PERFORMANCE-BASED EVALUATION OF CASSAVA STARCH AND MAKUBA MATRIX FOR THE STABILIZATION OF COMPRESSED EARTH BRICKS

Abstract

Although the major material(soil) for the production of Adobe or earth bricks isreadily available and affordable which,could provide a lasting solution to the need for affordable housing,it is not without some inherent problems.The problems associated with soil has led to drawback in the use of earth as a building material. These are lack of durability and need for frequent maintenance. Stabilising the earth with certain materials such as cement has helped a little however, many of these materials like lime and chemical stabilisers are limited in quantity some of them hazardous.Cementproduction highlycontributes to carbon dioxide emission, (a global concern) and it is majorly unaffordable to the common man. Cassava starch and makuba (CSM), are both applied for soil stabilisation in traditional building construction but no record of their usage exist in conventional construction. This Thesisexploresways to improve the strength and durability properties of Earth Bricks by utilising these locally available and affordable materials, CSM,to stabilise laterite soil. The work examined different techniques for soil stabilisation with CSM and various curing methods. Brick specimens with 0 to 20% content of CSM spaced at 5% intervalsas binder of laterite soil were produced. The specimens were subjected to tests of compressive strength, densification, abrasion resistance, moisture movements, elevated temperatures and a further confirmatory investigation in the form ofScanning Electron Microscopy. CSM Bricks (CSMBs) have shown improvements up to 64% in compressive strength beyond the minimum requirement of NBRRI and over 100% increased durability properties above un-stabilised laterite bricks. CSMBs could be utilised for application in building construction such as load bearing walls, partition walls, composite walls; parapets and for esthetic finishes as facing bricks since the surfaces of the bricks may not require finishing in the form of plastering, cladding or painting. This is due to the natural texture of laterite which is not altered by cassava starch paste but given additional red brownish tint by makuba

CHAPTER 1

INTRODUCTION

1.1 Background to the Study

Soil is the most abundant of all building materials found almost everywhere on this planet.This explains why majority of the population in the developing world live in Earth (mud) buildings and according to (Namango, 2006), will continue to do so out of necessity. Consequently, it has become a subject of concern to develop ways and means of improving the engineering properties of soil to enhanceEarth buildings.This involves improvement of building materials which, according to (HABITAT, 1998),are limited to basic ones such as those for walling, roof-cladding and low-strength binders.

The advantages of many alternative building materials such as furnace slag, rice-husk ash, carbide waste, and plant extracts are yet to be fully harnessed in Nigeria, and little is known of their conventional utilisation beyond laboratory tests. Some of the plant extracts are cassava starch and makuba, which are abundant and environmentally friendly additives that are in use as soil stabilisers in mud walls (adobe) and mud roof construction locally in some areas of this country. The starch from cassava, which is mainly used for laundry, is a by-product extracted from cassava tubers during the processing of cassava flour, alibo and gari.Khalil(2005), asserted that in Akwanga and Wamba towns in Nasarawa state, Nigeria, cassava starch is used in the manufacture of conical mud balls (local walling units) called ‘tubali’, and also in wall rendering as stabiliser.Makuba is a local building material also used in stabilising mud for wall rendering, mud decking and roof construction with a good water proofing property in many parts of Northern Nigeria. According to Abejide (2007),the aqueous solution of the empty pods of the African locust bean, (Parkia biglobosa), sometimes including the bark, was used in hardening the surfaces of Earth rammed floors and the sides of indigo pits. The extract, called makuba, is also appliedin pottery as gloss paint after firing Soil is stabilised for various purposes such as road and wall constructions. This is done to improve the engineering properties of soilsuch as Atterberg limits which is due to the extreme variability of its constituent minerals. According to Geotechnical-Manual (2001), the main components of soil are mineral/organic matters, moisture and air which differ in their proportions.Geotechnical Engineers according to Onunkwo, Uzoije, & Onyekuru (2014), have classified soils in terms of their engineering properties which determines the ability of the soils to function as support for foundations of structures or as building materials such as bricks. Terzaghi and Peck (1995) in (Onunkwo, Uzoije, & Onyekuru, 2014), asserted that laboratory analyses are important steps in evaluating the engineering properties of soils.

