Key Features:
Pages: 101
Chapters: Five
Format: Ms word
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Abstract:
Microbial Induced Calcite Precipitation (MICP) is one of the newest techniques used in soil stabilization, which involves the use of eco-friendly microorganisms to improve engineering properties of soil. This research focused on the treatment of lateritic soil with microbial–induced calcite precipitate (MICP).
Thirty-two Bacillus strains were screened for urease, an enzyme which initiates calcite precipitation and six strains were observed to produce urease enzyme reasonably.
Bacillus strain (CE9) had the highest urease enzyme production at pH 7. The unconfined compressive strength (UCS) shows that the lateritic soil specimens treated with urease producing strains (UPS) had more strength compared with the untreated lateritic soil sample (control). The best two Bacillus strains UC10 and UC11, Bacillus mycodies_MTO47265 and Bacillus sp respectively with the highest UCS were further tested, singly and combined were compared but UC11 was preferred.
The soil specimens were prepared in polyvinyl cylindrical molds of diameter 50 mm and 150 mm height. 52 soil specimens were prepared, in which 4 control specimens were untreated and not cured. 48 of the treated specimens were also cured at varying ages by covering with Polythene bags. This was done to evaluate the effect of age and curing on strength development in bio-cemented lateritic soil. The dominant minerals present in the lateritic soil used are Quartz (45%), Orthoclase (18%), Muscovite (17%), Kaolinite (18.4%) and Chlorite (1.2%).
Bacillus mycodies_MTO47265 was found to improve the performance of the tested soil specimens when compared with other strain and the consortium used. Increase in elemental concentration of calcium and carbon, after treatment with Bacillus mycodies_MTO47265, was found to be 0.32 and 1.02 respectively. The specimen treated with Bacillus mycoides_MTO47265 shows fully clustered crystals morphology of calcite cementing the soil matrix when compared with that of untreated specimen.
Table of Content:
TABLE OF CONTENTS
TITLE
PAGE
Title Page
Certification
Dedication
Acknowledge
Abstract
Table of contents
List of figures
List of tables
List plates
List of Appendices
CHAPTER ONE
1.0 Introduction
1.1 General overview
1.11 Lateritic soil
1.12 Microbial Induced Calcite Precipitation
1.13 Research on Engineering application of MICP
1.14 Strength characteristics of lateritic soil
1.2 Problem statement
1.3 Aim and objectives of research
1.3.1 Aim
1.3.2 Objectives
1.4 Justification
CHAPTER TWO
2.0 Literature review
2.1 Theoretical background
2.1.1 Soil stabilization
2.1.2 Shear strength on Lateritic Soil
2.2 Clay Cementation
2.3 Microbial Induced Calcite Precipitation(MICP)
2.3.1 MICP Chemistry
2.3.2 Clay plasticity and soil mechanics properties
2.3.3 The Ribbon test
2.4 Inoculun size of microbes
2.4.1 Microbes
2.4.2 Bacillus of Economic importance
CHAPTER THREE
3.0 Methodology
3.1 Material
3.2 Sampling
3.3 Properties of sample
3.3.1 Compaction test
3.3.1.1 Proctor compaction test
3.2.2 Sieve analysis
3.3.3 Organic impurities
3.3.4 Silt content
3.3.4.1 The hydrometer analysis of soil
3.3.5 Hydrometer analysis
3.3.6 Atterberg limits
3.3.7 PH Value
3.3.8 Organic content
3.3.9 Specific gravity
3.3.10 Moisture content
3.4 MICROBIOLOGICAL SETUP
3.4.1 Isolation and culture method
3.4.1.1 Enrichment culture and sample
3.4.2 Isolation of microorganisms from the samples
3.4.3 Culture Preservation
3.5 Screening and production of microbial calcite precipitation
3.5.1 Qualitative method(Urease Agar base test)
3.5.2 Urease activity
3.6 Phenotypic characterization
3.6.1 Molecular characterization
3.6.2 Sequence analysis
3.6.3 Phylogenetic analysis
3.7 Inoculum preparation
3.71 Properties expected on lateritic soil after the application of microbial induced calcite precipitation(MICP)
3.72 Scanning electron microscope
3.73 X-ray Diffraction
3.74 Unconfined compression strength test
CHAPTER FOUR
4.0 Results and Discussion
4.1 Preamble
4.2 Classification ( Index/physical properties of lateritic soil)
4.3 Isolation and screening of isolated bacillus strains
4.4 The quantitative screening
4.5 Identification of MICP bacillus strains
4.6 Physical property tests on lateritic
4.6.1 Compaction test
4.6.2 Sieve analysis
4.6.3 Organic impurities
4.6.4 Silt Content
4.6.5 Hydrometer Analysis
4.6.6 Atterberg limits
4.6.7 PH VALUE
4.6.8 Organic content
4.6.9 Specific gravity
4.6.10 Moisture content
4.7 The unconfined compressive strength
4.8 Geotechnical properties of the treated specimen
4.9 The Result of microstructural image test
4.9.1 Scanning electron microscopy
4.9.2 X-ray Diffraction
4.10 Urea and calcium ion formation in the treated specimen
4.11 Molecular identification of the selected bacillus strains used
CHAPTER FIVE
5.0 Conclusion and recommendation
5.1 Conclusion
5.2 Recommendations
5.3 Contribution to knowledge
REFERENCES
APPENDICES
Introduction:
CHAPTER ONE
