Can I Use Broken Concrete as a Sub Base? Explained and Analyzed

In the realm of construction and paving projects, the quest for the ideal sub base aggregate is paramount. A consistent and evenly graded material often determines the success and longevity of the pavement above. However, in the quest for sustainability and cost-effectiveness, the question arises: can broken concrete be utilized as a sub base? Surprisingly, the answer is affirmative. By breaking up and evenly grading the discarded concrete, it can find a new purpose beneath fresh paving projects. This practice not only promotes the repurposing of waste materials but also contributes to a stable and robust foundation. To truly maximize it’s potential, burying the broken concrete at the very base of the excavation and topping it with MOT Type 1 aggregate ensures optimal performance.

Can I Use Broken Concrete as a Base?

One common way to reuse broken concrete blocks is to crush them and use the resulting material as aggregate in new concrete. This is a cost-effective and environmentally friendly solution, as it reduces the need for new raw materials and minimizes waste. Crushed concrete can be blended with other aggregates to create a strong and durable base for various construction projects.

Using crushed concrete as a base for roads, driveways, or parking lots is another practical application. The crushed material provides stability and support, preventing the underlying soil from shifting or eroding. It can effectively distribute the load of vehicles and heavy machinery, ensuring long-lasting and reliable surfaces.

Before using broken concrete as a base, it’s important to carefully assess it’s quality and suitability for the intended application. The concrete should be free of contaminants, such as metal reinforcement or toxic substances, which can compromise it’s integrity or contaminate the environment. Additionally, the size and shape of the broken concrete should be appropriate for the specific project requirements.

When using broken concrete as a sub base, it’s typically necessary to prepare the site properly. This may involve excavating the area, leveling the ground, and compacting the soil to ensure a stable foundation.

Sure, for the majority of the substrate, crushed concrete can be used under a slab. However, it’s important to note that since crushed concrete retains water similar to the slab, it’s advisable to add a thin layer of stone on top as a capillary break. In such cases, using all stone instead of crushed concrete might be a more practical option.

Can I Use Crushed Concrete Under Slab?

Using crushed concrete as a sub base is a viable option for various construction projects, including laying slabs. It’s ability to provide a solid foundation and withstand heavy loads makes it a popular choice. However, it’s important to consider certain factors before deciding on crushed concrete as the sub base material.

One key aspect to keep in mind is the water absorption of crushed concrete. This can be problematic if it comes into contact with the slab, as it may lead to moisture-related issues. To mitigate this, it’s recommended to top dress the crushed concrete layer with a thin layer of stone. This acts as a capillary break, preventing moisture from reaching the slab and minimizing potential damage.

In some cases, it may be more practical to use all stone instead of crushed concrete as the sub base material. Stone, being non-porous, doesn’t absorb water and therefore eliminates the need for additional measures to address moisture-related concerns. This can simplify the construction process and provide a more reliable foundation for your project.

Factors such as cost, availability, and the intended function of the slab should be taken into consideration. Consulting with a professional in the field can help you make an informed decision and ensure the long-term success of your project.

Regardless of the material chosen, proper compaction during installation is crucial. This will ensure that the sub base is stable and able to support the load of the slab. Additionally, regular maintenance and inspection of the sub base are essential to identify any potential issues early on and prevent problems from developing in the future.

Topping it with a layer of non-porous stone can help create a capillary break and reduce the risk of moisture-related problems. Consider the specific requirements and conditions of your project before making a decision, and seek professional guidance if needed.

Pros and Cons of Using Crushed Concrete as a Sub Base

Using crushed concrete as a sub base has some pros and cons to consider.

One advantage is that it can be an affordable alternative to traditional sub base materials. Recycled concrete is often readily available and can be less expensive than other options.

Additionally, using crushed concrete as a sub base can be environmentally friendly. By recycling and reusing concrete, it reduces the demand for new materials and helps conserve natural resources.

However, there are also potential drawbacks. Crushed concrete may not be as strong or durable as other sub base materials, leading to potential issues with stability and longevity.

It’s crucial to properly assess the quality and characteristics of the crushed concrete before using it as a sub base. If it meets the necessary requirements and is properly installed and compacted, it can be a viable option. Consulting with a professional or engineer is recommended to ensure that crushed concrete is suitable for your specific project.

They’re widely available and easy to work with, making them a popular choice for DIY projects and small-scale construction. However, there are some important considerations to keep in mind when using concrete blocks as a base foundation.

Can You Use Concrete as a Base?

When using broken concrete as a sub base, it’s important to prepare the area properly before installation. First, remove any existing vegetation or debris from the area, ensuring a clear and level surface. Next, create a barrier to prevent any future weed growth by laying down a geotextile fabric. This will help to maintain the stability of the sub base.

Once the area is prepared, begin by laying down a layer of crushed stone or gravel to provide a stable base for the concrete blocks. The thickness of this layer will depend on the specific project and the intended use of the area. Generally, a layer thickness of around 4-6 inches is recommended. This base layer will help to distribute the load evenly and prevent any settling or shifting of the concrete blocks.

Next, begin laying the broken concrete blocks in the desired pattern or configuration. Make sure to align the blocks tightly and level them as you go. It’s important to note that the broken concrete should be clean and free of any loose or crumbling pieces. This will ensure a strong and sturdy foundation.

