Internal render not set

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Hi everyone,
I am new here, but can anyone help me with my internal render.
I have been rendering my new block work walls with render and one of my walls that i did 2 days ago has not set.
All the others are fine and have set hard but this one, the mix 5:1 sharp sand to white cement is still soft. rub it with your finger and it is moist and crumbles away. The cement that fell and dried just crumbles like dried sand.
I did notice that this batch when i mixed it was sticky and when i applied it to the wall it kept sticking to the metal tool, and also the cement mixer walls (not usual)
I am today now going to scrap the wall off and start again but can anyone shed some light as to why this has happened please (y)
 
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thanks stevethespeader.

drying too quick could be a possibility, maybe i didnt wet the wall enough?!

could the cement have gone off? it had been opened a week since i last used it?
 
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Are you sure it was cement, and not hydrated lime. It is normal for a lime render (especially with non-hydraulic lime) to take several days to set.
The "stickiness" also suggests a lime render.
 
Hi WannabeDIY and stevethespreader,

No its definately not lime or hyrated lime.

I have just scraped it all off and it is still wet. Usually its hard the morning after.

Could it be that i grey rendered 5 days ago over old block work and that it hasnt dried out enough yet?

IMG_2495[1].JPG IMG_2496[1].JPG
 
Ok getting a little bit confusing it's still wet but crumbly? I thought you said it was dry and crumbles like dry sand? It was 5 days ago like in last post or 2 like in earlier post? You also contradict yourself again by saying new walls now it's old walls
 
I am still suspecting it was lime, not cement:
Le ciment romain (roman cement) est une chaux hydraulique naturelle à prise plus ou moins rapide, dont le nom générique, anglo-saxon, provient de l'appellation commerciale donnée dans le brevet déposé en 1796 par James Parker
Le ciment romain est connu en français, depuis le début du xixe siècle, sous le nom de ciment naturel, ciment naturel à prise rapide ou ciment naturel prompt (Voir ciment prompt).
https://fr.wikipedia.org/wiki/Ciment_romain
and the translation:
The Roman cement ( roman cement ) is a natural hydraulic lime more or less rapid decision, whose generic name, Anglo-Saxon, comes from the trade description given in the patent filed in 1796 by James Parker
Roman cement is known in French ..under the name of natural cement, natural cement quick setting or prompt natural cement

Ciment naturel is a form of lime:
is an entirely natural cement, produced from a single geological layer of Argillaceous (clayey) limestone,
http://cornishlime.co.uk/information/prompt-natural-cement/
Prompt natural cement (PNC) is a natural hydraulic binder, manufactured from a single raw material.
http://www.cimentetarchitecture.com/en/Prompt-natural-cement/Definition

I suspect that as a lime render, it would require a longer mixing time, a wetter wall, and plenty of intermittent misting after finish.

There is no reason not to use a lime render on internal walls, as long as you deal with it as a lime render.
 
I am still suspecting it was lime, not cement:
https://fr.wikipedia.org/wiki/Ciment_romain
and the translation:
The Roman cement ( roman cement ) is a natural hydraulic lime more or less rapid decision, whose generic name, Anglo-Saxon, comes from the trade description given in the patent filed in 1796 by James Parker
Roman cement is known in French ..under the name of natural cement, natural cement quick setting or prompt natural cement

Ciment naturel is a form of lime:
http://cornishlime.co.uk/information/prompt-natural-cement/
http://www.cimentetarchitecture.com/en/Prompt-natural-cement/Definition

I suspect that as a lime render, it would require a longer mixing time, a wetter wall, and plenty of intermittent misting after finish.

There is no reason not to use a lime render on internal walls, as long as you deal with it as a lime render.
Lol she's posted a pic of a bag of opc so it's not lime
 
Lol she's posted a pic of a bag of opc so it's not lime
Yep, and it is not opc, it says "Ciment Portland Naturel" (sous le nom de ciment naturel,) plus the whiteness and stickiness suggests it is lime.

Also:
...
could the cement have gone off? it had been opened a week since i last used it?
Cement would be OK, but I have never used 'ciment naturel'. Whether that would go off in a week, I do not know.

Also found this:
upload_2017-3-5_18-15-20.png

http://www.cimentetarchitecture.com...a-technique-de-projection-de-beton-de-chanvre
The important bit translated (Delai de sechage, etc)

Drying time on average 1 month per 10 cm thick

This was for render with some sort of hemp binder.
 
Last edited:
Yep, and it is not opc, it says "Ciment Portland Naturel" (sous le nom de ciment naturel,) plus the whiteness and stickiness suggests it is lime.

Also:

Cement would be OK, but I have never used 'ciment naturel'. Whether that would go off in a week, I do not know.
Ciment is french for cement and it's portland and you still think it's lime?say no more
 
The cement in the bag in the pic is the same as UK ordinary grey portland cement only its got white pigments added.

Acknowledging the suggestions above:
1. the mix was wrongly knocked up.
2. the prep was wrong or missing.
3. 5:1 is too much - 4:1 might have been better.
4. was there a scratch coat?
5. How many coats were actually applied in 24hrs - 48hrs?

OP, what do you intend to do next?
 
Evening stevethespreader, WannabeDIY and Vinn,

Sorry i am a woman and maybe not explained myself or what i have done very well, i am sorry.

The block work was built 1 1/2 years ago, i have grey rendered ie scratch coat 4:1 - 5 days ago and 2 days ago white rendered 5:1.

It is white portland cement not lime and usually only takes over night to cure/harden (6h drying as on the packaging) . I do agree with you WannabeDIY it did behave like lime as i have used that before, but the packaging says ciment (cement) which i have used on the whole interior and no problem.

All my other walls have been ok apart from this time.

Vinn -
1. knocked up as usual
2. prep consistant (although it was only 3 days between the grey render and putting on the white render over the top)
3. mix 5:1
4. grey scratch coat
5. grey scratch coat 72hrs previous

not doing anything after the white render (see pic of other side of the kitchen) not perfect but it a french country house
IMG_2471[1].JPG

p.s have also emailed bostik for info on why this has happened
 

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