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Title: Stabilization of Oklahoma expensive soils using lime and class C fly ash

Abstract

This study uses lime and class C fly ash, an industrial byproduct of electric power production produced from burning lignite and subbituminous coal, to study the plasticity reduction in highly expensive natural clays from Idabel, Oklahoma. This study is important, especially in Oklahoma, because most of the native soils are expansive and cause seasonal damage to roadways and structures. The addition of lime or fly ash helps to arrest the shrinkage and swelling behavior of soil. Four soil samples with the same AASHTO classification were used in this study to show shrinkage variability within a soil group with the addition of lime and class C fly ash. The plasticity reduction in this study was quantified using the linear shrinkage test. It was found that soils classified within the same AASHTO group had varying shrinkage characteristics. It was also found that both lime and fly ash reduced the lienar shrinkage, however, the addition of lime reduced the linear shrinkage to a greater degree than the same percentage of class C fly ash. Even though it takes much less lime than fly ash to reduce the plasticity of a highly expansive soil, it may be less expensive to utilize fly ash, whichmore » is a waste product of electric power production. Lime also has a lower unit weight than fly ash so weight percentage results may be misleading.« less

Authors:
;  [1]
  1. (eds.) [University of Oklahoma, Norman, OK (USA). Dept. of Civil Engineering and Environmental Science
Publication Date:
OSTI Identifier:
21149608
Resource Type:
Conference
Resource Relation:
Conference: Geo-Denver 2007: new peaks in geotechnics, Denver, CO (USA), 18-21 Feb 2007; Other Information: russellbuhler@ou.edu; Related Information: In: Problematic soils and rocks and in situ characterization. Part of Geo-Denver 2007 - new peaks in geotechnics, proceedings of sessions of Geo-Denver 2007, by Puppala, A.J.; Hudgma, N.; Likos, W.J., CD-ROM pages.
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; FLY ASH; LIMESTONE; LIGNITE; COAL; USA; SOILS; FOSSIL-FUEL POWER PLANTS; COMBUSTION PRODUCTS; SHRINKAGE; SWELLING; WASTE PRODUCT UTILIZATION

Citation Formats

Buhler, R.L., and Cerato, A.B. Stabilization of Oklahoma expensive soils using lime and class C fly ash. United States: N. p., 2007. Web.
Buhler, R.L., & Cerato, A.B. Stabilization of Oklahoma expensive soils using lime and class C fly ash. United States.
Buhler, R.L., and Cerato, A.B. Mon . "Stabilization of Oklahoma expensive soils using lime and class C fly ash". United States. doi:.
@article{osti_21149608,
title = {Stabilization of Oklahoma expensive soils using lime and class C fly ash},
author = {Buhler, R.L. and Cerato, A.B.},
abstractNote = {This study uses lime and class C fly ash, an industrial byproduct of electric power production produced from burning lignite and subbituminous coal, to study the plasticity reduction in highly expensive natural clays from Idabel, Oklahoma. This study is important, especially in Oklahoma, because most of the native soils are expansive and cause seasonal damage to roadways and structures. The addition of lime or fly ash helps to arrest the shrinkage and swelling behavior of soil. Four soil samples with the same AASHTO classification were used in this study to show shrinkage variability within a soil group with the addition of lime and class C fly ash. The plasticity reduction in this study was quantified using the linear shrinkage test. It was found that soils classified within the same AASHTO group had varying shrinkage characteristics. It was also found that both lime and fly ash reduced the lienar shrinkage, however, the addition of lime reduced the linear shrinkage to a greater degree than the same percentage of class C fly ash. Even though it takes much less lime than fly ash to reduce the plasticity of a highly expansive soil, it may be less expensive to utilize fly ash, which is a waste product of electric power production. Lime also has a lower unit weight than fly ash so weight percentage results may be misleading.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}

