An Investigation Into the Properties of Stabilised Laterite Blocks
Chapter One
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;
- To determine the compressive strengths of stabilized laterite block samples at 5%, 15% and 25% cement stabilization.
- To investigate water absorption capacity of stabilized laterite block samples at 5%, 15%, and 25% cement stabilization, and
- To assess the resistance to abrasion of stabilized laterite block samples at 5%, 15% and 25% cement stabilization.
CHAPTER TWO
LITERATURE REVIEW
INTRODUCTION
This chapter literature related to stabilized interlocking blocks. This could be from previous studies and textbooks. This gives an insight into subject matter and provides guide for the study and researcher. It also suggests stakeholders of what needs to be done.
DEFINITION OF STABILIZED BLOCKS
According to Gooding and Thomas (1995), cement-stabilised building block is defined as one formed from a loose mixture of soil and/or sand, cement and water (a damp mix), which is compacted to form a dense block before the cement hydrates. After hydration the stabilised block should demonstrate higher compressive strength, dimensional stability on wetting and improved durability compared to a block produced in the same manner but without the addition of cement. This definition includes a range from hand-tamped soil blocks containing only enough cement to enhance their dry strength a little (but not to achieve any long term wet strength) to close-tolerance high-density concrete blocks, mechanically mass produced and suitable for multi-storey construction without a render. The spectrum of cement-stabilised building blocks has been split traditionally into two distinct fractions, sandcrete and soil-cement.
The key differentiating factors between soil-cement and sandcrete are then cohesion/strength of the freshly demoulded block and the block size. During the course of a survey it was found that block size effectively determined the marketed name, large blocks were sold as sandcrete while smaller blocks were sold as soil-cement.
The exceptions to this were in South Africa and Botswana where cement stock bricks are common. However these are typically smaller than soil-cement blocks, 100x225x87.5mm (width x length x depth) compared to 140x290x100mm for soil-cement and 150x460x230mm for sandcrete.
Stabilization is also possible with alternative cementitious binders such as lime. At present ordinary portland cement is the most widely available and quality-consistent stabilizer and is likely to remain so for the foreseeable future. Even if lime were to become widely available with assured quality, lime stabilization requires at least twice as long for initial curing. As quick curing has a significant economic value in block production, lime use is likely to remain less common than ordinary portland cement.
SOIL CEMENT BLOCKS AS A BUILDING MATERIAL
Research and development of stabilised soil as a building material is not new. The use of CSBs can be traced back 50 years (Fitzmaurice, 1958; Enteiche & Augusta, 1964; Fathy, 1973; Webb, 1988). From the early 1950s attempts were made to develop the material as an alternative walling unit to the modern and more expensive fired bricks and concrete blocks. The promotion of the material was originally introduced via the United Nations (UN Bulletin No. 4, 1950; Fitzmaurice, 1958).
The idea of compacting earth to improve its quality and performance in the form of moulded blocks however dates back to the 18th Century (Houben & Guillaud, 1994). The addition of a binder to stabilize the soil is more recent. Apart from the early work of the United Nations, the history of the spread of the CSB is not well documented. During the 1950s use of the material was widely disseminated worldwide. The 1960s and early 1970s were however stagnant years.
This was to change with the 1976 Vancouver Assembly of the United Nations Conference on Human Settlements (UNHCS, 1976; UNIDO, 1980). Noting with concern that the worlds population was expected to double by the year 2000, and worse still, to quadruple by the year 2030 (representing the largest single population growth in human history), the conference resolved to focus on the development of low-cost housing. Further momentum was to be given 12 years later following the declaration of the year 1987 as the International Year of Shelter for the Homeless (UN/IYSH, 1987). Subsequent proclamations were to follow in 1988 under the theme ‘Global Strategy for Housing by the Year 2000’. The key targets of these resolutions were the guaranteed access to decent and durable housing for all from the beginning of the new millennium. Renewed world-wide interest was soon to provide an immense impetus that has ensured the now vibrant spread of CSBs throughout the developing world (Okello, 1989; Schmetzer & Kerali, 1994; Kerali, 1996).
Continued interest in CSBs will in future evolve around the several merits and attractions associated with its use. Firstly, as the basic raw material is soil, its source will remain abundant. This facilitates direct site-to-service application, thereby lowering costs normally associated with acquisition, transportation and production.
Home ownership can then be delivered at comparatively low costs. Secondly, the initial performance characteristics of the material such as the wet compressive strength (WCS), dimensional stability, total water absorption (TWA), block dry density (BDD) and durability are technically acceptable. They are also comparable to those of rival materials (ILO, 1987; Houben & Guillaud, 1994; Houben et al, 1996).
