil. I'll scrape it out and use mortar.

[peacemaker]

yeah several thin coats are better

[Haynes Forest Products]

Keep in mind the shrinkage factor so small layers that dry and shrink and then fill the cracks. Make sure that you wet down whatever you are trying to stick together.

[Fred Henderson]

If your bicks are cut to a tight fit all you need to use is fire clay. I have done 3 arches and that is all I have ever used.

[red maples]

so now that I have experience there are 2 factors from what I am reading the first is you don't want to have big gaps to fill it takes too long for it to "set-up" the second is temperature. I put a space heater in front of the draft door and covered it up and I put in a thermometer with a wire attacked(the kind for indoor out door) and kept it around 80 degrees inside the arch and everything is nice and dry I have a few larger gaps that I filled in on sunday and this morning they shrunk and cracked a little and I just filled them in a little more and tomorrow I heat!! But temperature is the biggest factor with that stuff if its not 60F or better consistently than it won't dry!!

[Fred Henderson]

If you could cover the stack you could just hang a 100 watt bulb in it.

[3rdgen.maple]

Ahhh what do the directions tell you to do. Does it not need to maintain a certain temp and then a small fire need to be lit. I did mine in january last year and followed the directions and had zero problems.

[WESTVIRGINIAMAPLER]

Harware stores sell small containers in pint sizes that are for bonding metal to stone, metal to metal and some of the different types you can fill holes up to 1" and it works good and holds good. You have the right idea, just wrong material.

[red maples]

if all else fails read the directions...fired mine up today worked beautifully!!!!

I just wish it was sap and not water in those pans. but itwas hard to build a small fire. I want to get it ripping I did a little at the end but not to the fullest.