Bonding cement on cement

[Lee Nowell]

Hi all,

I am doing some patio renovations and have 2 related questions.

1. We have a rendered wall and the bit along the top has blown. It is around 5mm deep and runs between 2 plastic angle beads which form the corners. Before I redo the render, should I coat the cement it will be applied on top of or will it all bond together naturally. Trying to make sure it doesn't separate going forward.

1. I have a concrete base for some steps which needs to be adjusted before I can fit the tiles on to it. I need to build the front edge out around 70mm and the flat surface by around 10 to 20mm. Again do I need to coat the existing or do anything special or can I just pour the new concrete into position using timber forms?

Many thanks

Lee

[alan_m]

Add SBR to the cement mix and possibly seal the exiting surface with the same if the underlying is dust or the surface will suck all of the water out of your concrete before it has time to cure properly. See

Possibly add fibre to the mix Long video from a USA concrete contractor but part of it shows overlaying a shallow depth of concrete over a step (which they call a stoop). They coat it with what I assume is SRB (white when wet, clear when dry) BUT they also appear to be using a resin type concrete product.

Try 11 minutes in, then 15.5 minutes, 21.5 minutes, etc.

[Animal]

Fibres would help. SBR would help. Cleaning surfaces ditto. I assume you've tapped the render so you now there's no more loose. Wetting all surfaces & giving them 5 minutes to soak helps avoid the new cement drying prematurely. Wet surrounding ones too to slow drying.

[alan_m]

opps wrong link