Enhancing the engineering properties of expansive soil using bagasse ash, bagasse fibre and hydrated lime

University of Technology Sydney. Faculty of Engineering and Information Technology.Expansive soils exhibit massive volume change against fluctuations of moisture content. Shrinkage and expansion of soil can commonly take place near the ground surface, where it is directly subjected to seasonal and environmental variations. Construction of civil engineering structures on expansive soils is highly risky, as this type of soil is susceptible to seasonal drying and wetting cycles, causing significant deformations. Frequent soil movements can generate cracks and damage residential buildings, roads, and other civil structures directly placed on this type of problematic soil. Many efforts have been applied in practice to overcome the adverse effects of expansive soil including replacement of existing expansive soil with non-expansive soil, maintaining a constant moisture content, and ground improvement techniques such as the application of granular pile-anchors, sand cushion technique, and belled piers, and soil stabilisation with chemical agents (e.g. lime or cement) and so on. On top of that, lime stabilisation is the most commonly used method for controlling the shrink-swell behaviour of expansive soil due to seasonal variations. Lime reacts with expansive clay in the presence of water and changes the physicochemical properties of expansive soil, which in turn alters the engineering properties of treated soil. Moreover, soil stabilisation and reinforcement using lime combined with agricultural and industrial waste by-products (e.g. fly ash, rice husk ash, recycled fibres) can extend the effectiveness of lime stabilised expansive soil. This study presents an experimental investigation on the improvement of the geotechnical properties of expansive soil stabilised with bagasse fibre, bagasse ash combined without or with lime stabilisation. The agricultural waste by-products of bagasse ash and fibre, remained after crushing of sugar-cane for juice extraction, and the expansive soils, used in this investigation, were collected from Queensland, Australia. The stabilised soil specimens were prepared by changing the contents of bagasse ash from 0% to 25%, bagasse fibre from 0% to 2%, hydrated lime from 0% to 6.25%, and combined bagasse ash-hydrated lime from 0% to 25% by the dry mass of expansive soil. Several series of laboratory experiments have been performed on untreated and treated expansive soil samples with different additive contents and various curing times of 3, 7, 28, and 56 days. Another extensive microstructural analysis using scanning electron microscopy (SEM), pH measurements, and Fourier transform infrared (FTIR) techniques has been carried out to evaluate the microstructure development of untreated and treated expansive soils. The outcomes of these experimental investigations showed that when the addition of bagasse ash into the expansive soils increased from 0% to 25%, the linear shrinkage reduced by 47%, the free swell potential decreased from approximately 10% to less than 0.5%, the swelling pressure reduction was from 80 kPa to 35 kPa (about 60%), the compressive strength at failure and the corresponding strain increased significantly by 48% and 40%. Meanwhile, the combination of bagasse ash and lime to stabilise soils when combined additive content increased up to 25% caused a significant increase in the compressive strength of 815% and the secant modulus of elasticity from 7.2 MPa to 107.2 MPa; reduced the linear shrinkage of 84% and the free swell potential down to less 0.5%; significantly decreased the swelling pressure from 80 kPa to around 10 kPa (88% reduction) and the compression indices from 0.484 to 0.083, just to name a few. It was noted that the improved geotechnical characteristics were more pronounced for lime treated soils with the combination of bagasse ash or fibre. The utilisation of bagasse ash or fibre for expansive soil stabilisation without or with lime combination not only effectively improved the geotechnical properties of expansive soil as curing time and additive content increased, but also assisted in minimising the adverse effects of agricultural waste by-products on the environment. Numerical investigations based on the finite element method (FEM) incorporated in PLAXIS were carried out to evaluate a possible practical application of recycled fibre-lime reinforced soil as a replacement of geosynthetic reinforced traditional angular load transfer platform layer combined with columns or piles supported embankments founded on soft soils. An equivalent two-dimensional FEM model with proper modified parameters of structure and soil models has been adopted to investigate the performance of floating columns supported embankment reinforced without or with an FRLTP (fibre reinforced load transfer platform). Firstly, a series of numerical analysis was performed on the full geometry of columns supported embankment reinforced without or with an FRLTP of 0.5 m to examine the effectiveness of the FRLTP inclusion into the columns supported embankment system. The numerical results revealed that the embankment with FRLTP could effectively reduce the total and differential settlements, and the lateral displacement of the embankment by 20%, 74% and 46%, respectively, when compared with the embankment without FRLTP. Subsequently, several series of extensive parametric studies on the influence of FRLTP properties, and the improvement depth ratios of soft soils, have been carried out to assess the behaviour of the columns supported embankment with FRLTP. The findings of the extensive parametric study indicated that the platform thickness has a significant influence on the embankment behaviour, especially in improving the total and differential settlements, the rigidity and stability of the embankment, and the more load transfer from the embankment to DCM columns. Meanwhile, Young’s modulus of the FRLTP shows considerable effects on the differential settlement, the stress concentration ratio, but has a negligible effect on the lateral deformation of the investigated embankment. The improvement depth ratio reveals substantial impacts on the final settlement and the lateral deformation, but shows insignificant influence on the stress concentration ratio and the differential settlement during the embankment construction and post-construction time. The FRLTP shear strength parameters show significant influences on the stress concentration ratio and the differential settlement of the embankment. However, the enhancement in the embankment performance was more noticeable for the cohesion than the internal friction angle of the FRLTP

