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COMPARATIVE ANALYSIS OF RAMMED EARTH CONSTRUCTION AND

TRADITIONAL BURNED CLAY BRICKS CONSTRUCTION.

CHAPTER ONE: INTRODUCTION

1.1. Background of the study;

Provision of housing for developing countries is one of the most important basic needs of low-income groups. It is a very difficult requirement to meet, however, since land and construction costs are mostly beyond the reach of both the rural and urban poor. In order to address this issue various governments have undertaken housing schemes that aims to facilitate some form of housing ownership by low-income groups.

Due to limited means within developing countries, it is necessary to seek ways to reduce construction costs, especially for low- income as well as adopting easy and effective solutions for their repair and maintenance. Such objectives can be achieved partially through the production and use of cheap yet durable locally available building materials. Various traditional construction materials exist in Uganda which have proved to be suitable for a wide range of buildings and which have a great potential for increased use in the future.

Soil is one of the primary materials used for construction of traditional low-cost dwellings in Uganda and is well suited to local weather conditions and occupancy patterns. Soil construction methods are used in 80% of urban buildings in Uganda while this figure exceeds 90% in rural areas. Buildings are constructed entirely, or partially of soil, depending on location, climate, available skills, cost, building use and local tradition.

Challenges associated with delivering adequate and affordable housing to people in the low -income category is usually linked to the issue of construction materials and technology. Literature shows that materials constitute the largest single input in housing construction, accounting for 60– 70% of total cost in Ghana (Danso and Manu, 2017), around 65% in Nigeria (Mogbo, 2017), over 76% in Tanzania (Wells et a l., 2017)1998 and 68% in Kenya (Syagga, 1993). A number of scholars have established the fact that escalating cost of building materials is one of the major factors responsible for the widening gap between demand and supply of affordable and adequate housing (Adedeji, 2007;Zami and Lee, 2010; Assaf et al. , 2010; Kulkarni et al. ,2014) . Two- digit inflation on the price of construction materials, in the recent years, have resulted in continual increase in housing costs in some countries (Adegun & Adedeji, 2017).

Housing inadequacy is not only a function of rising prices. The impact of construction materials and technology on the environment deserves attention. Housing demand and investment opportunities that accompany urbanisation mean greenhouse gas (GHG) emissions through construction might double by 2050 (UNEP/CIDB, 2009). Most part of the resources needed to build houses for all are non-renewable. These problems motivate the need to reconsider the promotion of materials that result in lower construction costs and minimal costs to the environment.

Earthen construction materials, with a long history in Africa (Fathy & Denyer, 2107) are one of the most experimented technologies in the current search for economically and environmentally sustainable housing (Dayaratne, 2011). They are known for certain advantages and disadvantages which have not been sufficiently understood, documented or regulated, thus hampering appropriate knowledge sharing within Sub-Saharan Africa. Benefits associated with this material are not fully explored because research outputs have not been properly brought together Stanley, (OGBUAGU, & OKECHUKWU, 2014). The absence of aggregated empirical evidence on the touted benefits and little-known demerits of earthen materials motivates the review reported in this research.

We review literature providing evidence on the advantages and disadvantages of earthen construction in terms of cost, energy and thermal properties. By identifying and discussing available proofs, we seek to further arouse interest in earthen materials and technologies in housing projects in African cities. Review on an indigenous building material like this can inform policy in this part of the world where urbanisation is putting pressure on economic,earthen construction materials and technologies, as considered in this paper, are in four broad categories – simple clay (adobe) blocks, rammed earth, clay/soil plus other components and machined blocks.

Rammed earth has been dated back thousands of years in China, although the exact dates are unknown. “Excavations in China have uncovered rammed earth construction dating from the seventh century B.C.” (StJohn, Cao, Qian, & Easton, 2007). Various ancient forms of rammed earth have been found being used in the Great Wall of China, and areas in Africa. Europeans adopted the method later on, and eventually they brought the building methods to America.  It wasn’t until the early 1800’s until the rammed earth building method was introduced in America. It’s great to know that this method of building is still being used today in modern applications, although its popularity has dropped significantly since modern building techniques have taken over.

