Bricks didn't bond - too dry?

[^woody^]

Are you laying the bed right - deep, furrowing it and slidding the brick to get the suction?

 

[VDubDan]

Are you laying the bed right - deep, furrowing it and slidding the brick to get the suction?

That's the worst bit - I thought I was doing really well on the trowel

Was really feeling it! That said, initially I was putting too much mortar in (again, a bit used to getting away with it with engineering bricks where it's got somewhere to go) so perhaps I over compensated when I reduced it.

Good point though, I'll pay extra attention to how I'm placing them.

 

[VDubDan]

Right, got round to having another bash at it Saturday. As I'm still underground I did wet the bricks - they are exceptionally thirsty, that much is without a doubt.

Anyway, I'm definitely not going mad - things definitely went a LOT better this time, both in the short term (hard to describe, but I could just tell the bricks were sitting with more suction etc) and the next day everything was good apart from 2 which I'd knocked but thought I might get away with! Even the top of the corner was nice and solid - obviously I didn't push my luck, but they had definitely bonded and I could use it with a line etc.

Had another go yesterday and it was a bit more of a mixed bag - I've just been and had a look and most are fine, but I've got a few that aren't right.

One thing I'm going to change is that I was using some super concentrate plasticiser, but I'm only mixing 1/4 a bag of cement at a time so it ends up being something stupid like 2.5ml per mix. I've picked up a normal 5l can. Pretty sure I've seen builders put stupid amounts of plasticiser in, but I suppose it does reduce the moisture content in the mortar and that doesn't help so the less concentrated stuff will let me gauge it down a little.

 

[mrrusty]

something stupid like 2.5ml per mix

https://www.amazon.co.uk/Shintop-Sy...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

What I use for measuring small quantities - I like the super conc plasticiser

 

[^woody^]

Use the container cap

 

[mrrusty]

Use the container cap

The SIKA concentrate I use is only 5ml per 25kg cement. If I only make a small mix it's tricky to accurately measure ~2ml - far easier with a syringe

 

[^woody^]

It's building not a spice production laboratory.

 

[VDubDan]

So, still struggling a bit with this. I'm done underground now, so my next work will be visible - I'm 100% happy with my cement, my sand, my plaz etc. I did have a bit of a realisation that I was probably mixing my mortar a little too dry - found I could make it a bit wetter and leave it mixing longer and get quite a nice workable mortar.

BUT, conclusion is still much the same - if I take bricks out of the pack and lay them even with nice beds, I'll have a very weak bond, and the top brick probably won't bond at all. If I get them nice and wet, they bond perfectly. The stuff I've done underground is absolutely rock solid.

So not really sure where to go here? I know people have the same issues with lightweight blocks, but the conclusion seems to be it'll be okay once built. Obviously this is a free standing wall (with fairly long 6m runs) so it needs to be stable by itself.

As they're S2 bricks so hopefully low salt, I'm reaching a point where I might just have to dip them and brave efflorescence - especially for getting the corners up

 

[cdbe]

Just stack a few courses of your next day's bricks on top.