Tarpaulin is one of the commonly distributed materials by humanitarian agencies in emergency conditions. This tarpaulin is woven polyethylene fabric coated at both sides. Because of its durability and water-resistant quality, it is used for multiple purposes, but for displaced people, it is employed for building temporary shelters such as tents.
When natural or manmade disasters happen, a number of people are displaced loosing or abandoning their homes. However, only a few beneficiaries are chosen to have permanent houses. Therefore, most of displaced people end up leaving in temporary tents more than several years being exposed to upcoming natural disasters (Wadekar, 2021).
There are serious problems about this process. Because humanitarian agencies are building permanent houses with concrete blocks and local people do not have any knowledge of building houses with this western material (Reliefweb, 2001), it not only takes a long time to build by relying on the external skilled workers approved by the agencies, but also it is very expensive to build, resulting not distributing budgets fairly to all disaster-affected people.
Considering these problems - natural disaster, especially flood and the limitations of the response of humanitarian agencies, I have raised the question
Could displaced people be initiative to build their own permanent flood-resilient houses with locally available materials?
Could tarpaulin be used to build flood-resilient earthen structure?
To answer these questions, I have done a test by building a wall with two materials – soil as locally available material and tarpaulin as emergency-relief-material. For this test, I procured a similar type of tarpaulin that is distributed by humanitarian agency, which is woven high density polyethylene with over 200g/m2 and is coated on both sides, based on the specification provided by IFRC and Oxfam (2007). This tarpaulin formed rammed earth wall was built as part of my current flood test.
Construction
Fully unstabilised rammed earth walls are not normally built in a practice because the walls can be very much susceptible to water. If the bottom part of the rammed earth walls is undermined heavily, the integrity of a whole structure – not just walls but also roofs will be deteriorated being collapsed eventually. Being different with a conventional practice, for the flood test, I intentionally built a unstabilised rammed earth wall from bottom to top with the tarpaulin formwork. There were two major reasons for this. Firstly, to test the performance of tarpaulin as a protective layer for rammed earth against seepage of water. Instead of using chemical stabiliser, I intended to examine if tarpaulin helps to enhance the flood resilience of rammed earth. Secondly, for a simple construction. Considering the scarcity of materials in emergency conditions, I planned to see the flood resilient performance of rammed earth built with simple materials – fabric and soil, not using any stabiliser.
Outcome and Findings
Tarpaulin formwork was also very easy to remove just like other fabric formwork. But, when the tarpaulin was peeled off, some amount of soils was attached to the tarpaulin, and this, in turn, affected the surface of tarpaulin-formed rammed earth wall. If the surfaces of the tarpaulin formed rammed earth (TFRE) and permeable fabric formed rammed earth (PFRE) are carefully observed and compared, TFRE has less smoother surface than permeable fabric-formed rammed earth. It is presumably because air and water were trapped within the impermeable fabric during the ramming course. Because tarpaulin as laminated on both sides as waterproofing fabric, moisture and air could not be extracted from the fabric during the ramming course. This is very contrasted with the materials’ performance of PFRE during the ramming course because superfluous water and air are removed from the permeable fabric. Based on this contrasted difference in surface and materials’ performance during the construction process, it is presumed that the density of two walls will be quite different. Therefore, the density of each wall will be also tested after the flood test.
Despite some small patchy surfaces, tarpaulin-formed rammed earth came out nice generally, and this showed that tarpaulin can be certainly utilised to build rammed earth walls.
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