1.0 INTRODUCTION
1.1 GENERAL OVERVIEW
1.11 LATERITIC SOIL
Laterite is both a soil and a rock type rich in iron and aluminum 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 long-lasting weathering of the underlying parent rock (Nnochiri and Aderinlewo, 2016), usually when there are conditions of high temperatures and heavy rainfall with alternate wet and dry periods. 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. . (madu et al., 1976). Alao (1983) studied the engineering properties of some soil samples from Ilorin area and discovered that they could be stabilized by compaction and that the samples could yield maximum strength if they are compacted on the dry side of their optimum moisture content (OMC). Ogunsanwo (1989) evaluated CBR and shear strength of some compacted lateritic soils from southwestern part of Nigeria. He reported CBR of 27% in unsoaked and 14% for soaked sample for laterite soils derived from Amphibolite’s. A literature review as revealed that the geo-technical characteristics and engineering behavior of red soils depends mainly on the genesis and degree of weathering (i.e. decomposition, laterization, desiccation and hardening). Morphological characteristics as well as the type and content of secondary minerals are another genetic characteristic (Agbede et al., 1992). This resulted in the formation of lateritic soils which are of relatively good quality for road construction works. Furthermore, in rural areas of Nigeria they are used as building materials for molding of blocks and plastering.
1.12 Formation
Laterites are formed from the leaching of parent sedimentary rocks (sandstones, clays, limestone); metamorphic rock (schists, gneisses, migmatites); igneous rock (granites, basalts, gabbro, peridotites); and mineralized proto-ores; which leaves the more insoluble ions, predominantly iron and aluminum. The mechanism of leaching involves acid dissolving the host mineral lattice, followed by hydrolysis and precipitation of insoluble oxides and sulfates of iron, aluminum and silica under the high temperature condition of a humid sub-tropical monsoon climate (Hill, I. G.; Worden et al., 2000).
An essential feature for the formation of laterite is the repetition of wet and dry season. Rocks are leached by percolating rain water during the wet season; the resulting solution containing the leached ions is brought to the surface by capillary action during the dry season. Laterite formation is favored in low topographical reliefs of gentle crests and plateaus which prevents erosion of the surface cover(Dalvi et al.,2004)
1.13 Differences in laterites
All laterites are marked by an enrichment of iron and a decrease of silica together with the highly soluble alkalis and alkaline earths. But a part of these characteristics the composition and properties of laterites can be quite different and are strongly controlled by the chemical and physical features of the parent rock. In essence two principal groups can be distinguished:
1. Laterites on mafic (basalt, gabbro) and on ultramafic rocks (serpentinite, peridotite, dunnite). These rocks are free of quartz and show lower silica and higher iron contents.
2. Laterites on acidic rocks. In this group not only granites and granitic gneisses but also many sediments as clays, shales and sandstone shall be included. These rocks contain quartz and have higher silica and lower iron contents. (W. Schellmann).
1.2 Strength characteristics of lateritic soil
1. Unconfined compression strength of lateritic soil; This stand for the maximum axial compressive stress that a cohesive soil specimen can bear under zero confining stress.
2. Shear strength of lateritic soil; This is an indicative of its resistance to erosion. Specifically defined as the resistance to deformation by the action of tangential shear stress. Soil shear strength is made up of cohesion between particles and resistance of particles sliding over each other due to friction or interlocking.
Average cohesion and angle of internal friction are 16.2KN and 25.2 degree. The unsoaked CBR ranges from 5.8 to 24%. Unconfined compression strength (UCS) and undrained shear strength cohesion parameter (Cu) were found to be within the range of 38 to 134 kPa and 19 to 67 kPa respectively.
Laterite is mostly used as fill for road construction in Nigeria and most tropical countries. Most of the previous work done on laterite is by Faniran 1970,1972,1974, 1978 and Adekoya et al 1978). Traditionally, most stabilization of soil has been achieved via with lime, cement, fibers, waste materials and geo-polymer materials. The issue with most of these soil stabilization methods is that they are generally very expensive, require specialized equipment and contractors, limited in terms of their effectiveness, leachates from the soil can contaminate ground water and can be harmful for the environment, an alternative approach for soil improvement that has gained traction in recent years is microbial induced calcite precipitation (MICP).