Economic assessment of use of pond ash in pavements

The paper introduces a new type of industrial waste-based subbase material which can replace conventional subbase material (CSM) in pavement construction. Utilisation of this industrial waste, namely pond coal ash produced from a thermal power plant in road construction will help to reduce the disposal problem of this waste and also will help to reduce the problem of scarcity of CSM. Lime and fibre were also added to the pond ash at various percentages to improve the suitability of this type of mix as subbase material. The optimum service life of pavement is studied with the help of numerical modelling and the cost benefit is also presented in the current study. The study reveals that stabilisation of the coal ash with 2% lime may produce an optimal material and, even though a greater thickness may be required to deliver the same pavement performance, direct cost savings of around 10% may be achieved in addition to less easily quantifiable environmental benefits. Design charts are provided to exploit the findings

An Overview of Waste Materials for Sustainable Road Construction

Untreated soil typically has low shear strength, swelling behavior, high compressibility and its characteristics were highly dependent on the environment. In general, such problematic soil will lead to severe damages in road construction industry such as bearing capacity failure, slope instability, and excessive settlement. Agricultural waste, construction waste, and municipal waste have recently gained considerable attention as a sustainable material in road construction application due to its availability, environmental friendly and low-cost materials. Therefore in this review, randomly distributed fiber reinforced soil and oriented distributed fiber reinforced soil will be extensively discussed based on the emerging trend. It further reviewed the feasibility of using waste materials as a reinforcement material for the road construction industry. The review also attempts to evaluate and compare the engineering properties of soil and sustainable materials in order to enhance soil performance as well as help to improve the environment affected by growing waste materials

Experimental approach to investigate reinforced clay

Soil reinforcement with discrete flexible fibres has always been an issue for further research. In Geotechnical engineering field, the research on sandy soil has considerably been more than the clayey one. The main reason for this lack can be expressed as the complexity of clayey material due to their cohesion and interaction between clay and reinforcement.The present research aims to show possibility of discrete fibre usage in clay. For this purpose, selection of material has been conducted with special care to make the project outcome applicable to industry projects. The fibre which was used for this research prepared by BASF Company in Western Australia and currently is used in fibre reinforced concrete for infrastructure projects. Kaolin has been used as soil part and provided by Prestige Company.Experimental approach was applied to investigate the effect of different parameters on composite soil strength. These tests cover the variety range of soil mechanics tests from compaction tests to triaxial compression tests. The results from all the tests were presented in the thesis.A theoretical model was also developed for clayey material for the first time with the use of modified cam clay model to predict the behaviour of samples precisely. This model is based on the rule of mixture and considers the effect of soil and fibre separately. The model was validated with the results from CD triaxial test

Shear strength behaviour of sugarcane bagasse reinforced soils

Sugarcane is considered as the most abundant plant based crop grown in the tropics and part of the temperate climates. Its by-product, sugarcane bagasse, constitutes 30% of the total production. In the past, it was considered as waste material but contemporaries through innovative research projects over the years have found uses for it. Among these projects is soil reinforcement, which provides an alternative application to industrial by-products and natural fibres as a way of reducing their environmental footprints and contributing to sustainable geotechnics. Although bagasse morphological composition contains structural elements ideal for reinforcement and composite materials, it has received little research as a standalone reinforcement material. Because of this, a direct shear test was therefore initiated to establish the usefulness of using sugarcane bagasse as a soil reinforcement material by comparing the extent of shear strength and stiffness response due to its inclusion to unreinforced soil. Three different types of bagasse, fibre, millrun and pith, were added to unreinforced soil in percentage by weight content of 0.3 - 1.7. The bagasse was added to Klipheuwel sand, Cape Flats sand and Kaolin Clay at both dry and moist conditions. In addition, durability studies involving 12 cycles of wetting and drying, and soaking for a period of 14 days were constituted

Uji Triaksial Unconsolidated-Undrained pada Campuran Tanah Lanau - Kapur - Abu Sekam Padi dan Serat Karung Plastik

Geotechnical and mechanical behaviour of soil stabilized with lime-rice husk ash and strengthened by randomly placed plastic fiber depends on the portions of the added materials and curing time. This research investigates the effect of the waste plastic sack fibers portion and the curing time to the stress – strain relationship and to the shear strength parameters of the mixture. In this study the portions of lime and rice husk ash were set as constant to the value of 12% and 24% respectively. The effect of four waste plastic sack fibers portion variation from 0.1% to 0.8% was measured by unconsolidated-undrained triaxial test. The samples were tested at 7, 14 and 21 days after mixing. In general, according to the test result, the inclusion of randomly waste plastic sack fiber and curing time have enhanced the shear strength parameters, the peak stress and the strain before failure.  With 0.2% fiber content, the cohesion and the internal friction angle values of the samples have increased 335% and 409% respectively compared with those of the samples having no added materials

