How to build concrete countertop for outdoor kitchen?

Question

I'm looking into pouring my own outdoor kitchen workbench and splashback with either Dingo High Strength or MaxPro mix. Can you pls advice which one is better suited.

The plan is to pour 40mm thick slab in a formply form, with reinforcement steel, and then turn it over for a smooth surface finish, before sealing.

About 3 square meter in total, 40mm thick, across multiple pieces, the largest being 1 square meter.

In the products spec. sheet (including within the sheet) and the bunnings website are conflicting information about the yield of the concrete mix bags. In my calculation, everything between 0.208 to 0.275 square meter per bag at 40mm thick. So I don't know how many I will need.Is the yield different between the two products?

MitchellMc · Answer

Hi @volkerku,

It appears the

https://www.bunnings.com.au/dingo-20kg-hi-strength-concrete_p0760378

is stronger at 55MPA, versus MaxPro's 50MPA. You'd typically go for the harder concrete when creating a benchtop. Most of the previous benchtop projects we've seen use the strongest concrete available. The Hi Strength is also formulated for smooth surfaces, where the MaxPro isn't, and the MaxPro is fast setting and that's not really a trait you want when working with forms. You don't want it setting up before you have time to vibrate the form and release air bubbles.

So, if the Hi Strength version is available, that is what I would suggest you go with. Alternatively, if you do want to use the MaxPro, please let us know your local store and we can let you know where the closest stock is.

Please let me know if you have any questions.

Mitchell

volkerku · Answer

Thank you, looks like I got my math wrong.

Still wonder which product is better suited for a workbench slab.

The MaxPro is harder to get, none of my local Bunnings seem to stock it. It would be good to do a test pour with both, but I need to drive an hour to get a bag, and not sure if Bunnnings discontinue the product. Can you find out?

EricL · Answer

Hello @volkerku

Thank you for sharing your question about building a concrete countertop for your outdoor kitchen.

Based on the information provided, the two products have very similar yields, but the coverage figures are presented differently, which is what makes them appear inconsistent.

Based on the information provided, the two products have similar yields, but the calculations need to be derived from their respective datasheets rather than comparing the coverage figures directly.

For

https://www.bunnings.com.au/dingo-20kg-maxpro-concrete-mix_p0097689

, the datasheet states that one 20kg bag covers 0.67m² at 15mm thickness. Converting this coverage to volume:

0.67m² × 0.015m = 0.01005m³ per bag

This means each bag produces approximately 10 litres of concrete.

For

https://www.bunnings.com.au/dingo-20kg-hi-strength-concrete_p0760378

, the yield table indicates that approximately 15 bags are required to cover 10m² at 15mm thickness. The total volume represented by this area and thickness is:

10m² × 0.015m = 0.15m³

Dividing this by the 15 bags required:

0.15m³ ÷ 15 = 0.010m³ per bag

This means each bag also produces approximately 10 litres of concrete.

To determine the coverage at your proposed thickness of 40mm (0.04m), divide the volume per bag by the thickness:

MaxPro:

0.01005m³ ÷ 0.04m = 0.251m² per bag

Dingo High Strength:

0.010m³ ÷ 0.04m = 0.250m² per bag

This shows that both products have effectively the same yield, covering approximately 0.25m² per 20kg bag at 40mm thickness.

For a total project area of approximately 3m² at 40mm thickness, the estimated quantity required would be:

3m² ÷ 0.25m² per bag = 12 bags

Allowing for normal wastage, overfilling of forms and minor variations in batching, it would be prudent to allow 13 to 14 bags for the project.

The apparent discrepancy between the datasheets is largely due to the different ways the yield information is presented. When converted back to volume, both products produce approximately 0.01m³ (10 litres) of concrete per 20kg bag, resulting in virtually identical coverage at a given thickness.

I also suggest having a look at this discussion - Concrete tabletop project by @markw. It's a great example of how to put together a concrete countertop.

Please remember to wear personal protection such as gloves, goggles and a mask.

If you need further assistance, please let us know.

Eric