Mudcrete, not concrete

Natural materials last for long, while produced ones have to perish someday, says architect Sathya Prakash Varanashi

This is a fact – longevity of construction hinges around one simple phenomenon: Natural materials last for long, while produced products have to perish someday. Even cement and concrete which are ruling the building industry today are not as strong or durable as the construction industry is making us believe so.

Incidentally, the idea of mixing fine particles, coarse aggregates and binding materials together was originally discovered during the days of Roman Empire, nearly 2200 years ago. They used broken bricks or stones with volcanic ash or pozzolona mortar, adding slaked lime too.

The Pantheon dome spanning 142 feet and rising to the same height has no reinforcement; it’s just the Roman Concrete, still standing tall after 2000 years. Innumerable markets, large gateways with wide vaults and many structures all over their ruled area stand testimony for this wonderful material. The parts of Roman ports submerged in the sea are still there, undisturbed.

After the fall of the Roman Empire, the making and building with concrete got lost. What we call as concrete today could be theoretically same as the older version, but the materials we mix and their proportions are not the same. However, we use the same name, despite the paradox that our concrete may not even live up to 100 years and in no way it can last 2000 years!

One example is the use of Portland cement, a manufactured product which deteriorates over age. Lesser the cement in concrete, more the durability of the total mix. What options do we have – can we try to make concrete with minimal cement; sand or M. sand; un-sieved mud and broken bricks, stones, construction debris or such large aggregates?

With minimal research and testing in this possibly new material that has been termed as mudcrete or earthcrete, not many people have confidence in this combination. However, in areas where load transfer has to happen only by compression, i.e. foundation, walls and such others, mudcrete is an economical and simple option.

Cheaper alternative

In civil engineering applications, stabilised mud mix has been successfully tried as a cheaper alternative for rock fill under roads and also in land reclamations. There have been a few structures built at Auroville. Many rural areas continue to mix mud with local brick waste and pebbles for varied applications. Yet, very little information is available from co-professionals and even on the Internet.

The quality and composition of mud varies between places; as such it is important to check the gravel, silt and clay contents of the mud to ensure the prescribed proportion is maintained. Brick bats, stone pieces and many other such materials are better suited as the larger aggregates.

Principles followed in rammed earth walls are also partly used here, though heavy ramming may be disastrous. If we were to revive mudcrete, many more ideas about how to use it will emerge.

(The writer can be contacted at [email protected])

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