Workshop floor / concrete.

[FridgeFreezer]

Bummocks.

Looks like I'll just have to make do with a slightly uneven workshop floor then.

Al - couldn't you save a lot of hassle and just keep your build in this?

[Astro_Al]

Bummocks.

Yuhuh.

If it was just for the vapour I wouldn't bother...

Al.

[bishbosh]

The best way to remove your puddles Fridge is to use an epoxy repair mortar.

Goes off in about an hour and can be laid in thin layers. Just avoid a feather edge as that will fail - go round the edge of the depression with a grinder and cut a lip at least 10mm deep. That will form a good strong edge to your repair. Make sure the rest of the depression is at least 10mm deep too.

As with all decent gear, it wont be cheap, but it will be strong and long lasting.

Look for Metaset or similar.

[africanpete]

I agree with all the comments above and it looks like you have 3 choices:

1, Accept the floor as it is now but this will bug you when it finally becomes your workshop

2, Go with bishbosh's epoxy repair mortar, will probably be the easiest option as can be almost self levelling.

3, Go with at least a 40-50mm screed with some light mesh re-inforcement. You would'nt have to screed over the new slab as you could set this to the height of the screed but I have to say that unless you have screeded before you will probably get a similar finish on the screed as you got on the original concrete, laying screed flat is not easy (no dis-respect intended) plus this is not an ideal floor for a workshop.

I think that both options 2 and 3 are going to be expensive but I think the epoxy will be easier and better suited to a workshop/garage environment, remember that most/all workshop or warehouse floors are polished or floated concrete slabs, thats's why they last.

My bro in law has just had a concrete pad laid in his garden. Mixer turns up and only mixes what you need. Much cheaper way of doing it. Charge by the 1/4m. The more you have the less the charge per m. Chute on the back had a 5m reach.

You can't go wrong with this ^

Pete

[Astro_Al]

Current bit starts here!

Hi guys, sorry to drag this back up.

I have just ordered 25 cubic metres of C35 with fibres to be delivered in 10 days. Since the roller shutter door is a few cms too short for the concrete lorries to get inside, I have had to (being too lazy to wheelbarrow it myself) order a pump truck with a boom and hose.

So now its serious. I need some tips.

1. A lot of concrete companies I got quotes from said that steel reinforcement is not necessary with fibres, so at this point I have no plans to use steel mesh. Do people agree with this?

2. Has anyone used a pump truck to deliver concrete through a hose? Any tips on the how to (it'll be me on the hose, and the guy running the pumps)?

3. Once I've squirted it in, I'm looking at a little vibrating poker action before me and a mate get busy with the tamping. Does anyone know where I can beg borrow or steal a vibrating poker?!? What is the required action with the tamping thingy? Also, how the smeg do you tamp the bit that is next to the wall, when you can't have a person either side???

4. I'm not planning on leaving any expansion gaps or anything - just pour it in on some damp proof plastic stuff between areas of existing concrete. Am I mad?

Ta for the pointers, Al.

[pete3000]

Current bit starts here!

Hi guys, sorry to drag this back up.

I have just ordered 25 cubic metres of C35 with fibres to be delivered in 10 days. Since the roller shutter door is a few cms too short for the concrete lorries to get inside, I have had to (being too lazy to wheelbarrow it myself) order a pump truck with a boom and hose.

So now its serious. I need some tips.

1. A lot of concrete companies I got quotes from said that steel reinforcement is not necessary with fibres, so at this point I have no plans to use steel mesh. Do people agree with this?

No not really I would still be inclined to reinforce, if it cracks then it won't get very far, or droop.

2. Has anyone used a pump truck to deliver concrete through a hose? Any tips on the how to (it'll be me on the hose, and the guy running the pumps)?

No not really mine was done by freebarrow, and about 5 eastern european types

3. Once I've squirted it in, I'm looking at a little vibrating poker action before me and a mate get busy with the tamping. Does anyone know where I can beg borrow or steal a vibrating poker?!? What is the required action with the tamping thingy? Also, how the smeg do you tamp the bit that is next to the wall, when you can't have a person either side???

try hire shops, city hire tools or hss or similar, weekend should be around 25 notes. As for leveling I used a 6 inch wide board on edge and drag/knock up and down on two references. These can be the top of the shuttering you used to contain the concrete. If I was doing it I think i'd knock a few thin planks in against the wall and use them as your floor level. That way you won't need anyone on the wet side of the concrete.