Microbial Induced Calcite Precipitation (MICP) has emerged as a new method for improving the properties of granular soils. This technology involves harnessing bacteria to produce calcium carbonate that binds soil particles together. Microbiological process is more environmentally friendly than other conventional treatment methods (Wath and Pusdhar, 2016).
1.3 MICROBIAL INDUCED CALCITE PRECIPITATION (MICP)
Microbial induced calcite precipitation (MICP) is a biologically mediated method to induce in-situ cementation of granular soils through the bacteria-driven urea hydrolysis, which is calcium rich (Mortensen and DeJong, 2011; Fauriel and Laloui, 2012).
The innovative technique that harness the activity of bacteria to improve the physical properties of soils as a sustained and environmentally responsible method foe soil strengthening and other engineering applications (Durojaye et al., 2022). The advantage to using MICP as a geotechnical improvement technique as opposed to the more traditional ground improvement methods is that MICP’s sustainability because it is an organic process (DeJong et al. 2009). Applications where MICP may be used in lieu of traditional geotechnical improvement methods may eventually include liquefaction prevention, geotechnical damage mitigation, building settlement reduction.
The common use of MICP for soil strengthening or ground improvement today is preceded by a number of applications including:
1. Microbial enhanced oil recovery (MEOR) (Kantzas et al. 1992; Chai et al. 2015; Liange et al. 2015)
2. Restoration and improvement of calcareous stone materials (Tiano et al. 1995; Castanier et al. 2000; Stocks-Fisher et al. 1999; Rodriguez-Navarro et al. 2003)
3. Wastewater treatment (Hammes et al. 2003)
4. Bioremediation (Ferris 2003; Fujita et al. 2000; Warren et al. 2001; Achal et al. 2011)
5. Concrete crack repair (Ramakrishnan et al. 1998; Ramachandran et al. 2001)
6. As a sealant and for structural improvements (Gollapudi et al. 1995)
7. As a bioclogging mechanism for brick (Sarda et al. 2009; Soon 2013)
8. Evaluation of geotechnical properties of bio cement-treated lateritic soil (Durojaye et al., 2022)
More recently, it has been suggested that MICP may be used to stabilize slopes (Salifu et al. 2016) or mitigate wind erosion (Maleki et al. 2016)
Lee Min Lee et al., 2012) on shear strength and reducing hydraulic conductivity of sandy soils and residual soils (Sandy Silt). The results showed that MICP could effectively increase the shear strength (1.41—2.64 times) and reduce hydraulic conductivity (1.14—1.25 times) for both soil types. Wei-Soon Ng et al. (2012) conducted a study to find optimum conditions for improving engineering properties of residual soil using MICP (Wei-Soon Ng et al., 2012; Ng Wei Soon et al., 2013). Under optimum conditions, the improvements achieved for the undrained shear strength and hydraulic conductivity were 69.1% and 90.4% respectively. In general, MICP can be achieved by urea hydrolysis, aerobic oxidation, denitrification, sulphate reduction, etc. (Van Paassen et al. 2010) suggested that urea hydrolysis possesses the highest calcite conversion rate compared to other studied processes (Harkes et al., 2010; Whiffin et al., 2007). Urea hydrolysis refers to a chemical reaction where urea (CO(NH2)2) is decomposed by Urease enzyme that can be either supplied externally (Greene et al., 2003), or produced in situ by Urease-producing microorganisms (DeJong et al., 2006). The latter process requires Urease positive type bacteria, i.e., general Bacillus, Sporosarcina.
1.4 PROBLEM STATEMENT
Civil Engineers deals with a lot of problems when constructing structures with certain regional soil deposits with poor geotechnical properties. Furthermore, over the year most soil stabilization has been achieved via chemical additives such as cement, lime, sodium silicate, asphalt, fibres which are toxic, costly, not eco-friendly, also contaminate the underground water.
1.5 AIM AND OBJECTIVES OF RESEARCH
1.5.1 AIM
The aim of this research is to improve the strength of lateritic via Microbial Induced Calcite Precipitation technique.
1.5.2 OBJECTIVES
The specific objectives are to:
i. Carry out index properties and strength test on the untreated lateritic soil;
ii. Isolate characteristics and produce bio-cementation medium for the lateritic soil;
iii. Apply microbial induced calcite precipitation (MICP) to the untreated lateritic soil;
iv. Determine the strength of the treated lateritic soil at different interval between 1 to 60 days.
1.6 JUSTIFICATION
Compared to other soil stabilizers like lime, cement, fly ash, asphalt, fiber, geo synthetics materials, which are toxic, not eco-friendly, costly, produces leachate that contaminates underground water. Microbial induced calcite precipitation (MICP) is a new and sustainable technology which utilizes biochemical processes to create barriers by calcium carbonate cementation.
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