Shear strength characteristics of fiber reinforced fly ash

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Use of Waste material recuces cost of construction and encourages sustainable development

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Shear strength characteristics of fiber reinforced fly ash

  1. 1. A.K.Choudhary*, J.N.Jha**,K.S.Gill** *National Institute of Technology, Jamshedpur **Guru Nanak Dev Engg. College, Ludhiana
  2. 2. <ul><li>Introduction </li></ul><ul><li>Laboratory Investigation </li></ul><ul><li>Result and Discussion </li></ul><ul><li>Peak deviator stress and strain at failure </li></ul><ul><li>Elastic moduli </li></ul><ul><li>Shear strength parameters </li></ul><ul><li>Conclusions </li></ul><ul><li>References </li></ul>
  3. 3. Introduction <ul><li>Soil Reinforcement </li></ul><ul><li>Conventional method of soil reinforcement </li></ul><ul><li>Inclusions:Oriented in preferred direction and introduced sequentially in alternate layers </li></ul><ul><li>Plane of weakness: Develop parallel to the oriented reinforcements </li></ul>
  4. 4. <ul><li>Randomly distributed discrete fiber reinforced soil </li></ul><ul><li>Similar to admixture stabilization in preparation </li></ul><ul><li>Maintenance of strength isotropy and absence of potential plane of weakness </li></ul>
  5. 5. Major geotechnical project <ul><li>Local availability of Good quality soil </li></ul><ul><li>Transportation of good quality soil incur good amount of project cost </li></ul><ul><li>Replacement of soil by local Industrial wastelike flyash if found suitable; Reduction in construction cost and encouragement for sustainable development </li></ul>
  6. 6. Flyash <ul><li>Disposal of flyash :Big problem, </li></ul><ul><li>Can’t be used due to low strength </li></ul><ul><li>Fiber if added as admixture may improve engineering behaviour </li></ul><ul><li>Flyash properties depends on nature of coal burnt and are source sensitive </li></ul><ul><li>Require separate study for different sources </li></ul>
  7. 7. Present Problem <ul><li>To study the effect of fiber inclusion on the strength characteristics of flyash obtained from local thermal power station by carrying Triaxial test (unconsolidated undrained) </li></ul><ul><li>Effect of aspect ratio and fiber content on peaK deviator stress, elastic moduli and shear strength parameters </li></ul>
  8. 8. Laboratory Investigation <ul><li>Physical and Engineering Properties of Fly ash. </li></ul><ul><li>  </li></ul><ul><li>Property Value </li></ul><ul><li>Specific Gravity 2.09 </li></ul><ul><li>Grain size distribution (%) </li></ul><ul><li>Sand: 16.0 </li></ul><ul><li>Silt: 82.0 </li></ul><ul><li>Clay: 2.0 </li></ul><ul><li>Liquid Limit (%) 44.0 </li></ul><ul><li>Plastic Limit Non -plastic </li></ul><ul><li>Optimum moisture content (%) 36.50 </li></ul><ul><li>Maximum dry density (kN/m 3 ) 10.52 </li></ul>
  9. 9. Physical and Engineering Properties of Fibers <ul><li>Property Value </li></ul><ul><li>Type Polyethylene (Synthetic) </li></ul><ul><li>Colour White </li></ul><ul><li>Cut length, l f (mm) 5,10,15 (variable) </li></ul><ul><li>Dia. of fiber d f (mm) 0.20 (constant) </li></ul><ul><li>Aspect ratio (l f / d f ) 25,50,75 (variable) </li></ul><ul><li>Fiber content, f c 0.25,0.50,1.0 </li></ul><ul><li>(% by mass of dry fly ash) (variable) </li></ul><ul><li>Tensile strength (Mpa) 60 -120 </li></ul><ul><li>Tensile elongation (%) Greater than 100 </li></ul>
  10. 10. Sample preparation/Result & discussion <ul><li>Dry mixing of flyash and fiber </li></ul><ul><li> (Even distribution of fiber) </li></ul><ul><li>Amount of water added (corresponds to OMC of flyash) </li></ul><ul><li>Length of specimen =76.2mm </li></ul><ul><li>Diameter of specimen= 38.1mm </li></ul><ul><li>Confining pressure: 98.1kPa, 96.2kPa,294.3kPa </li></ul><ul><li>Strain rate:1.20mm/minute </li></ul>
  11. 11. Peak deviator stress vs Fiber content Sr.No. d f l f l f / d f Confining pressure (kPa) Fiber content (%) Peak deviator stress (kPa) 1.0 0.20 5.0 25 98.10 Nil 177 0.25 255 0.50 294 1.0 372 2.0 0.20 10.0 50 196.20 0.25 436 0.50 488 1.0 549 3.0 0.20 15.0 75 294.30 0.25 706 0.50 763 1.0 1044
  12. 12. Peak deviator stress vs Aspect ratio Sr.No. d f l f Confining pressure (kPa) Fiber content (%) l f / d f Peak deviator stress (kPa) 1.0 0.20 5 98.10 0.25 25 255 10 50 275 15 75 367 2.0 5 196.20 0.50 25 415 10 50 488 15 75 604 3.0 5 294.30 1.0 25 570 10 50 692 15 75 1044
  13. 13. Strain at failure vs Fiber content Sr.No. d f l f l f / d f Confining pressure (kPa) Fiber content (%) Strain at failure (%) 1.0 0.20 5 25 98.10 0.25 3.50 0.50 3.50 1.0 6.50 2.0 10 50 196.20 0.25 3.50 0.50 4.50 1.0 6.50 3.0 15 75 294.30 0.25 6.0 0.50 7.50 1.0 10.50
  14. 14. Elastic moduli vs Fiber content Sr.No. d f l f l f / d f Confining pressure (kPa) Fiber content (%) Initial tangent modulus (kPa) Secant modulus at failure (kPa) 1.0 0.20 5 25 98.10 0.25 7848 7286 0.50 9810 8400 1.0 10791 5723 2.0 10 50 196.20 0.25 14715 12457 0.50 15696 10844 1.0 16677 8446 3.0 15 75 294.30 0.25 20209 11767 0.50 21092 10173 1.0 21876 9943
  15. 15. Shear strength parameter vs Fiber content Sr.No. d f l f l f / d f Fiber content (%) Cohesion C uu (kPa) Angle of internal friction Ø uu ˚ 1.0 0.20 5 25 0.25 49.0 18˚26’ 0.50 59.0 22˚15’ 1.0 98.0 23˚18’ 2.0 10 50 0.25 59.0 23˚12’ 0.50 69.0 24˚12’ 1.0 108.0 25˚17’ 3.0 15 75 0.25 69.0 25˚28’ 0.50 88.50 26˚34’ 1.0 118.0 30˚58’
  16. 16. <ul><li>The increase in peak deviator stress may be due to the shear transfer mechanism which has been induced by the inclusion of fibers </li></ul><ul><li>The increase in aspect ratio provides more surface area that causes increase in resistance, resulting in higher strength of reinforced flyash </li></ul><ul><li>The failure of specimens in case of reinforced fly ash is of progressive nature indicating ductile behavior induced by the fiber inclusions </li></ul>
  17. 17. Conclusions <ul><li>Mixing of synthetic fiber can increase the strength of flyash. </li></ul><ul><li>The stress- strain behaviour of flyash improved considerably due to increase in fiber content and aspect ratio </li></ul><ul><li>Elastic moduli increases with increase in fiber content and aspect ratio </li></ul><ul><li>Shear strength parameter;cohesion and angle of internal friction also increases with increase in fiber content </li></ul>
  18. 18. <ul><li>Thankyou................. </li></ul>

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