Can I use recycled concrete in my rammed earth soil mix?

Mixing Recycled Concrete with Rammed Earth

When incorporating recycled concrete into your rammed earth soil mix, it’s crucial to crush the material into a fine aggregate, typically 1/4 inch (6 mm) or smaller. This will help distribute the crushed concrete evenly throughout the mix, allowing for better compaction and reduced risk of unevenness. A suitable proportion of crushed recycled concrete is 10-20% by volume, with the remaining 80-90% consisting of natural soil, sand, and aggregate.

Thermal Mass and Insulation Considerations

In desert and arid climates, incorporating recycled concrete into your rammed earth mix can increase the thermal mass of the wall, helping to regulate indoor temperatures. However, it’s essential to balance this benefit with the potential for increased thermal bridging and heat gain during hot periods. To mitigate these effects, consider incorporating insulation materials like wool or fiberglass batts within the formwork, particularly in areas prone to high temperatures. A recommended insulation thickness is 2-3 inches (50-75 mm) in desert climates and 1-2 inches (25-50 mm) in arid regions.

Best Practices for Formwork and Compaction

To ensure a successful rammed earth construction using recycled concrete, it’s vital to maintain a consistent moisture content throughout the soil mix, ideally between 8-12%. This can be achieved by adding small amounts of water to the mix during compaction, while also ensuring adequate drainage and ventilation within the formwork. A recommended formwork design includes a 1-2 inch (25-50 mm) gap between the formwork and the rammed earth wall to facilitate drainage and reduce the risk of water accumulation.