Has anyone reinforced concrete with chopped fibreglass strands >

[DAPPH]

Like the title says has anyone made reinforced concrete using chopped 12mm or so long fibre glass strands in the base & floor topping mix instead of rebar or chain link fencing ? If so did you use a water proofer & plasticizer in the mix instead of a WPM on blinded tamped stones etc

 

[Onoff]

What's this for as I'm king of the weird concrete mix?

Got a bit obsessed for my wet room corner (and elsewhere for the lime mortar mix for my flints):

This taken from a post I put on another forum:

Toying with a "resinous" mix for this cast in situ wet room corner I was toying with a 3:2:1 sand/10mm pea shingle/cement mix with added fibres and SBR. I've now found this Word document on the web. Mix Design No4 looks a possible, maybe with added fibres?

Whatever needs to be strong and tough to cope with walking on long term whilst I finish the walls, shower plumbing etc.

"P.R. EPOXY - SBR POLYMER SYSTEM

TECHNICAL DATA SHEET

USES.
P.R. Epoxy - SBR Polymer System is used for screeds, floor repairs, waterproof renders, waterproof fine concretes and bonding.

DESCRIPTION
P.R. Epoxy - SBR Polymer System has been formulated to enhance the physical and chemical properties of cement mortars and concretes. It is compatible with most forms of cement, sands and aggregates. Together with the cement, it forms a powerful adhesive to bond the aggregates together, producing a tougher, waterproof and more impact and abrasion resistant floor, repair mix, render or bonding primer.

PROPERTIES
The properties of the cured mix will vary depending on the type of cement, sand and aggregates used.

COMPRESSION
AGE. N/mm²
1 day 14 – 18
28 days 40 – 50
(Strength is dependent on mix design)

PREPARATION
Surfaces to which P.R. Epoxy - SBR Polymer System mixes are to be applied must be clean, strong and free from oil, grease and with a rough profile. Best preparation is with a scabbler or power washer. If metal surfaces area to be covered they must be rust free and wire brushed or grit blasted. Cement based substrates must be damped with clean water and excess water removed. A primer coat of 1:1 P.R. Epoxy - SBR Polymer System/cement is brush applied to the prepared surface. Refer to relevant standards and codes of practice.

MIXING & APPLICATION
Hand mix or use a forced action mixer. The components of the selected mix are measured by weight or volume and dry mixed. The P.R. Epoxy - SBR Polymer System and water is added to give the desired consistency. In an efficient mechanical mixer, mixing should continue for 2-3 minutes. When hand mixing, mix the cement, aggregate and sand dry then add sufficient of the P.R. Epoxy - SBR Polymer System/water until a homogeneous consistency is achieved.
The mixed mortar is applied to the prepared and primed surface whilst the primer is still wet/tacky, using conventional screeding, rendering and concreting techniques. Apply as required on to wet or tacky primer, compact well and finish. If the primer dries, crosshatch scratch and reapply. If necessary apply mortar in multiple layers to achieve total thickness, priming between layers with P.R. Epoxy - SBR Polymer System :cement primer.

STORAGE
P.R. Epoxy - SBR Polymer System must be stored unopened in dry warehouse conditions between +5°C and 25°C and out of direct heat and sunlight. In these conditions P.R. Epoxy - SBR Polymer System should have a shelf life of approximately 12 months.

PACKAGING
P.R. Epoxy - SBR Polymer System is available in 5, 25 and 240.0litre containers.

HEALTH & SAFETY
There are no emissions of noxious or offensive fumes, P.R. Epoxy - SBR Polymer System is alkaline when mixed with cement and sand; do not allow prolonged contact with skin. Health & Safety information is available.

