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SOME MATERIAL IMPROVEMENT OPTIONS FOR EARTH

CONSTRUCTION IN NORTHERN GHANA: A KEY FACTOR INREDUCING THE IMPACT OF RECENT FLOODS ON HOUSING

Manu, F. W.1, Baiden-Amissah P.D.2, Boadi, J.K.3, Amoa-Mensah, K.4

1C.S.I.R (Building and Road Research Institute), K.N.U.S.T., Kumasi, Ghana2Optimum Shelter Group, UPO box, Kumasi, Ghana

ABSTRACT: Ghana and the entire West African sub-region have been heavily affected bythe global climatic change. Temperatures are higher, dry seasons prolonged and rainy

seasons pronounced and intense most often leading to floods. The recent floods in theSahel region of West Africa including the Northern part of Ghana recorded very highdestructions in 2007 and 2008. The destruction of housing was huge. More than 15,089housing units were lost in the three Northern Regions in 2007. Majority of these were inearth. This has worsened countrys housing delivery deficit which was at 600,000 units in2006 and increasing annually at about 100,000 units.

Among the causes for the high level of destruction was the fragility of the materials andinappropriateness of methods applied to stabilise the earthen materials. The indigenousconstruction methods available for walls in the region are sun dried earth bricks andblocks, atakpame or in-situ hand pressed and wattle and daub methods.

The paper seeks to present solutions to reduce the impact of the floods on earthbuildings with reference to material improvement based on available but lesser-usednatural and locally processed materials. These materials and their technology areavailable and readily adoptable in parts of the Northern Region. Fused laterite, claypozzolana, lime and plant material such as yellampour are some of the suggestedmaterials. Some of these materials were unearthed and mapped through researchactivities conducted at the CSIR (Building and Road Research Institute) in its efforts toincrease the appropriateness of earth as a building material. Research data is presentedto substantiate the efficiency of the materials. Remarkable advantages including savings incost of construction of the materials are enumerated and examples of some projects given.This is meant to make researchers, academia, construction industry and all interested in

the West African sub-region aware of options to build durable and sustainable housesthrough locally available material improvement technology. This will promote thedevelopment agenda of West African states and achieving the Millennium DevelopmentGoals by 2015.

KEYWORDS:indigenous, laterite, stabilization.

1 Researcher, fwirekomanu@yahoo.co.uk2

Researcher, kofiamissah2003@yahoo.com3 Researcher, boadijonas@yahoo.4 Researcher and consultant,kamensas@hotmail.com

Proceedings of the 11th International Conference onNon-conventional Materials and Technologies (NOCMAT 2009)6-9 September 2009, Bath, UK

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1. Introduction

Ghana is a 52 year old independent country in the West Coast of Africa. The Northern partof Ghana has pronounced dry and wet seasons, with the wet or rainy season occurringbetween the months of May and August. Dickson andBenneh (1988). This climatic area is

beginning to experience the effects of the global climatic change. This has manifested insevere flooding annually in the north from year 2007. For instance in August 2007, therewere heavy and persistent rains which flooded a lot of areas in the north. Ghana had in theprevious year experienced scanty and erratic rainfall leading to the low level in waterbodies and the near shut down of the Akosombo Hydro-electric plant. The most severeflooding occurred in the three northern regions of Ghana. Sandema, Nawulli and Bongo,were three of the towns affected by the floods in the region.

This region falls in the warm-dry humid climatic zone with a single rainfall regimepeaking usually in the third quarter of the year. Most of the north is founded on voltaianrock formation (Gidigasu and Mate-Korley, 1980) with fused laterite and rock outcrops inthe generally lateritic soil. Due to its relatively low level, there are basically drainage

problems resulting in the silting up of the water bodies some of which are fed by the Whiteand Black Volta. The banks of these silted up water bodies are being used for bothhousing construction and farming activities. This results in the removal the groundvegetative cover, leading to erosion and compounding siltation of the water bodies.