4. I'm not planning on leaving any expansion gaps or anything - just pour it in on some damp proof plastic stuff between areas of existing concrete. Am I mad? depends how big an area it is really might be worth creating a sump at one end for clening/drainage

HTH Pete

[bishbosh]

1. Don't need mesh. Out of interest are your fibres steel or polyprop?

2. You'll need more than just you! The concrete will be delivered quickly and you'll want someone on the poker and a couple of people on the screed board too.

3. Hire shops for a poker, you'll need a compressor too. Be carefull vibrating - you can over vibrate and segregate your mix. What consistence class is the concrete? If you ask for S4 it will self compact so you would only need to level it out. You will probably be getting S3 if you haven't specified it which is a stiffer mix and will require more encouragement. Then again, with no reinforcement to get in the way I would be inclined not to poker it and just level and tamp with a board.

4. I am guessing here, but with 25 cubes your floor area is going to be nearly 100 square metres? Once the concrete has started to cure - about 12 hours should do it, you want to cut the top face about 25mm deep all the way from one side to the other every 4-5m. If you have one side longer than the other, i.e. your orkshop is not perfectly square, make these cuts perpendicular to the long side. they will act as crack inducers and hopefully stop the rest of the slab cracking.

I would strongly suggest you put out a forum SOS for help on the day. 25 cubes is a lot of concrete and it will kill you if you try and do it all on your own!!!

[freeagent]

I probably would chuck some reinforcing down, even if its not strictly required.. a few sheets of weld-mesh won't cost you a great deal, and is worth it for the peace of mind.

(we put a single layer of 75x75 weld mesh in the floor of our workshop)

I'd certainly put a bit near the door, and under any planned heavy machinery...

[steve_d]

Unless you are making the slab thicker than 6" I don't see a need for the poker.

Mesh may not be a necessity but would be worth doing considering it will not cost too much.

What is the narrowest dimension of the slab as this is the length your tamp bar will need to be. If it is long then you may need to make one looking a little like a shallow roof truss otherwise it may sag in the middle.

If one edge is against a wall then you will need to nail a batten along it at your final floor level to run the tamper on. I would say at least an inch thick.

You will need a lot of hands on this. Give me a shout if you want help I'm not that far away.

What is the final use? If you want a really smooth finish then you may want to hire a power float (bit like an upside-down helicopter) or one of those things like a giant trowel with a long handle.

Lastly find someone who knows what they are doing as getting it right first time is way easier than remedial action.

Steve

[FridgeFreezer]

I have just ordered 25 cubic metres of C35 with fibres to be delivered in 10 days.

Gosh darn it, I'm very busy that day too

[Astro_Al]

Hi guys, thanks a lot for the great inputs, I'm really losing my concrete virginity in an experience vacuum here... I wouldn't mind but this is an expensive way to make a mistake.

I figured I could be a bit more helpful, so here's the situation. This is a diagram of the area to be done. The shaded areas are already concreted, and the red areas are the parts I'm doing. It all adds up to 165 square metres of concrete, 6" deep. I figured thats around 25m cubed. The black lines are the doors.

Here is a pic from a while back when I was part way through moving my junk in. I should have done the concrete then... My crappy camera is too narrow angle to get the whole place in, but you can see the central concrete bit, and some of the dusty earthy bits next to it.

So its great that everyone can agree on the need for mesh and whether or not I need to do some vibrating.

Where would you find mesh, Jewsons or somewhere? I asked at brundles the other day, but they don't do it, despite having it in their catalogue...

If the costs aren't too bad, I'll probably do both just for piece of mind.

The plan is for the pump truck to arrive at 8am to set up, and for the concrete to arrive every hour starting at 9am for 4 hours. Then there will be a final re-calc on the remaining area before the final truckload. I've got one mate coming to help, and thats it. I figure with the stuff coming out of a hose we should be ok-ish by ourselves?

