Correct concrete mix for holding landscaping rocks in place?

[terrywang]

Hi all,

Noticed some of the landscaping (bushrocks) rocks moved and shifted due to excessive rainfall in last 24 months or so, to avoid more sink/move/shift, looks like I'll need to pour something (crushed pebbles, sand?) into the gap and then use cement / concrete to fill the gaps to stop them from moving.

It seems that previous gardener / landscaper simply used cement without sand or other materials in it so the cured stuff does not have any flexibility, therefore the cracks.

Any suggestions on best practices regarding fixing this type of problems?

[EricL]

Hello @terrywang 

You're absolutely right the excessive rainfall has penetrated between the rocks and concrete. When the rainwater gathered in large quantities it was enough to soften the soil underneath causing the rock to shift. My suggestions is to use Australian Builders 20kg Mortar Mix to fill and fix the gaps in your rock path. 

Once the concrete has fully cured, I recommend using a concrete sealer for the entire area. This will prevent water from entering the concrete and the gaps in between. Sealing the concrete and the stone will also prevent mould from taking root.

If you need further assistance, please let us know.

Eric

[terrywang]

Thanks @EricL for input.

I'll wait for the rain to stop and some good weather to work on this

I reckon I'll need some flat square & pointing trowels to do the job, what else is essential (I have a wheel barrel)?

[EricL]

Hi @terrywang 

Investing in a wheelbarrow is always a plus. It lets you transfer large piles of debris from one point to another. You can mix concrete in it and serves as a handy truck when moving soil. Please make sure to wear personal protection such as gloves, goggles and a dust mask when mixing and using the cement.

If you need further assistance, please let us know.

Eric

[MitchellMc]

You might also want to consider a tuck pointing trowel @terrywang, as it will allow you to fill smaller cracks easily.

If there are any floating and loose pieces of cement, removing them and filling the area would be a good idea. This will allow you to pack the mortar into any gaps or hollows beneath the piece. For this, a bolster and club hammer will come in handy, as although the pieces of cement might be loose, getting them out in one piece could be troublesome. Use the bolster and hammer to break the pieces for easy removal.

Painting the internal edges of the areas you'll be filling with Bondcrete will help assist with the new mortar sticking to the old and the blocks. You might like to also mix a little in with your mortar mix.

Do you have a pressure washer? If so, I'd encourage you to give the area a good going over prior to completing these repairs. Not only with the area look fantastic when you're done, but blasting loose debris out of the cracks will provide a solid substrate for the mortar to adhere to.

Please let us know if you have further questions.

Mitchell