For a ‘mudcrete foundation’
The composition may vary between places, though the basic considerations may include cement as the binding material.
The first material early humans discovered for their construction purposes must have been mud under their feet and strangely it continues to be valid even today.
To deepen this exciting thought, just imagine a case where we dig out mud and put it back as the foundation! Yes, it was proven as a simple and fast system in many villages of Karnataka for small houses.
Excavated mud is added with broken tiles, stones or pottery with jaggery, lime and water. The mix is well trampled for two days while keeping wet, so it gains the required strength to be placed back.
Despite being a time-tested method, mainstream-size stone approach replaced it, and now sadly, the concrete column foundation is side-lining even the stone one, though RCC is mostly unwanted, costing more and damaging nature even more.
Concrete is like hard rock, but is a human product with cement, sand and coarse aggregate. If cement content can be reduced, the mix can last longer, but the prescribed mix strength cannot be compromised with. This is where mudcrete can step in.
One safe area to replace concrete by mudcrete is in the foundation where the soil is hard with good bearing capacity. With both wall sides, the trench will never give way.
A normal 1:4:8 concrete mix at the trench bottom may act as a levelling and anti-termite course. Subsequently, mudcrete may be placed in layers of 9 inch each, compacted to about 6 inch thickness. At maximum two courses a day, a 3-ft.-deep foundation can be raised in 3 days, very safely.
The composition of mudcrete may vary between places, though the basic considerations may include cement as the binding material; sand to reduce shrinking and cracking; lime to resist termite attacks; mud as the base inert material; and brick bats, aggregates from rubble, broken stone pebbles or construction waste as the coarse material.
Proportions also change based on specific characteristics of mud and size of brick bats.
If the mud has more than half as gravel, about one-fourth silt and minimal clay, around 10% , it suits the purpose. Likewise, brick bats could be 20 to 40 mm in size, more of it in the lower sizes.
Given this, cement, sand, mud and the coarse material can be around 1:2:7:10 for a stronger foundation, and can increase mud to 10 and brick bats up to 20, based on site studies. Of course, all this needs expert supervision and engineering calculations.
A major step towards reviving it happened recently near Bengaluru for the house of Timmaiah along with students of architecture from KSSA, hoping to train the next generation. Mudcrete concept is diluted today for varied reasons, mainly lack of applied knowledge among the younger generation, hence failures. The ideal soil composition and availability of coarse aggregates could also be the causes.
However, there is no real reason why this should not be revived, at least for small and safe applications. May be it’s a matter of mind and time.