Thread: How to fill 30mm gap in slab.

Hi Matrix, I thought about sikaflex, mortar, engineering grout, etc but you will still have problems with sponginess, mortar cracking etc etc. The best idea I can come up with is to get a piece of heavy gauge steel(about 50-60mm wide should be enough) from the metal yards and recess it into the concrete over the joint, even just in the areas where you are wheeling machinery if the whole width sounds too much. Use a diamond wheel on the angle grinder to make a couple of straight cuts to the depth of the steel or a bit more then remove the waste with the grinder/bolster. If you go down a bit lower than the steel depth, you can seat it nicely flush with the slab on some sikaflex.

Cheers
Michael

Hi Matrix,

What Michael has proposed is a good Rollsroyce solution - maybe you aren't interested in the work associated with it.

If your slab is internal (as it sounds) and in a building that doesn't require a truly fabulous solution you could put into the gap a non-shrink mortar solution (just pour non-shrink grout into it). That's what I would do anyway.

A slab will not expand and become longer if it is not exposed to the sun and likely to heat up.

A slab will shorten over a time duration of 30 years - it will shorten 80% of it's total shortening over the first 2 years from when it is poured. Usual shortening is about 0.6mm per metre length of slab - so why is your gap so big? Was it poured with a gap? Has the building moved? If any of these then you have separate issues.

Hi Matrix, if I remember correctly your original post said the gap was 50 to 60mm wide now 30 metres wide (I think you mean 30 mm). Either way it seems good if the crack has closed from 50-60mm to 30mm then soon it will be closed and not need filling.

Just bog it up with a strong mortar mix.

Al

Mic-D, your soultion is probably the smartest, but too much effort for my lazy butt this weekend

Originally Posted by TEEJAY

Hi Matrix,

What Michael has proposed is a good Rollsroyce solution - maybe you aren't interested in the work associated with it.

If your slab is internal (as it sounds) and in a building that doesn't require a truly fabulous solution you could put into the gap a non-shrink mortar solution (just pour non-shrink grout into it). That's what I would do anyway.

A slab will not expand and become longer if it is not exposed to the sun and likely to heat up.

A slab will shorten over a time duration of 30 years - it will shorten 80% of it's total shortening over the first 2 years from when it is poured. Usual shortening is about 0.6mm per metre length of slab - so why is your gap so big? Was it poured with a gap? Has the building moved? If any of these then you have separate issues.

Hi Teejay, at at guess I would say the slab is pretty much hitting the 30 year old mark about now, so I guess it has done most of its shrinking. They did build a house next door about 12 years ago which had fairly extensive excavation right up to the boundary(about 2mtrs from the shed wall ) so that might be the reason for some extra movement.
Cant remember if the gap has always been that big. You couldn't always see the floor .

Originally Posted by TEEJAY

Hi Matrix, if I remember correctly your original post said the gap was 50 to 60mm wide now 30 metres wide (I think you mean 30 mm). Either way it seems good if the crack has closed from 50-60mm to 30mm then soon it will be closed and not need filling.

....edited now.

Originally Posted by ozwinner

Just bog it up with a strong mortar mix.

Al

Now that sounds like the solution I was after. Do Bunn!*&s sell anything suitable for this method?

You can get bags of premix from bunnies or any garden supply centre.

Al

Matrix, I would use concrete mix instead of mortar mix - it will hold together a bit better under load.

Hi everyone,
First post here. Have lurked around for a few months so decided to join a few weeks ago.

I am not much of a handyman but hope to get some good advice here.

Basically bought our first house a few months ago and am trying to do bits and pieces here and there.

I too have this problem where I need to fill a gap betwen 2 pieces of concrete. My brother in law who is a brickie suggested Builders grout but the places I have checked do not seem to know what that is.

Is there anything out there that I can buy ready made up in a container which is fairly strong so i can try and fix this gap.

All help appreciated.

Cheers
tourgy

Hi Tourgy,

What I would do to fix your path (if it were mine) is -

firstly remove the rubbish in the joint full depth of the path.

then drill into one side of the path (see attachment) and put fixings into this (dynabolts or something similar) to allow the infill to bind to this side of the path.

then brush onto the drilled face a rich mix of cement/water to help the infill bind to this face.

tie along the joint a bar 8mm dia or 10mm dia (piece scrap mesh reo will do)

then place onto one face a layer of 10mm ableflex.

then fill the gap with non-shrink grout and trowel a long the edge against the ableflex a curved edge to prevent spalling

The purpose of the above is to get the concrete to bond to one side, to reinforce it so it won't crack up and lastly to have a full depth compressible filler (ableflex) to allow the path to grow and shrink withou this destroying the gap filler.

Now you can do what you wish but this is what i would do

Hi TEEJAY,
Thanks for the response. This sounds like it will really fix it for sure .

Problem is, when I said I was not much of a handyman I really meant it .

I am ashamed to say I can barely use a power drill let alone be able to complte the procedure you have outlined.

I was more hoping there may be something like the grout you mentioned, ready mixed which I could just fill the gap up after it was cleaned out.

Cheers
tourgy

Tourgy,

If you can't get the holes drilled and bolts in place then i suggest you consider hammering in some masonry nails instead - don't tell me you can't use a hammer and nail

Goodluck

Check this stuff. I've used it to dress the edge of a slab: http://www.ardexaustralia.com/produc...did=16&catid=1

Pricey (about $70 a bag) but it's the duck's nuts. Might be suitable for your application.

Originally Posted by TEEJAY

Tourgy,

If you can't get the holes drilled and bolts in place then i suggest you consider hammering in some masonry nails instead - don't tell me you can't use a hammer and nail

Goodluck

Hi blokes,
Sorry been out of the loop for a while. Almost needed a Bex and a laydown at the thougt of doing this . Also looking at diverting guttering to raintank. Bwaaahaaaa haaaa haaaa. That will be a learning experience for me.

The above sounds a bit easier TEEJAY. How many nails would you suggest. And this grout seems to be a mysterious substance that I cannot find yet.

Originally Posted by silentC

Check this stuff. I've used it to dress the edge of a slab: http://www.ardexaustralia.com/produc...did=16&catid=1

Pricey (about $70 a bag) but it's the duck's nuts. Might be suitable for your application.

The above looks perfect silentC. May be a bit much for my needs though.

cheers
tourgy

I would forget about trying to use concrete nails, they are really only meant to be used on fresh concrete