Hi!

Got an area of the garden that I want to turn into a sort of patio (terrace). Ain't a large area, roughly 4 by 5 metres (12 by 15 foot). Reckon I'll have to use concrete, but know nothing about mixing concrete up. The GF insists I do the job myself - she just hates to see me relaxing, heh, heh! The patio wouldn't be supporting heavy stuff, just some tables and chairs, flower pots (lots of 'em) and other things. Maybe also a roof, if that makes any difference.
The said area is pretty level - I'm aware that I'll have to level it off where it's needed. Oh, the garden soil is sandy - it's definitely not "earth". Don't want tiling done or anything fancy - just the bare concrete. Don't have (or want to have!) concrete mixers or other machinery - the job has to be done using the bare essentials.

Question is, how the hell do I mix concrete (by hand) and how thick does the layer need to be? Does the whole area have to be concreted at the same time, or can part of it be done - and the rest later ? What is actually the difference between concrete and cement? A step-by-step guide would be great!

Any hints (polite ones, preferably!) ? Thanks!

[quote="scooter"]Hi!

Got an area of the garden that I want to turn into a sort of patio (terrace). Ain't a large area, roughly 4 by 5 metres (12 by 15 foot). Reckon I'll have to use concrete, but know nothing about mixing concrete up. The GF insists I do the job myself - she just hates to see me relaxing, heh, heh! The patio wouldn't be supporting heavy stuff, just some tables and chairs, flower pots (lots of 'em) and other things. Maybe also a roof, if that makes any difference.
The said area is pretty level - I'm aware that I'll have to level it off where it's needed. Oh, the garden soil is sandy - it's definitely not "earth". Don't want tiling done or anything fancy - just the bare concrete. Don't have (or want to have!) concrete mixers or other machinery - the job has to be done using the bare essentials.

Question is, how the hell do I mix concrete (by hand) and how thick does the layer need to be? Does the whole area have to be concreted at the same time, or can part of it be done - and the rest later ? What is actually the difference between concrete and cement? A step-by-step guide would be great!

Any hints (polite ones, preferably!) ? Thanks![/quote]

Please have a look here:
http://www.diydoctor.org.uk/projects/mi ... ncrete.htm

Acually you can buy ready mixed backs. All you need add is water. Cementhai or any supplier will expain anything else to you. MAybe it is wise to lay some steel gritts inside to stabalise the hole platform. Ask for this too at the supplier, they have anything you need.

Scooter, you will be suprised at how much concrete you may need. I would anticipate 10cm/4inches depth would be plenty adequate, but you could get away with half that if you wanted.

Best bet is not to do it yourself as you will end up with a bad back, aches and pains and levelling the concrete (and providing a slight drain slope if neccessary) is very difficult for a first timer to produce a smooth surface.

You will need a sand cement mix of about 4 to 1 ratio (4 parts sand to 1 cement) before it hardens to "long life" concrete. The area can be dug out and sectioned off with wooden squares/rectangles, after completing a section the wood can be extended to move on to the next section. The mix can be done in a wheelbarrow or trough, but you will be suprised how many of these will be needed to complete your "small" area. A wheelbarrow mix would typically be a whole 25kg bag of sand hollow out the centre of the sand and pour in approx 1/4 a 25kg bag of cement powder in, start to "dry" mix and add water from a hose, when the powder and sand are of a thick but completely mixed and "fluid" not "runny" texture (should only take 4 to 5 minutes of stirring, gradually adding water as you go, it will be ready to be poured and levelled before leaving to set slightly hard, moving the wooden section to next area leaving one side open against the setting concrete and continue the process.

I would strongly advise getting a professional in to at least assist even if not do the job completely.

My father-in-law (near Ban Phu) is an expert, I can put you in touch with him if you require?

If you want it risen, you will have to buy some timber, make a frame for the cement to sit in. Ideally though, you want to dig down 10cm and put the wooden frame in that.

