Sand & Cement "anti-crumble additive"

Cursitor Doom

unread,

Mar 13, 2015, 7:15:38 PM3/13/15

to

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.

meow...@care2.com

unread,

Mar 14, 2015, 1:14:00 AM3/14/15

to

crumbling is due to failure of tensile strength, so PVA etc would do it. As its a shower I'd use SBR instead.

NT

Martin Brown

unread,

Mar 14, 2015, 3:56:16 AM3/14/15

to

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.

--
Regards,
Martin Brown

Tim Watts

unread,

Mar 14, 2015, 10:38:35 AM3/14/15

to

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.

JimK

unread,

Mar 15, 2015, 6:32:00 AM3/15/15

to

/Tim Watts
- show quoted text -

SBR would be an extreme option. /q

+1

Jim K

stuart noble

unread,

Mar 16, 2015, 3:28:59 AM3/16/15

to

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.

Martin Brown

unread,

Mar 16, 2015, 5:48:49 AM3/16/15

to

Modern instructions do specifically advise it.

--
Regards,
Martin Brown

Tim Watts

unread,

Mar 16, 2015, 7:42:18 AM3/16/15

to

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.

JimK

unread,

Mar 16, 2015, 5:04:19 PM3/16/15

to

/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

sm_jamieson

unread,

Mar 18, 2015, 9:53:57 AM3/18/15

to

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.

JimK

unread,

Mar 18, 2015, 12:46:29 PM3/18/15

to

/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

Jockfixer

unread,

Mar 13, 2017, 6:44:11 PM3/13/17

to

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.

--
for full context, visit https://www.homeownershub.com/uk-diy/sand-cement-anti-crumble-additive-1032521-.htm

Roger Hayter

unread,

Mar 14, 2017, 5:07:00 AM3/14/17

to

Jockfixer <caedfaa9ed1216d60ef...@example.com> wrote:

> 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.

--

Roger Hayter