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Everything You Need To Know About Different Concrete Patching Materials

Infilling of PT Pans - Concrete Patching

by Daniel Green

Concrete is one of humankind’s finest concoctions. Exceedingly durable, long lasting, easy to work and when you consider its lifespan – cheap!

But it’s not invincible.

Over time and with heavy use it can chip, crack, delaminate and straight out collapse. And that’s assuming it was correctly prepped and poured to begin with! Often repairs are necessary to give it back its intended lifespan. Patching is a great, low-cost solution that can rectify damaged concrete. It can also be used in a purely aesthetic sense to change the entire look of existing concrete. Magical stuff!

Before we get into it it’s important to know that concrete is made of four basic materials: cement, sand, aggregate and water. Mixed in the correct proportions these ingredients will create a good, solid concrete mix that will last a long time. It makes sense therefore that the substance used to patch concrete be of the same general material.

There’s three categories of patching materials. However, render is used so often we’re going to investigate it anyway.

  1. Patching compounds.
  2. Concrete.
  3. Mortar.
  4. Render.

Within those four are hundreds of sub-variants that will require unique product knowledge – knowledge that we simply don’t have. The way to choose a repair method is dictated by the type of damage and the desired outcome. Let’s take a look!

Patching Compounds

These are largely chemical based synthetics that, using modern technologies, far outlast traditional masonry based patching products such as mortar and concrete. There are hundreds of varieties and brands so for more detailed information its best to speak to your supplier.

Some Advantages of Patching Compounds

Manufacturers throw millions of dollars at RnD so their products to gain market share so they’re pretty high tech. What’s the result of this wizardry? Some pretty awesome space-age patching compounds that can work miracles in ways traditional repairs cannot. They possess behavioural characteristics such as zero sag on vertical surfaces, rapid cure times in cold and wet conditions and an MPa equivalent to or greater than the concrete they’re being used to repair. They can also be used to ramp from deeper flaws right the way down to zero depth. Try that with the grey stuff straight out of the barrow!

Some Disadvantages of Patching Compounds

Unfortunately all these advancements come at a cost or two. One is actual cost as they can be expensive, especially next to concrete and mortar. The second is the environmental cost as they’re often made from ingredients not quite as earthy as sand, rock and water. And because of the chemical nature of compounds, the need for PPE is quite high. Speaking from experience, trying to patch a vertical core hole from above is hard enough without adding dishwashing gloves into the mix. More so, if some of these products makes its way to your skin you might have some excess baggage for the next few weeks.

Patching Compounds – The Short Version.

  • Good for hard to patch places.
  • Superior strength.
  • Versatile.
  • Excellent in poor curing conditions.
  • Expensive.
  • Environmental impact.
  • PPE required.


The grey stuff is a great solution. It’s the same material as the slab it’s been brought in to fix, so the base material will never, ever reject it.

Some Advantages of Concrete

Its four basic ingredients are found the world over, meaning it’s cheap. It’s been used for thousands of years so it’s proven. It can be found at any hardware store any time of the day or night and it’s very easy to use. Because it’s made from earthen materials clean up is simply done with water.

Some Disadvantages of Concrete

Concrete’s strength lies in its mass. If it’s too thin it will crumble and needs to be 50mm think at a minimum, with the ideal pour more like 100mm. It requires formwork to retain it until it sets, which is extra cost and time. Preferably you’d reinforce it, which is an additional cost. Concrete needs good weather for it to properly cure, meaning it will need special additives if used in excessively cold or wet climates. And because it’s thick and heavy it won’t stick to vertical surfaces.

Patching With Concrete – The Short Version.

  • Inexpensive.
  • Superior strength.
  • Extremely workable.
  • Easy clean up.
  • Needs formwork.
  • Needs reinforcement.
  • Won’t cure in poor weather.
  • Won’t work on vertical surfaces.

Old School Construction Tip: Add PVA glue to masonry-based products to give them extra binding strength. Works a charm!


In the right conditions, as a patching material mortar can be very effective. It differs from concrete in that it is a masonry bonding agent whereas concrete serves as the masonry itself – so their strength is vastly different. This means that it should only be used in low strength applications in lower volumes.

Some Advantages of Mortar

Similarly to patching compounds, mortar is aggregate free so it can ramp down to zero height. Concrete can’t do this due to the mass required for it to have strength as well as the stone aggregate within. It’s ridiculously cheap with one 20kg bag costing only $10. Its water-based design makes clean up very easy and in the right mix and application it will work on vertical surfaces.

Some Disadvantages of Mortar

Primarily, it’s lack of strength. It’s designed to be roughly 10mm thick and to bind stronger materials [bricks] together as opposed to being the agent of strength itself. It won’t bear as much traffic as concrete and even then it will support only foot traffic.

Patching With Mortar – The Short Version.

  • Ridiculously inexpensive.
  • Ramps to zero height.
  • Extremely workable.
  • Easy clean up.
  • Won’t support high traffic areas.
  • Technically not a patching material.
  • Not made for strength.
  • Won’t cure in poor weather.


This is perhaps the weakest form of patching, so if its strength you’re after then this isn’t the method. Render is made specifically for, funnily enough, rendering. It’s a thin coating of masonry material for largely aesthetic use. As a kid I remember breaking off pieces of render from the walls on my Dad’s rental with my bare hands.

Some Advantages of Render

It’s designed to adorn, so it will attach to vertical surfaces without sagging until it can cure. It’s cheap – $17/bag. It’s light and easy to work with. It contains no aggregate so it can be ramped to zero height and like mortar it’s water-based so tools and workers are easy to clean.

Some Disadvantages of Render

It holds almost no strength, so it would be good for patching only the smallest of imperfections in low traffic areas. Like the two masonry examples above it needs good weather to cure.

Patching With Render – The Short Version.

  • Loves vertical surfaces.
  • Ridiculously inexpensive.
  • Ramps to zero height.
  • Extremely workable.
  • Not for use anywhere strength is required.
  • Won’t cure in poor weather.
  • Technically not a patching material.

Self-Levelling Floor Compounds

While we’re here we’d be remiss to not include these modern miracles of ground repair. And while they’re technically not for patching, it must be noted that their viscosity makes them suitable for floors only. This is because their self-levelling aspect relies on their flow characteristics – of which is mostly gravitational.

Their primary role is to flood low spots in damaged flooring to bring them up to height, followed by setting a new height by just a few millimetres. So the quantity of compound used is crucial. Best used in residential or low traffic areas, it does need some skill to move it around and get the final height nice and smooth. If you get it wrong it will require heavy demolition, negating its use in the first place.

So that’s it – concrete patching options in a nutshell. The choice of product really depends on how much material you’re trying to build up, what its intended use is and the type of construction you’re rectifying.


CAN I PATCH CONCRETE MYSELF? Of course, and we encourage you to try. However, what will happen if it doesn’t get the desired result and will need even more rectification?

WHAT DOES CONCRETE PATCHING COST? The type of repair will dictate the product and the time spent patching. There are may variables. It is however, far less expensive than demolition and repouring. Contact Perfect Concrete Care today for a quote.

See below for more information:

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