Should i see fibers in my concrete ?

[michaelthegardener]

ok so I had a bit of concrete left over Friday chucked it in a paint tray today I broke it out should I be seeing fibres in it ? and if I should and they didn't put them in how much of a problem do I have

[Brucieboy]

Did you ask for fibres to be added? If yes, did you specify any particular type? Most common are the monofilament ones but macro fibres are used for certain applications.

If the supplier used monofilament ones, they are very fine (much smaller diameter than a human hair) usually about 12mm in length. Have a very close look at the broken concrete to see if you can see them. If you asked for fibres or told they were going to be included and they weren't, I'd take this up with the supplier and see what they say.

Monofilament fibres are principally used to control plastic shrinkage that occurs in first few hours after placing. They do not enhance the structural strength of the concrete. They're not absolutely essential providing you cure the concrete properly after placing. You've used a plastic sheet for 24 - 48 hours so your slab should be fine. Can you see any hairline cracks now - have a close look?

Presumably you didn't you use any mesh reinforcement? It's useful but not necessarily critical for a shed base. Most important is to have a well compacted base prior to placement which I believe you had.

[rxbren]

If you had a volumetric mixer the operator would have had a bucket of fibers which he would throw in every time the cement tank was vibrated

[michaelthegardener]

didn't see any fibres at all he just turned up and we cracked on I just assumed it was what I ordered :p

[rxbren]

Check your invoice all the ones we had they had to manually add them unless newer wagons have automated system

[Captain Concrete]

Most modern volumetric lorries should come with automated system for fibres manly for use with screed.