You can do it part at a time, but its really now that difficult to do. If you do not buy pre made bags (which are alot easier) you will need to work out how much sand you need. For a patio you dont need anything stronger than a 5 or 6:1 ratio. You dont need steel reinforced concreate as you are not building anything that requires that kind of tensile strength (and we dont get many earthquakes here).

You need ballast which has small stones in it. Now just sand. I recommend the stones about the same size as 10baht coin.

All you do, is have a pile of sand and a bag of cement, Shovel maybe 10 lots of ballast to the centre, then 2 shovels of cement, then another 10, and 2 again. This should be a nice healthy pile.

Then you shovel all of that to one side, and then shovel is all back to the other, and it should therefore be mixed together. Then you part the centre of the mixture so you create a bowl shape. Pour in the water and let it soak over the newxt few minutes, then you drag the top of the bowl shape into the middle, and once you think it has been soaked enough, you then start to spread it out.

You need another piece of wood, to "wap" the top. This will smooth it out, and it make sure there are no bubbles etc in the finished product. Once this has been done a long piece of wood that spans the frame will make sure its all level.

DO NOT do small layers. Just start in one corner, and you will not have a problem. Again don't do it in like 2-3cm layers, keep it thick.

E

BanPhu wrote:I would strongly advise getting a professional

very good advice

Now, I have to laugh, not at you Sooter at my own feeble attempts at concreting.....

I had a similar sized area 6m x 5m behind our main bedroom that I wanted turned into a breakfast patio. Was going to concrete it and maybe tile as well..

After 2 weeks screwing up the mix and wasting countless bags of cement and deliveries of sand and stone, levelling, what the hell is that all about...? and having the neighbours in stitches most of the time I threw in the towel and had the local builders come in. they completed it in 2 days (that also included removing my "rockery", cos thats what my attempt turned out like........). I consider myself quite the handyman, well with electrics, plumbing and woodwork anyway......

Do yourself a favour, get a professional in..it's cheaper in the long run and much faster..

scooter, Don't know what type visa you have, but when my wife tries to get me to do something like what you are talking about, I tell her visa say "NO WORK";o) The advice others have given is well founded, cement work just ain't fun.

concrete is easy enough to do, but if you have never done it before, don't try. but supervise, at least 4in/10 cm, put wire in it, basic stuff, since no great weight on pad. form it out one day, pour the next day, early in the morning, you want to finish at one time. mix, not sure, but i think, 2 parts sand, 2 parts stone, 1 part water. check google for 'portlland cement' should have, well know cement producer. use good cement, portland, or similar. they use 2 types here, foundation/pads, and chap, final coat on walls. supervise the mix, every one, if you turn your back, they will put too much water in it, makes it easier to mix and handle, but it will crack or chip or peel. final finish, give it a rough leveling w/ slight pitch for water run off. let is cure a bit, then come back finish it. if you try to finish all at once the mag will pull too much water to surface and it will peel. if you do it yourself, have couple helper to do the mixing, as it is a work out and you will hurt yourself, unless extremely fit and used to manual labor.

if you pour the cement and notice water on surface right away, there is way too much water in mix, this is the most common mistake, plus the cheap cement. if diluted, it will crack.

good luck

I am not an expert but 3:2:1 comes to mind.

(3-2-1) 3 Shovels of rock, 2 sand, 1 cement.

Here is USA, they sell concrete in 90 lb bags. So 270 lbs of rock,
180 of sand and 90 lbs of concrete.


You would be suprised at how little volume the above mix fills!