Conference:
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  • A state-of-the-art review of FGD sludge stabilization using lime/fly-ash admixtures covers recent experimental results on the improvement of physical and strength characteristics of scrubber sludges stabilized by fly ash alone or in combination with lime, cement or silica; chemical analyses of leachates from FGD sludges fixed by fly ash and lime; and data on crystalline structure of raw and fixed sludges obtained by scanning electron microscopy, X-ray diffraction, and energy dispersion X-ray analysis. The stabilized sludges appear to attain reasonable strength and relatively low permeability, but some chemical species present in the leachates, such as lead, mercury, copper, selenium, chloride,more » and sulfate, may pose environmental problems. The final fixed sludge matrix appears to be a mixture of ettringite, tobermorite, calcium aluminosilicate, and calcium hydroxide.« less
  • The strength gain in lime-fly ash mixtures begins only after a delay in time, which is due to the induction period for the reactions that take place between lime and fly ash particles. This research work studies this induction period using unconfined compressive strength (UCS) tests and differential scanning calorimetry (DSC) tests. Based on nucleation and diffusional growth theories, the induction period is qualitatively explained and the relevant equation for its quantitative prediction with regard to curing temperature is proposed. The suggested equation is evaluated using the UCS and DSC test results. It is concluded that the induction period canmore » be predicted quantitatively and that accelerated curing can be used to estimate the induction period for any curing temperature. Furthermore, DSC tests can be used successfully for predicting the induction period.« less
  • Pozzolanic-based stabilization/solidification (S/S) is an effective, yet economic technological alternative to immobilize heavy metals in contaminated soils and sludges. Fly ash waste materials were used along with quicklime (CaO) to immobilize lead, trivalent and hexavalent chromium present in contaminated clayey sand soils. The degree of heavy metal immobilization was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) as well as controlled extraction experiments. These leaching test results along with X-ray diffraction (XRD), scanning electron microscope and energy dispersive x-ray (SEM-EDX) analyses were also implemented to elucidate the mechanisms responsible for immobilization of the heavy metals under study. Finally, the reusabilitymore » of the stabilized waste forms in construction applications was also investigated by performing unconfined compressive strength and swell tests. Results suggest that the controlling mechanism for both lead and hexavalent chromium immobilization is surface adsorption, whereas for trivalent chromium it is hydroxide precipitation. Addition of fly ash to the contaminated soils effectively reduced heavy metal leachability well below the non-hazardous regulatory limits. However, quicklime addition was necessary in order to attain satisfactory immobilization levels. Overall, fly ash addition increases the immobilization pH region for all heavy metals tested, and significantly improves the stress-strain properties of the treated solids, thus allowing their reuse as readily available construction materials. The only potential problem associated with this quicklime/fly ash treatment is the excessive formation of the pozzolanic product ettringite in the presence of sulfates. Ettringite, when brought in contact with water, may cause significant swelling and subsequent deterioration of the stabilized matrix. Addition of minimum amounts of barium hydroxide was shown to effectively eliminate ettringite formation.« less
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  • Fourteen coal-fired power plants in the Ohio Valley totaling 13,500 MW`s use the magnesium-enhanced lime flue gas desulfurization (FGD) scrubbing process. The discharge of these scrubbers is an aqueous slurry of water containing magnesium and calcium sulfites, and solid particles of calcium sulfite and calcium sulfate. Most of these plants dewater the FGD sludge and mix the 35--45% solids cake with coal fly ash and/or bottom ash and pulverized quicklime to cause a cementitious chemical reaction. This type of pozzolanic and hydration reaction can be described as lime reacting with alumina from the fly ash which in turn react withmore » the calcium sulfite and sulfate FGD waste to form ettringite minerals. With a proper mix design and compaction, the resulting material can be used in a beneficial application as a roller compacted FGD base course (RCFGD) for pavement construction. The mix design procedure for RCFGD is described; it includes extra fly ash and lime materials than that used for landfill disposal to yield additional strength and durability. RCFGD was produced in a portable pug mill and placed trying several at a 10,000 sq. ft. cattle feedlot. Mix design criteria and factors affecting strength and durability are discussed. Results of unconfined compression tests as well as of durability tests are reviewed.« less