Sbr pointing mortar - How long is a barrel/drum mix workable?

[KAMIKAZEE DIY]

Got pointing to do, approx 7m2 of setts and 5m2 slabs.

Unfortunately my budget doesn't stretch to get the fancy jointing compounds, but I've got week off work so time to do it (hopefully).

Slabs getting delivered tomorrow and want to do the laying and pointing together so it all binds together as one.

Going to go with Tonys suggested from site mix of 3/1 sand cement plus 200 ml SBR per kg cement. Tony mentions it can set fast? How fast? I was hoping to mix only one barrel of mixer to guarantee consistent colour?


Would this mix set before I had time to complete the pointing (working off trowel, semi dry)Or is it quite feasable? Weather forecasts on my side.

Garden is north facing and paving will get pressure washed spring /autumn that's why I want it to be strong.

Did some setts earlier in year and pointed 3/1 and chucked SBR in, waied couple weeks then pressure washed (reclaimed) setts and zero damage to pointing.


Any advice appreciated.

Cheers

[lutonlagerlout]

I have never laid and pointed at the same time
it is possible but the next day works for me
the weather is looking good as any showers can have a dramatic effect in a bad way

if you butter as you go it will be ready for striking in roughly 1-2 hours
LLL

[mark_buildnrepair]

Echoing LLL's comment, our experience is lay the slabs then point up after.

An SBR modified mortar will have much the same "pot life" as one without SBR. SBRs neither accelerate nor retard to any significant degree. They do improve workability.

At 20oC you'd want to use mixed mortar within 20-30 minutes before it starts to lose workability.

Don't be tempted to add more liquid to try and liven it up as you'll weaken it and make it more likely to crack.

As to how much SBR to add, we recommend 9 litres to 50kg of cement which is in line with Tony's recommendation. In practice on site, mix your cement and sand dry, then dilute SBR with water 1:1 and enough diluted SBR to the cement/sand to give required workability.

All this is based on 47% solids SBR i.e. professional grade polymer rather than watered down jollop.

See Own Brand SBR or Market Leading Brand Ronafix .

[Carberry]

I wouldn't put any SBR in your pointing mix. Too much of a pain in the ass to clean off.

[KAMIKAZEE DIY]

Thanks for your help guys.

Sorry LLL don't think I worded that well, I meant lay all paving then do all pointing after not bit by bit.

Has someone got mobile number I can send a picture too, it's got my setts I pointed earlier in the year below sleepers and I reckon they're fine.

I'm a technophobe and it will be Xmas before a picture goes up.

Cheers

[Tony McC]

An SBR modified mortar will have much the same "pot life" as one without SBR. SBRs neither accelerate nor retard to any significant degree. They do improve workability.

Can't agree with that.

A standard mortar with a typical plasticiser will remain workable for maybe an hour. I've rarely, if ever, had an SBR-mortar that is anywhere near workable after 20 minutes. The mortar becomes too stiff, lacks plasticity and becomes too tacky to use freely.

You could (but shouldn't) wet it up and get another 10 mins, but never in a month of Sundays does it have the same working life as 'normal' mortar.

[John156]

second that with the sbr. Definitely makes it go off faster.

[Nigel Walker]

In the very rare occasions where I use mortar pointing, we always try to joint the flags as we go along.
Lay the flag on full bedding mortar, butter the sides of the flag you have just laid with the pointing mortar (which is mixed seperately and in a separate bucket) - then lay the next flag so it butts up against the flag you have just laid. Mortar will squeeze upwards - scrape this off with a trowel put it back in the pointing bucket and do the same again and again.
You have to look out for when the pointing is ready to strike - weather dependant could be 1 hour or 3-4 hours.
When the pointing mortar is ready - strike it with a pointing iron then brush off later on
This way the pointing mortar and the bedding mortar set together and become as one
The alternative is to point the day after on your hands and knees and try not to stain the flags. It actually takes a bit of skill to point correctly and not stain.
You could use a pointing gun, but very difficult to get the consistency of the mortar right - it needs to be wet enough to come out of the gun

This is why its a whole lot easier using resin jointing.
We joint pretty much all of our flags with Weatherpoint 365. Wonderful stuff !
Yes it costs a lot, but the time you save using it compared to traditional mortar jointing is better value

[mark_buildnrepair]

Hello again.

Tony says "A standard mortar with a typical plasticiser will remain workable for maybe an hour". If a typical plasticiser includes a retarder, then I have incorrectly made a comparison between SBR mortar and "standard" mortar.

My "standard" mortar was based on cement, sand and water. No additives or admixes. So my apologies for any confusion.

[Tony McC]

No additives or admixes whatsoever? I wouldn't want to work with that! Nothing messier than 'dead' mortar.

[KAMIKAZEE DIY]

So would it be possible to mix up a full mixers worth of 3:1 plus SBR, and keep mixer turning so it stays fresh/workable?

I reckon I have full days pointing tomorrow, but is it bad practice to keep one barrel mixing all day and take a buckets worth as needed?

It is not one whole area to be pointed so its possible to break it down into sections and mix smaller loads but I'm keen to mix only one load for exact colour match.


Cheers

[lutonlagerlout]

kamikaze better to knock up small batches as you go

gauge the sand and cement with a small measure i.e. a pint glass

if you use old muck it will fail sooner rather than later
cheers LLL