Thread: Ol' guy DIY concrete throughput?

Do you have a mixer? Are you using bags of premix or trailer loads of sand and aggregrate? Do you have a wheelbarrow and various other tools for leveling.

No this is not a job I have done. But a better result is acheived doing it all at once.

If my maths are right then a 4 x 1 metre slab 75 mm (3") thick requires .3 of a cubic metre. If you have a concrete mixer then check it's capacity and work out how many loads are required and decide if you can manage it. 12" of gravel in a '6 x 4' trailer is .7 of a cubic metre if that helps with your decision.

I have some concreting to do on the dam spillway on my property I will also be pacing my self or if I'm sensible get a younger friend to help.

Whitewood

Hi All,
Yeah, sorry, re-reading my question I see that I didn't mention that I'll be using a small mixer (capacity unknown) and I'll be using raw materials (cement, sand aggrigate).

Since I've never done this before, I'm just looking for an idea on how long it takes to mix and dump a specific volume by hand.

Norm

Originally Posted by fly1835

Hi All,
Yeah, sorry, re-reading my question I see that I didn't mention that I'll be using a small mixer (capacity unknown) and I'll be using raw materials (cement, sand aggrigate).

Since I've never done this before, I'm just looking for an idea on how long it takes to mix and dump a specific volume by hand.

Norm

4 sqm at 100 mm thick is 0.4 cubm which is ~1 ton of concrete. All up you have to mix and lay 25 tons of concrete.

To really answer your question we need to know the capacity of your mixer and barrow. Most small mixers can only mix ~150 kg of concrete at a time, so 1 ton of concrete is then 7 loads which becomes a PITA to mix because you will be spending a lot of your time mixing. Another factor to consider is if you are too slow then by the time you are mixing the 6 and 7th loads the 1st and 2nd will be starting to set so finishing the surface won't be as easy as getting it mixed up in fewer larger loads.

Better would be a 250 kg mixer, but then you will need a really good barrow. Remember you have to lift all that sand, aggregate and cement up into the mixer.

Another key factor is, how close to the shed can you get the stuff delivered and the quality of your humble barrow. It would even have been an idea to deliver some of materials on the spot ie inside the area before the roof went up so you could have mixed the stuff on the spot.

If you have to barrow this much concrete for more than about 25 m at a time then this is what is going to knacker you more than anything else. Having a really good barrow will be as important as a high capacity mixer. If you can get one with long handles and a square profile wheel this will make things easier.

Also how are you knees? Laying concrete involves spending a lot of time on your knees.

It's much easier with two people, it halves the barrowing effort and while one person is mixing the other can be laying. When I did this by myself I found myself running between teh mixer and the floor like blue arsed fly.

G'day Norm,
You're picking the right time of the year to be doing your concreting. The last path I did the weather was a bit warm and the conc' nearly got away on me.
I don't like going under 90mm thick and I always lay reinforcing mesh. 80sqm lets assume 8x10. Here's how I'd do it. Use F62 mesh, this means 6mm bars and 200mm squares.I think the sheets are 6x2.4 so I'd need about 4 sheets. The mesh holds your small slabs together so it won't matter what size they are. I'm going to do it in 1m strips so set out a piece of form accordingly. I use a length of 35x70 pine, raised to the finished height of the conc' makes it easy to screed off. Cut a piece of pine the width of the strip for an end stop, this way I can throw it across when I decide I've mixed enough for the day. There's a quarry at The Lakes, not far from here and I use their road base (be careful some RB is totally unsuitable). I buy 20kg bags of cement and the mix I use is 14 shovels (small sqr mouth) of gravel and 10kg of cement. I fire 10 shovels of gravel in then 1/2 bag of cement, let it mix a bit, then the rest of the gravel. Thats it. Doing 1m strips allows you to reach from either side when you're trowelling off.
Norm the mesh is bloody expensive, you can get it with bigger squares and probably lighter guage, which will be cheaper, and still do the job. You've got a fair job in front of you, but remember, you CAN eat an elephant, just not all at once.
Cheers Geoff.

Originally Posted by Boringgeoff

Doing 1m strips allows you to reach from either side when you're trowelling off.

Bloody good idea - wish I had thought of that when I did my shed!

Norm,
good advice from BobL. Yes I try To get my raw materials as close as possible to the job as I can.
When I've mixed my first mix I tip it into the barrow then chuck another load into the mixer. That way its mixing while you're delivering to the job, tip into the formwork and knock it down roughly with a shovel. A second shovel is handy here.
Every 2 or 3 loads screed it off and you're laughing.
Geoff.

Thanks for all your replies:

To respond to the points raised:

BobL: I'd go with the smaller mixer (~150 kg of concrete at a time). I find walking easier than carrying. I'll make 20 trips carrying 10kgs rather than 10 trips carrying 20kgs. Besides, as you say “you have to lift all that sand, aggregate and cement up into the mixer”.

I have, what seems to me, a good wheelbarrow. It's an old Kelso with the iron handles and iron spoked wheel. It's good and solid.

The concrete, sand, and aggregate will be 12m (at the most – and decreasing as the pours progress) from the mixing site and I'm thinking that I can dump the mix directly into the forms. It seems to me that I can move an empty mixer to the form site and place it such that when the mix is done it'll dump into the forms????

Finally, BobL, my knees are fine and so is everything else. It's just that I can only work hard for about three or so then I have to take a good nap.

