1、Designation: D7762 11Standard Practice forDesign of Stabilization of Soil and Soil-Like Materials withSelf-Cementing Fly Ash1This standard is issued under the fixed designation D7762; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers procedures for the design of stabili-zation of soil and soil-like materials using self-
3、cementing coalfly ash for roadway applications, treatment of expansivesubgrade or organic subgrade, and limiting settlement of fillsbelow buildings. The coal fly ash covered in this methodincludes self-cementing fly ashes described in SpecificationD5239.1.2 The testing and engineering practices for
4、self-cementingcoal fly ash are similar to generally accepted practices for soilstabilization with fly ash and other pozzolans that require lime.1.3 The test methods in this guide are applicable to thecharacterization of mechanical properties of in situ mixedself-cementing fly ash stabilized material
5、s. There are otherrelated fly ash stabilization standards. Practice D5239 can beused to characterize the general types of fly ash for use in soilstabilization. Specification C593 can be used to evaluate theperformance of fly ash and other pozzolans that require limesoil stabilization. Guide E2277 ca
6、n be used to characterizeproperties of fly ash and bottom ash in structural fills andrelated design and construction considerations.1.4 The standard units are the SI units, unless other units arespecified.1.5 This standard does not purport to address all of thesafety concerns, if any, associated wit
7、h its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.6 This guide offers an organized collection of informationor a series of options and does not recommend a sp
8、ecificcourse of action. This document cannot replace education orexperience and should be used in conjunction with professionaljudgment. Not all aspects of this guide may be applicable in allcircumstances. This ASTM standard is not intended to repre-sent or replace the standard of care by which the
9、adequacy ofa given professional service must be judged, nor should thisdocument be applied without consideration of a projects manyunique aspects. The word “Standard” in the title of thisdocument means only that the document has been approvedthrough the ASTM consensus process.2. Referenced Documents
10、2.1 ASTM Standards:2C593 Specification for FlyAsh and Other Pozzolans for UseWith Lime for Soil StabilizationC597 Test Method for Pulse Velocity Through ConcreteD75 Practice for Sampling AggregatesD420 Guide to Site Characterization for Engineering De-sign and Construction Purposes3D653 Terminology
11、Relating to Soil, Rock, and ContainedFluidsD698 Test Methods for Laboratory Compaction Character-istics of Soil Using Standard Effort (12 400 ft-lbf/ft3(600kN-m/m3)D1557 Test Methods for Laboratory Compaction Charac-teristics of Soil Using Modified Effort (56,000 ft-lbf/ft3(2,700 kN-m/m3)D1883 Test
12、Method for CBR (California Bearing Ratio) ofLaboratory-Compacted SoilsD4609 Guide for Evaluating Effectiveness of Admixturesfor Soil StabilizationD5102 Test Methods for Unconfined Compressive Strengthof Compacted Soil-Lime MixturesD5239 Practice for Characterizing Fly Ash for Use in SoilStabilizatio
13、nD5759 Guide for Characterization of Coal Fly Ash andClean Coal Combustion Fly Ash for Potential UsesD5918 Test Methods for Frost Heave and Thaw WeakeningSusceptibility of SoilsE2201 Terminology for Coal Combustion Products3E2277 Guide for Design and Construction of Coal AshStructural Fills31This pr
14、actice is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.14 on Geotechnics ofSustainable Construction.Current edition approved Dec. 1, 2011. Published January 2012. DOI: 10.1520/D7762-112For referenced ASTM standards, visit the ASTM
15、website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright AS
16、TM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.2 AASHTO (American Association of State Highway andTransportation Offcials) Standard:4AASHTO T 307 Standard Method of Test for Determiningthe Resilient Modulus of Soils and Aggregate Materials2.3
17、TRB (Transportation Research Board) Standard:5NCHRP 1-28A Harmonized Test Method for LaboratoryDetermination of Resilient Modulus for Flexible Pave-ment Design2.4 ACAA (American Coal Ash Association) Soil Stabiliza-tion Manual:6Soil Stabilization and Pavement Recycling with Self-Cementing Coal Fly A
18、sh3. Terminology3.1 Definitions:3.1.1 For definitions related to Coal Combustion Produc-tions, see Terminology E2201. For definitions related togeotechnical properties, see Terminology D653.4. Significance and Use4.1 Self-cementing coal fly ashes are suitable materials forthe stabilization of soils,
19、 recycled pavement materials and roadsurface gravel. Fly ash stabilization can result in improvedproperties, including increased stiffness, strength and freeze-thaw durability; reduced hydraulic conductivity, plasticity, andswelling; and increased control of soil compressibility andmoisture. Fly ash
