A Comprehensive Study Of Laterite And Portland Cement As Stabilizing Agent Of Laterite Soil

Description

ABSTRACT

Soil stabilization is a process to treat a soil to maintain, alter or improve the performance of the soil as a construction material and very important to minimize the cost of earth work in case of unavailability of good earth at nearby source. The use of Stabilizing agent, for sub-grade with weak soil, improves strength parameter such as cohesion and improvement in cohesion leads to strengthening of embankment. This will ultimately lower down the road construction cost. This paper specifically addresses about soil stabilizing agent which are used to stabilize weaker soil to improve subgrade quality.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

1.0      INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

• AIM OF THE PROJECT
• OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• BENEFITS OF SOIL STABILIZATION
• DEFINITION OF STABILIZATION

CHAPTER TWO

LITERATURE REVIEW

• OVERVIEW OF LATERITE SOIL
• USES OF LATERITE
• OVERVIEW PORTLAND CEMENT
• HISTORICAL BACKGROUND OF THE PORTLAND CEMENT
• USE OF PORTLAND CEMENT
• TYPES PORTLAND CEMENTS
• SAFETY ISSUES OF PORTLAND CEMENT
• ENVIRONMENTAL EFFECTS OF PORTLAND CEMENT
• REVIEW OF THE RELATED STUDY

CHAPTER THREE

METHODOLOGY

• MATERIAL AND EXPERIMENTAL METHODS
• PORTLAND COMPOSITE CEMENT (PCC)
• UNCONFINED COMPRESSION STRESS (UCS) TEST
• CORRELATION BETWEEN FIELD CBR AND ELWD VALUE

CHAPTER FOUR

• RESULTS AND DISCUSSION
• INFLUENCE OF LIME AND CEMENT ADDITION ON UNCONFINED COMPRESSION STRESS

CHAPTER FIVE

• CONCLUSION
• REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

Roads are main consumers of aggregate and the influence of aggregate cost is added in total construction cost of the roads. In India, use of recycled aggregate from building waste has been studied with the purpose of reduce the material cost (Gopala Raju et al., 2010). Similar to this study, the improvement of lateritic soil with cement mixing was  modified for base course materials to improve performance. There are many reasons for using LSC, ranging from lack of crushed rock to a desire to reduce crushed rock usage for environmental reasons. The locations of Quarry sites for crushed rocks  for  road  construction  are  getting  more difficult to access and are depleted in  many  areas  of  Thailand. The costs of transportation materials from further away may also increase, thus compounding the problem. An2other reason for using the LSC is the financial and environmental cost of energy used in the production stage of such highway materials. The increased awareness of environmental impacts has lead to some restrictions being imposed on extraction of natural resources. The crushed rock production process consumes a considerable amount of energy for mining, transportation, burning and which contributes to the total CO₂ emissions to the atmosphere. The environmental issues to be addressed include the need to reduce the levels of CO₂, emissions. Low cost and environmental friendly features are the added benefit of the stabilization.

Lateritic soils are soil types rich in iron and aluminum, distributed in many areas of the world. It is not suitable for const1uction of base cour s e . The selected materials such as crushed rock are usually used for this purpose. The production of crushed rock aggregate involves drilling, blasting, crushing and transportation which can create serious environmental problems. With suitable additive, properties of lateritic soil can be improved. Ordinary Portland cement type 1 is one of the most suitable materials used for road stabilization (Ruenkrairergsa T, 1982; Anon, 1990; Mitchell JK, 1981).

Portland cement was mixed with the soil at a mix proportion 3, 5, 7 and 9% by weight of dry soil, used water content at the optimum moisture content (OMC). Modified compaction specimens were prepared for UCS tests at  curing times  of 3,  7, 14 and 28 days, respectively. Method of XRD and  SEM were performed to investigate the development of microstructures, chemical components and mineral components of soil cement, respectively. The objective of this paper was therefore to investigate major hydration products which contribute of the strength development of LSC by using UCS. Since lateritic soil was mixed with cement for economical and environmental propose, the cement content in the additive should be as low as possible. The appropriate ratio was  obtained from UCS not less than 1. 721 MPa in accordance with Department of Highways Thailand.

1.1                                          BACKGROUND OF THE STUDY

Soil stabilization techniques for road construction are used in most parts of the world although the circumstances and reasons for resorting to stabilization vary considerably. In industrialized, densely populated countries, the demand for aggregates has come into sharp conflict between agricultural and environmental interests. In the less developed countries and in remote areas the availability of good aggregates of consistent quality at economic prices may be limited. In either case these factors produce an escalation in aggregate costs with maintenance costs. The upgrading by stabilization of materials therefore emerges as an attractive proposition. Kogbe (1975) stated that in pre-cambian times, Nigeria consisted of uplifted continental landmass made up of basement sediments. This resulted in the formation of lateritic soils which are of relatively good quality for road construction works.

The addition of adequate percentage of Portland cement to a soil can significantly modify the properties of the mixture produced, independent of the soil used. However, excessive addition of cement becomes uneconomical. The importance of cement stabilization of lateritic soils has been emphasized in the past (Bulman, 1972; Ola, 1974; and Portland Cement Association, 1959). It is important to note that it is difficult to estimate precisely the adequate amount of cement required in soil-cement mix. However, the Nigerian General Specifications (1997) established the usual range of cement requirements for various AASHTO group classifications of soils in Nigeria. Hence, possible trial cement content adopted for the red and yellow lateritic soils were 1%, 3%, 5%; and 3%, 5%, 8% respectively by weight of the dry soil.

