Mud is one of the ancient building materials. Typically, mud is treated with a variety of other materials before forming them into bricks or using as it is. These materials enhance the properties of mud; for example, preventing cracks, increase binding between mud particles, increase strength etc. The different proportion of these additional materials can be used to vary the final properties of mud, as required. In modern usage, mud is typically ‘stabilized’ using materials like cement before moulding them into blocks.
In the past, mud has been extensively used across the world to build small houses as well as stunning landmarks like the city of Shibam in Yemen (a UNESCO World Heritage site) or the Great Mosque of Djenné in Mali, Africa. In India, mud buildings were once quite common for independent homes. There are examples of its use in large buildings; like the Leh Palace.
One of the key benefits of using mud is its lower heat capacity than materials like concrete. Mud does not tend to act like a large heat reservoir like concrete; capturing it during the day and releasing it in the night. This helps in preventing what is known as an ‘Urban Heat Island’; where large urban areas tend to be warmer than the surrounding rural ones. Mud also has good properties in terms of strength, sound insulation, almost no emission of harmful Volatile Organic Compounds (VOCs), low environmental impact etc.
However, the usage of mud for construction is on the decline for many years. Over the years, mud has come to be seen as an inferior material used only by those who can’t afford modern building materials. Even in rural areas, red clay bricks are commonly used with roofs ranging from asbestos sheets to concrete.
In more recent times, there has been considerable interest in mud as an ecofriendly material and promoting its usage in modern buildings. Pioneering architects like Louis Baker have used mud extensively in their creations; keeping the interest going until such time solutions can be found to use mud more extensively. Of late, there is interest and research on using mud for building affordable homes. It’s easily availability, simple construction method, ecofriendly nature and low cost are attractive for this application. In order to reduce the stigma of using ‘outdated’ mud construction, research is focusing on making materials like mud bricks, which look and feel similar to ordinary bricks. The Auroville Earth Institute has developed Compressed Stabilized Earth Blocks (CSEB) which uses mud as one of the key ingredients. It is made using mud, sand, cement and water. It does not require top soil as a source of mud, thereby conserving the land for other purposes like agriculture.
The key challenge to usage of mud in large projects is product standardization in terms of ingredients, size, technical properties etc. and ability to produce mud based products in large quantities using mechanization. All other common building materials like cement, steel, sand and aggregates are standardized and mass produced, thereby reducing cost. Further, the final product should be at par or superior to competing materials. For example, mud bricks do not offer insulation to the extent offered by products like AAC blocks. They also need protection from heavy rain and moisture. Much work is needed on the above before mud can be considered as an alternate building material for mass usage in the future.
Let us hope that research on mud as a building material will be a success and soon mud products will become commercially viable for large projects. It will help in moving towards a more sustainable future!