During the floods, 12 lives were lost and 2428 houses were destroyed in the 3 Districtalone (http://www.mint.gov.gh/ghanafloods/statistics_ueast.html) National resources hadto be employed to mitigate the effects of the flood, School buildings were used astemporary shelter for over four months, thereby interfering with the educational calendar inthe region and jeopardizing the future of children in the affected area.

1.1 Objectives

The paper seeks to do the following:

Study the physical and environmental conditions causing flooding in northernGhana where the towns of Sandema, Nawull and Bongo are situated.

Unearth available indigenous materials for construction and methods for protectingearth buildings

.These results are meant to help researchers, policy makers, academia, building industryexperts and all interested to engineer and implement specific solutions for the protectionand reconstruction of earth buildings in this and other communities in Ghana and the West

African Sub-region.

1.2 Research Methods

This paper is captures discussions, observation and documentation made during site visitsby the authors to the three towns affected by the 2007 floods three weeks after the event.This was to ascertain first hand information on the devastation and its effect on earthbuildings. The studies conducted were analysed and proposals made for the protection ofexisting buildings through indigenous building materials from research outputs from CSIR-Building and Road Research Institute (CSIR-BRRI and other Research Institutes) over theyears.

http://www.mint.gov.gh/ghanafloods/statistics_ueast.htmlhttp://www.mint.gov.gh/ghanafloods/statistics_ueast.html

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2. Discussions

2.1 Physical and Environmental Conditions

2.1.1 Climate

The Northern part of Ghana has warm-dry humid climatic conditions characterised by hightemperatures. Temperatures as high as 40 oC could be recorded. There is a single rainfallregime from May to September. Humidity is below and above average for dry and wetseasons respectively.

2.1.2 Geology70% of Ghana land surface is covered by laterite. (Gidigasu and Mate Appeagyei, 1989)The results of studies on laterite materials revealed that, the dominant lateritic materials inGhana range from rocks, boulders, cobbles, and pebbles through gravels to fine-grainedsandy, silty, and clayey soils.Gidigasu (2005)

The area falls mostly in the zone of the Voltain sandstone basin. This is a relatively youngrock formation. Importantly there are natural fused laterites or hard pan, rock outcropsidentified in many areas. The basin also has lots of clay which has the effect of reducingpercolation of water into the ground.There are four areas identified with major limestone deposits with reserves ranging from 6to 500 million tonnes. Gidigasu (2005)

2.1.3 Water bodiesThere are seasonal water bodies flowing through the area. Wind water and activities ofman have caused the land to lose its vegetative cover resulting in the loosening of soilaggregates which have silted up the riverbeds making it possible for water to flow at a highlevel.

2.1.4 VegetationThe vegetation is varied but it is mostly grassland interspersed with trees. This has forcedpeople to farm close to the banks of rivers leading to aggregates being eroded into theriverbeds

2.1.5 TopographyMost of the region is low lying and this has created difficulty in draining of water from thesurface of the ground.

The results of these conditions are high transmission of heat into interiors, stagnation ofwater around buildings leading to flooding and resultant destruction of life and properties.

2.2Material and Methods Available for Wall Improvement

2.2.1 Sun dried bricks/blocks

The use of earth as a building material has moved from the atakpame and wattle and daubmethods to sun dried or adobe bricks/blocks. The popular reason is that it is easier, fasterand gives better quality assurance. It has been used for the construction of about 60% of

all buildings in rural areas in Ghana. Manu (2006). Traditionally, mostly laterite in thenearby environment is used after some tests are conducted based on the community-

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specific knowledge and skills in earth construction. Improvement on its compressive,tensile and abrasive strengths is being re-confirmed. This has been achieved by additionsand and rice husk to various grain size laterite. Mix proportions differ based on theproperties of the laterite available. 28 day wet compressive strength of 1.5 MPa has beenachieved. Due to its vulnerability to the rain, its use on the exterior without rendering with

an impervious material should be discouraged.

