Not so sticky mortar

[bevanlowe]

Hi everyone,

I'm a couple of days into my build and have just changed mortar from Vesuvius Tuffset premix to FFR dry mix and have noticed the mx yourself dry stuff is nowhere near as sticky as the premix.

I've read in here that that shouldn't be a problem but it just doesnt seem right while doing it. I changed simply because when I picked up m mortar the guy was really friendly and gave me a 3/4 full tub of premix that he'd opened and now wasn't going to use, so I used it first.

Should I be concerned the dry mortar doesn't get as sticky or better still, are there additives that will make it stickier?

I've tried detergent and lime but they didn't seem to make a noticeable difference.

Thanks,

Bevan.

[bevanlowe]

Re: Not so sticky mortar

The mortar does seem to be sticking well after a couple of days so I shouldn't have worried, and I'm now getting it to flow a lot better by soaking the bricks for a couple of minutes beforehand and spraying the bricks it will go on too.

I do have another question though about filling gaps. There seems to be lots of theories and every theory has a supporter and a objector. I'm thinking that if you can make concrete by adding aggregate to mortar, then why can't you make refractory concrete by adding aggregate to refractory mortar and use it to fill the gaps and give some strength?

If I add 4-6mm river stones to my mortar, can I use it to fill larger gaps? Has anyone ever tried this?

Thanks,

Bevan.

[david s]

Re: Not so sticky mortar

I'm not sure about this but the river rocks may have a different thermal expansion rate than the mortar and this could present problems. The smaller the aggregate the more this problem would be reduced. Grog (fired ground up clay) would be a safer bet IMO as would be the brick dust from cutting your bricks. However the river rocks may also work, we only fire to around 500 C, but that is the temp where some materials start to undergo rapid thermal expansion.

[brickie in oz]

Re: Not so sticky mortar

Go and buy some premixed in the tub, problem solved.

[bevanlowe]

Re: Not so sticky mortar

Thanks for the replies guys. Just by chance I came across the Darley Firebrick company which happens to be just around the corner from my house - don't know whay it hadn't come up in any of my searches in the past couple of months!

Had a good chat to the owner there and he was incredibly helpful. Got some new mortar (cement fondue) and will be giving it a try over the weekend.

I asked about making a castable or concrete and yes, you can just make it by adding aggregate to the mortar, but he agreed that river pebbles may cause problems as you don't know what the composition is. But, washed riversand can be used to bulk it out as it has a high silica content and I'll need to make a bit of my own grog to help also. I would have bought some grog also but they were out due to problems at the factory.

Turns out that the Vesuvius mortar I was using is an airset product that is no good for gaps over about 3mm or exposed joins as water disolves it! Beautiful to use in the right situation though (inside the dome on neatly fitting bricks). Might have to rework a couple of joints - bummer.

For anyone in Melbourne, Australia, who needs products though, this is a great place to go to.
Darley Firebrick Pty Ltd, Melbourne, Victoria

Bevan.