Soil stabilisation which is the alteration of any property of a soil in order to improve its engineering performances can be in form of physical, mechanical, chemical or a combination of two or more of these techniques. According to Matawal (1990), compaction of soil, usually by mechanical means, reduces air voids and subsequently controls moisture content changes; increases unit weight by densification; enhances shear strength of soil; reduces permeability; and makes soil less susceptible to settlement under load. On the other hand, compaction alone may be inadequate because according to Matawal & Tomorin (1996), the best soil for construction often falls short of required standards of strength for stable and strong structures. To improve the soil characteristics to the minimum standard requires a certain amount of stabilisation. Some research works on soil as a building material or component have confirmed that,using soil without stabilisation with additives for the construction of structures give low compressive strength and are less resistant to environmental factors, (Balami & Izam, 1998). The properties of stabilised soils vary not only with changes in soil types, but also with the type and quality of stabilising material. Subsequently, studies into the utilisation of soil as construction material such as (Matawal & Tomorin, 1996) and (Balami & Izam, 1998), have centered on examining the suitability of stabilising agents and soil types for different purposes In stabilising soil for producing building elements, cement is commonly used, (Matawal & Tomorin, 1996). Its high cost owing partly to transportation, especially to rural areas has prompted researches into the use of alternative materials to partially or fully replace it. Other reasons include high demand for energy in its production and itsgreenhouse effects. According to Khalil(2005), some research works geared towards developing affordable means of stabilising soils using locally sourced materials have yielded certain levels of strength reasonable for construction. Examples include: Strength Properties of Compressed Earth Bricks (CEB) using Earthworm Cast as Stabiliser by Kamang (1998);Unconfined Compressive strength and durability of Lime-Clay Soil for Building Construction by Okoli (1998); Properties of Compressed Earth Bricks Stabilised with Termite Mound Material by Olaoye & Anigbogu(2000); and Performance of Soilcrete Blocks with Plant Extract Additive by Abejide (2007). These works established that the stabilisers have resulted in increased strengths ranging from 0.9N/mm² to 2.55 N/mm² for use in low rise buildings. Other works by Dahiru & Zubairu(2007); and Dalziel 1948 in Abejide(2007)for example, have applied other alternative materialsdue to their abundance or in the recycling of wastes as soil stabilisersor replacements for cement. These are furnace slag, bitumen, rice-husk ash, carbide waste, dye waste, horse hair, gum Arabic, plant extracts and starches from grains/tubers. Cassava starch and makuba (CSM), apart from being used locally in mud buildings, have been individually put to laboratory tests with results indicating increase in compressive strengths of cassava starch stabilised soil as high as 3.55N/mm². However, cassava starch stabilised soil specimens turned out to be weak in terms of resistance to water penetration, (Khalil, 2005). On the other hand, makuba was reported by Abejide (2007), to possess higher resistance to water absorption. Even though makuba also improved the strengths of soil up to 2.04N/mm²,(Ibrahim, 2010), the specimens were observed to be brittle hence, failure of makuba stabilised specimens under compression could be instant without any form of warning. The combination of cassava starch and makuba could be a great advantage because the shortfall of one could be compensated by the other.

Earth construction provides comfortable living environment due to its high thermal and heat insulation values. It also offers other important factors that contribute to the achievement of good planning, design and construction solutions for the provision of shelter, (Marwan & Nasim, 2016).Itcan also provide employment opportunities and savings in the funding of projects as all materials (laterite and CSM), with the exception of tools, may be readily available without high need for transportation, especially in rural areas.

1.2 Problem Statement

Majority of developing countries are faced with the issues of providing adequate, affordable and sufficient shelter with the conditions getting worse due to scarcity of resources, (Kerali, 2001). The fundamental need for shelteris a concept that is as old as the recorded history of mankind and it has been universally accepted as the second most important human need after food,Daniel et al(2010);Onuoha (2013).In the year 2007, the World Bank identified 152 developing countries Nigeria inclusive, where one in every three people is without adequate shelter, (HABITAT, 2008). This Organisation is working towards lowering the statistics through the provision of low-cost, sustainable building materials and technologies. According to theUnited Nations Centre for Human Settlements,UNCHS(2000) in Danjuma(2010), political independence has influenced the rate of urbanisation in Africa, which is the fastest in the world. Migration from rural to urban centers in search of education and/or greener pastures is a contributory factor to the scarcity of shelter in urban centers.Housing delivery is a major problem confronting the underdeveloped world with several housing policies put in place but without housing delivery. Not only is the population growth rate higher than the rate of housing provision, the actual housing delivery processes are more often than not over-ambitious hence, not sustainable, (Daramola et al, 2013). I developmental activities such as Earth Brick production are encouraged in rural areas, this trend may change directions and influx to urban cities may reduce. Since the mid-1980s, Nigeria has been going through series of economic crises such as hike in the cost of common commodities and services. These crises have devastating effects on the cost of building materials and housing supply in the country alongside the escalation of house rents. The major factors responsible for this development are the low financial standing of people, and low level of awareness in the use ofcheaper and energy conserving construction materials such as CSEBs which serve as alternative to the Sandcrete/Concrete blocks used all over the country, (Daramola, 2005).