CHAPTER THREE
RESEARCH METHODS
INTRODUCTION
This chapter shows the methods employed to investigate the properties of stabilized laterite blocks used in construction projects.
EXPERIMENTAL PROCEDURE
COLLECTION OF LATERITE SAMPLES
Laterite samples were collected from the Otta area in Ogun State, Nigeria; based on previous work which stated that the samples obtained from this place produced good interlocking blocks that met minimum standards (Falola & Adeyeye, 2007). These samples were stabilized with ordinary Portland cement using 0%, 5%, 15% and 25% by weight of the binder; 0% stabilization being the control. The stabilized samples were then used to produce stabilized blocks which were tested for strength and durability. All the processes were carried out with reference to the International Labour Organization manual (1987), Nigeria Building and Road Research Institute (NBRRI, 2006) and National Building Code (2006) specifications.
PREPARATION OF LATERITE SAMPLES
The laterite samples were air–dried for seven days in a cool, dry place. Air drying was necessary to enhance grinding and sieving of the laterite. After drying, grinding was carried out using a punner and hammer to break the lumps present in the soil. Sieving was then done to remove over sized materials from the laterite samples using a wire mesh screen with aperture of about 6mm in diameter as recommended by Oshodi (2004). Fine materials passing through the sieve were collected for use while those retained were discarded.
CHAPTER FOUR
PRESENTATION OF FINDINGS
INTRODUCTION
This chapter presents all the findings of this study as a result of the laboratory experiments carried out. The result of the experiment are presented using tables for easy understanding. This enables readers and observers to have an overview of the results and findings of this study.
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATION
INTRODUCTION
This chapter contains the conclusions gathered from this study based on the findings made as regards cement stabilized laterite interlocking blocks. It also contains various recommendation based on the findings of the study as well as possible areas for further studies.
CONCLUSION
From the findings of this report, it can be concluded that
- The resistance of the laterite interlocking blocks to abrasion increases with the addition of cement as stabilizing agent. Hence, it is safe to conclude that that stabilization is required to enhance the durability of the laterite interlocking blocks.
- Water absorption of laterite interlocking blocks decreases with increase in the percentage of stabilization. The unstabilized laterite interlocking blocks have no water absorption capacity hence it will dissolve in water.
- The maximum water absorption of 12% as recommended by Nigerian Industrial Standard (2004) for laterite interlocking blocks was satisfied by all the stabilized blocks samples.
- The compressive strength of cement stabilized interlocking blocks increases as the percentage of stabilization increases.
- Furthermore, with 15% cement stabilization, the stabilized blocks satisfied the minimum 28 days dry compressive strength.
RECOMMENDATION
Despite durability and water absorption standards for stabilized interlocking blocks are met at 5% cement stabilization, it is not recommended for use because stabilized lateritic interlocking blocks with 5% cement stabilization do not satisfy the minimum compressive strengths as specified by the operating codes. Hence, 15% stabilization is recommended for use. The extra 10% cement content over what was used by Madedor (1992) is compensated for by the non usage of mortar in laying the interlocking blocks.
AREA OF FURTHER STUDIES
Due to the scope and limitations of this study, the study could not compare the cost of producing a unit of stabilized lateritic interlocking blocks at 15% stabilization with other materials such as sandcrete blocks. This is an area where further studies can be carried on.
REFERENCES
- Bell, F.G. (1993). Engineering Treatment of Soil: Soil Stabilization. E and FN SPON: London, UK
- Falola, O.O. and K.J. Adeyeye. (2007). “Production and Testing of Cement Lateritic Interlocking Blocks”. Unpublished B.Tech. Thesis. Department of Civil Engineering, Ladoke Akintola University of Technology: Ogbomoso, Nigeria.
- International Labour Organisation. (1987). “Small-Scale Manufacture of Stabilised Soil Blocks”, Technical Memorandum No.12. International Labour Office: Switzerland.
- Madedor, A.O. (1992). “The Impact of Building Materials Research on Low Cost Housing Development in Nigeria”. Engineering Focus. April – June, Publication of the Nigerian Society of Engineers. 4(2):37-41.
- Microsoft. (2001). “Laterite”. Encyclopedia Britannica. Microsoft: Redmond, W.A.
- National Building Code. (2006). Building Regulations. LexisNexis: Butterworths, O.H.
- NBRRI. (2006). “NBRRI Interlocking Blockmaking Machine”. NBRRI Newsletter. 1(1):15 – 17.
- Nigerian Industrial Standard. (2004). Standard for Sandcrete Blocks. ICS 91.100.20, NIS: Abuja, Nigeria.
- Oshodi, O.R. (2004). “Techniques of Producing and Dry Stacking Interlocking Blocks”. Nigerian Building and Road Research Institute Workshop on Local Building Materials: Ota, Ogun State, Nigeria.