Hi all,
THe instructions for the shower base I'm installing say I need to add an "anti-crumble" compound to the S&C mix. I can see how this would be desirable since the shower base will be sitting directly on this bed of mortar, but I've not come across such an additive before and don't recall ever seeing such a thing, either. Is this just a fancy term for PVA or is something more specific required?
cheers, cd.
crumbling is due to failure of tensile strength, so PVA etc would do it. As its a shower I'd use SBR instead.
NT
They sell the stuff you want in the larger sheds near the cement and sand and at any proper builders merchants. Typically SBR or similar.
SBR would be an extreme option.
But unless you wax/oil/sheet-with-clingfilm the underside of the tray, do be aware that it will bond solid to the mix and will be impossible to take off without a kango. I've used it in difficult situation and it sets like iron.
I think for this application a drop of PVA would be sufficient - the load is spread far and wide and I've not even heard of show tray beds needing additives until now.
/Tim Watts
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SBR would be an extreme option. /q
+1Jim K
What is never mentioned is that SBR can't easily be incorporated into a s/c mortar. Unlike pva, it leeches out of the mix, and does its own thing as the mortar dries, to the point where you might as well apply it to the substrate instead.
Modern instructions do specifically advise it.
Having used it a little, I would disagree. Yes, it does tend to come out. The secret is (as I was doing with floor screed) is to have a very dry mix - the SBR acts as a plasticiser so it feels "wetter" than it is anyway. Anyway, there's more than enough stays in the mix to turn it into iron. I tried chiseling a high spot off my screed a couple of weeks later and a scutch comb on an SDS was barely touching it.
Screed mix would be a good bed for the shower tray.
/Having used it a little, I would disagree. Yes, it does tend to come out. The secret is (as I was doing with floor screed) is to have a very dry mix - the SBR acts as a plasticiser so it feels "wetter" than it is anyway. Anyway, there's more than enough stays in the mix to turn it into iron. I tried chiseling a high spot off my screed a couple of weeks later and a scutch comb on an SDS was barely touching it. /q
+1 Indeed, i've used sbr in this manner quite easily with impressive results. Usage info gleaned from on here (or goggle) iirc (its not in the wiki)...Jim K
I've got a screed section with SBR and glass fibres ! I used it over a joint in the underlying slab which was unlikely to move, but better safe than sorry. I made an inch thick "concrete" slab with the left overs. It is a very interesting object ! Simon.
/I've got a screed section with SBR and glass fibres ! I used it over a joint in the underlying slab which was unlikely to move, but better safe than sorry. /q
Hadron collider?? :-)
Jim K
replying to Cursitor Doom, Jockfixer wrote: I came accross this last week too. Neither the supplier, (Eastbrook) nor the manufacturer would comment other than to reiterate that an anti-crumble agent was necessary. They referred me to the cement manufacturer. I spoke to the Technical Director of the major manufacturer who, like me, (30 years in the trade) had never heard of such an additive. I will be writing to the supplier and tray manufacturer complaining about their spurious directions and will report back if there is any interest still on this string.
I might wander back in another couple of years and continue the conversation.
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