Ol' guy DIY concrete throughput? [Archive]

Norm.Mareeba

6th May 2011, 09:26 PM

Hi All;

My age isn't very important to me. Sure, I'm not as fast or as strong as I once was. My work style is now more “paced” and smarter – less brawn, more brain.

I recently put a shed type roof over the area between my workshop and the house. It took me a couple of months to do. A younger me would have done it in half the time.....

I'd like to put a hard surface on the newly covered area. I've checked out the various options (pavers, slab, roadbase) and got quotes for some of the options – all too rich for my piggy bank.

I've decided that I'll to pour a concrete slab myself.

Sure, I won't be able to mix and pour it all in one go (80sqm) but I could handle, say 4 sqm. It would only take me 20 days to do the whole area. Trouble is I don't know if I could actually mix up and spread 4 sqm.

Ok, so my question is how much volume can an Ol' guy like me, working steady, mix and pour in say three hours? That's about my time limit for hard yakka.

Thanks, Norm

…. “How much wood would a woodchuck chuck if a woodchuck could chuck wood?”...

Handyjack

7th May 2011, 08:20 AM

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.

whitewood

7th May 2011, 08:48 AM

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

Norm.Mareeba

7th May 2011, 09:23 AM

BobL

7th May 2011, 10:35 AM

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.

Boringgeoff

7th May 2011, 10:41 AM

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.

BobL

7th May 2011, 10:59 AM

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!

Boringgeoff

7th May 2011, 11:04 AM

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.

Norm.Mareeba

7th May 2011, 10:10 PM

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

Boringgeoff

7th May 2011, 10:20 PM

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.

Boringgeoff

7th May 2011, 10:50 PM

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.

Norm.Mareeba

7th May 2011, 11:12 PM

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

Boringgeoff

7th May 2011, 11:26 PM

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.

ian

7th May 2011, 11:49 PM

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..

NormNorm
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

Norm.Mareeba

8th May 2011, 04:54 PM

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

ian

8th May 2011, 11:16 PM

Hi Norm
you've got your work cut out
1st you'll need to remove all that grass and some of the soil underneath, to a depth of 150mm or so
2nd you'll need to spread and "sort of" compact some sort of base material -- crusher dust or out of spec road base would be suitable
you should be able to hire a self drive bob cat to do most of the excavation and levelling work -- just make sure you have had a bit of practice before getting too close to the house or shed -- and a wacker plate to do the compacting
when you've finished with leveling the select fill you would want to have a flat central section with the last 2m or so at the open ends sloping into the rest of the yard so water runs off.

concrete wise,
if your lifting preference is two 10kg loads over one 20 kg one, 150kg of wet concrete from each mixer load will be a real challenge
Allowing for the barrow to give you a 2.5 to 1 mechanical advantage, 25kg of wet concrete equates to a 10kg lift and carry at the barrow's handles.
so one 150 kg mixer load would require about 6 trips with the barrow. Candidly, I don't think you are up to that and it would result in a really really crappy surface unsuitable for rolling the table saw about on.

A better option would be to arrange the mixer so that the mix dropped straight into your forms -- meaning all you have to do is load the mixer, mix, drop the wet mix where you want it and level it out. Working this way you might manage enough concrete per 3 hour window, to do a 4m x 1m strip.
Don't forget that your 3 hour window has to include cleaning up your tools, mixer and barrow

Formwork
Given your intent is to produce a surface suitable to wheel your table saw about on, leaving the formwork in place is not a good idea.

If a single 80 sq.m slab by a contractor is too much in one hit
• the cost should reduce significantly if you do the site preparation yourself
• you could pour the slab in 4 sections, using a mini mixer to deliver 2+ cu.m each time. Spreading the cost over several months / pension cycles

Norm.Mareeba

29th June 2011, 09:40 AM

Hi All;
Thanks for your input - just thought you'd like to see the progress so far.

Each pour turns out to be a two day process. Day one I put down the forms and day two mix and pour, and etc. On the "pour day" it's a continuous one-man process - one bucket of cement, while mixing do some more screeding, one bucket of "handymand mix", more water and more screeding while that mixes, and so on.

I'm making the mix a bit wet as it's easier to handle in the forms - about the same wetness as what comes out of a ready-mix truck.

Using the above process I'm able to work all morning and pour 6 squares (1Mx1Mx75mm). In the afternoon of a pour day, I finish off each square by edging it and putting on a brush finish.

