Grinding concrete before installing replacement tiles

[jacoscar]

I removed some tiles and broken the concrete underneath need to gain access to some drainage. I now need to cover this hole with concrete, use a leveller to bring the surface flush (or just shy) of the existing one and installing new tiles.
Do I have to grind the concrete that is visible in the picture but not broken so that the new tiles sit flush with the existing ones?

Also, what grade of concrete should I use?

 

[aveatry]

Looks like you have had a "mare" there.
I don't see why the new tiles should not sit flush with the original ones try offering one up and it should be lower - so with some adheasive it will be level.
Any concrete will do but I might be inclined to somehow make it easier for any future maintenance without concrete.

 

[jacoscar]

Looks like you have had a "mare" there.
I don't see why the new tiles should not sit flush with the original ones try offering one up and it should be lower - so with some adheasive it will be level.
Any concrete will do but I might be inclined to somehow make it easier for any future maintenance without concrete.

I actually replaced an open gully with a sealed section and a rodding point. There will be a fillable access hatch to provide access to the rodding eye.

 

[aveatry]

I actually replaced an open gully with a sealed section and a rodding point. There will be a fillable access hatch to provide access to the rodding eye.

Good thinking.
You may want to also re instate the DPC some how

 

[jacoscar]

Looks like you have had a "mare" there.
I don't see why the new tiles should not sit flush with the original ones try offering one up and it should be lower - so with some adheasive it will be level.
Any concrete will do but I might be inclined to somehow make it easier for any future maintenance without concrete.

I tried and it sits higher; it looks like there is some adhesive the same color of the concrete or they have been ‘concreted in’

 

[aveatry]

Right yes you can see the inprint of the underside of the tile. You need to get it down enough to have room for some adheasive.
The bad news is that you should not be able to lift up a tile like that and leave the inprint behind as it shows that they are not stuck down right

 

[jacoscar]

Right yes you can see the inprint of the underside of the tile. You need to get it down enough to have room for some adheasive.
The bad news is that you should not be able to lift up a tile like that and leave the inprint behind as it shows that they are not stuck down right

What does it mean? Wrong adhesive was used? Too much? Too little?

 

[aveatry]

What does it mean? Wrong adhesive was used? Too much? Too little?

Difficult to know but usually with bad laying you will see blobs of adheasive instead of a full coverage. When its done properly the back of the tile is usually "buttered" as well as the adheasive spread out with a notched trowel which then when the tiles are pressed down the notched adheasive spreads out. And the adheasive is usually a different colour to the concrete so it looks to me that some one has just layed the tiles straight onto wet concrete and they have not properly adhered. Looks like the tiles came up clean on the bottom, it basically should of been impossible to lift them without breaking them if it was done right.

 

[jacoscar]

Difficult to know but usually with bad laying you will see blobs of adheasive instead of a full coverage. When its done properly the back of the tile is usually "buttered" as well as the adheasive spread out with a notched trowel which then when the tiles are pressed down the notched adheasive spreads out. And the adheasive is usually a different colour to the concrete so it looks to me that some one has just layed the tiles straight onto wet concrete and they have not properly adhered. Looks like the tiles came up clean on the bottom, it basically should of been impossible to lift them without breaking them if it was done right.

It actually was quite difficult to lift them up without breaking them using an sds drill with chisel; I ended up breaking them all