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AN INVESTIGATION INTO THE PROPERTIES OF STABILISED LATERITE BLOCKS

CHAPTER ONE

1.0INTRODUCTION

1.1       BACKGROUND OF THE STUDY

The importance of housing in human history cannot be overemphasized. Housing is seen as one of the best indicators of a person’s standard of living and of his or her place in society (UNCHS, 1993). Furthermore, Venkatarama (2004) is of the view that housing and building conditions also reflect the living standards of a society. Thus, the importance of access to adequate and affordable housing took the front burner in the mid 20th century. The low-income group whose population is on the increase due to rapid urbanization and population growth evidently became the most vulnerable in terms of lack of access to decent and affordable housing in developing countries. This has led to various researches into development of locally available building materials and construction techniques to enhance access to housing for all.

In 1976, the Human Settlements conference in Vancouver gave new impetus to this approach, condemning the transposition of Western building techniques for low-cost housing and recommending the design of technologies suited to climatic, social and cultural contexts (Rigassi, 1985 cited in Alagbe, 2008). The conference also recommended the gradual reduction of imports of products and services linked to construction, and the drawing up of norms and regulations which covered the basic needs of end-users whilst taking account of their economic possibilities. The acquisition of local building materials and techniques to guarantee access to decent and durable housing for all by the year 2000 was adopted in December 1988 by the General Assembly of the United Nations with the slogan “Global Strategy for Housing to the year 2000”. The Assembly proposed relying on a vast formal and informal private sector participation in housing provision. This strategy was aimed at removing the dependence on the public sector for housing provision by exploring the erstwhile ignored wealth of existing human resources and their building cultures and social dynamics (UNCHS, 1993).

The building culture of pre-independence Nigeria was an absolute dependence on earth building techniques such as use of adobe bricks (sun-dried bricks) and wattle and daub (mud wall construction). These techniques were predominant in major rural and semi-urbanized towns and cities in Nigeria. These techniques were durable, adequate and accessible enough for them to meet their housing needs. The techniques were also sustainable since they do not deplete the natural resources of the environment neither do their production processes lead to the emission of gases that causes global climate change. However, post-independence rural centres in Nigeria acquired new status as a result of independence on October 1, 1960. This period was immediately followed by the “oil boom” of the 1970 and 1980 which brought about an unprecedented prosperity and development of the nation. There were massive improvements on infrastructural development particularly in state capitals and major cities and towns. Thus, the towns became increasingly urbanized and became an urban-oriented society. The crave for Western building techniques led to the gradual extinction of the erstwhile earth building techniques. Thus, while other countries were developing various earth building techniques to meet the housing needs of their populace, the technique became associated with the poor in Nigeria and not fashionable for housing purposes.

1.2       STATEMENT OF THE RESEARCH PROBLEM

Sustaining housing development especially to the medium/low-income group of the society has become a huge challenge particularly because of the huge capital outlay required to do so. Thus, acquisition of indigenous building materials by way of Compressed Stabilized Laterite Bricks (CSLBs) has been suggested as a way out (Alagbe, 2008). Despite the cost benefits of using stabilized blocks for building construction (Alagbe, 2008), the use of stabilized laterite blocks still appears to be on a low profile. It is opined that this could be due to the properties of stabilized laterite blocks. This research evaluates CSLBs as a building material for sustainable housing construction and investigates the properties of CSLBs. The study focuses primarily on evaluating its physical properties as a building material as well as a measure of its level of acceptability for housing construction among the populace.

1.3   AIM AND OBJECTIVES OF THE STUDY

The aim of this research is to investigate the properties of stabilized laterite blocks at 5%, 15%, and 25% stabilization.

The specific objectives are;

i) To determine the compressive strengths of stabilized laterite block samples at 5%, 15% and 25% cement stabilization.

ii) To investigate water absorption capacity of stabilized laterite block samples at 5%, 15%, and 25% cement stabilization, and

iii) To assess the resistance to abrasion of stabilized laterite block samples at 5%, 15% and 25% cement stabilization.

1.4   RESEARCH QUESTIONS

The research questions are;

i)  What are the compressive strengths of stabilized laterite block samples at 5%, 15% and 25% cement stabilization?

ii) What is the water absorption of stabilized laterite block n at 5%, 15% and 25% cement stabilization?

iii) What is the resistance to abrasion of stabilized laterite block samples at 5%, 15% and 25% cement stabilization?