OTHER INFORMATION
Mix Design’s

1. Floor Screeding and Screed Repair (min. 6mm)
by weight by volume
50kg cement 1 pbv
150kg medium sand 2.5 pbv
10 litres SBR (1:1 SBR:water
9 litres water* (add to consistency
Yield approx 0.1m³

2. Heavy duty floor toppings (min. 12mm)
by weight by volume
50kg cement 1 pbv
75kg medium sand 1.25 pbv
75kg 6-3mm grano chips 1.25 pbv
10 litres SBR (1:1 SBR:water
9 litres water* (add to consistency
Yield approx 0.11m³

3. Waterproof Renders (min.6mm)
by weight by volume
50kg cement 1 pbv
125kg medium sand 2 pbv
10 litres SBR (1:1 SBR:water
9 litres water* (add to consistency
Yield approx 0.1m³

4. Water Resistant Concrete (min.25mm)
by weight by volume
50kg cement 1 pbv cement
100kg medium sand 1.5 pbv
100kg 10-5mm pea shingle 1.5 pbv
5 litres SBR (1:3 SBR:water
13 litres water* (add to consistency
Yield approx 0.14m³

5. Bonding Screeds, Plaster, New Concrete to Old
by weight by volume
1kg cement 1 pbv cement
1 litre SBR 1 pbv SBR
Yield approx 3-4m² per litre

6. Floating Screeds (min. 38mm)
by weight by volume
50kg cement 1 pbv
150kg medium sand 2.5 pbv
4.5litres SBR (1:3 SBR:water
13.5 litres water* (add to consistency
Yield approx 0.1m³

• * = add to working consistency.
• All sands must be medium grade sharp.
• Aggregates must be clean, well graded and not “to dust”.
All P.R. Epoxy Systems products’ are manufactured to a high standard of quality. Whilst we aim to ensure that any advice, information or recommendations given are reliable and correct, the Company cannot accept any liability directly or indirectly arising from the use of its products, as we have no direct or continuous control over where or how its products are applied. No undertaking can be given against infringement of any patented processes."

Then, based on the above, I went with:

Interesting mix that was! Smells like when you work with plastic. Pretty sticky!

5l bucket cement
7.5l bucket 10mm pea shingle
7.5l bucket sharp sand

So 1 : 1.5 : 1.5

3:1 water to SBR

A handful of fibres

Repeat!

Seemed to go in alright though:

 

[Barking Mat]

Yep, apparently it's great, I'm not convinced.

For me a concrete floor is a good concrete floor.

 

[Onoff]

When I did the main floor in the bathroom I forgot to add the fibres. The slab does mind have A142 mesh in it. Also mixed strong with Everbuild 202 waterproofer that doubles as a plasticiser.

 

[dieselsamurai]

I cast all the padstones in my loft conversion in situ with glass fibre strands , I did some test casting and after curing the reinforced one was so much stronger than the one without

 

[Munkul]

My uncles were great believers in fibre reinforced cement and would order it for cementing farm yards etc and saving money by avoiding rebar.

It didn't work, really. It still cracked after a few years.

When you need steel reinforcement, you can't avoid it by adding some magic fibres.

 

[awemawson]

All my concrete in my workshops and tractor shed - oh also the pig sty floors, have chopped strands of fibre glass added, but this is to reduce surface cracking. They all have mesh reinforcement as well.

 

[cocker]

It's worked alright for me in the past , with water proofer . On dpm .

 

[Seadog]

Like the title says has anyone made reinforced concrete using chopped 12mm or so long fibre glass strands in the base & floor topping mix instead of rebar or chain link fencing ? If so did you use a water proofer & plasticizer in the mix instead of a WPM on blinded tamped stones etc

Yes.

 

[Smallfry]

My workshop floor is 8 inches thick, with fibres but no rebar. Only because the supplier let us down time and again, then the ready mix and pump arrived.

I thought the fibres were to prevent surface cracking, not a substitute for rebar or mesh ? I have always wondered how it becomes evenly distributed throughout the mix, and they never seem to put enough in to be worthwhile IMO.

Workshop surface has small cracks.

 

[Migmac]

I follow a guy who does concrete work. He uses rebar or mesh along with fibres in the concrete.

 

[Onoff]

I follow a guy who does concrete work.

What, like a stalker?

 

[DAPPH]

Over 30 years ago, I observed a large local building supply company construct a massive 40 x 40m storage shed. The floor was specified as concrete reinforced with glass fiber strands. The method involved mixing the fibers dry for so long as the mix lorry travelled then wetted up for five min on site so the mix passed a set slump test to ensure even distribution.

The site architect I spoke with mentioned that numerous tests had proven the simplicity and strength of this concrete laying technique the guys trying to fix the ,linked racking isles were beside themselves as the still green concrete floated to a polished floor was burning out their tungsten SDS drill bits as they put in the racking's chemical anchor bolts . I suggested to them they were trying to drill too fast , so slow down and with SDS hammer it should work out better it did too.