How quickly after the hose can it be vibrated - if I've got my hose on full-flow, can he just come behind me with his vibrator?

If so, we'll just work our way along each 'trench', me hosing, him vibing not far behind, and when each truck runs out, we'll go back and tamp it while we 'wait' (ha ha) for the next one. Sound like a plan?

Final use is workshop type stuff, no need for megasmooth top, especially as the rest of it has an annoying cross-hatching on it. Anythings better than that!

Steve - many thanks for the offer, thats very generous of you. Sadly its a Monday morning, otherwise I'd happily provide the beers for a forum laying session

Bish - not sure on the fibres, polywhatsits I think. the mix is a 'pump mix', which I imagine has a bit more water so it doesn't clog up the pump lorry. now you see the layout, what do you suggest about these 'cuts'? And with what?

Cheers folks!

Al.

P.S. - Fridge, get your posterior over here! Monday the 10th, 8 am.

[bishbosh]

I still wouldn't bother with mesh or a vibrator.

Make sure the edges you but up against are sound. I presume you are going to dig out the earth to get an even depth across your slab. Before you pour wet the earth down so it doesn't suck the moisture out of your concrete.

Make sure you have a shutter along the wall to give you a level.

Saw cut across each strip every 5 m to be sure. With a floor saw (a grinder with a depth stop effectively!)

Pump mix as you correctly said will flow nicely.

If you do use mesh you will need to think about how you are going to position it in the depth of the slab so it doesn't float.

[Les Henson]

Tamping will raise the fat/settle the mix anyway, so it can be floated, tamped, or brushed without the need for a poker. Mesh is a bit overkill in my opinion unless you're planning on putting a lot of weight on it. My shed base is 20-feet x 10-feet x 6-in thick on a whacked scalpings base. No mesh in it and it's still fine since I did it about 15 years ago. If there's any cracking - it's going to occur between the joint of old and new and will only be hairline anyway.

Les.

[steve_d]

Now we know the size of the strips you are doing.

They are not wide enough to benefit from mesh.

They will not need vibrating.

The width means you can reach across and float if required or just brush late on in the cure.

Unless the other strips have a damp proof membrane I would not bother with your new strips.

And finally, I retired at Christmas so Mondays are just one of the days in a week (having trouble with this bit as I keep loosing track of what day it is)......anyway the offer still stands.

Steve

[FridgeFreezer]

I still wouldn't bother with a vibrator.

Do you prefer the more traditional flowers & chocolates then?

[Steve Hiatt]

You do not need mesh with fibres, which will be poly. Your concrete will be wet, probably 80 - 100 slump and I think the poker will slow you down more than it will help. Spend your time and money making the right sized tamps with handles.

You need more mates C35 with fibres goes off very quickly. I laid just three metres yesterday between two slabs and it was going off where in contact with the slabs before we had gone over it twice.

[Mark]

Can't help or contribute to the concrete tech, but still... nice shed. Would love to have that much space.

[SiWhite]

I'm off too - sure you don't need a hand?

[Les Henson]

A forum concrete mix I might be able turn up as well and do nothing much.

Les

[steve_d]

A forum concrete mix I might be able turn up as well and do nothing much.

Les

Apart from eat the hobnobs.

Steve

[Night Train]

I wouldn't do it all in one day if I were you. You would be lucky to get two sections right in a day given that you don't know what you are doing. You will be seriously exhausted by the end of the day unless you have lots of mates around who know what they are doing and the concrete will have gone off before you have finished. Even though it is still wet it will be going off and further working will damage it so you could end up with a pile that you can't get rid of nor can you spread and tamp down. Two shorter days would be easier both for the job and your backs.

H&S: You will need overalls, goggles, rubber work gloves, wellies and plenty of water for cleaning and washing. Cement is caustic and will cause burns on contact, especially on damp or sweaty skin, and splashes can seriously damage your eyes. You will need overalls and you should remove all clothing that has contact with the concrete immediately you have finished work. Wash hands before going to the toilet as cement burns on the penis is nasty and you won't know until much later on. Whenever you stop for a rest wash any exposed skin and dry with clean towels. Getting mucky with concrete (or any cement based material) is not like playing in a muddy field.

