Published on December 12, 2016
1. MOISTURE SUSCEPTIBILITY OF SUBGRADE SOILS STABILIZED BY LIGNIN-BASED RENEWABLE ENERGY COPRODUCT 1
2. • Among the various natural resources is biomass, in particular, plant biomass, which is considered a renewable source of energy, such as biofuel and ethanol, and an alternative to fossil fuels. • Plant biomass is a lingo cellulosic material consisting of cellulose, hemicellulose, and lignin. INTRODUCTION 2
3. • Lignin, is a large complex polymer of phenyl propane and methoxy groups, a non carbohydrate poly phenolic substance that encrusts plant cell walls and cements plant cells together. • It is not possible to define the precise structure of lignin as a chemical molecule. • The definition in common is, it is a dendritic network polymer of phenyl propane basic units. 3
4. 4Fig: Structure of Lignin source: http://www.ili-lignin.com/aboutlignin.php
5. EXTRACTION OF LIGNIN Lignin is extracted from biomass by • Formic acid/acetic acid treatment • Peroxy formic acid/peroxy acetic acid (PFA/PAA) treatment • Bleaching • Isolation of lignin 5
6. 6 FORMIC ACID/ACETIC ACID TREATMENT: • Known as Pulping. • Biomass cut into small pieces placed in a conical flask. • 85% organic acid mixture is added to the flask. • Flask is boiled on a hot plate for 2 hours and then cooled. • Contents are filtered in a funnel and washed with 80% formic acid followed by hot distilled water.
7. 7 PEROXY FORMIC ACID/PEROXY ACETIC ACID TREATMENT: • Filtered matter is delignified by treating with PFA/PAA in hot water bath at 80°c for 2 hours. • Delignified matter is filtered to separate cooking liquor from cellulose and washed with hot water.
8. 8 BLEACHING • Delignified fibers treated with 14ml 35% H2O2 solution in hot water bath at 8°c for 2 hours. • It is washed with distilled water to remove residual lignin. • Process is repeated to remove lignin completely.
9. 9 ISOLATION OF LIGNIN • After Pulping and Delignification, residue is heated at 105°c. • Precipitated by adding distilled water and then filtered. • Precipitated lignin is washed with distilled water and vacuum dried over P2O5.
10. 10 SOIL STABILIZATION • Process of blending and mixing materials with soil to improve properties of geotechnical materials. • Traditional soil stabilizing additives includes hydrated lime, Portland cement and flyash. • Lignin also plays a positive role in soil stabilization. • Lignin increases soil stability by causing dispersion of clay fraction.
11. 11 EXPERIMENTAL PROGRAM MATERIALS: • Soil: Natural soils collected from a construction site in Calhoun country. • Additives: Two types of Biofuel co-products are taken. Co-product A - dark brown, free flowing liquid fuel with a smoky odor formed in a process called fast pyrolysis wherein plant material are exposed to 400–500°C in oxygen free environment. Co-product B - Powdered Alkaline-washed corn hull obtained in the process of converting corn into ethanol.
12. 12 • Co-product A contains about 25% lignin and up to 25% water with a pH value of 2.2. • Co-product B contains about 5% lignin, 50% hemicellulose, 20% cellulose, and other components. • Ottumwa Class C fly ash is selected as the traditional additive against which we compare biofuel co-products. • It is a coal combustion by-product obtained from Ottumwa the Generating Station (OGS) located near Chillicothe, Iowa.
13. 13 TESTS: • UCS tests after “dry” and “wet” conditioning • Dry and wet specimens are subjected to UCS tests to evaluate the moisture susceptibility of additive-treated specimens. • The stabilization effect of a soil additive is measured in terms of the increase in load bearing capacity as indicated by UCS. • Visual observations of Soaked specimens. • Specimens are fully soaked in water and observed to see if they fail because of moisture.
14. 14 SPECIMEN PREPARATION: • Natural soil collected is dried and broken down to pass through 4.75mm IS sieve. • Additives are also dried to remove initial water, making homogenous soil blend. • The additives are Co-product A, Co-product B, Co-product A/flyash, Co-product A/Co-product B mixtures. • From experience the amounts of additives are found to be 12% of uncombined additive, 10% Co-product A/2% flyash and 10% Co- product A/2% Co-product B to provide strong soil mixtures.
15. 15 • Untreated soil mixtures with no additives are also prepared. • Blended soil samples are statically compacted in the cylindrical mould (51 × 51 mm). • Compacted specimens are allowed to cure at 25°C and 40% relative humidity. • Curing periods are 1 and 7 days after sample preparation for the UCS test.
16. 16 Unconfined Compression Strength Test: • Compacted specimens of each mixture are subjected to dry and wet preconditioning procedures for UCS tests. • Specimens in the dry precondition are tested without water saturation, whereas specimens in the wet precondition are tested after specified water saturation procedures. • The wet test procedure in this research included full saturation and half-saturation of the specimen. • Full saturation requires complete immersion of the specimen on its side in a water bath for 1 h.
17. 17 • Half-saturation is conducted because some of specimens are broken in full saturation. • One side of the specimen is soaked in water for 5 min. A specimen subjected to full saturation or half-saturation was then removed from the water and allowed to drain for 5 minutes. The specimen was then subjected to UCS testing.
18. 18 Fig: Fly ash-treated specimen under half-saturation procedure Source: Journal Of Transportation Engineering © Asce / November 2012 / 1283
19. 19 Experimental Treatment Group Combinations for UCS Tests:
20. 20 Soaking Test: • Compacted specimens of each mixture after 1 day of curing are subjected to soaking tests. • Specimens are fully soaked in water. • Two sets of specimens are prepared for these tests. • Test Set 1 include Untreated soil (pure soil) 12% fly ash-treated soil 12% Co-product A-treated soil and 12% Co-product B-treated soil.
21. 21 • Test Set 2 include 10% Co-product A/2% fly ash and 10% Co-product A/2% Co-product B-treated soil. • Specimens were observed for failure for 7 days after soaking. Fig: Soaking tests: (a) Test Set 1; (b) Test Set 2 Source: Journal Of Transportation Engineering © Asce / November 2012 / 1283
22. 22 RESULTS AND DISCUSSION UCS Test Results: Fig: Results of UCS tests Source: Journal Of Transportation Engineering © Asce / November 2012 / 1283
23. 23 Fig: Results of UCS tests Source: Journal Of Transportation Engineering © Asce / November 2012 / 1283
24. 24 Fig: Results of UCS tests Source: Journal Of Transportation Engineering © Asce / November 2012 / 1283
25. 25 • Additive-treated soils are in all cases stronger than untreated soils under dry and wet conditions. • The fly ash-treated soil test results show the most improvement in UCS under dry conditions. • However, fly ash-treated soil specimens disintegrated in the wet precondition or are reduced in strength after the wet precondition compared with co-product-treated soil specimens. • Duration of curing has less influence on the strength gain of soil specimens treated with Co-product B than on other soil specimens.
26. 26 • Quantitative assessments of the degree to which additives improve strength and moisture resistance are made using the following equations. SI(%) =