modification of clayey soil using iron ore tailing

Description

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

Soil modification is the process of altering the physical and chemical structure and texture of the natural soil to make sure it offers sufficient stability to the foundation of your road or structure. The stability of structures or roads founded on soil depends to a large extent on the interaction of the said soil with water. Clayed absorb large amount of water during the rainy seasons and do not allow easy passage of such water.  This consequently results in a large volume increase which  drastically reduces during the dry season. This phenomenon has substantial effect on structures founded on such soils. Also, road bases built with soils that are not easily drained are affected by the development of pore water pressures which causes the formation of potholes and, eventually, the total failure of such roads. In an attempt to minimize these effects, such soils are subjected to treatments aimed at either disallowing water into them or allowing easy passage (drainage) of water to prevent pore water build up (Alhassan, 2018).

Problematic soils such as expansive soils are normally encountered in foundation engineering designs  for  highways,  embankments,  retaining  walls,  backfills,  etc.

Expansive soils are normally found in semi – arid regions of tropical and temperate climate zones and are abundant where the annual evaporation exceeds the precipitation (Chen, 2018; Warren and Kirby; 2014).

Clayed soil is an expansive soil (Osinubi et al., 2010). It is found in the north eastern part of Nigeria, Cameroon, Lake Chad Basin, Sudan, Ethiopia, Kenya and South Zimbabwe. The soil is also found in India, Australia, south west of United States of America (Ola, 2018), South Africa and Israel (Plait, 2013).

Two groups of parent rock materials have been associated with the formation of expansive soils. The first group comprises sedimentary rock of volcanic origin, which can be found in North America, South Africa and Israel (Plait, 2013), while the second group of parent materials are basic igneous rocks found in India, Nigeria and South Western U.S.A. (Medjo and Riskowiski, 2014). Morin, (2011) gives the engineering definition for clayed soil as dark grey to black soil with a high content of clay, in which montmorillonite is the principal clay mineral and which is commonly expansive.

They have the tendency to expand and shrink with changes in moisture and appreciable plasticity due to the clay fraction.

Clayed soils are expansive soils also referred to as tropical black clay. They are so named because of their suitability for growing cotton. Clayed soils have varying colours‟ ranging from light grey to dark grey and black. The mineralogy of this soil is dominated by the presence of montmorillonite which is characterized by large volume change from wet to dry seasons and vice versa. Deposits of black clayed soil in the field show a general pattern of cracks during the dry season of the year. Cracks measuring 70 mm wide and over 1 m deep have been observed and may extend up to 3m or more in case of deep deposits (Adeniji, 2011). These soils are poor materials to employ for highway or airfield construction because they contain high percentages of plastic clay. In areas where they occur, usually there are no suitable natural gravels or aggregates and most deposits cover significantly large areas that avoiding them is not possible.

Although poor and undesirable for engineering purposes, its properties could be improved to meet standard specification by modification processes. Modification of the soil with chemical admixtures is a common method of reducing the swell – shrink tendencies of the soil and also makes the soil less plastic (Ola, 2013; Balogun, 2011; Osinubi, 2011). In traditional practices, stabilizers such as cement, lime, and bitumen, alone or in combination, are used as additives to modify soils. However, there is a variety of non-traditional soil modification additives available from the commercial sector such as polymer emulsions, acids, lignin derivatives, enzymes, tree resin emulsions, and silicates. To achieve modification, the additive must be incorporated with the soil (Newman and Tingle, 2014).

Researchers  (Ola, 2013) reported that appreciable improvements in the geotechnical properties of black clayed soils were observed when treated with lime, as well as lime admixed with cement. The need to reduce the rising cost of soil stabilizers and overdependence on industrially manufactured soil improving additives (cement, lime, etc.), has led to intense global research towards economic utilization of wastes for engineering purposes (Oriola and Moses, 2010).

Research  works  (Osinubi et al., 2019) in the field of geotechnical engineering focus on the search for cheaper and locally available materials for use in modification. A large percentage of such materials are agricultural wastes that produce cementituous compounds on addition of moisture. These studies tried to match the need for safe and in the north-central Kogi State of Nigeria.

Itakpe iron ore processing plant produces a waste material of about 64 % of its capacity.  At  a  production  rate  of  4,737  tonnes/day,  large  quantities  of  tailings  are obtained as waste product of the beneficiated iron ore (Adepoju and Olaleye, 2011). The management of tailings from iron ore mines is an important issue, from the point of view not only of pollution control but also of the conservation of resources (Ghose, 2017).

1.2 Statement of the Problem

There are always compromises that have to be made when it comes to construction sites. You might get a great location, but the soil may be poor and unusable as fill material.  Excavating the entire site, hauling the bad soil away and replacing it with better soil is not only expensive and time-consuming, but also unnecessary.  Soil modification techniques are much less expensive than excavation, undercutting, and replacing the poor soil with stone material.  Modern technologies allow us to modify existing soil to your specifications, providing quality fill material for your project.