You will need a rake and a shovel each to move the concrete around. It will be like raking thick heavy clay in a field.

The concrete pump will pump almost as fast as the concrete lorry can pour it. That is a lot of concrete that needs spreading about.

One person on the pump outlet, two/three people with rakes moving it. Due to the risk of splashing they should all be wearing goggles.

As you work along the pour another person can be following up tamping.

As you are walking about in the pour with wellies try not to get any muck in your wellies. If you do wash out the wellie and your foot and change your socks immediately before it burns your sweaty toe skin.

To tamp the side strips get a length of timber about 3.5 m long and rest it on the existing pad next to the fresh pour. 'Saw' the timber back and forth as you move it along the wet surface. What you are doing is settling and scraping the surface and it will mean that every now and again you will need to remove the pile up of concrete in front of the timber and redistribute it as you go making sure that there are no low spots. You will then needs to float the surface with a large float. That means you skim the surface gently pushing the gravel down and raising the water to the surface. For the centre sections the wood can rest on the existing concrete on each side. You might need a float on a long stick for the reach.

When I last did this I had a 5.5m x 5.5m floor to do in a basement while underpinning a house. I got a barrow mix lorry as it slowed down the delivery and ensured the last mix was as fresh as the first. It took three of us (plus one supplying tea and biscuits) best part of four hours to get that finished. We started from the furthest point from the chute and worked back and towards our exit. By the time we finished the last bit the first bit was almost solid enough to walk on without leaving imprints. So even 30minutes or so and the mix is unworkable (even if it still moves about) so you need to be able to process each batch within that time.

Good luck.

[Kim Horsevad]

(...)

So its great that everyone can agree on the need for mesh and whether or not I need to do some vibrating.

Where would you find mesh, Jewsons or somewhere? I asked at brundles the other day, but they don't do it, despite having it in their catalogue...

If the costs aren't too bad, I'll probably do both just for piece of mind.

The plan is for the pump truck to arrive at 8am to set up, and for the concrete to arrive every hour starting at 9am for 4 hours. Then there will be a final re-calc on the remaining area before the final truckload. I've got one mate coming to help, and thats it. I figure with the stuff coming out of a hose we should be ok-ish by ourselves?

(...)

If you were making a new floor I would definately use mesh and get the floor vibrated. In this situation - where you are adding sections of concrete to al alreade made structure - I dont think you will get much benefit from the extra work/cost. Adding mesh (and making sure it sits at the right level) is time consuming if you are in a hurry - which you are. Without a retarder this cures quite fast.

No matter what you do you will get small cracks between the old and new sections. Only way to make the additions without cracks would be to hammer away the edges of the old concrete, so that the mesh gets exposed. Then tie the new mesh in to the old mesh. I would not bother!

You are terrible undermanned for such a project! This concrete gets pumped out quite fast. You need one man to steer the hose, two to level with shovels and two others to make the final levelling. And it will still be very hard work!

[FridgeFreezer]

Can't help or contribute to the concrete tech, but still... nice shed. Would love to have that much space.

Remember Al's got a lot of vapour to store

[Astro_Al]

Remember Al's got a lot of vapour to store

I take it you're coming to help out then Mr Fridge???

Thanks for the inputs guys, this starting to sound a bit daunting / impossible with just 2 of us... I guess I figured with the wet mix from the pump truck we'd hav more time to fiddle with it before it went off. I might have to invoke the Forum A-Team Rapid Response Concrete Disaster Recovery Team.

Realistically though, its a pretty early start for people (concrete starts arriving at 9, I'll probably get there about 7.30 for the pump truck at 8). I can only provide tea and biscuits (so all the resources needed to build an empire), and my gratitude.

I don't mind if people want to come to point and shout (if they know a bit about concrete), or if they want to muck in that'd be good too.

Thanks for the cautionary notes Night Train.

Cheers all, Al.

[bishbosh]

Thanks for the cautionary notes Night Train.

You'll do well to heed his warnings Al - we just had a safety bulletin at work about a YTS trainee (not one of ours) who is now blind because he splashed some concrete in his eyes.

Not too clever on your skin either....