Cement production requires a great amount of energy, so finding materials that can favourably substitute for it will make appropriate environmental sense. The Environmental Building News,Environmental (2009), reported that the production of Portland cement used in the United State of America (U. S. A.), leads toemission of greenhouse gasinto the atmosphere, which is comparable to operating 22 million cars. In addition, the U. S. A. imports about 20% of the 100 million metric tons of cement it uses annually, leading to additional cost burden and energywastage. Cement situation in Nigeria is far worse than that of the U. S. A. Cement production in Kogi, Gombe and Sokoto states for example, are resulting in the devastation of land in the process of raw materials acquisition, (gypsum, limestone, shale and clay). Reclamation is an additional cost burden thus; farm lands around these areas are fast thinning out. Another major constraint in the manufacture of cement in Nigeria is power. The erratic power supply apart from crumbling small scale cement producers, has heightened the price of cement beyond the reach of the rural and urban poor, (Fiakpa, 2008).

There are some inherent problems associated with Earth buildings which includes drawback of earth as a building material due to its lack of durability (low resistance to water penetration) and need for frequent maintenance; problem of earth construction leading to high shrinkage, cracking and low strength; unstable nature of earth when used for the construction of houses above two stories.Even at that, walls of ground floor need to be thicker than those for upper floors in the same building.

1.3 Justification for the Study

Although the techniques of producing CSEBs using variety of stabilisers are widely practiced, the combination of cassava starch and makuba to produce cassava starch/makuba bricks (CSMBs) is new. Among studies in stabilising soils for all construction, cement remains outstanding as indicated in the works carried out by Matawal (1990); Ufford (1990); Matawal& Tomorin(1996); and Daramola(2005). These works utilised cement to measure the responses of different lateritic soils to stabilisation. Unfortunately, cement is relatively expensive compared to some soil stabilisers like lime, furnace slag and other industrial wastes. According to Ufford(1990), theNigerianconstruction industry in the 1980s suffered a depression as a result of the continual increase in the cost of construction materials. Cement, one of the most widely used is the most expensive construction material. Thus study into the development and utilisation of locally available raw materials which can partially or wholly replace cement in order to reduce its quantity in construction works has become imperative.The rising cost of conventional building materials in Nigeriahas necessitated intensification in the search for alternative building materials of simple and cheap construction techniques to be developed, (Taiwo & Adeboye, 2013). The negative impact of the problems facing housing delivery in Nigeria may be reduced to some extent where locally sourced materials are tested for possible application inbuilding construction works. This, in a way, may contribute to reducing the effect of the scarcity and hence high cost of cement and other construction materials as well as conserving Nigeria’s foreign reserve spent on the importation of these materials. When the technologies of utilising local materials are articulated, it may not only reduce the overdependence on conventional building materials, but can also contribute to the reduction in environment pollution arising from agricultural and industrial wastes.

Earth-based housing may provide a lasting solution to the need for affordable housing throughout the developing world,(James, et al., 2016). Adobe construction (using sun-dried earthen bricks) has been an ecologically sound, affordable building technique in many parts of the world for thousands of years. Historical and current use of adobe in the southwestern part of the United States for example, which is based on economic; social; and environmental considerations, indicate that in that region, adobe is truly an ‘appropriate’ technology: it is long-lasting, conserves energy, uses local building materials, creates jobs, requires little capital, and ‘fits’ culturally, as documented by (Villagearth, 2010). Before the advent of cement and its subsequent use in the production of blocks, earth bricks/blocks were the main walling materials but characterised with low qualities especially, compressive strength and resistance to water penetration and fire. With the introduction of regulated amount of cement to local mud bricks, CSEBs evolved. The quantity of cement in CSEB is minimal compared to that used in sandcrete blocks. This is because with large quantity of cement in soil,shrinkage may be high in the soil bricks and the consequences of eventual hydration of isolated cement grains may result in the formation of cracks and destabilisation of wall components.The controlled and regulated amount of cement in soil only improves strength and retards moisture movement to a certain degree within minimum requirements, hence the need to conventionally put to test, locally available raw materials with convincing local history of application to produce more durable and affordable Earth bricks.

