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Fixing Brick Steps Part II - Can new mortar be applied to old mortar?
Posted by: Wailer
Date: September 27, 2011 02:51PM
Yesterday's original post

Short synopsis: Trying to 2 loose bricks on a heavily trafficed step.

I was hoping I could have used an epoxy, glue or adhesive, but I was talked out of this by the guys at the hardware store. They recommend the right way is to re-mortar and add a concrete glue to the mortar mix to make it more adhesive.

So I have removed the 2 bricks and cleaned them. I'm cleaning the spot they were in but I noticed that they were sitting on about 4" of mortar which still seems good condition (I'm not sure what is below that. Maybe concrete?). Anyway, when I lay the bricks back back into their original voids, they are almost flush with the step. So if I don't do any more chiseling, there will only be a thin layer of new mortar between the old mortar and the brick. There will be entirely new mortar on the sides and backs of the bricks, though.

1) The 4-inch "mortar-slab" seems pretty solid, I'd hate to have to chisel that out. It might undermine the other bricks too. Is it required to remove all mortar or does new mortar bond to old mortar well? Assume the old mortar is in good condition.

2) I'm not too concerned about how it looks but I'd like it to stand up to heavy traffic. I don't have a lot of confidence in mortar's resistance to shear or tension. Should I ignore their advice and just go with a "landscape block adhesive" (that was previously recommend)?

Thanks again.
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Re: Fixing Brick Steps Part II - Can new mortar be applied to old mortar?
Posted by: cbelt3
Date: September 27, 2011 02:53PM
acid etch and steel brush both sides. I have used Liquid Nails in similar circumstances, but cleaning down to the bare brick is best.
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Re: Fixing Brick Steps Part II - Can new mortar be applied to old mortar?
Posted by: RonT
Date: September 27, 2011 03:07PM
I glued a steel framed boot cleaner similar to this:



to a cement block buried in the ground outside of the entrance door to our utility room with Franklin brand subfloor adhesive 20+ years ago and it's still there.
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Re: Fixing Brick Steps Part II - Can new mortar be applied to old mortar?
Posted by: billb
Date: September 27, 2011 03:31PM
you want an inch ( or so, you have to match whatever was originally there obviously) on all the bonding edges. You << might >> get away with adhesive on the bottom, but the old mortar should chisel out with not too much work.

You are working with wet bricks ?
The mortar is supposed to set better if you do.
(and adhesive probably doesn't)



Logen Aryn Ryley - Happy Birthday
July 25
The Truth Will Always Be
another favorite
candy
"I was walking along a path with two friends - the sun was setting - suddenly the sky turned blood red - I paused, feeling exhausted, and leaned on the fence - there was blood and tongues of fire above the blue-black fjord and the city - my friends walked on, and I stood there trembling with anxiety - and I sensed an infinite scream passing through nature."






one Great Gig in THe Sky meets another
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Re: Fixing Brick Steps Part II - Can new mortar be applied to old mortar?
Posted by: Wailer
Date: September 27, 2011 05:34PM
Thanks all.

If I were going to use mortar, I'd want all the surfaces to be wet since the curing process needs water to prevent cracking.

I think with almost no mortar, I may try the adhesive route.
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Re: Fixing Brick Steps Part II - Can new mortar be applied to old mortar?
Posted by: Microman
Date: September 27, 2011 06:59PM
Try that adhesive I told you about on something, anything. , to see how you like it and if you think it will work. Remember sometimes the help you get at these stores is good , but then why would they sell a product designed for gluing blocks and bricks together unless it's for repairs like this. It's less than $5. Glue two bricks together let it sit for a day then try and get apart. If bricks break, there is your answer. When I went to the store they didn't understand my job and would try and sell cement mix for bricks , but after thinking of what I wanted and what the job needed just bought the landscape block adhesive
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Re: Fixing Brick Steps Part II - Can new mortar be applied to old mortar?
Posted by: Mike Johnson
Date: September 27, 2011 11:13PM
I'm really not qualified to answer your question. (I don't think the guys at the hardware store are, either.)

When you first posted, I thought about jumping in and saying I wasn't sure if I'd trust block adhesive on a step. Then I thought long and hard about it and decided I should shut up -- the block adhesive should work as well as a mortar repair, especially since the surfaces are already mated to one another.

#1. New mortar does stick well to clean old mortar. It's one of the reasons brick & (portland cement) mortar is such a popular choice. Repointing is easier than rebuilding.

That said, a thin bit of mortar faces a couple hurdles to set well. First, there has to be enough sand so that the cement in the mortar can flow around it and physically key it all together. You want the 3D matrix to be really complicated, and if it's approaching a bare smear a couple grains thick, there's just not enough of a tangle, so to speak. So you'd want a nice new bed, with no places where the brick is touching the old dry mortar. And you may need to gouge the old mortar to physically lock the old and new together. Second, thin mortar will tend to dry much too quickly and crack. The brick and old mortar will greedily wick the moisture out of the new stuff before your very eyes. You'd have to have the brick and old mortar very well saturated before you start, and mist it regularly during the cure. But not too much -- too much moisture will ruin it.

Normally, if you were repointing old work, I'd say forget the froufrou bonding agent and focus on physically keying the old and new together. A lot of people think bonding agents are a waste of money. But if I was relying on a very thin bed of mortar I'd use it.

Such a hassle. So to answer #2, yes, definitely.



That's a lot of pesto.
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Re: Fixing Brick Steps Part II - Can new mortar be applied to old mortar?
Posted by: Wailer
Date: September 28, 2011 05:34AM
Thanks for the insight all. It's fascinating that cement, sand and water can be so adhesive.

Given that a full 1" of new mortar would be very involved, I'm going to go try adhesive. I'm still going to "rough up" the existing mortar and clean the contact points very well (wire brush, vacuum, etc).

I'll followup for sure! Thanks again.
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