Previously it was decided that the best approx 1" thick partition would
be a 1" thick fibre cement panel, which would be very stiff and strong.
Well, what I have decided to do is render-up a panel (vertically) to
approx this thickness against a ply former and mesh etc. But I want the
mix to be almost fibre-cement concrete, so it's very strong. What mix
of cement, sharp sand, fibres and aggregate would be best to us ? The
result should be very strong but also render-able without all aggregate
sinking to the bottom etc.
Cheers,
Simon.

wrote:
sm_jamieson wrote:

Previously it was decided that the best approx 1" thick partition would
be a 1" thick fibre cement panel, which would be very stiff and strong.
Well, what I have decided to do is render-up a panel (vertically) to
approx this thickness against a ply former and mesh etc. But I want the
mix to be almost fibre-cement concrete, so it's very strong. What mix
of cement, sharp sand, fibres and aggregate would be best to us ? The
result should be very strong but also render-able without all aggregate
sinking to the bottom etc.
Cheers,
Simon.

3:1 sand:cement, as this gives the strongest end result. Stronger mixes
will microcrack during cure, thus weakening.

5% chopped alkali-resistance glass fibre will give you proper fibre
reinforced cement. There are other fibre options too, but this is whats
mostly used now that the asbestoses are out of fashion.

Will you use ss screws half way in top and bottom then the crete laid
over them to fix it in place?

Not sure what you mean about this last bit. I will be using mesh to
render onto. I can see screws half way in for a mega-good key, but not
sure what you mean by "top and bottom".
Also, I wondered if putting in any larger aggregate than sand might
help to make it a bit more like concrete ?
Thanks,
Simon.

sm_jamieson wrote:
wrote:
sm_jamieson wrote:

Previously it was decided that the best approx 1" thick partition would
be a 1" thick fibre cement panel, which would be very stiff and strong.
Well, what I have decided to do is render-up a panel (vertically) to
approx this thickness against a ply former and mesh etc. But I want the
mix to be almost fibre-cement concrete, so it's very strong. What mix
of cement, sharp sand, fibres and aggregate would be best to us ? The
result should be very strong but also render-able without all aggregate
sinking to the bottom etc.
Cheers,
Simon.

3:1 sand:cement, as this gives the strongest end result. Stronger mixes
will microcrack during cure, thus weakening.

5% chopped alkali-resistance glass fibre will give you proper fibre
reinforced cement. There are other fibre options too, but this is whats
mostly used now that the asbestoses are out of fashion.

Will you use ss screws half way in top and bottom then the crete laid
over them to fix it in place?

Not sure what you mean about this last bit. I will be using mesh to
render onto. I can see screws half way in for a mega-good key, but not
sure what you mean by "top and bottom".
Also, I wondered if putting in any larger aggregate than sand might
help to make it a bit more like concrete ?
Thanks,
Simon.

Sorry, got it ! Screws in vertically to keep the entire panel in place.
Cheers,
Simon.

sm_jamieson wrote:
sm_jamieson wrote:
wrote:
sm_jamieson wrote:

Previously it was decided that the best approx 1" thick partition would
be a 1" thick fibre cement panel, which would be very stiff and strong.
Well, what I have decided to do is render-up a panel (vertically) to
approx this thickness against a ply former and mesh etc. But I want the
mix to be almost fibre-cement concrete, so it's very strong. What mix
of cement, sharp sand, fibres and aggregate would be best to us ? The
result should be very strong but also render-able without all aggregate
sinking to the bottom etc.
Cheers,
Simon.

3:1 sand:cement, as this gives the strongest end result. Stronger mixes
will microcrack during cure, thus weakening.

5% chopped alkali-resistance glass fibre will give you proper fibre
reinforced cement. There are other fibre options too, but this is whats
mostly used now that the asbestoses are out of fashion.

Will you use ss screws half way in top and bottom then the crete laid
over them to fix it in place?

Not sure what you mean about this last bit. I will be using mesh to
render onto. I can see screws half way in for a mega-good key, but not
sure what you mean by "top and bottom".
Also, I wondered if putting in any larger aggregate than sand might
help to make it a bit more like concrete ?
Thanks,
Simon.

Sorry, got it ! Screws in vertically to keep the entire panel in place.
Cheers,
Simon.

yes, as invisible fixings all along top and bottom. I dont know exactly
how adding coarse aggregate would affect it.


