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Hello @MarioTedone
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about how many concrete bags you'll need for your concrete base.
To calculate how many 20kg bags of concrete you will need for your base, we start by determining the total volume of concrete required. The base dimensions are 4 meters long, 1 meter wide, and 120mm (0.12 meters) deep. To find the volume, multiply the length by the width and the depth: 4 × 1 × 0.12 = 0.48m cubic meter. This means the total volume of concrete required is 0.48 cubic meters.
Next, we need to determine how much volume a single 20kg bag of pre-mixed concrete can cover. Typically, a 20kg bag covers about 0.01 cubic meters of volume when mixed. This figure can vary slightly depending on the specific product, so it's worth checking the coverage information provided by the manufacturer of the concrete mix you’re using. Finally, we calculate the number of bags needed by dividing the total volume required by the volume covered by each bag. In this case, 0.48 ÷ 0.01 = 48.
Therefore, you will need approximately 48 bags of 20kg concrete to complete your base. It’s a good idea to purchase a couple of extra bags to account for any spillage, uneven levelling, or other unforeseen needs during the project.
However, if you your bag is 80kg you'll need to determine the coverage of an 80kg bag. Typically, an 80kg bag of pre-mixed concrete covers about 0.04 cubic meters when mixed. Dividing the total volume by the coverage per bag, 0.48 ÷ 0.04, shows that you’ll need 12 bags of 80kg concrete. To ensure you have enough for the project, it’s advisable to purchase one or two extra bags to allow for other unforeseen needs.
Please remember to wear personal protection such as gloves, goggles and a mask when working with concrete.
If you have any other questions we can help with, please let us know.
Eric
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