How to fix cracks between concrete plates in driveway?

Question

Looking for innovative suggestions for fixing/ patching cracks like this in a complex driveway.  The complex sinking fund was never intended to fund major driveway repairs so we are looking for as many suggestions as possible that could enable fixing and ongoing maintenance / prevention of cracks of this nature - given the funds available are less than $10k

Nailbag · Answer

Hi @JRS2026

I like the idea of @Dave-1 in installing a channel drain with metal grate though. These are stronger and hold their shape better than PVC. It would require you to hire a demolition saw to make a straight cut along both sides to accommodate it.

Having said that, I would be inclined to get a domestic structural engineer to have a look at it first. You need to establish why this has ocured and to ensure it's now settled.

Nailbag

Dave-1 · Answer

Good Morning @JRS2026

How many cracks like that do you have to deal with? I like @EricL's suggestion of using concrete as the distance is fairly wide. I do see it as a temporary solution tho as the question as to what is happening underneath would be wise to get looked at.

You could always use the seperation to your advantage and consider cutting one side and then running drainage/power across the driverway and then concreteing the section, even install tie bars between the slabs to bind them. Tho the reason for seperation still comes to mind. Id do the drainage and also concrete and install the expansion joint to keep it as close to the original as possibe,

With teh drainage I was refering to, there are two types, solid PVC for carrying water away and Socked Ag pipe to help extract the subsurface water. It may also be an idea to have a look where the water flows/pools when it rains as it could be the root cause of the slabs shifting downhill.

Dave

EricL · Answer

Hello @JRS2026

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about fixing the cracks in the concrete plates.

One possible way to fill the gap is to use

https://www.bunnings.com.au/dingo-20kg-fast-set-hi-strength-concrete_p0760407

. Generally speaking, I would often suggest using mortar or a liquid filler of sorts, but in this case the gap is so big it would be possible to use concrete. I would also suggest looking at

https://www.bunnings.com.au/dunlop-20kg-construction-grout_p6650143

as a repair agent.

The key to a durable repair is proper surface prep plus a bonding slurry or epoxy bonding agent, and ideally using a non-shrink repair mortar rather than normal high-strength concrete. Start by mechanically preparing the chipped edge because that’s your best bonding face. Use a grinder with a diamond cup wheel or a cold chisel to remove any weak or dusty concrete and create a rough, open-pore surface. You’re aiming for a clean, solid substrate with exposed aggregate, not a smooth finish. Vacuum thoroughly, then pressure wash if possible. Let it dry to a damp-but-not-wet condition. Avoid acid etching if you can, mechanical prep bonds far better.

Before placing repair material, apply a bonding coat. This can be either a proprietary bonding agent or a cement slurry. A simple method is mixing a slurry of cement and a liquid bonding additive such as

https://www.bunnings.com.au/lanko-5l-751-lankolatex-sbr-latex-additive_p0967244

to a paint-like consistency and brushing it firmly into the surface. The repair mortar must be placed while this slurry is still tacky, not dry. For best durability, a polymer-modified repair mortar or non-shrink grout performs much better than high-strength concrete because it bonds stronger and shrinks less.

Due to the amount of stress the driveway goes through, I can't guarantee the how long the repair will last, it will however temporarily cover the gap and prevent the leading edge of the slab from getting damaged further. My only other suggestion is to get a professional detailed quote for the repair. In this manner you will not be making too many guesses as you you'll have a detailed list of steps in regards to the repair.

Let me call on our experienced members @Dave-1, @Nailbag and @Remarka6le for their recommendations.

If you need further assistance, please let us know.

Eric