Rammed earth is an ancient construction technique that utilizes only the earth to create thick, durable walls, which can be load bearing, low-cost, heat-storing and recyclable. It was developed independently in many parts of the world, and is also commonly known by its French name “Pise”. The technique of rammed earth is simply based on compacting soil between vertical formwork boards, which are then removed leaving a mass soil wall. Usually this technique is used in regions whose soil composition is unsuitable to make sun dried clay bricks (Keable, 1994; Easton, 1996). Excavations in China have uncovered rammed earth constructions dating from the 7th century B.C. as parts of The Great Wall of China, begun more than 5,000 years ago were built of stone and rammed earth (Easton, 1996). Rammed earth technique was used in the arid regions of North Africa and the Middle East, where earth was the only logical building material, where the massive high walls with their small openings protect them from the heat and dust of the desert.

Rammed earth had been seen as a quick, easy construction technique to build fortifications; a cheap way to build dwellings; and has been recently recognized as a sustainable construction technique which uses only what is available at the site. Since the 1970’s the use of rammed earth has been prompted in Europe and the United States as a sustainable construction material. Rammed earth is based on naturally damp and crumbly earth which is compressed into form and left to dry and harden. It is the heaviest form of earthen building.

Rammed earth structures can therefore be load bearing. The earth is filled into a form and compressed in layers similar to conventional in-situ concrete. Alternatively large rammed earth blocks can be pre-cast in molds and then assembled on site much like brickwork on a larger scale. Earth has been used as a building material by all ancient cultures in the world for both housing and elaborate religious structures. Examples of ancient earthen structures are the Great Wall of China and The Great Mosque at Djenne. Locally, earth has also been used as a construction material by several ethnic groups, especially communities that live in hot and dry areas (Fig. 1.1).

Fig. 1.1: An image showing an ancient rammed earth building in Morocco.

Source: (Sitati, 2011)

It’s popularity as a construction material declined in the western world during the Industrial Age with the popularisation of frame construction .In Kenya, the decline of earth construction among local communities began during the colonial period when the British introduced the use of natural stone as a construction material and locals began to view earth as an inferior material. Earth construction started gaining popularity again in the 1970’s especially with the increased global environmental consciousness. People in the Western world came to realise that earth was a far more sustainable material than concrete, steel and sandstone.

Several institutions and individuals began to carry out research on earth construction. These include:-

The Centre for the Research & Application of Earth (CRATerre) was founded in France in 1979. It offers a Master’s degree in Earth Architecture. David Easton: This is a Stanford University graduate who built his first rammed earth project in 1975.HRDU at the University of Nairobi which has carried out extensive research on the use of stabilized soil blocks. The research carried out by these institutions contributed to the evolution of earth architecture from traditional construction to contemporary earth construction techniques, which include the use of stabilised earth blocks, rammed earthworks and sandbag construction.

Traditional burned brick construction is one of the oldest manufacturing building materials in the world. This cavity between the two Wythes provided an exit point for any moisture entering the first layer of brick. With the creation of the cavity wall, came the idea for a brick with pre-developed voids.

1.2. Problem statement:

The  increase in  demand  of  construction  over  the  past years  has  led  to general increase  in  the cost  of housing. Countrywide, the yearly demand for housing has greatly increased leading to people to seek for an alternative method in regard to cost of construction materials. Such high demand calls for vast amounts of natural resources for construction materials such as sand, earthen soil and especially cement production. Specifically, the cost of building materials such as cement, granite and aggregates continue to increase and this poses a great challenge to most constructors. The world’s cement market currently  stands at  approximately  2 million  tonnes  of  cement,  80%  of  which  is  consumed  in  emerging  countries like Uganda, therefore this research seeks to obtain a comparative analysis of rammed earth construction and traditionally burned clay bricks.

Earth construction was traditionally used in Kenya by majority of Kenyan communities, and the material was used to express culture through the architecture. The construction techniques responded to regional considerations in their respective localities. During and after the colonial period however, earth construction was abandoned for industrialised materials and construction techniques which the local communities did not own. Industrialised construction materials and techniques thus became accepted as ‘conventional’. These materials include glass, concrete, natural stone and ceramic tiles.

Industrialised construction materials and techniques have several demerits which include being expensive and unsustainable. The majority of people want to use industrialised materials because they are ‘fashionable’ and ‘modern’. In the Kenyan context, it has proven difficult to meet our shelter requirements using these industrialised construction materials and techniques. In addition to being expensive and unsustainable, some of these materials do not respond to the climatic context in which they are used.

