Quick Answer
Moisture retention in rammed earth walls refers to the ability to maintain a consistent level of moisture within the wall, which is essential for its stability and performance. Effective moisture retention helps to prevent drying shrinkage, cracking, and degradation of the wall.
Importance of Moisture Retention
Moisture retention in rammed earth walls is crucial, especially in desert and arid climates where the soil is prone to drying out quickly. A well-designed rammed earth wall can retain up to 40% of its weight in water, which helps to regulate the wall’s temperature and maintain a consistent moisture level. This is achieved by using a mixture of clay, silt, and sand, which has good water-retentive properties.
Designing for Moisture Retention
To ensure effective moisture retention, the soil mix should have a high clay content, typically above 20%. The mix should also be compacted uniformly, with a density of around 1800-2000 kg/m3. This can be achieved using a combination of hand rammers and mechanical compactors, such as a plate compactor or a hand tamper. The compacted mix should also be allowed to cure for a period of 7-10 days before being exposed to the elements.
Formwork and Moisture Retention
The formwork used for rammed earth construction also plays a critical role in moisture retention. The formwork should be designed to minimize water loss from the wall, with a system of drainage and irrigation to maintain a consistent moisture level. This can be achieved by using a combination of permeable and impermeable materials, such as a mixture of sand and gravel for drainage, and a waterproof coating for the exterior of the formwork.
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