New (2nd) build in Brisbane

[cobblerdave]

Re: New (2nd) build in Brisbane

G'day
New vitrified house bricks are cleaned off with hydrochloride acid and high pressure spray. It acts on the cement mortar. Problem is the blocks are cement so you could damage them doing it that way.
Go with wire brushing them off for the moment that mortars still " green" and will lighten up in colour as well .
Sorry I'm a bit reluctant to use acid myself. I've seen some really bad builders cleans you can really ruin things if you do it wrong.
Regards dave

[applor]

Re: New (2nd) build in Brisbane

I have read and am worried a wire brush will permanently scratch the surface of the bricks and ruin the finish though.

Problem is as you say the block is porous so the grey mortar appears to have soaked into the blocks around the joins.
I could just try a hose and brush tonight but failing that acid may be the only way to get it out of the surface.

[cobblerdave]

Re: New (2nd) build in Brisbane

G'day
The block around the mortar is wet ....is what you'd expect, and any mortar is still green and dark. Let everything dry off and cure. Time and distance sometimes solves the problem better than knee jerk action.
Regards

[applor]

Re: New (2nd) build in Brisbane

But that can also be applied vice-versa. Often you need to act quickly before things set and cannot be fixed.

We were going to use a hose and brush to try and scrub off the excess. Are you saying we should wait and that it will dry out and either be invisible or brush off?

[cobblerdave]

Re: New (2nd) build in Brisbane

G'day
From my armchair internet view of your pics it doesn't look that bad.
If you plan to brush it down now as long as you don't get stuck into it with anything powered or chemical it will be alright. It can't hurt.
When the cement is cured and dry that mortar will look a lot better I'm sure
Regards davr

[cobblerdave]

Re: New (2nd) build in Brisbane

G'day
To quote the disclaimer on most items these days
" Try in an inconspicuous spot "
If you want to try something you might think dangerous to the finish. Experiment on the inside of the block work.
Regards dave

[applor]

Re: New (2nd) build in Brisbane

Well the good news is with a fair bit of elbow grease using a steel scrubber and water, most of the mortar is gone.
It is not perfect but it is much much better and will do.
I can take a picture tonight to show you the difference.

Now I just have to be careful to keep my mortar much drier for the remainder and hopefully I don't have this problem again.

Thanks Dave

edit: attached picture

[applor]

Re: New (2nd) build in Brisbane

Spent Friday and Saturday finishing the block work.

Sunday I spent a good hour or more cleaning the mortar again. I was tidier this time - some blocks hardly required any cleaning, while my last batch of mortar was too wet again and they needed a bit more.

Then bought a masonry blade for my angle grinder so I could cut the tops of one side of blocks to get the rebar in.

I will be installing all the supports for the suspended slab, installing rebar etc. tomorrow morning ready for the pour tomorrow afternoon.

My only concern is wet concrete seeping down the side of the formwork. it's only a 1-2mm gap at most on a couple of parts so quite tight - nothing big will get in but it may stain the block work.

Overall I am happy enough with things so far. I am a perfectionist so will never be completely happy with the block work but it is solid and level, good enough. The back side isn't quite a straight line though (not shown) because the concrete isn't quite flat and also because my first run of blocks for the WFO area were a bit thin on mortar.

[cobblerdave]

Re: New (2nd) build in Brisbane

Gday
Use that gray plastic "gaffa" tape to seal the edges of your formwork, nothing will bleed through that. Leave any screws proud of the surface and tape them as well. Makes them easy to find and you cant fill the heads with concrete either.
Regards dave

[applor]

Re: New (2nd) build in Brisbane

Yes but the question is where to use the tape. If I use the tape on the topside of the formwork to the side of the blocks, the tape will be stuck into the concrete and won't be removable.

If I tape from the underside I could get concrete leaking down the side of the formwork until it reaches the tape on the underside - so there will be 17mm of concrete stains (the thickness of the formply)

Understand what I mean?

[Gulf]

Re: New (2nd) build in Brisbane

Yes but the question is where to use the tape. If I use the tape on the topside of the formwork to the side of the blocks, the tape will be stuck into the concrete and won't be removable.

If I tape from the underside I could get concrete leaking down the side of the formwork until it reaches the tape on the underside - so there will be 17mm of concrete stains (the thickness of the formply)

Understand what I mean?

Place the tape on top of you blocks. But, only lap about 3/8ths of an inch up on to the form. You can later cut the tape with a utilty knife. The tape that remains between the blocks and the slab will be ok.

Another option would be to caulk the seam. That is, if you allow enough time for it to dry, before the pour .

[applor]

Re: New (2nd) build in Brisbane

I had considered caulking the seam with silicone though I am concerned it will adhere to the formply and the surrounding block too well and I would struggle to get the formply out.

I can always lever the formply off though, since I designed my pour/front lintel so the formply could be removed forward out the front. Avoids problems where the formply doesn't want to drop down after removing the supports.

My other option was to use blue-tac as a filler.

Do you think blue-tac or silicone would work better?

[Toomulla]

Re: New (2nd) build in Brisbane

The standard approach in the construction industry is to sue an acrylic mastic

[david s]

Re: New (2nd) build in Brisbane

The standard approach in the construction industry is to sue an acrylic mastic

The trouble with that approach is that it takes so long and can be very expensive if you don't win.

[cobblerdave]

Re: New (2nd) build in Brisbane

G'day
See taped! lots of seams so I could get that melamine out from around a central pillar. Not a dribble.



Simple, available, and above all works!

Regards dave