Mortar mix - advice for hitting that sweet spot?

[kingandy2nd]

Hey all,

In the hot weather last weekend I was having a real battle with my mortar mix, and getting it to a nice consistency for laying bricks.

My mix was 4:1 with plasticiser, also liquid mortar tone. I was measuring ratios with 2 buckets of sand to half a bucket of cement. 40ml of plasticiser and probably 100ml of tone (as I wanted black mortar).

It was very hot/sunny, which of course has an impact, but the mortar was really hard to work after about 15 mins... even when in the shade and taking only a couple of shovel fulls out the mixer at once.

I know the obvious answer is add more water, but I did this to one mix and it was just really sloppy and was staining the brickwork.

I watched this video from Stu Crompton, and he's just lashing the plasticiser in (1:02 in the video and 5:05) - which is the same brand I've got and recommends 60-125ml for 25kg of cement.

Would be interested to hear any tips/tricks I'm missing - especially if others are more generous with the plasticiser as is this guy in the video?

Also, is adding more water to the mixer after it's sat in there a while while I'm laying ok, or is that a no no?

Thanks in advance
Andy

 

[VDubDan]

I never quite won this, but I recently saw some advice that said to mix more vs adding water.

Personally, I had real problems with my mortar going off quickly last summer and to some degree in heatwave weather you're never gonna win.

Use a plastic spot board if you can and damp everything down.

Will be interested to hear the replies.

 

[johnny2007]

Half a cup of water sorts it out.

 

[^woody^]

Work faster.

 

[23vc]

Don’t over plasticise it, but add enough water so that your trowel can cut through it like chocolate mousse and it still holds its shape
As you say if it’s too hot you’ll hit problems in any case like when you come to joint up and it’s too dry
You can add a bit of water to liven it up as you go

 

[stuart45]

If it's really hot rub up just the bed joints when you have finished a course. Then when rub up the perps in later and go over the beds again. This is done in hot countries as the bed joints give you more problems when they go off quick and you get burn marks on them.

 

[noseall]

Machine mix essential.
Dont turn all the mortar out of the drum.
Mixes later in the day perform better than the first mix.
Small amounts of Fairy perform better than large amounts of febmix.

 

[^woody^]

Seriously, people think its great, but bricklaying in summer is crap.

Wetter mixes go off just as fast and you can't use them to start with anyway, more fairy or plasticiser just gives you a fluffy mix and once those joints go off, you never get a good face on them - and you know about it after the first frosts. Soak the bricks and you get nice efflorescence later. Try and plumb that block 20 seconds after laying and you have no chance, but you do get a permanently unbonded block.

Readymix with a retarder is the best thing you can use. Otherwise, like it or not work fast with small mixes is the only good advice you will get.

I recall the hot summer of 1990, we were starting 4 AM till 12 to miss the heat as we otherwise could not get anything done.

 

[stuart45]

What about 76, 90 was for wimps.

 

[^woody^]

What about 76, 90 was for wimps.

I was playing with my school mates then gramps!

 

[noseall]

Seriously, people think its great, but bricklaying in summer is crap.

Agree. Was laying some solid (zero - frog/perf/indent) Oast Russets which is a very porous brick, in the heat of the sun. Pillars too!

 

[kingandy2nd]

Thanks all. Except for the wind, I had a much better day yesterday.

Things I changed :
- I halved the amount I mixed in any one go.
- Half a bucket of water in the mixer with the plasticiser first
- Mixer on level ground
- Adding water to the mixer via hose pointed to back of mixer, rather than from a bucket

 

[stuart45]

Letting it mix a bit longer helps. On site the Hoddies were usually in a rush to get it on to the boards, so to make it workable it needed extra water to get it there quicker. If less water is added at the start and it's left to mix a bit longer more air gets into the mix to make it workable. Plaz helps get the air in, and the tiny air bubbles are like a load of mini ballbearings.
When using an NHL lime mortar with a drum mixer you usually mix for about 20 minutes to start with.