Laying a concrete drive?

[N.O.S.]

Can we read anything into the fact that the 'pro's have so far made no comment about the use of reinforcing fibres? :whistle:

[Rover8FFR]

Engineered mixes would be overkill for a simple slab......IMHO! You would only want to use polypropylene fibers anyway as the metal ones rust on the surface.

 

For those that want to know more.

 

http://en.wikipedia.org/wiki/Fiber_reinforced_concrete

 

Happy Days!

[N.O.S.]

Aha - thanks for that, Wayne. Looks like the fibre's main application is in reducing shrinkage cracks, any additional mechanical strength is minimal - article says it does not replace use of structural reinforcing (e.g. rebar).

 

A friend of mine uses fibre mix for everything now (weighbridge slabs, workshop floors), but I'm not so sure he is getting as much benefit from it as he thinks.

[mike65]

Can we read anything into the fact that the 'pro's have so far made no comment about the use of reinforcing fibres? :whistle:

 

Reinforcing fibres have there uses.

Metal ones make good tooth picks, but not so good on the teeth.

 

You need to ensure they are spread evenly throughout the slab and that the concrete is well compacted. They are mainly used in large pour building slabs with a power float finish. Allows thinner slabs and larger bays between joints. Don't ask me how to design one as it is a black art, with only a few people who actually know the full details.

Also need to bear in mind that the companies whom provide these slabs seem to go down the pan every few years. A new one starts up with basically the same people and of course the warranty on the slab is completely useless if it goes wrong. Not often but it occassionally happens.

If metal fibres are near surface they rust and discolour concrete. They look awful when they are at surface level and if they are sticking up on your driveway the first you know about it is when you sit on it.

Of course glass fibre reinforced concrete has been about for a while but is mainly used for precast bits like drainage channels etc.

 

Mike

[mike65]

Engineered mixes would be overkill for a simple slab......IMHO!

 

Probably right but it is worth comparing ready mix to DIY concrete for a small area, especially if you need to hire a mixer. Mind you 1.4 cu.m is not a full load.

 

Whichever way you go make sure you do the slab in one continuous hit without long breaks between adding concrete you are mixing.

Bearing in mind the shorter, colder and wetter days, if you cannot do it in one hit postpone or divide the slab into sections with a simple butt joint. A piece of timber as a vertical shutter will do this.

If you don't it will crack and spall at the meeting point.

 

Do you think we should bore and baffle them with slump tests?

 

Mike

[N.O.S.]

.....Do you think we should bore and baffle them with slump tests?

 

Mike

 

No, go straight to the dangers of buying cheap ballast with chalk inclusion :cool2:

[Degsy]

Avoid using Granite based aggregate as although it is very hard wearing due to low PH it encourages the growth of algae and moss.

[LoggyDriver]

I used to spend many a long night concreting when I was a Tower Crane Driver. It's like Pringles, once you start you just can't stop.