I can remember doing a job like this with my Dad. Of course I was
aroud 14 and did all the shoveling and mixing

I found this link by goggling 3:2:1 cement mix:

http://www.marshallconcreteproducts.com/mainfun.html


Thanks Dad

I am surprised no one has mentioned "Ready mix" Prepare the area, get the lorry in, level it off, "Bobs your uncle" finished.

valentine wrote:I am surprised no one has mentioned "Ready mix" Prepare the area, get the lorry in, level it off, "Bobs your uncle" finished.

might work 2 cubic meters, the good stuff runs around 1650, but for this could get away with 210, about 1500 per cu meter. Make sure your forms hold They also might charge extra because of small load, check around for the best price, and good luck, they will only pour it, you will have to spread it and level.

www.coolthaihouse.com or

http://coolthaihouse.com/forum/viewtopic.php?t=672

Oils ain't Oils and concrete ain't concrete. In the metric world concrete goes by the compression strength, Mpa mega pascals or PSI.
In down town Oz the usual mix ordered from the premix truck delivery is 20/20/80 =20Mpa 20mm stone 80mm slump, they test the slump by placing the concrete in a cone 500 high and then removing the cone to see how far the concrete slumps, the more slump the more water has been added. Here is where the good practice comes into place,

Concrete strength is based on the cement water ratio, more water the more cement you need to add, What KILLS the concrete strength is not enough cement and to much water.

Preperation is vital for a long lasting good finish, all concrete should have a sand bed of 50mm under it to allow for movement, and a sheet of 200um plastic 0.2mm, this stops ground water from rising up bringing salts ETC to the top of the slab , keeps the slab moist when drying, stops the moisture from being sucked out of the slab to quick.

A good slab will have steel mesh through out it to control crack movement, all ground slabs have a crack control joint inserted about every 2400mm, when it cracks, it will crack along the control joint, usually a small groove placed about 10mm into the slab

If tiling or other hard finish, the tiles start either side of the control jont, so not as to crack the tile, Silicon or other flexiable compount is used between the tiles where the control joint is,

Keep the slab wet for 3 weeks, moist so to let dry out slowly to give maxium strength, NEVER lay or treat the slab with paint tiles or other finishes for a least 30 days, to much moisture is being expelled from the slab during the drying period, you risk the finish product comming off, the glue , paint Etc will bubble off from the curing reaction.

A well preped slab as above, good mix not to wet, and if Thais know what a vibrator is good , Vibrated slab will increase the density and strength, Have not seen one being used on the domestic job there, but a stick with a flat board paddle about 150mm x 150mm 6 inch x 6 inch square ramed up and down over the slab while being poured will do fine, helps remove the bubbles, the paddle will only sit on the surface and moved up and down about 30mm for about 10 strokes then move it along, can be up to a foot square.

Come back in 20 years and you still have a first rate slab, no cracks showing, well worth the time and effort to do it right so the slab remains in good condition over the years.

Nothing is more sad than see a cracked slab only a few years old, with lifting tiles or finishes on it.

Do the job right and you will have a first class slab for life.

Thai compression strength is Kilos per centimetre/ Mpa is 0.1kilo per square metre, SO 20Mpa concrete is 2000 tonns pressure per square metre, Thais 1600 mix concrete is 1600 tonns per square metre, before the concrete cracks, under a test conditions, using a sample of concrete 100 mm diam 200mm high on a steel bed with a hydralic press.

In real life you have ground movement, soft under soils, so you will never be able to get those loadings, with a thin slab, so steel, sand , plastic sheeeting and good practice will make for everlasting concrete.

As for finishing we call it EXPOSED finish, river stones are used in the mix or thrown on top of the slab during placement, worked into the slab, and after it has gone off in a hour or 2 , just so you can walk on it, you use a soft hair broom and a hose with a fine spray to wash out the cement, to leave you with the stones exposed, you can get some good coloured river stones, Never quarry stones , as you will not to able to walk on the sharp quarry stone, must be round river stone.

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Kally,that was an excellent summary!!

BKKSTAN wrote:Kally,that was an excellent summary!!

agree

Think I just assumed scooter knew he was going to have to tire 9mm steel. You can't just dump concrete on the ground and call it a slab.

Think in the end you will want to tile it. Just look for some locals and get a price for the completed job. Much cheaper in the end Your only responsibility will be to water it, day & night (thai's don't like water), and follow Kally's advice for when to apply the tiles, and inform the workers