Outside in a massive heavy goods vehicle [ark & out door storage yard they were putting down big slabs of 8 inches of the same mix joined with metre length of 20 mm rebar , after vibrating it flat it got a wire brush across the top to give a bit of grip.
I was amazed how they cast the yard sections, like the black square on a chess board , so many in the morning then as the quick set went off took out the shuttering blanking off the open edges and infilling the white square in the afternoon .

The owner was adamant that he should also put in 10 mm 150 x 150 square reinforcing mesh . so that's what was being done , The architect could barely hide his laughter . The telecoms ducting was put down weeks preciously and supposedly fed with the wires . I was connecting them up with private wires etc ... found one pipe blocked with this concrete , had fun locating where it was then got some of guys to cut out the floor till we found the pipe and draw the right cable in .

I'd often wondered how successful the adding of cut fibres was when considering it as my new mancupboard's floor, . One kg ( £13 ) of fibre ought to make 1.34 cubic metres of concrete thus covering around 11 sq mtrs of floor at 10mm thick ....a lot cheaper and lighter work than dragging 2x3 m of reinforcing mesh panels 50 mtrs down the garden , it seems to be in common commercial use these days .

 

[Trevorleach]

we used fibre reinforced concrete two inches thick surrounding large chunks of polystyrene to make floats for pontoons.

 

[Migmac]

What, like a stalker?

Of course

 

[Pete.]

Concreting is t just a matter of "yes this works, no that doesn't ". The mix is designed and approved for each situation. The designer will supply a minimum spec, then the contractor will get a mix design from the supplier and forward it for approval by the designer. Once it's approved, that's what is used.

That's o e reason why the Hanson 40n bags are so popular despite their cost the spec is well known and can be approved quickly for minor jobs without too much to-ing and fro-ing.

 

[frank horton]

cant buy the strands here.....so used miles of mesh for my w/floor..........mesh is a trip hazard.....hate the stuff....
only plus was I bought the galv finished mesh....so much nicer to handle........

 

[Agroshield]

Glass fibres might not be the most appropriate type for this application. They are normally used in very thin items (decorative pre-cast panels so they do not self-destruct from flexing when lifting and handling). For a thicker, poured-in-place section, the fibres are normally polypropylene. I have also seen steel fibres used.

The ones we used were from Grace construction products, and looked like Tesco carier bags (in the days before you were charged 10p for one) that had been in a blender. They came in a paper sack, which the driver threw in the back of the truck before leaving the plant. The agitation and abrasion of the mixer destroyed the bag and distributed them through the mix.

For anything less than a power float finish (i.e. standard Easifloat), the slab surface the next morning looked like someone who did not shave for three days. We had to go around with a weed burner and singe the bumfluff flush.

The steel fibre one was worse in that respect as it looked like someone with ginger stubble after a bit of rain. The Desperate Dan barbering technique did not work on metal.

Slabs made with fibres are horrible to demolish. With a pecker, a normal slab breaks into lumps. With a fibre slab, the pecker just makes a round hole in the slab.

---

The two mistakes most people make with concrete are too much water and poor curing.

The 'best' amount of water is the minimum necessary to fully hydrate the cement. This is normally expressed as a water/cement ratio. If you mix at that ratio, the stuff is unworkable as it is too stiff, hence any extra water added above the minimum needed for the chemical reaction trades strength and durability for ease of handling.

As an alternative to just adding water, chemical additives (plasticisers) have been developed. These are slightly misnamed as they are really 'water-reducing admixtures'. They contain chemicals that allow the materials to slip over each other but which do not affect the strength of the concrete. They allow you to drive the w/c ratio right down but still have a workable mix. They have the additional effect of acting as a retarder, giving the mix a much longer open time. They are extremely sensitive to dosing rate (like a tablespoon extra per cubic metre turns the mix into soup) so need care and good process control when batching.

Traditionally concrete leaks because it cracks. It cracks because it shrinks. It shrinks because a) it has too much water in it b) it gets too hot and c) is not cured properly. It gets hot because the only way to achieve the specified strength at the workability required was to add OPC. That gives out heat as it hydrates. It has too much water because it was the only way people could obtain a workable mix.

