Concrete Additives?

jdpl28

Hi, does anybody know where you'd get concrete additives - specifically concrete fibre additives?

thanks,
Justin

C Eng

How much concrete or fibres do you need, ie: is it a big pour?

jdpl28

em, no. maybe just 1-2 bags of cement.

CJhaughey

What are you looking for exactly? Polyester fibres? Chopped glass?
Is it for a sink or some kind of decorative "concrete at home" project?
There are additives out there but I need to know what exactly you want.
Not all places carry all types of additive.

jdpl28

Fibre additives. Need to make the concrete really strong & resistant to cracking.

Also, doesn't pollybond improve the concrete strength as well?

CJhaughey

If it is only a small amount of fibre you need the best stuff is polypropylene fibres, these will stop cracking.
Alternatively you can get fibreglass mesh, I used this on my render coat on the house, it has 0.5cm squares and comes on a big roll from STO.
All depends what you are doing with it.

jdpl28

where would you get the polypropylene fibres? any building merchant?

thanks,
J

jdpl28

hey, went to the local building suppliers, and they hadn't heard of them. Is this kind of a specialist product that you'd need to buy from a specialist store? if so, is there one in Dublin?

thanks,
J

Martron

maybe if you told us what you need with it. we could offer some suggestions

jdpl28

Martron wrote: »

maybe if you told us what you need with it. we could offer some suggestions

sorry, if you look up slightly further in the thread...

I need them to improve the strength of a concrete slab I'm laying.

Martron

sorry i did not see anything about the slab.

what size is it? you said a few bags of cement but that is an ingredient of concrete and although gives a small indication of the amount of concrete it does not give an idea of the surface area.

if its a small area chances of cracking is minimal. What will the slab be used for? how deep do you intend it to be? inside or outside?

expansion joints could minimise cracking.

jdpl28

ok basically I want to make the concrete really really strong. I'm installing a floor safe and embedding it in concrete, so that's basically why I want to make it as strong as possible.

thanks,
J

C Eng

Why dont you add a layer of mesh reinforcement and opt for a stronger mix in that area along with deepening the slab locally

Martron

mass concrete should be good enough( no reinforcement)

the fibres will only increse its tensile strenght. but a kango hammer will break through it liek regular unreinforced concrete.

To make it awkard for breaking i would put steel mesh inside the concrete. you can get a sheeet from any builders providers at 2.4m by 4.8 iirc.

a142 ( mesh grade) should be good enough for you.

As for the slab itself you would want to make it an irregular shape so it will not be easilt pulled from the ground.

i would suggest an inverted t shape. so the extra toe on the slab will increase subterrain surface area thus making it harder to pull from the ground.

35 newton concrete should be strong enough with that reinforced mesh.

if you pm me i will email you a rough sketch which might explain my idea better

jdpl28

hey, thanks for your reply. Just one thing - whats 35 Newton concrete? Is this just a particular mix? or a type of portland cement?

thanks,
J

CJhaughey

It is the concrete strength.
When you order concrete from a factory, they will ask you what strength you want and what grain size, so you might order 35N10 which is 35 newton strength and grain size 10mm and down.
This will polish well and be strong especially if you use steel mesh with it.
I would try and use a concrete vibrator as well to get the air out.

bauderline

I have been looking at the cheng design stuff. Does anyone know where you can source the fibre additives and colouring in this country or is it an order over the Internet job ?

Constructing a concrete worktop looks like a nifty little project....

P.

CJhaughey

Internet is your friend for that stuff I imagine, but If you find a local supplier that won't rob you let me know!

bauderline

You can get the fibres (black knight) and pigment off ebay for what appears to be reasonable money...

P.