I'm about 1/3 done - all in a week so at this rate, another 3 weeks should get all 80 squares done.

I'm not finding it too hard now. After the first few pours, I was really knackered - muscles so sore that I could hardly walk but my body is hardened up now. Besides I've learned a few tricks to help take the weight off the job. Like putting a bench close to the mixer where I can rest a full bucket of sand before having to lift it over the lip of the cement mixer.

Any, a few pictures and thanks again...

Norm

ian

29th June 2011, 10:03 PM

Great to see your progress Norm.

If you don't mind me asking, when you say you're making the mix a bit wet, approximately how much water are you using? about the same size bucket as you're using for the cement or a bit less?

Also great to hear that your body has hardened up.
when this job is done you'll have to find another to keep yourself in shape :)

Norm.Mareeba

29th June 2011, 10:42 PM

Hi Ian;
Water ratio - hard to say.

I'm using a 10L plastic bucket. I'm using a 1 cement to 4 buckets of "Handyman mix", which I've been told is 50/50 of sand and gravel.

I add water by hose in between each dump of the 10L bucket. Enough to keep mixture from klumping but not so much that it runs like water.

The final bucket of "Handyman mix" turns it back into a klumping mix. I then add water slowly so that it ceases to klump and starts to flow off the mixer blades. Too much water and it pours off the blades, not enough and it sticks. Such a fine line....

I tried the .6 water to cement ratio (6 litres) and all it did was make big 150mm concrete balls - impossible to spread into the forms.

Anyway, that's about the best I can do to answer your question.

As for part two "hardening up", I've always got a new project on the go.. Trouble is, each new project seem to tax an entirely different set of muscles.

Norm

3RU

29th June 2011, 11:03 PM

Sitting on the side and watching this unfold is an education in it self. Great job Norm.

Takes me back a few years on a friday arvo in the workshop talking about the coming weekend. One of the fellas tells us how he is going to put down 20 meters of concrete on Saturday .... on his own. Plenty of laughter and off we go.

Monday morning "Harry" arrives bright as a button .. How did you go??..... Yep all fine and done by 10am. Yep right, you and what army??.... No ... just me by myself.

Sure ?? Well, My Mum is really pleased with the 20m of new concrete garden edging.

Garden edging ?? Yes it looks great !

ian

29th June 2011, 11:22 PM

Thank you Norm
have you tried changing the order in which you add the material to the mixer?
something like 2 buckes of the handiman mix, then the cement, then 2 more of the mix before you add the water?

I ask because the mix you're making sounds very weak and I'd hate all your slabs to carck and move all over the shop a few months after you finish.

Christos

30th June 2011, 09:40 AM

Great work fly1835. Little by little it gets done.

Sure ?? Well, My Mum is really pleased with the 20m of new concrete garden edging.

Garden edging ?? Yes it looks great !

:roflmao:

wun4us

1st July 2011, 10:41 PM

Looks good Norm little by little, bit like the saying"softly, softly, catchy monkey".

All good things come to those who wait.:2tsup:

Boringgeoff

20th September 2011, 09:33 AM

G'day Norm,

just thought I'd check in and see how you got on with your project.

How about a photo of the finished area?

Regards,

Geoff.

Norm.Mareeba

20th September 2011, 05:32 PM

Hi Geoff;

Yes, it's all done! Thanks for asking...

Some numbers: It was 80 sq mt. I was able to pour 4 sq mt per day. So it took me 20 days. The estimate to get it done was $6000. The materials cost me $2000. So I paid myself $4000 or $200 per day. Not bad wages, eh?

I move all the contents of my shed out onto the slab after it (the slab) had curred for 15 - 20 days so I could give it (the shed) a good clean-out.

I'm now at the stage where the shed is clean and I'm slowly moving "stuff" back in.

I've decided to put everything in the shed on wheels and picked up locking caster off of eBay. 24 wheels, 3 inch dia, 65kg load, for $220.

I've just completed a wheeled plywood/lumber/scrap carrier and wheeled carriers for sander, grinder, drill press, and band saw. I saw an interesting picture where one bench tool was bolted (upside down) to another bench tool. The tools rotated about a central pivot point. The desired Tool was rotated to the bench top and, of course, the other tool was hidden beneath the bench top. I liked it!

Anyway, here is some pictures showing both the shed and the slab...

Norm