Quick Answer
The durability of rammed earth walls is determined by factors such as soil mix composition, compaction, water content, surface finish, and external weathering conditions. Proper soil mix design and compaction techniques are crucial to prevent erosion and degradation. A well-designed and well-constructed rammed earth wall can last for centuries.
Soil Mix Composition and Compaction
The durability of a rammed earth wall is heavily dependent on the soil mix composition. A mix of 10-20% sand, 60-70% silt, and 10-20% clay is generally preferred, as it provides adequate strength, stability, and water resistance. The soil mix should be well-mixed and have a moisture content of 15-20%. Compaction is critical to remove air pockets and prevent erosion, with a recommended pressure of 100-150 kPa. A compaction gauge or a steel plate with a weight can be used to ensure proper compaction.
Surface Finish and Weathering
A well-finished surface is essential to prevent erosion and degradation. A natural plaster or lime render can be applied to protect the surface from weathering, with a thickness of 1-2 cm. In desert and arid climates, a more durable render such as a polymer-modified lime render can be used. Regular maintenance and repair of cracks and fissures are also crucial to prevent water ingress and prevent further degradation.
Thermal Mass and Climate Considerations
Rammed earth walls can be designed to take advantage of thermal mass, with thicker walls (40-60 cm) providing better thermal performance in desert and arid climates. The thermal mass can help regulate indoor temperatures, reducing the need for air conditioning and heating. In these climates, it’s also essential to design the wall with a sloping surface to prevent water accumulation and runoff.
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