Plate 1. An adobe construction site for Mr and Mrs Gubbels in Bongbini in theMamprusi East District of the Northern Region

2.2.2 Compressed earth blocks (CEB)

The CEB technology offers an alternate kind of building walls of guaranteed quality. Themove to use compressed earth buildings in Ghana began at the Kwame NkrumahUniversity of Science and Technology in the 1970s. The TEK block technology systemdeveloped by the Department of Housing and Planning of the Kwame Nkrumah University

of Science and Technology, Kumasi was the foremost. TEK block press was used inputting up few public buildings and houses by the use of laterite with 5-10% cement. Theintroduction of pozzolana as a replacement of 40% of Portland cement has improved itschemical properties (refer to 2.2.5) and cost. 2 to 5 MPa has been achieved for 28 daycompressive strength. The attempt to integrate it into the formal and informal sectors andindustry was however short-lived. Other compression systems available are the CINVARAM and many other locally manufactured presses. The numerous uncontrolledfabrications of presses have led to low quality bricks and wall construction evident in someproject.

Plate 2. TEK-block (compressed earth block) used in the construction of walls andvault in Gambigigo, Upper East Region on Ghana

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2.2.3 Lime (cottage industry-base) stabilised earth blocks

Though lime-earth stabilisation is one of the oldest ways of improving fine-grained earth forconstruction, its utilisation is uncommon. The lime in Ghana is produced from limestone,dolomite deposits and clam shells on small scale basis even though good reserves exist in

the Northern part of the Country at Buipe, Nauli and Bongo. Reserves range between 6-500 million tonnes. The local lime-earth block production capacity depends on the quantityand quality of the lime, nature of the earth material, the availability of laboratory forevaluating the lime-earth mix, method for moulding the blocks, curing procedures and theage of the blocks. On the average a mixture of lime: laterite proposed is 1:10. However 6-7% of lime mixes have also been successful at CSIR-BRRI exposure site.

2.2.4 Lateritic stones

Laterite stone construction is a common feature in most parts of the country. The commontypes of these stones are the ferruginous and aluminous rocks. The aluminous laterite

stones are generally abundant in high rainfall areas while the ferruginous ones aredominant in the semi-arid and dry sub-humid areas. The specific gravity of the lateritestones range from 2.6 to 3.0 g/cm3. The compressive strength also ranges from 3.1 to 17.2MPa. It is used together with pozzolana-portland cement or lime mortar. Some fusedlaterites have been found to possess even greater compressive strength than engineeredbricks. Two ways of using the material are in the natural regular or irregular forms.Irregular ones take a lot of mortar making it most often uneconomical. When it is used forthe substructure it is recommended that it be cut to rectilinear forms to avoid rendering.This walling material has been used in other regions such as Brong Ahafo, Ashanti and theEastern. Churches such as the Catholic Cathedral of Nandom and former Bishopsresidence of Navrongo are built from it. Making use of improvement in stone processingtechnologies, the great potential of these stones can be successfully used for structuraland non structural portions of houses. Lateritic stone quarries have been opened upBolgatanga-Bawku, Techiman, Kokoben and Trabuom. There are some good outcrops oflateritic stones which have been mapped by the CSIR (BRRI). Gidigasu and Appeagyei(1989)

Plate 3. A laterite blocks construction of a residence and church in Nandom in the UpperWest Region, Ghana.

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Plate 4. A laterite block quarry in Nandom

2.2.5. Pozzolana-Portland cement stabilisation

Pozzolana production from identified clay deposits in Ghana and used to replace as muchas 40% of the Portland cement content in building and road construction. Thedevelopment, production and use of less costly pozzolana are of a great impetus to costreduction in the construction industry in Ghana. Pozzolana is a material containing silicaand alumina as well as other constituents which react with the constituents in Portlandcement. The advantages of its use include providing a more plastic and workable pastewhen used with Portland cement, binding better than Portland cement mortar, greaterresistant to water and gaining more in strength even after a year.This is a form of stabilisation in which cement mortar is used to bind aggregates, burnt

bricks, stones, fused laterite etc to give the walls the needed strengths. Test blocks shouldbe made on site to determine the suitability and proportions of the mixture. In its

application in sandcrete block moulding, 28-day compressive strength of 3 MPa wasachieved with 14.3% by volume Portland pozzolana cement as compared to the required2.28 N/mm2. Hugo and Hubert (2001)