Once the concrete blocks are in place, it’s recommended to fill the gaps between the blocks with a fine aggregate such as sand or crushed stone. This will help to stabilize the blocks and prevent any movement. Additionally, it’s important to compact the sub base by using a compactor or tamper to ensure a solid and even foundation.

It provides a cost-effective and environmentally friendly alternative to traditional methods. However, it’s important to ensure proper preparation and installation to guarantee the longevity and stability of the project.

One of the sustainable methods in construction involves utilizing old concrete to produce new concrete. Instead of disposing of old concrete, it can be repurposed as fill material for new concrete, providing additional bulk, compressive strength, and stability. Recycling old concrete not only helps in reducing waste but also contributes to the conservation of resources. To achieve this, the old concrete must be crushed into small pieces, which can be done through professional services or by undertaking the task yourself.

Can You Use Old Concrete to Make New Concrete?

Can you use old concrete to make new concrete? The answer is yes, you can! In fact, utilizing old concrete as fill for new concrete is an effective way to create aggregate and add bulk, compressive strength, and stability to your project. It not only provides an eco-friendly solution but also allows for the recycling of materials, reducing waste and preserving natural resources.

Firstly, it reduces the need for additional raw materials, such as natural aggregates, which helps to preserve the environment. Additionally, it provides a cost-effective solution, as old concrete is often readily available and can be obtained at a lower cost compared to other construction materials.

Moreover, incorporating old concrete into new concrete also helps to reduce the amount of waste that would otherwise end up in landfills. Concrete isn’t biodegradable, so recycling it ensures that it’s put to good use rather than being discarded. This not only reduces the strain on landfills but also contributes to sustainable construction practices.

The crushed concrete particles fill in the gaps, creating a denser mixture, and improving the load-bearing capacity of the structure. This can be particularly beneficial in applications that require high compressive strength, such as foundations, driveways, or roadways.

The Process of Recycling Old Concrete and Incorporating It Into New Concrete

  • Breaking old concrete into smaller pieces
  • Sorting and separating the different components in the concrete, such as aggregates and cementitious materials
  • Crushing and grinding the old concrete to create recycled concrete aggregate (RCA)
  • Testing the quality and properties of the RCA to ensure it meets the required standards
  • Incorporating the RCA into new concrete mixes as a replacement for natural aggregates
  • Adjusting the mix design and proportions to account for the use of RCA
  • Producing new concrete using the recycled materials
  • Transporting and placing the recycled concrete in construction projects
  • Bonding the new and old concrete together through proper curing and finishing techniques
  • Monitoring the performance and durability of the recycled concrete over time

Source: Can You Use Old Concrete As Fill for New Concrete?

Additionally, using old concrete as a subbase can help to reduce the demand for new construction materials and promote sustainability in the building industry. This environmentally-friendly practice not only saves resources but also reduces landfill waste. Therefore, utilizing old concrete as a subbase provides a cost-effective and eco-friendly solution for various construction projects.

Can I Use Old Concrete as a Sub Base?

Yes, you can use old concrete as a sub base. Old, unneeded concrete can be recycled and used to create recycled aggregate, which can be used as a sub base material.

The resulting recycled aggregate can then be used as a replacement for virgin materials in various construction applications, including as a sub base. The use of recycled aggregate not only reduces the demand for virgin materials but also helps to divert waste from landfills.

When using recycled concrete as a sub base, it’s recommended to mix it with fresh or virgin materials to improve it’s overall strength and stability. This combination of recycled and virgin materials can help create a more durable and stable sub base for your project. The specific ratio of recycled to virgin materials will depend on the specific requirements of your project and should be determined by a qualified engineer or contractor.

Consulting with a qualified engineer or contractor can help you make an informed decision and ensure the successful implementation of your project.

The Process of Recycling Concrete Into Recycled Aggregate

The process of recycling concrete into recycled aggregate involves several steps:

1. Collection: Broken or unwanted concrete is collected from construction sites, demolition projects, or renovation sites. This can include concrete chunks, slabs, and other debris.

2. Crushing: The collected concrete is taken to a recycling facility, where it’s crushed into smaller pieces. Specialized machinery is used to break down the concrete into manageable sizes.

3. Sorting: After crushing, the recycled concrete undergoes a sorting process. Materials like metal, wood, and other contaminants are removed to ensure the quality of the final product.

4. Screening: The crushed and sorted concrete is then screened to separate it into different sizes. This allows for the production of different grades of recycled aggregate.

5. Washing: In some cases, the recycled aggregate may be washed to remove any remaining impurities or contaminants.

6. Usage: The final recycled aggregate can be used as a sub base for various construction projects. It can be used as a replacement for traditional aggregate in road construction, as a base for new concrete, or as a fill material in landscaping projects.

Recycling concrete into recycled aggregate not only helps reduce waste and preserve natural resources but also offers a sustainable solution for construction projects. It provides a cost-effective alternative to using virgin materials while maintaining the necessary structural properties.


While a consistent and evenly graded sub base aggregate is ideal, broken concrete can serve as a suitable alternative if it’s properly prepared. By breaking up the concrete and ensuring that it’s evenly graded, it can be buried at the base of the excavation for new paving projects. To ensure optimal stability and durability, it should be topped with MOT Type 1. This approach not only promotes the efficient use of resources by recycling broken concrete, but also contributes to the overall longevity and sustainability of the construction project.

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