fibre re-inforced concrete/cement followup

[sm_jamieson]

In case anyone is interested, I cast a sample panel with 1:1 sand/cement and 2.5% chopped alkali-resist glass fibres from Fibre Technologies International, see

75 quid for a

20kg bag, the smallest they could supply. 10kg sand, 10kg cement and 500g fibre made a panel (well more like a paving slab) 30mm thick and approx 0.25 sq meters size, weighing, unsurprisingly, just over 20kg. The resulting panel was quite impressive, although not really big enough to test tensile stresses much. It certainly "seems" strong, which is as scientific as it gets at the moment. Although 1:1 mix, no signs of cracking (former was open on two sides) which a mixture without the fibres would have done. This is for the thin strong wall previously discussed. Since the cement ratio is high, obviously such panels are not as cheap as one would like. Apparently this stuff is cutting-edge technology for the building trade ! Cheers, Simon.

[Weatherlawyer]

Better than accoustic plasterboard?

[meow2222]

Out of interest, why 1.3:1? Presumably youre loooking for max poss strength, but doesnt 1.3:1 microcrack badly, reducing its strength advantage?

Your fibre cost is high, but that will make a lot of cast crete. Last time I was quoted something like =A32 for a bundle of polypropylene.

NT

[Dave Plowman (News)]

Isn't this the way they make promenade tiles which have been around for many a year? GRP reinforced concrete?

[sm_jamieson]

Tell me more, I'm new to all this.

1=2E3 ? You're including the weight of the fibres ? I understand the fibres prevent cracking, but I don't know if this is the same as preventing micro-cracking ? I understand for max strength you need max cement without the cracking. What mix would you suggest ? If more sand will improve things, obviously that's good as it will cost less !

I believe glass fibres are better at reducing cracking since they flex less than polypropylene.

Cheers, Simon.

[sm_jamieson]

I guess acoustic plasterboard is just heavy plasterboard. The fibre-concrete is certainly heavier than that, so I guess it would be better. Simon.

[marvelus]

Did you buy if from them directly?

[sm_jamieson]

I did - I was having great difficulty finding any suppliers, so I went for the first one. Most of the glass fibre around is for fibreglass and not alkali-resistant I phoned them up - most helpful, suggested the mix, type of fibre etc for my application. They also suggested a superplasticiser to reduce the water content (more cost), but I thought I'd start my experiments without it. I think it is used where very fine moulds must be filled, and the stuff must flow freely. On top of the price I mentioned was VAT and delivery - not too cheap over all. The fibres actually come from Japan I think - its marked on the bag. I will check the actual source, and post it later. Simon.

[sm_jamieson]

I think that also contains a polyester resin, i.e. its actually a mix of fibreglass and cement. Simon.