Clayey soils belong to the smectite group, which includes montmorillonite that are highly expansive and are the most troublesome clay minerals when encountered in construction. Primarily, the problem that arises with regard to expansive soils is that their deformations are significantly greater than the elastic deformations and therefore cannot be predicted by classical, elastic or plastic theory. Movement is usually in an uneven pattern and of such a magnitude as to cause extensive damage to the structures and pavements resting on them (Nelson and Miller, 2012).

Clayey soils pose great threat and dangers to engineering structures because of their expansive characteristics. Expansive soils cause more damage to structures, particularly light buildings and pavements, than any other natural hazards, including earth quakes and floods (Jones and Holtz, 2013).

Though such damages are yet to be quantified in Nigeria, evidence of colossal damages on buildings and road pavements are very obvious in regions of the country especially in the North – eastern part of the country where black cotton soil exists extensively (Osinubi, 2015). Because of the above mentioned problems and because the clayey soils occupy  an estimated area of 104,000 km² in the north- eastern part of Nigeria, there is need to further investigate cost-effective ways of modifying them.

1.3              Justification for the Study

The rising cost of traditional additives such as cement and lime has motivated the search for cheaper and locally available materials for improving problematic or deficient soils to  meet  geotechnical  engineering  requirements  in  the  construction industry. The safe disposal of industrial and agricultural waste products demands urgent and cost effective solutions because of the debilitating effect of these materials on the environment and to the health hazards that these wastes constitute (Oriola and Moses, 2010).

Recent  trend  in  research  works in  the  field  of  geotechnical  engineering and construction  materials  (Osinubi and Eberemu, 2019) focused more on the search for cheap and locally available materials such as bagasse ash, fly ash, blast furnace slag etc. as modifying agents for the purpose of full or partial replacement of traditional modifiers or stabilizers.

Therefore, the possible use of other locally available  industrial and agricultural wastes (such as iron ore tailings) with pozzolanic properties as possible substitutes or as admixtures to main stabilizers  to modify/stabilize clayey soils, will considerably reduce the cost of construction and as well as reduce or eliminate the environmental hazards caused by such wastes.

1.4              Aim and Objectives of the Study

The aim of this research was to evaluate the effect of iron ore tailing (a by-product of mining process) when used to modify clayey soil. The following specific objectives were designed to be achieved:

1. Determination of the oxide compositions of iron ore tailing and clayey soil.
2. Determination of the moisture – density relationships of the natural and treated soil using various compactive

• Evaluation of cation exchange capacity (CEC)

1. Determination of the strength and durability properties of the treated soil
2. Determination of the optimal quantity of iron ore tailing needed to modify soil
3. Microanalysis of optimally treated clayey soil

• Statistical analysis of the results using analysis of variance (ANOVA) method

1.5      Scope of the Study

This research was carried out to determine the suitability of iron ore tailing (IOT) as additive for clayey soil modification. Tests were carried out to determine the effect of  IOT  at  various  compactive  efforts  (British  Standard  light  (BSL),  West  African Standard (WAS) and British Standard heavy (BSH)) on the properties of clayey soil. All tests were carried out in accordance with procedures outlined in BS 1377 (1990) and BS 1924 (1990).

1.6 Research Methodology

All tests on the natural and modified soil were carried out in accordance with BS 1377 (1990) and BS 1924 (1990), respectively. Clayey soil was treated with IOT in stepped concentrations of 0, 2, 4, 6, 8, 10, 12, 14 and 16 % by dry weight of the soil.

The following tests were carried out:

1. Sieve analysis
2. Atterberg limits

• Compaction

1. Unconfined compression
2. . California bearing ratio
3. Cation exchange capacity

• Microanalysis of specimens Durability

1.7                                                   RESEARCH QUESTION

At the end of this work answers to the following questions shall be provided:

1. How is clayey soil formed?
2. What are the characteristics of a clayey soil?

• What is soil modification?

1. What are clayey soils?
2. How is clay soil modified?
3. What are different methods of modification of soils?

1.8                                                  LIMITATION OF STUDY

This research is primarily focused on discussing modification of clayey soil using iron ore tailing which involves altering the physical and chemical structure and texture of the natural soil of the selected part of Auchi Edo State, to make sure it offers sufficient stability to the foundation of your road or structure.

1.9                                             STUDY AREA

This study was carried out in Auchi Edo State. Auchi is the second-largest city in Edo State, Nigeria, after Benin City, the capital. Auchi lies between Latitude: 7° 4′ 0.7104” N, Longitudes of 6° 16′ 29.1828” E. However, the soil sample used for this study was collected beside Auchi Polytechnic entrance gate.

1.8                                                  DEFINITION OF TERMS

CLAYEY SOIL: It is a type of soil that consists of a large number of clay particles and a very small amount of humus and silt. This soil is so compact that it cannot trap air.

SOIL MODIFICATION:  is the process of altering the physical and chemical structure and texture of the natural soil to make sure it offers sufficient support (stable) to the foundation of your road or structure.

IRON ORE: is the raw material used to make pig iron, which is one of the main raw materials to make steel—98% of the mined iron ore is used to make steel.