Construction specification commonly requires that compaction and final shaping should be carried out as soon as possible after mixing/placing is completed, but usually this not the case. Sometimes, there is a delay between mixing/placing and compaction because of some unforeseen circumstances like machine breakdown, injury to workers in the field, among others. Some researchers (Osinubi, 1998; Obeahon, 1992; Osinubi and Katte, 1991) have worked on elapsed time after mixing with lateritic soils. In most cases, the works were focused on modified lateritic soils. Besides, soils have peculiarities of structures and variations in behavior at mixing operation. This may be the case even when they have similar plasticity index but may depend on the size and strength of their aggregates (Osinubi, 1998).

There are many definitions of laterites, of note to this study is as defined by (Ola, 1983), where laterites was defined as the products of the tropical weathering with red, reddish brown and dark brown colour with or without nodules or concreting and generally (but not exclusively) found below hardened ferruginous crust or hard pan. According to Maignien (1966) and Gidigasu (1976), three major stages are involved in the process of laterization, they are as follows: the first stage, which is the decomposition. It is characterized by the physico- chemical breakdown of primary minerals and the release of constituent elements. The second stage involves leaching, under appropriate condition of combined silica and bases and the relative accumulation or enrichment from outside sources (absolute accumulation) of oxides and hydroxides of sesquioxides (mainly Al₂O₃ and Fe₂O₃, the most resistant component to leaching). The third stage is the hydration or dessication which involves partial or complete dehydration (some involving hardening) of the sesquioxide-rich materials and secondary minerals.

Lateritic soils are generally used for road construction in Nigeria. Lateritic soil in its natural state generally have low bearing capacity and low strength due to high content of clay content of clay. When lateritic soil contains a large amount of clay materials its stability and strength and stability cannot be guaranteed under load in presence of moisture (Alhassan, 2008), lateritic soil consists of high plastic clay, the plasticity of the soil may result to cracks and damage on pavement, roadways, building foundations or any civil engineering construction projects. The improvement in strength and durability of lateritic soil in recent times has become imperative, this has geared researchers towards using stabilizing materials that can be sourced locally at a very low cost (Bello et al., 2015). Where in most cases sourcing for alternative soil may prove economically unwise, to improve the soil by way of stabilizing available soil to meet the desired objective becomes a viable option (Mustapha, 2005; Osinubi, Liming and cement stabilized were employed to improve the mechanical properties of laterite soil in this study. In order to assess the suitability of the stabilized laterite soil as a subbase layer or foundation of road construction, this study conducted several laboratory and field investigations as the devise criteria to which stabilized laterite soil must comply in order to qualify for a use in a road pavement structure.

1.2                                                               AIM OF STUDY

This study examines the geotechnical properties of lateritic soil and Portland cement as a stabilizing agent

1.3                                              OBJECTIVE OF THIS STUDY

This objective of this study is therefore to investigate the use of cement and sand as a stabilizing agent. It is used in this study as the stabilizing agent while water was employed in lateritic soil, sand and Portland cement until a uniform colour was obtained.

1.4                                           SIGNIFICANCE OF THE STUDY

Soils that do not possess the desired characteristics for a particular construction can be improved by adding one or more stabilizers. Each stabilizer can fulfill one (or at the most two) of the following functions:

• Increase the compressive strength and impact resistance of the soil construction, and also reduce its tendency to swell and shrink, by binding the particles of soil together.
• Reduce or completely exclude water absorption (causing swelling, shrinking and abrasion) by sealing all voids and pores, and covering the clay particles with a waterproofing film.
• Reduce cracking by imparting flexibility which allows the soil to expand and contract to some extent.
• Reduce excessive expansion and contraction by reinforcing the soil with fibrous material.

1.5                                            BENEFITS OF SOIL STABILIZATION

Substantial Savings

By choosing to stabilize the existing subgrade, the costs associated with excavating the existing soil, removing it from the site, and replacing it with suitable materials are eliminated. This can result in substantial savings to the owner.

Reduces Weather Related Delays

In areas where the climate and weather conditions prevent site work during certain times of the year, soil stabilization may be utilized to treat unstable soils in order to continue site work. This can impact construction schedules in a positive way and translate in a cost savings for an owner who does not have to wait for good weather to continue work on the project.

Eliminates Supply Problems

In areas where suitable materials to replace existing materials is in short supply or if the site is in a remote area where aggregate supply is cost prohibitive to import, soil stabilization becomes a cost effective alternative.

Additional Material Reduction

In roadway sections or parking areas, the sections of base material and asphalt paving may be reduced if the existing subgrade is stabilized in order to create sufficient strengths. This reduction in the sections of base material and asphalt paving can also create cost savings to the owner.

1.6                                                DEFINITION OF STABILIZATION

According to Oyediran and Kalejaye, (2011), Stabilization was defined as a means by which Soil properties are improved and made more suitable for construction purpose, which can be mechanical, chemical and sometimes biological. Ogunribido (2011) affirmed that local materials identified for use in stabilization can be classified as either agricultural or industrial wastes. The ability to blend the naturally occurring lateritic soil with some chemical additives to give it better engineering properties in both strength and water proofing is very essential.

CHAPTER TWO

2.0                                                          LITERATURE REVIEW

2.1                                                  OVERVIEW OF LATERITE SOIL

Laterite is a soil and rock type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by intensive and prolonged weathering of the underlying parent rock. Tropical weathering (laterization) is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils. The majority of the land area containing laterites is between the tropics of Cancer and Capricorn…