Modern mix design is for a low heat mix (as low OPC content as possible, with as much cement replacement - GGBS or PFA- as possible) and as low a w/c ratio as possible. Adjust the workability by superplasticisers.

Spend your money on mix design and good workmanship and you do not need a waterproofing additive. Curing it properly assists in durability and waterproofing. The cheapest curing agent is sodium silicate. Finish (trowel the slab) and spray it well with that. Cover overnight with polythene or frost blanket according to season to keep it moist/humid. What you do in the first 12 hours will make or break it.

 

[Morrisman]

Glass fibres might not be the most appropriate type for this application. They are normally used in very thin items (decorative pre-cast panels so they do not self-destruct from flexing when lifting and handling). For a thicker, poured-in-place section, the fibres are normally polypropylene. I have also seen steel fibres used.

The ones we used were from Grace construction products, and looked like Tesco carier bags (in the days before you were charged 10p for one) that had been in a blender. They came in a paper sack, which the driver threw in the back of the truck before leaving the plant. The agitation and abrasion of the mixer destroyed the bag and distributed them through the mix.

For anything less than a power float finish (i.e. standard Easifloat), the slab surface the next morning looked like someone who did not shave for three days. We had to go around with a weed burner and singe the bumfluff flush.

The steel fibre one was worse in that respect as it looked like someone with ginger stubble after a bit of rain. The Desperate Dan barbering technique did not work on metal.

Slabs made with fibres are horrible to demolish. With a pecker, a normal slab breaks into lumps. With a fibre slab, the pecker just makes a round hole in the slab.

---

The two mistakes most people make with concrete are too much water and poor curing.

The 'best' amount of water is the minimum necessary to fully hydrate the cement. This is normally expressed as a water/cement ratio. If you mix at that ratio, the stuff is unworkable as it is too stiff, hence any extra water added above the minimum needed for the chemical reaction trades strength and durability for ease of handling.

As an alternative to just adding water, chemical additives (plasticisers) have been developed. These are slightly misnamed as they are really 'water-reducing admixtures'. They contain chemicals that allow the materials to slip over each other but which do not affect the strength of the concrete. They allow you to drive the w/c ratio right down but still have a workable mix. They have the additional effect of acting as a retarder, giving the mix a much longer open time. They are extremely sensitive to dosing rate (like a tablespoon extra per cubic metre turns the mix into soup) so need care and good process control when batching.

Traditionally concrete leaks because it cracks. It cracks because it shrinks. It shrinks because a) it has too much water in it b) it gets too hot and c) is not cured properly. It gets hot because the only way to achieve the specified strength at the workability required was to add OPC. That gives out heat as it hydrates. It has too much water because it was the only way people could obtain a workable mix.

Modern mix design is for a low heat mix (as low OPC content as possible, with as much cement replacement - GGBS or PFA- as possible) and as low a w/c ratio as possible. Adjust the workability by superplasticisers.

Spend your money on mix design and good workmanship and you do not need a waterproofing additive. Curing it properly assists in durability and waterproofing. The cheapest curing agent is sodium silicate. Finish (trowel the slab) and spray it well with that. Cover overnight with polythene or frost blanket according to season to keep it moist/humid. What you do in the first 12 hours will make or break it.

I had several concrete projects built in the Philippines, small garage, driveways etc. Watching the local guys work was painful, they had no concept of the ratio of cement, sand and water. I got my wife to ask several times and they simply did not get the ‘ratio’ idea, they just chucked ingredients in to the pile until it ‘looked okay’, mixing it with shovels. And they slopped loads of water in so it filled the shuttering with less work.

The result was concrete sometimes so soft you could scratch it away with your fingernail. Or rock hard, like steel, but brittle and dark gray.

Then we had a whole 3 storey house built, out of concrete blocks and huge reinforced beams, as it was in an earthquake zone. The contractor was an American guy, who claimed to be a ‘concrete god’. He did indeed know his stuff and had put together a great team of local guys, and he watched them like a hawk to ensure they used the correct mix etc, and he explained loads about concrete to me. And, unusually, he had proper mixers, and also had the vibrator prods to settle the concrete in place and get the air out.