Based on a common concrete mixing ratio, you will typically need 12 bags (20kg each) of cement to make 1 cubic metre of concrete using builders mix (also known as concrete blend or all-in aggregate).
Understanding the Mix
When making concrete, builders mix provides the essential aggregates (sand and gravel). Cement acts as the binder that hardens when mixed with water, creating the solid concrete. The ratio of these materials is crucial for achieving the desired strength and consistency of the concrete.
As referenced, a common simple mixing ratio involves combining 4 shovels of concrete blend with one shovel of cement. Following this guideline:
- Reference Information: When mixing concrete simply mix 4 shovels of concrete blend with one shovel of cement. At this ratio you will require 12 bags (20kg each) of cement per cubic metre of concrete.
This means that for every cubic metre of concrete you intend to produce using this specific mix ratio, you will consume 12 bags of 20kg cement.
Practical Application
Knowing the quantity of cement needed per cubic metre is essential for planning and budgeting construction projects.
Here's a quick breakdown:
| Material | Quantity per 1 m³ Concrete |
|---|---|
| Cement (20kg bags) | 12 bags |
| Builders Mix | Approx. 1 m³ |
| Water | Variable |
- The volume of builders mix required is approximately 1 cubic metre, though this can vary slightly depending on the exact proportions and how densely the materials are packed.
- The amount of water needed will depend on the moisture content of the builders mix and the desired workability of the concrete.
Important Considerations
- Mix Ratio: The 4:1 blend-to-cement ratio is common for general-purpose concrete. However, specific projects might require different ratios for higher strength or durability (e.g., 3:1 or even richer mixes). A richer mix (more cement) will require more bags of cement per cubic metre. Always follow engineering specifications or professional advice for critical applications.
- Bag Size: The reference specifies 20kg bags. Cement is also commonly sold in 25kg bags. If using 25kg bags, you would need fewer bags per cubic metre (e.g., 12 bags * 20kg/bag = 240kg; 240kg / 25kg/bag = 9.6 bags, so you'd likely round up to 10 bags).
- Yield: 1 cubic metre of dry builders mix and cement does not always yield exactly 1 cubic metre of wet concrete. There can be some volume loss upon mixing. The calculation of 12 bags per m³ already accounts for the required amount of cement relative to the final concrete volume.
Understanding these factors helps ensure you order the correct amount of materials for your project, minimising waste and cost.