Application of jute fiber in soil stabilization

Abstract: This research focuses on the use of jute fibers as a soil stabilizer to stabilize the soil. Stabilization is the process of changing the properties of a soil to improve its engineering performance, and it is used in a range of engineering projects. This study investigates the potential of jute fiber as a soil stabilizer when cutting in lengths of approximately 30 mm. Various percentages of jute fiber pieces have been used and combined with soil, including 0.5%, 1%, 1.5% and 2%. To observe the change in the technical properties of the soil, laboratory tests such as the California Bearing Ratio (CBR) test, modified compaction tests and direct shear strength tests were performed. Based on the results of the experiments, it can be concluded that stabilizing the soil with 30mm pieces of jute as a stabilizer improves the strength properties of the soil, allowing it to be used as a reinforcement material for road construction, parking lots, land development projects, airports and many other applications where basements are not suitable for building

Geotechnical properties of fiber reinforced pond ash

In the recent past huge amount of Fly ash and Pond ash are generated by the thermal power plants. It is a major cause of concern for the people living around the power plants. The current rate of deposition of Pond ash in India has reached 170 million tons per annum. About 90,000 acres of precious land is used for the storage of abandoned Pond ash. But current rate of utilization of ash is only about 35-40%.The unused ash leads to an ever increasing ponding area for storing ash and related environmental issues for the people around the power plants. Besides this, over the last few years, the construction of highways and roads has taken a boost. This requires a huge amount of natural soil and aggregates to excavated or to be deposited. Again this is an environmental issue and economical too. These are some issues now-a-days which motivates in development of alternative methods to overcome those environmental and also the economic issues. This leads to the reuse of suitable industrial byproducts which can fix those issues and also fulfill the specifications. Pond ash is one such byproduct. It is a non-plastic and lightweight material. During this work, the effect of moisture content, degree of compaction, synthetic fiber as a reinforcement etc. on various geotechnical properties of pond ash are studied. A series of tests such as direct shear test, CBR test, light compaction as well as heavy compaction test, Unconfined compression test are done to estimate the strength characteristics of compacted pond ash using synthetic fiber as a reinforcement as well as tests like specific gravity test, grain size distribution test by mechanical sieve analysis and hydrometer test etc. are performed to obtain some physical properties of the pond ash.These results will be very much helpful for the successful application of pond ash in different fields such as embankment construction, road base and sub-base construction, designing of retaining walls etc. as well as the disposal of pond ash in an ecofriendly manner

CBR test on reinforced clayey sand

Composite soils have been widely used in civil engineering applications, especially in slopes, embankment dam and landfills. This paper aims to investigate effect of fiber inclusion on CBR values of composite soil (i.e. sand composite). A series of laboratory CBR tests carried out to evaluate fiber effect on CBR values behavior of composite sand. Clayey sand was selected as soil part of the composite and natural fiber was used as reinforcement. The fiber parameters differed from one test to another, as fiber length were changed from 20 mm to 50 mm and fiber content were varied from 1% and 3%. For each test, CBR values were calculated and compared. The results proved that inclusion of fiber affected CBR values of sand composite so that increasing in fiber content and length caused increasing in CBR

The engineering properties and mechanical behaviour of fibre reinforced clay

Embankment slope failure due to insufficient strength, weak bearing capacity, excessive deformation and desiccation cracking of problematic soils is commonly observed on the UK road network, and this leads to huge expenditure in the maintenance and repair of highway projects every year. It is necessary to reduce these engineering problems and economic losses through environmentally and economically friendly methods. Previous studies have shown that randomly distributed fibres can significantly improve various soil properties. However, there is a lack of comprehensive study on the engineering properties of fibre reinforced high plasticity clay. Also, limited mechanical models have been proposed for predicting the shear strength behaviour of fibre reinforced clay. In order to investigate these problems, a series of laboratory investigations including compaction, bearing capacity, one-dimensional consolidation, linear shrinkage, desiccation cracking, direct tensile strength, triaxial compression tests were conducted on unreinforced and polypropylene fibre reinforced London Clay. A mechanical model was proposed for predicting the shear strength of fibre reinforced clay. The experimental results showed that fibres can significantly improve the engineering properties of London Clay. As fibre inclusion ratio increased, the bearing capacity, coefficient of consolidation, tensile strength and shear strength of the soil increased; the compression index, swelling index, linear shrinkage and desiccation cracking area of the soil decreased. As fibre length increased, the bearing capacity and desiccation cracking area of the soil decreased; the tensile strength and shear strength of the soil increased. The mechanical model was proposed based on the conception of equivalent confining stress and the predicted stress-strain-pore water pressure response and stress path behaviour of fibre reinforced soil were compared with the experimental results. The comparisons showed that the model was capable of predicting the shear strength behaviour of fibre reinforced clay