1.5  SIGNIFICANCE OF THE STUDY

This study has the following significance; It shows the compressive strengths of stabilized laterite blocks at 5%, 15% and 25% cement stabilization. This helps in finding out if there is any significant difference in the compressive strength at the various degrees of stabilization. This will aid decision making when making stabilized bricks as it will inform what percentage of cement will be needed to achieve a specific compressive strength. The study finds out the water absorption of stabilized laterite blocks at 5%, 15% and 25% cement stabilization. This helps in finding out if there is any relationship between the degree of stabilization and the water absorption capacity of stabilized laterite blocks. This will be helpful when making stabilized bricks as it will inform what percentage of cement will be needed to achieve certain degrees of water absorption. It tells the resistance to abrasion of stabilized laterite blocks at 5%, 15% and 25% cement stabilization. This helps in finding out if there is any significant difference in the resistance to abrasion at the various degrees of stabilization. This will aid decision making when making stabilized bricks as it will inform what percentage of cement will be needed to make the stabilized blocks resistant to abrasion.

1.6  SCOPE AND LIMITATION

This study will focus on making various laterite block samples with cement stabilization at 5%, 15%, and 25%. The samples are cured and then made to undergo laboratory tests to determine their compressive strengths, water absorption capacity and resistance to abrasion. The laterite block samples will be made from laterite clay sourced from Ogun state, Nigeria.

1.7   DEFINITION OF KEY TERMS

ADOBE - A Spanish word often used in English (and French) to refer to a mud brick. This technique consists of moulding laterite bricks without compaction and allowing them to dry in the sun, hence their also being commonly known as laterite blocks.

CEMENT - A mixture of limestone and clay heated at a temperature of About 15000C after which gypsum would be added and the resulting mix ground to a fine powder. It is indeed the addition of gypsum that prolongs the setting of limestone and clay when in use.

COMPACTION - This is a mechanical process aimed at increasing the density of the material, thereby reducing porosity as well as its characteristics. It also reduces its susceptibility to water.

COMPRESSED LATERITE BRICKS - This refers to the tampering of laterite in a mould where it is compressed using a press.

GYPSUM - This is a term used to refer to a soft mineral called hydrated calcium sulphate which is the source of plaster of Paris and other plasters. It is produced by heating gypsum rock to about 1700 C. At this temperature, about 75 percent of crystallization water would have been driven off, leaving a white powder. This powdery substance gets hard after mixing with water and settles over a short period of time.

HYDRATED LIME - The production of hydrated lime is carried out in two stages. The first stage requires the calcination of limestone in a kiln at about 9000 C. At this stage, carbon dioxide will be expelled and quick lime (calcium oxide) will be produced. Second stage involves slaking or hydrating quick lime with a certain volume of water which causes the production of hydrated lime (calcium hydroxide).

LATERITE - This is a term that is used to refer to formation of soil, particularly clay and silt, by weathering of rocks especially in a tropical climate, composed mainly of iron and aluminum hydroxides. It is the term used to describe all the reddish residual and non-residual tropically weathered soils formed from decomposed rocks through clays.

LIME - This is a term used to refer to a white caustic earth (calcium oxide, quicklime, caustic lime) which is got by calcining calcium hydroxide (slaked lime) got by adding water to quicklime.

OPTIMAL MOISTURE CONTENT - This is defined as the moisture or water content at which a specified amount of compaction would produce the maximum dry density.

SOIL STABILISATION - This is a term that refers to the process of obtaining a better quality soil by improving the characteristics of the local soil in order to create a perfectly suited material for construction works. It assists in reducing the volume of the spaces between the solid particles thereby reducing its porosity.

STABILISERS - These are complementary additions of products intended to enhance the qualities of the earth materials further, and above all, guarantee that the properties will endure over time. They are also referred to as stabilizing agents.

STABILISED LATERITE - Refers to the mixture of sandy clay, water and a given quantity of stabilizing agents such as lime, cement, bitumen emulsions etc. These stabilizers increase water resistance. Mostly used for making walls, bricks etc