2.2.6 Stone in pozzolana Portland cement mortar.

Stones available in this region are rocks of the igneous and sedimentary origins. Theseare suitable as components for structural aspects of buildings though they are seldomused. This is because of the high of Portland cement (the predominant binder in the area).However, with the reduction in the volume of Portland cement used as a result of itsreplacement by pozzolana, its used is highly recommended. The caution is that porousstones should not be used. Important positions for these stones in the structural elementssuch as foundations, columns and beams, and walls.

2.2.7 Coal tar/bitumen stabilisation

In this form of stabilization, heated bitumen is added to a mixture of earth and sand.Bitumen is effective for earth which has low clay content. Hugo and Hubert (2001)Emulsified tar, though more expensive could be used. The best mix ratio should bedetermined on test samples. A 28 day compressive strength of between 2 to 5MPa hasbeen achieved with this method with 5 to 9% bitumen emulsion. Hugo and Hubert (2001)

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2.3 Material and Methods Available for Wall Finishes Improvement

2.3.1 Earth renders

Three forms of stabilising the earth rendering material occur. An indigenous mixture of

dawa dawa fruit extract, cow dung, ash and yellampour- a local climbing plant meant tolast up to 8 years. Coal tar or bitumen as described in 2.2.3 and stabilization with a weakpozzolana Portland cement mix gives a very good bonding and strength when used withearth. Pozzolana use performs well with earth as a result of the fact that its component isalso clay.

2.3.2 Lime-earth renders

Lime stabilisation has its greatest effect on clayey soils when it is in large quantities, oftenover 10%. A lime-stabilised rendering is best applied to a stabilised surface. The mixshould be determined on test samples.

2.3.3 Bitumen-stabilised renders

Bitumen-stabilised soils should neither be too clayey nor too sandy and dusty. Thequantity of bitumen ranges from 2 to 6%. They are usually cut-backs which should beheated without exceeding 100 oC. Where bituminous emulsions are used the mixture mustbe made slowly in order to avoid any breakdown of the emulsion.

2.3.4 Painting

Pozzolana-Portland cement slurry, emulsified and oil based paints are used on externalwalls as supplement to the sealing of pores and bonding of particles. Local extracts fromplants and shale are also available particularly in the South, can be imported and appliedin the northern regions.

3. Conclusions

With the implementation of these proposals, earth buildings can be protected from floodingand be able to satisfy its structural requirements. This will be a great motivational factor forpromotion of improved earth construction and increased housing delivery in Ghana.

4. References

DICKSON, K.B. and BENNEH, G. 1988. A New Geography of Ghana. London: Longman.Field, M.J. 1943.

GIDIGASU, M.D and MATE-KORLEY, E.N. 1980, Stabilisation Characteristics of SelectedGhanaian Soils (Technical Paper HM/6 Paper 12): Building and Road research Institute,Council for Scientific and Industrial Research, U.P.O. Box 40, Kumasi Ghana

Ghana Floods Inter-Ministerial task force website for the management of the recent floodsin Ghana

http://www.mint.gov.gh/ghanafloods/statistics_ueast.html

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GIDIGASU, M.D. and APPEAGYEI, E. 1989, Characterisation of a Typical Lateritic LoamyClay for the Production of Adobe and Local Lime Stabilised Walling Blocks : Some LocalRaw Materials for Low Cost Housing in Ghana (part 2): Commonwealth Science Council,Commonwealth Secretariat, Marlborough House, Pall mall, London SWIY 5HX,

HUGO H., and HUBERT G. Earth Construction: A Comprehensive Guide

GIDIGASU, M.D. (2005) Lateritic Soil construction for housing in Ghana

MANU, FREDERICK WIREKO(2006)The Forgotten Hands-Documentation of GhanaianIndigenous Knowledge And Skills In Earth Construction-Case Study Of Kogle, Upper WestRegion, Ghana