rapid set concrete

[w0rksh0p]

hi folks

please excuse the novice question, but is rapid set concrete suitable for deck posts?

i'm building a 4x4m deck from T/P. 90x90mm H4 posts.

i've been told that i should use traditional concrete for the posts as it is stronger over the long term.

am i being il-informed?

thanks

[pawnhead]

No. (You're not being ill informed)

[HappyHammer]

If you use the quik-crete stuff (although advised against) wear gloves as it burns like buggery if you get it under your nails or in any open cuts.

HH.

[manoftalent]

quick set concrete is as it says .....it "turns" in around 15 minutes or less depending on the warmth of the day......if your short on time, it will do the job ...but its better to use "standard" concrete .....it may take a day or so to set ( go off)..but its density is much better than quickset .....it traps less air bubbles because it has time to "fall" into place ....quickset starts setting the moment you add water to it and so creates small air holes ...thus leaving a lesser density than standard concrete ...and more option to fracture at a later time ...

mark out your deck ....dig the holes .....level the posts and use offcuts nailed onto them to keep them straight while you add concrete......recheck levels after concreting....and wait ....

[rrich]

Quick set concrete is best for patches where traffic is expected immediately. I've used quick set concrete and it is amazing how quickly the stuff becomes un workable.

Quick set usuaslly comes in smaller quantities and would tend to be more expensive for a larger job. Quick set used for setting posts for a deck would offer no advantage that I can see. I don't think that you could mix enough quick set concrete to set a single post for your deck. The quick set concrete would be hard before it was completely mixed. Remember when setting deck posts in concrete footings it is better to err on the side of too much concrete than too little.

[Chumley]

I don't think that you could mix enough quick set concrete to set a single post for your deck. The quick set concrete would be hard before it was completely mixed.

[Warning: personal opinion coming up...]
If you use quick set I think the idea is to dump the dry mix into the hole, then add water and stir it around -- completely goes against the grain of what concrete is about, and really only suits those awful TV makeover shows where everything needs to be done as fast as possible to fit the weekend away of the owner (and the 30 minute show) -- take the time to do it right and enjoy the benefits.
Cheers,
Adam
[end of personal opinion]

[bpj1968]

Otehr way around, water first then quickset. The falling of the quickset through the water is the only mixing that occurs, although it is premixed. It's main purpose is NON-STRUCTURAL work, fenceposts letterboxes and the like, not footings.

[patty]

Spot on BPJ1968 Rapid set states it should not be used for structural applications in saying that i tend to use small amounts of it on posts just to get them into position then top them up with the good stuff!

[Chumley]

Otehr way around, water first then quickset. The falling of the quickset through the water is the only mixing that occurs, although it is premixed.

The ground's so dry here if you pour water into a hole it'll disappear before you get a chance to add the mix.

[oohsam]

yeah you're supposed to put water in the hole first, presoak the hole the day before with water so the ground does not absorb it.
I just used some quickset on some here on some posts that were being used for a step for my deck. The stuff is rubbish. It did not dry in 15 mins, and the post has some wobble in it. I only half filled the hole though, i filled the rest with real concrete that i mixed. Much better.

[rrich]

If you use quick set I think the idea is to dump the dry mix into the hole, then add water and stir it around -- completely goes against the grain of what concrete is about,

Adam,
Absolutely brilliant! I would have never thought of that.

Here a 20 pounds of quick set costs about $11 while a 90 pound bag of bag of standard concrete mix for about $3.37.

[Bloss]

Read the instructions on the bags of mix and you will get the right info - or go to the various sites for technical papers and other info. Thsi site is amngst the best although very technical:

http://www.concrete.net.au/index.php

For all practical purposes it depends on the height of the deck and how much load is going to be on it (in all directions). For a deck below about 600mm from top to ground you could use quick set as its reduced strength will have little impact so long as you use correct footing hole sizes etc.

But as others have said mostly there is no need to spend the extra money as the normal construction methods allow for siting stable posts (using angled struts etc) in position and the pouring of regular concrete mix around them (or around the stirrups if these are being used).

Main use is on fence posts etc or to get a temporary fix in place before pouring regular concrete into place.

And although it is not as per instructions I have often mixed rapid set in a barrow and placed it where needed to ensure an even mix - as with regular concrete the mix needs to be wet enough to put in place and settle, but not runny. Have to work quickly though especially in hotter weather.

All concrete is strongest when there is sufficient water to ensure a full chemical reaction and no more. Over-wet concrete will end up as a weaker structure whether rapid set or regular concrete - that's why accurate measurement of all parts of the mix is essential.