Cast concrete joints

[Triassic]

I’m about to start building my ICF all off my freshly cast concrete raft, then someone said have you power washed the joint face? Really, this is news to me!!    Thoughts!

 

[Ian]

@Triassic

I guess what they are trying to say is that you should get rid of any surface laitance as this forms a weak dusty layer on the top of many if not most new concrete slabs.

http://www.contractflooringjournal.co.uk/blog/why-it-s-essential-to-get-rid-of-laitance/

[Alexphd1]

New to me aswell. Our concrete seemed pretty solid. Is that not more for screeds? I can't say I have ever seen anybody power washing concrete between pours Inc big commercial projects.

[Mr Punter]

Yes, frequently jetwashed.  Sometimes scabbbled as well to expose some aggregate to act as a key.

[willbish]

I heard someone mention power washing the face, I think what they were trying to achieve was a good key for the next pour to adhere to. They were going to power wash when the concrete was still soft enough that it would blast away some of the fat and leave the aggregate exposed. I think this is totally unnecessary, your ICF walls aren't going to slide in any direction.

[Alexphd1]

We had a ridiculous amount of vertical 12mm rebar between slab and icf (no retaining walls). Next build with a basement think I might just give power wash can't do any harm? Every day is a school day. 

[Russell griffiths]

I don’t think they are talking about ICF in general 

its because you have a basement

the correct method is to place a batten in the concrete before it sets, then spray the surface with a retarder this stops the top couple of mm from setting too hard, when the concrete is green you pull out the batten and power wash the surface of the concrete to expose the aggregate. 

The indent left where the batten was gets filled with a water bar, and your next pour adhered to the aggregate 

 

I think your basement is only 3 sided isn’t it, so with a good French drain and dimple mat you probably have nothing to worry about. 

 

 

On a different note it’s funny how structural engineers differ

in my icf system he has not specified any starter bars and I have asked him twice. 

[Mr Punter]

If you place timber into concrete and you want to remove it, cover it in clingfilm, as otherwise the timber swells and is "tricky" to remove!

[Triassic]

I don’t have a power washer so I’ve removed th surface dusty layer using an angle grinder and a cup wire brush, I’m now on my second angle  grinder and third cup wire brush.

 

Below you can see the difference where I’ve cleaned off the concrete dusty layer.

 

[Bitpipe]

1 hour ago, Russell griffiths said:

I don’t think they are talking about ICF in general 

its because you have a basement

the correct method is to place a batten in the concrete before it sets, then spray the surface with a retarder this stops the top couple of mm from setting too hard, when the concrete is green you pull out the batten and power wash the surface of the concrete to expose the aggregate. 

The indent left where the batten was gets filled with a water bar, and your next pour adhered to the aggregate 

 

I think your basement is only 3 sided isn’t it, so with a good French drain and dimple mat you probably have nothing to worry about. 

 

 

On a different note it’s funny how structural engineers differ

in my icf system he has not specified any starter bars and I have asked him twice. 

 

My basement guys used the batten method on slab and walls to leave a water bar channel in the kicker and on each edge of vertical wall sections - however they did not scabble the previous pours but did use a blowtorch to ensure wherever a new section was being poured, the faces were dry and warm enough for the waterbar adhesive to adere (September so not that cold really).

 

Sika waterproofing system and poured under inspection by their rep so was apparently good enough for the warranty.

 

 

 

[mvincentd]

Basement?.......so the slab/wall junction is underground and earth retaining?.............you're too late for retarder/pressurewash but if it was my basement i'd want both a scabbled surface to key to and a waterbar so i'd find a way to create it.  You're aiming to end up with a monolithic structure, not something with a weak seam exactly where water is likely to be.

[Triassic]

The architect detail has the water bar glued and nailed in place down the centre of the joint. I can’t get a scabbler in due to the bars, I might try a needle gun.

 

 

Edited May 17, 2018 by Triassic

[Triassic]

This morning I started settling out the ICF basement walls. Lots of double checking setting out dimensions and making sure the blocks are level.

 

[PeterW]

Does that toe have a water proofing layer ..? Is there some sort of membrane or are you just putting some sort of drain at the bottom ..?