Friday, January 23, 2015

Understanding stabilised mud blocks

Earth or mud has been in use as a building material for wall construction in all parts of world. Explains Dr. Yogananda, "The unstabilised mud walls generally being thick have the advantage of good thermal insulation. Various traditional techniques of construction using mud are still in practice. They are the adobe, cob wall, rammed earth and wattle and daub. However, use of plain mud in wall construction has some disadvantages. These walls have good dry strength but hardly have any wet strength and they are more prone to termite-related problems in moist conditions. The walls thus built using plain mud require regular maintenance."

Stabilization is a technique of improving the properties of mud in such a way that it will possess the adequate wet strength, durability and dimensional stability (retains its shape and size both in dry and moist conditions) without burning. Compacting a mixture of sandy soil with 7% cement and small quantities of lime at optimum moisture in a press results in stabilised mud blocks (SMB). The overall energy consumption in SMB is quite small (about one-third) in comparison with the burnt bricks. Compaction of soil-stabilizer mix can be done by using a manually operated or a mechanised press. The press should be capable of generating sufficient force to produce a dense block. It is advantageous to use a manually operated press to eliminate additional energy needs in terms of electricity or diesel. The blocks have to be cured for three weeks by keeping the block surfaces moist. Additives like fly ash, quarry dust from crushers, granite fines or stone dust from stone cutting and polishing industries and various other mine or factory wastes can be used effectively along with the natural soil. One such example can be seen in TVS Brakes India factory (foundry division) in Tamil Nadu. The foundry waste was utilised along with the locally available soil to produce SMBs.

Alternatively, other construction techniques like rammed earth and stabilised adobe can be used without the need of a mud block press. Utilisation of demolished building debris is very essential in the present-day scenario. They can be recycled back into buildings.