According to the International Institute of Tropical Agriculture, IITA/Crops (2004),cassava has taken an economic role in the world in that the starch from it is used as binding agent in the production of paper and textile in south-east Asia and Latin America. In a research work by (Khalil, 2005), five soil types (sandy, clayey, loamy, laterite and gravelly soils), were stabilised with cassava starch. Laterite soil yielded outstanding improvements in strength and durability properties like abrasion resistance and resistance to impact loading. Compressive strength was improvedup to 3.55N/mm² at 20% starch content at 28 days. This is an indication of the likelihood that cassava starch could take up the place of cement even if partially, in the stabilisation of laterite soils for the production of earth bricks. The only observed shortcoming of cassava starch as a soil stabiliser is its affinity for water. The water absorption of stabilised specimens had no significant differences when compared to the control specimens, although absorption rate was slowed down with increase in starch content, (Khalil, 2005). This is where makuba may come in as it has been in use from time immemorial in local mud roof construction as a stabiliser. A research work that stabilised laterite with makuba and cement byAbejide(2007), discovered that the water absorption rate of blocks produced with laterite and makuba was 10% less than the water absorbed by those produced with laterite and cement.

This research work utilised a matrix composed of these agricultural products (CSM), which are both abundant all over the tropical regions of the world,(Olanipekun, 2012); (Lawal, 2012), in stabilising laterite to produce CSMBs. The study into the possibility of using CSM matrix in stabilising laterite soil is justifiedowing to the fact that buildings, out of necessity are going green. In green construction, energy wastage is minimised by avoiding the generation of heat or reducing it in the production of building materials.At the same time green building provides several advantages observed by Kasai & Jabbour(2014), such as appreciation in the value of the property, reduction in water and energy consumption as well as reduction in waste generation. Apart from the escalating cost of cement, some alternative materials to cement such as (rice husk ash and bitumen) for example, require high heat in transforming to ash or melting to required viscosity before application. After the application of these synthesised materials, environmental pollution may not be avoided and emission of harmful gasses from walls and other elements may continue due to reactions with other materials. Therefore, local materials with binding effects requiring little or no heating will be favourable to the production of green buildings. The significance of this study is further informed by some other reasons. Among them are, energy saving in buildings; aesthetic values as CSMBs may require little or no finishing as a result of the natural colour of laterite and beauty when pointed; ease of construction and socio-economic benefits that will be derived by both rural and urban populace through generation of employments; increase in the cultivation of these plants, which will retard desert encroachment; and wealth derivation by bricks production. The choice of laterite soil instead of clay is because the latter is expansive and that is one reason for the need to fire clay bricks at high temperatures. This is not necessary with laterite, thus making it anappropriate building material.

1.4.     Aim and Objectives

1.4.1    Aim

This research work is aimed at investigating the performance of Cassava Starch and Makuba matrix in stabilising laterite soil with a view to maximizing their utilisation as alternative materials to cement in building construction.

1.4.2    Objectives

The specific objectives are to:

1. Investigate engineering properties of the research materialsprior to designing matrix mixes.
2. Establish optimum percentage levels of CSMmatrix in brick samples.
3. Determine durability properties of CSMBs within 28 days of curing.
4. Assess strength characteristics of the different mixes of CSMBs.
5. Evaluate the performance of CSMBs as walling units under elevated temperatures.
6. Examine the morphology of CSMBs through Scanning Electron Microscopy.
7. Develop analytical models for the prediction of CSMB strength characteristics.

1.5 Research Design

The research carried out in this Thesis was designed in three stages as displayed in figure 1.1. The introductory stage consists of the formation of the research topic and giving it a proper tittle; highlighting the problem statement of the research; drafting of the aim and objectives of the Thesis and scoping the work. The input stage comprised of the main body of the work were the objectives were treated through laboratory experiments. The third stage is made up of discussion and interpretation of the research findings that lead to the conclusions.

Adapted from Abdul-Azeez, 2012]

Figure 1.1: Research Design

1.6   Scope and Delimitation

1.6.1    Scope

Although laterite is used in the production of roof slates, rammed floors, tiles, cast walls etc., this work extensively focused on Compressed Stabilised Earth Bricks (CSEBs). Preliminary laboratory tests of strength and durability were maintained within 28 days of curing while strength tests were extended to 360 days.

1.6.2    Delimitation

An attempt was made for a detailed study for confirmation of the suitability of cassava starch and makuba as potential soil stabilisers. It was expected that the water proofing property of makuba would complement the stickiness effect of cassava starch for the production of appropriate walling units. However, the economic viability of using CSMBs may not be feasible as at now due to the fact that as a first attempt at combining local alternative materials not as replacements to cement to produce earth bricks, all efforts were directed at establishing durability properties and strength characteristics only.

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