concrete step ?

My neighbour has his drive monoblocked and then some steps down to the front door, whoever done the monoblock the last row at the top of the steps has come loose, looks like to keep it level with the drive there was the thinnest of layers of mortar to hold it in place. As I have some cement I offered to repair it for him but I realise that to keep everything level there would only be around half centimeter layer of cement to hols it in place (too thin) so decided maybe best just make a mix and in effect create a concrete `step` I was thinking of a 3:2:1 mix would that be ok? It looks like a straightforward job unless I am missing something.
The step would be about 3 feet wide and the depth & height as for a mono block around say 4 inches.
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If its only 4" front to back I expect it will soon start to topple just like the blocks have.
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On 07/09/2012 13:43, dennis@home wrote:

So whats the answer then? i am at a loss on how to repair it.
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ss wrote:

1/. Smash dennis' head against it to break it up 2/. Recast a new one
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Lots of potential ways..
make it bigger front to back make it deeper and bury it in the ground more fix the blocks together so they form a bigger unit
it depends on the ground conditions.
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writes

Two thoughts... the last row of blocks could be *thinned* by judicious use of an angle grinder allowing a thicker bedding course.
Some suitable reinforcing; galvanised weldmesh perhaps, could be secured to the ground before the concrete step is cast.
regards
--
Tim Lamb

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On Friday, 7 September 2012 08:33:35 UTC+1, ss wrote:

Maybe you could make up a bonding slurry of straight cement and exterior PVA to help 'glue' it in position.
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On Friday, September 7, 2012 8:33:35 AM UTC+1, ss wrote:

2 things not yet mentioned:
1. use epoxy mortar instead 2. mix lots of plastic fibres into the cement to give it more tensional stength. I wouldn't be confident that would give it enough, but it may well do if you put plenty in.
NT
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On 08/09/2012 12:13, snipped-for-privacy@care2.com wrote:

stength. I wouldn't be confident that would give it enough, but it may well do if you put plenty in.

I rarely use mortar and the stuff I have is left over from my shed base but I am not quite understanding the replies. The replies are implying that a strip of mortar 3 feet long x 4 inches deep x 4inches high laid on a concrete base and backing onto some mono block bricks would crack up or otherwise disintigrate in a short space of time. Aplogies if I appear ignorant but a paving slab is only what 2 or 3 inches thick and doesnt normally crack up. I take the points about additives but as its for a neighbour I wont be buying anything additional.
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On Saturday, September 8, 2012 9:46:04 PM UTC+1, ss wrote:

stength. I wouldn't be confident that would give it enough, but it may well do if you put plenty in.

If its 4" deep I'd just lay it. I might mention that if he had a piece of 100% synthetic cloth it would be good to shred it into fibres and mix it in to achieve a longer life.
NT
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On Friday, 7 September 2012 08:33:35 UTC+1, ss wrote:

I think the reason the block has become loose may be that it doesn't weigh very much in itself and is having a lot of force applied to it, possibly on one edge, which can cause it to overturn or come loose. Paving slabs only have downwards force on them and in any case are abutted on all sides by other paving slabs. Even were the mortar to fail, you probably wouldn't notice.
Once a slab is small, light, not held in position on all sides by other blocks, and subject to uneven stresses, it can work loose. You may have seen low solitary walls topped with a row of bricks before, especially in public spaces, even when the bricks are laid flat (as opposed to 'soldiers') the brick at either end is often held in place by an L-shaped galavanised metal reinforcement bar laid in the mortar bed. Otherwise some divvy will soon have a sjkate board on top of the wall and knock the end bricks off.
So, in circumstances like this, some brickwork/slabs/blockwork has extra effort put in to holding it in place - better bonding techniques than plain mortar, or reinforcing metal bars . I used a PVA mix in with the tile cement to better bond my external garden slate steps to the concrete beneath for intstance.
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On 08/09/2012 22:06, snipped-for-privacy@gmail.com wrote:

very much in itself and is having a lot of force applied to it, possibly on one edge, which can cause it to overturn or come loose. Paving slabs only have downwards force on them and in any case are abutted on all sides by other paving slabs. Even were the mortar to fail, you probably wouldn't notice.

blocks, and subject to uneven stresses, it can work loose. You may have seen low solitary walls topped with a row of bricks before, especially in public spaces, even when the bricks are laid flat (as opposed to 'soldiers') the brick at either end is often held in place by an L-shaped galavanised metal reinforcement bar laid in the mortar bed. Otherwise some divvy will soon have a sjkate board on top of the wall and knock the end bricks off.

effort put in to holding it in place - better bonding techniques than plain mortar, or reinforcing metal bars . I used a PVA mix in with the tile cement to better bond my external garden slate steps to the concrete beneath for intstance.

Thanks for the reply eeyore, I think I understand your explanation, I was assuming there would be a level of bonding with the mortar mix to the concrete it is being laid on and to the existing monoblock bricks. As I am doing it for free for my neighbour I am just trying to use what materials I have, I do have some PVA so do I just add this to the mix? what ratio? Could I drill into the concrete below and insert say 3 bolts and then `lay` my step of wet mortar on this? Would that stabilise it?
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On Saturday, 8 September 2012 23:16:26 UTC+1, ss wrote:

I'm not sure what monoblocks are, except to guess they are a small brick-like concrete block, but assuming that you are trying to lay a block(s) on top of an existing concrete base then if you remove the old mortar bed on top of the concrete (if it's still there), mix up a 2:1:1 cement:pva:water slurry, paint it on the concrete, trowel your mortar on top of that, then place your monoblock on top of the mortar - but - paint some slurry on the base of the block first, too.
Quite frankly, I don't know who to believe about bonding mixes. Some advocate just PVA and water, but you are supposed to paint it on and wait for it to go tacky before proceeding and I've seen mixes of 1:3 PVA:water to 3:1 PVA:water mentioned.
Some people put sand in their slurry to so a mix might be 2:1:1:1 sand:cement:PVA:water.
Take your pick.
Of course, plain mortar has some bonding strength of its own, but remember that mortar is generally used to spread the load between bricks and blocks in masonry structures. It doesn't usually have to provide any tensile strength and if it does they generally put steel reinforcement in. Plain sand would do just as well as mortar if it didn't pour out at the edges of the brickwork.
I believe that you get a much better bond between cement type mortars if the surface you are freshly mortaring to hasn't fully cured yet, which isn't the case with your problem with an old concrete base. When they built the Hoover dam in the USA they had to keep pouring concrete over concrete on a continual basis so it bonded well, although I believe it was reinforced by steel too.
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