NT

wrote:
sm_jamieson wrote:
sm_jamieson wrote:
wrote:
sm_jamieson wrote:

Previously it was decided that the best approx 1" thick partition would
be a 1" thick fibre cement panel, which would be very stiff and strong.
Well, what I have decided to do is render-up a panel (vertically) to
approx this thickness against a ply former and mesh etc. But I want the
mix to be almost fibre-cement concrete, so it's very strong. What mix
of cement, sharp sand, fibres and aggregate would be best to us ? The
result should be very strong but also render-able without all aggregate
sinking to the bottom etc.
Cheers,
Simon.

3:1 sand:cement, as this gives the strongest end result. Stronger mixes
will microcrack during cure, thus weakening.

5% chopped alkali-resistance glass fibre will give you proper fibre
reinforced cement. There are other fibre options too, but this is whats
mostly used now that the asbestoses are out of fashion.

Will you use ss screws half way in top and bottom then the crete laid
over them to fix it in place?

Not sure what you mean about this last bit. I will be using mesh to
render onto. I can see screws half way in for a mega-good key, but not
sure what you mean by "top and bottom".
Also, I wondered if putting in any larger aggregate than sand might
help to make it a bit more like concrete ?
Thanks,
Simon.

Sorry, got it ! Screws in vertically to keep the entire panel in place.
Cheers,
Simon.

yes, as invisible fixings all along top and bottom. I dont know exactly
how adding coarse aggregate would affect it.


I'll do some experiments and post the results.
Cheers,
Simon.

wrote:
sm_jamieson wrote:

Previously it was decided that the best approx 1" thick partition would
be a 1" thick fibre cement panel, which would be very stiff and strong.
Well, what I have decided to do is render-up a panel (vertically) to
approx this thickness against a ply former and mesh etc. But I want the
mix to be almost fibre-cement concrete, so it's very strong. What mix
of cement, sharp sand, fibres and aggregate would be best to us ? The
result should be very strong but also render-able without all aggregate
sinking to the bottom etc.
Cheers,
Simon.

3:1 sand:cement, as this gives the strongest end result. Stronger mixes
will microcrack during cure, thus weakening.

5% chopped alkali-resistance glass fibre will give you proper fibre
reinforced cement. There are other fibre options too, but this is whats
mostly used now that the asbestoses are out of fashion.

Any idea where to get the glass fibre from ? Not having much luck on
the web.
Cheers,
Simon.

sm_jamieson wrote:
wrote:
sm_jamieson wrote:

Previously it was decided that the best approx 1" thick partition would
be a 1" thick fibre cement panel, which would be very stiff and strong.
Well, what I have decided to do is render-up a panel (vertically) to
approx this thickness against a ply former and mesh etc. But I want the
mix to be almost fibre-cement concrete, so it's very strong. What mix
of cement, sharp sand, fibres and aggregate would be best to us ? The
result should be very strong but also render-able without all aggregate
sinking to the bottom etc.
Cheers,
Simon.

3:1 sand:cement, as this gives the strongest end result. Stronger mixes
will microcrack during cure, thus weakening.

5% chopped alkali-resistance glass fibre will give you proper fibre
reinforced cement. There are other fibre options too, but this is whats
mostly used now that the asbestoses are out of fashion.

Any idea where to get the glass fibre from ? Not having much luck on
the web.
Cheers,
Simon.
Also, what about polypropylene fibres - these seem to be used in
ready-mix fibre reinforced concrete ?
Simon.

sm_jamieson wrote:
sm_jamieson wrote:
wrote:

3:1 sand:cement, as this gives the strongest end result. Stronger mixes
will microcrack during cure, thus weakening.

5% chopped alkali-resistance glass fibre will give you proper fibre
reinforced cement. There are other fibre options too, but this is whats
mostly used now that the asbestoses are out of fashion.

Any idea where to get the glass fibre from ? Not having much luck on
the web.
Cheers,
Simon.

I looked into all this several years ago, dont know if I've got any
links.
Ah...

glass fibre in 1:1 mix for moulding:
http://www.cem-fil.com/cf_grc_manufacturing.html

List of articles
http://www.tfhrc.gov/structur/concrete/subj4.htm
http://en.wikipedia.org/wiki/Reinforced_concrete
http://www.pavingexpert.com/reinfrc1.htm

I found a company supplying bundles of fibres for bridge building, only
£1-2 per bundle for 10 or 12mm poly.


Also, what about polypropylene fibres - these seem to be used in
ready-mix fibre reinforced concrete ?
Simon.

Yes, I'd use them if I couldnt get any glass, but IIRC (and I might
not) 5% glass will give a lot stronger end result, so is the choice
fibre.

IIRC all fibres dont do the same thing. Poly acts primarily as crack
control, and secondarily it increases the crete's tensile strength a
few times. But this isnt the same thing as glass reinforced sheet,
which needs a much higher tensile strength.

Its a while since I read up on all this tho.


NT