Boringgeoff: I was thinking along the same lines. 1m wide form size and 35x70 forms. My thought was to use pressure treated pine and leave them in place. I wasn't going to use mesh as I figured the forms would allow the squares to “float”...

I'm interested in your use of roadbase – are you using this instead of sand and gravel?

Finally – back to my original question of throughput. I've got that three hour window of hard work. Assuming everything is as suggested in the responses, how much volume can be loaded, mixed, and poured. I'll take any realistic estimate. Like two mates made a patio x wide, y long, and z thick in nn hours. I can extrapolate that information to figure what I can do in three hours.

Norm

G'day Norm,
Just a bit more about that reinforcing mesh, its been gnawing at me all day. Because you're under cover you don't really need it, but because you're going to do it in a series of small pours you have to have some way of keeping the individual slabs level, in relation to each other, so that over time you don't get a join that you're going to trip over all the time. Years ago I helped a bloke pull up an old slab and it was full of chook netting, so maybe thats something to think about. But mesh can be a pain in the #### because you've got to keep it up off the ground , it's hard to wheel you're barrow over when its up and its costly which is one of the things you're trying to avoid.
To get back to basics, what you want is a hard stand area under cover which isn't going to cost an arm and a leg. You mentioned road base as too expensive well what about cracker dust (or crusher dust or metal dust). This is what quarrys have left over after they've screened their smallest product off, be it 7mm or 5mm whats left is dust and because its a byproduct it should be very inexpensive. You put that down, level it, wet it with the hose and you will end up with a reasonable surface.
Norm, I hope I'm being helpful here and not confusing you too much.
Geoff.

sorry Norm i missed your last post, writing mine, it takes me bloody ages because I only use two fingers, my son calls it hunt and peck.
The road base available here is from a hard rock quarry and i came across it accidentally.We've only been at Bakers Hill for 4 years since we moved down from the Pilbara. I bought some premix which is, as its name suggests, a ready made concrete mix. I ran out before I had finished what i was doing and went and saw our local contractor. He had this roadbase and it looked ok to me so I grabbed a ute load. It was better than the premix, and a lot cheaper. That's all I've used since. But the road base that I've ever seen before would not have been suitable as it's generally got too much clay content. A lot of concrete companies sell premix but they also are generally fairly expensive. I prefer to use a premix as against individual heaps of sand and aggregate. Geoff.

Originally Posted by Boringgeoff

You mentioned road base as too expensive.....
Geoff.

When I mentioned roadbase, it was in the context of quotes and getting someone in to do the job. The raw materials are all pretty reasonable..

Roadbase here is going for $38 / m3. I just checked TCB price list for that price when I noticed a column labeled Concrete Mixes with a sub-heading labeled Handyman Mix 10mm for $58 / m3. E/Gad - if that's premix with everything (cement, sand, and aggregate), I'll take it!! That's cheaper than buying the cement alone..

Norm

No Norm put the E/Gad on hold, handy man mix won't have the cement in it (if cement it had, it's hard she'd be going a'fore it got out of their depot) but what it is, is all the ingredients you need, apart from cement, and that is probably a reasonable price all the same. Geoff.

Originally Posted by fly1835

When I mentioned roadbase, it was in the context of quotes and getting someone in to do the job. The raw materials are all pretty reasonable..

Roadbase here is going for $38 / m3. I just checked TCB price list for that price when I noticed a column labeled Concrete Mixes with a sub-heading labeled Handyman Mix 10mm for $58 / m3. E/Gad - if that's premix with everything (cement, sand, and aggregate), I'll take it!! That's cheaper than buying the cement alone..

Norm

Norm
that concrete mix will be a mix of sand and aggregate to which you will add cement.
The normal home mix would typically be 80 kg of coarse aggregate and 40 kg of sand to each 20kg bag of cement. (The standard 4-2-1 mix, to which you add about 6 litres of water, preferably less)

in terms of your output, you could time yourself
a wheelbarrow of concrete is about 2 cubic feet which matches the capacity of a small mixer
in even numbers there's 36 cubic feet to a cubic metre
so after 18 small mixer loads you will have about 1 cubic metre of concrete.
4 square metres at 100mm thick is .4 of a cubic metre (which coincidently is equivalent to 1 tonne)
your 80 sq.m slab, if 100mm thick, will require 8 cubic metres + an allowance for uneven ground.

Figure on a 2 hour working window, as after 2 hours finishing the first load will be problematic.

Your schedlue might be
Day 1 form up for the pour
Day 2 mix - pour - finish
Day 3 strip the forms and set up for the next pour (a release agent on the forms will make stripping easier)
repeat Days 2 and 3 till you finish

By all means use a structural mesh to hold all the small slabs in approximate alignment

Planks or similar smooth surface will make moving the concrete easier
Use a barrow with a properly inflated tyre

now load up your barrow with wet soil or sand and push it around the yard to see how many loads you can move before you need a serious rest.


An alternative would be to cover the area with a mix of crusher dust and power station fly ash -- the local concrete plant (or quarry) should be able to supply it as a dry pre-mix.
Once it's all laid and leveled, wet it with water and it'll gradually go nice and hard

Thanks everyone, for the advice.

I've attached two pictures to show the new covered area between the house and my shed.

It'll be nice to roll my tablesaw (and such) out of the shed and be able to work in the open air.

Norm