The Influence of Mineralogy and Particle Size on Mud House Construction in Rural Bangladesh

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1 The Influence of Mineralogy and Particle Size on Mud House Construction in Rural Bangladesh D J C Laming Herrington Geoscience and Housing and Hazards Group (UK) R L P Hodgson University of Exeter and Housing and Hazards Group (UK) M J Heath Sheffield Hallam University and Housing and Hazards Group (UK)

2 The challenge Some 90m Bangladeshis live in rural non engineered houses that provide inadequate protection against natural hazards. Housing & Hazards is a network of professionals dedicated to developing improved technologies for use in rural Bangladesh

3 Diversity in House Construction Traditional house types, from fragile bamboo and straw shelters to substantial mud structures, appear to occur at random on the alluvial plains of Bangladesh. Variations in construction method commonly reflect the local availability of construction materials and their characteristics, including the geological materials present

4 Materials used The results of a survey of wall construction materials made in N Bengal, This is fairly typical of national statistics. Other, 4% Brick, 4% Woven Bamboo, 11% Layered mud 51% Bamboo + Mud 30% Local variations can occur. A recent survey in a sandy river bank area found that 95% of houses were of woven bamboo because the muds Carter M L (1997). Rural housing and affordable innovation, Housing & there were not sufficiently Hazards Monograph No 1, 101pp cohesive.

5 Focusing on mud building A high proportion of Bangladesh's rural homes are composed partly or entirely of mud, which collapse readily when flooded. One focus of H&H's research has been to investigate better ways of using and stabilising mud. This paper relates soil type to options for cement stabilisation.

6 Distribution of Soil Types Brammer (1996) identified 23 physio graphic regions in Bangladesh and the associated soils. Broadly, soils grade from light sandy silty in north to heavy clays bordering Bay of Bengal Brammer H (1996). The geography of the soils of Bangladesh. University Press Ltd, Dhaka, 287pp.

7 Study locations Field studies made at three locations in Dinajpur (sandy), Manikganj (silt/clay), & Gopalganj (peaty). Paper reports findings in terms of local soil types and in relation to the national soil distributions

8 Community Participation Studies used Action Research to engage communities in housing improvements. Participants shared experiences of the building process and developed appropriate improvements. Village construction workshop, Dinajpur District

9 Cement stabilised Mud Practical and laboratory experiments showed that OP Cement can be used economically to make building mud resistant to flooding. Different pozzolans were tried but only OPC gave water resistance at an OPC-mud blocks after 3 months economic cost inundation at BUET

10 Building with Cement Mud It may be formed into blocks to construct walls Or used in place of traditional solid mud building materials. Building first stabilised mud house, Dinajpur 2002

11 A simple soil test The success of cement stabilisation process is governed by the clay content of the soil. Too much clay and the result is badly mixed and weak. A simple sedimentation test can be made in the field, as shown here.

12 How much cement? Location Sand/ Silt% Clay % Stabilisation process Dinajpur >80 <20 3 5% cement Manikganj >60 <40 5% cement Gopalganj <20 >80 8 9% cement + 20% sand Soil properties and cement stabilisation details for each of the study sites NOTE that Gopalganj is in an area of organic soils

13 Extending this experience Based on this, the Brammer soil map suggests that flood resistant cement reinforced mud houses could be built in about half of Bangladesh s low lying rural areas, although more detailed fieldwork is needed to identify the most suitable soils in each locality

14 Other relevant soil properties Mineralogy and organic content also important Swelling minerals (montmorillonite) may occur in the lower Meghna/Padma delta. Lime is available in some areas. This presentation is the start of wider investigation into options for improving mud construction in Bangladesh

15 Changing Practice Ranges of soil types will be found in any given area due to variations in depositional environment. Experienced mud builders will choose the most cohesive soils available. In sandy areas builders may not consider mud building at all. Changing traditional practice is A CHALLENGE This group remains adamant that they cannot build mud houses with their sandy soils

16 Barriers to new techniques There are also socio economic barriers to low cost home improvement. Home owners aspire to modern materials. Some cannot afford any extra cost. Women have little influence over 'men's work'

17 Other H&H studies Housing & Hazards' links have also conducted experimental research into wind effects on small buildings and into appropriate ways of disseminating technical information. Wind tunnel tests in Exeter Mud mixing training, Dinajpur

18 Conclusions Soil data from the study sites demonstrate the importance of soil characteristics in understanding present practice, and in developing novel technologies with the aim of providing hazard resistant homes in many parts of rural Bangladesh The study data can be extended nationally using published soil information Work is still needed to confirm local conditions and to address attitudes and socio economic barriers to development.

19 Thank You! Kantaji Temple, Dinajpur. A reminder that durable structures can be built!