Due to this phenomenon, it became necessary to carry out research on contemporary earth construction in order to ascertain earth as an affordable and sustainable material that can be used to satisfy the shelter needs in Kenya. (Sitati, 2011)

Although rammed earth has been around for so long the building method hasn’t changed very much. The difference from the traditional burned clay bricks construction and the rammed earth construction has been the strength, durability and environmental impacts. Rammed earth construction strength’s is increased through the addition of cement, rebar, and the compaction method, which has changed from manually to pneumatically. Although in some places manually compressing the soil is still being used.

Some of these places that still compress the soil manually are usually rural parts of the country with little money to afford the modern approach, and are able to reap the benefits of having great soils where they live, located mostly in the tropics because of their laterite soils that suit rammed earth building well. This way they are able to use the soil around them, and not pay for expensive materials, or transportation costs.

Many of today’s rammed earth applications in the Uganda are not only used for their building qualities, but used to show off how beautiful a building can be when constructed with rammed earth. This is seen with the beautiful soil layers developed within the rammed earth. Today’s applications include purposely layering the soil with different colors to make the layers the center of attention. Rammed earth is still not very prevalent in the Uganda but it’s a great way to build something if you have the appropriate soils and want to build something with sustainable advantages as compared to traditional burned clay bricks.

1.3. Objectives

1.3.1. General Objective

To carry out a comparative analysis of rammed earth construction and traditional burned clay bricks construction

1.3.2. Specific objectives

1. To study the viability  of  rammed  earth  construction  with  locally  available  soil,  by  optimizing the  quantity  of cement and water to be added for stabilizing the soil.
2. To determine the axial compressive strength characteristics of cement stabilized rammed earth as to traditionally burned clay bricks.
3. To identify, describe construction techniques and environmental impacts of rammed earth construction and traditionally burned clay bricks.
4. To assess the cost benefit of rammed earth construction as to traditionally burned clay bricks construction.

1.4. Research Questions

1. How is rammed earth and traditionally burned clay bricks construction carried out?
2. Do the engineering properties of rammed earth construction warrant it to be used as a construction material?
3. How does the rammed earth construction and traditionally burned clay bricks perform as partial replacement material for masonry construction perform with conventional construction techniques in terms of environmental sustainability?
4. What is the cost-benefit of using rammed earth construction as partial replacement materials for traditionally burned clay bricks in construction?

1.5. Justification

In relation to durability of the structure, rammed earth construction has showed to be more durable compared to traditional burned clay bricks. Rammed earth construction walls can act as a structural walls to support the loads imposed on it, for instance there is no need for column construction required if one is to construct one floor above it.

Traditional burned clay brick construction has led to degradation of the environment, for instance the burning of the bricks to improve on their compressive strength and durability has polluted the environment by doing so, and therefore this study as well seeks to establish what construction technique is eco-friendly. Traditional burned clay brick construction has greatly been considered to be expensive in relation to material purchase therefore this study seeks to establish the viability and identify what construction technique is adaptable to the people as a construction material.

Therefore the study seeks to establish the viability of rammed earth construction as to traditional burned clay bricks as a contemporary earth construction technique country wide in addition to traditionally burned clay bricks with the aim of contributing to the acceptability of earth as a ‘conventional’ construction material.

1.6. Scope of the Study

Lacking of details on the environmental analysis of rammed earth in comparison to traditionally burned clay bricks for instance lack of air velocity data minimizes the environmental analysis. Otherwise more details on the environmental impacts can be possible.

Rammed earth construction and traditionally burned clay bricks were sampled from Kampala and its environs, targeting construction sites, areas of Gayaza Canaanite Estates. Gayaza where earth material was obtained moulded into a brick then burned to ascertain its strength and durability. Gayaza was the location as to where the study was carried out and its construction process as well. This study involved massive excavation of earth material around the site location .Next, the engineering properties of rammed earth and traditionally burned clay bricks was limited to the physical properties determined using the relevant standards. However, the engineering properties of both rammed earth and traditionally burned clay brick were determined to verify similarities as well as warrant their use as a construction material.

Finally, the cost benefit of using rammed earth and traditionally burned clay brick a construction material was limited to comparing the performance and its cost. The benefits in terms of the environment were also evaluated .This was assessed to determine the suitability of rammed earth as a construction material as to traditionally burned clay bricks in production for low cost housing construction.