20、 stabilized materials (FASM) may be used inroadway construction, such as working platforms during con-struction, stabilized subgrade, subbase, and base layers. Fly ashstabilization can also be used in limiting settlement of fillsbelow buildings.4.2 This guide is intended for use with self-cementing
21、flyash that can be used separately or along with other stabilizingadmixtures to improve soil properties.4.3 The guide describes the unique design considerationsthat may apply to stabilization of soils and soil-like materialswith self-cementing coal fly ash. The requirements for stabili-zation of spe
22、cific materials may vary due to local conditions orthe intended use of the stabilized material, or both.4.3.1 This guide is not intended to limit the flexibility ofdesign in stabilization. The degree of success attained instabilization with coal fly ash is highly dependent on theparticular combinati
23、on of soil, fly ash, and other additives andthe construction procedure used. The selection of appropriatematerials, applicable tests, acceptance criteria, and specifica-tion is the responsibility of the design engineer.4.4 The test methods in this guide are intended for thedetermination of mechanica
24、l properties of FASM. The charac-terization of mechanical property improvement with self-cementing fly ash will assist in the evaluation of the fly ashstabilized materials.4.5 The use of self-cementing fly ash in geotechnicalengineering application may be regulated by state and localcodes. The codes
25、 should be consulted.5. Stabilization Applications5.1 GeneralHigh calcium oxide content and self-cementing properties of subbituminous coal fly ash (self-cementing fly ash) can be used effectively in stabilization, suchas drying wet soils to facilitate compaction and increasesubgrade support, improv
26、ing stiffness and strength and reduc-ing compressibility of both cohesive soils and granular mate-rials. However, the effectiveness depends on specific materialto be stabilized and specific fly ash and has to be determined ona case-specific basis.5.2 Stabilization of Fine-Grained SoilsIn the fly ash
27、stabilization of fine-grained soils, flocculation, agglomeration,and cementitious reactions may occur. Self-cementing coal flyash has been demonstrated to be an effective stabilization agentfor a range of fine-grained soils in increasing subgrade supportcapacity for pavements, in reducing swelling p
28、otential ofexpansive soils, in increasing shear strength of organic soilsand fine-grained soils, and in reducing the compressibility offills under foundations. The fly ash stabilized section alsoprovides a more stable platform (working platform) duringpavement construction over very soft subgrades.
29、Such stabi-lized subgrade working platforms can be treated as a subbasesection in the pavement thickness design.5.3 Stabilization of Coarse-Grained MaterialsIn coarse-grained materials, such as aggregate base, gravels, recycledpavement materials, recycled road surface gravel, cementationthrough pozz
30、olanic reactions and hydration within the self-cementing coal fly ash can cause strength gain and enhancedurability. The reaction rate depends on the self-cementing coalfly ash used.5.4 Pavement Recycling: Full Depth ReclamationRecycling or reclaiming existing flexible pavements withself-cementing f
31、ly ash as a stabilizing agent has been demon-strated to be an efficient and economical method of pavementrehabilitation for roadways. The process is accomplished bypulverizing the entire pavement section to the subgrade andstabilizing the pulverized mixture by adding self-cementingcoal fly ash and w
32、ater (as needed). The recycled sectionprovides an enhanced base for a new hot mix asphalt (HMA)wearing surface. Self-cementing fly ash stabilized recycledsections have structural capacities (enhanced modulus andreduced plastic deformations), which are considerably betterthan a crushed-stone aggregat
33、e base and can be equivalent toan asphaltic concrete base section.5.5 Gravel Road Recycling: In Situ ReclamationRecycling or reclaiming existing road surface gravel (RSG)with self-cementing fly ash stabilization is an economicalmethod for converting gravel roads to paved roads. Theprocess is accompl
34、ished by placing the appropriate amount ofself-cementing fly ash over the entire road surface and thenblending it into the RSG down to the required depth to form abase for the HMA layer. The self-cementing fly ash stabilized-RSG has similar or better properties as a high-quality crushedaggregate bas
35、e course in the stabilized section. The recycled4Available from American Association of State Highway and TransportationOfficials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,http:/www.transportation.org.5National Cooperative Highway Research Program, Transportation ResearchBoar
36、d, Washington, DC.6American CoalAshAssociation Educational Foundation, 15200 E. GirardAve.,Suite 3050, Aurora, Colorado 80014-3955.D7762 112and stabilized RSG section provides an enhanced base for anew HMA wearing surface.6. Laboratory Mix-Design6.1 GeneralA laboratory mix design is developed toesta
37、blish the optimum fly ash content, optimum moisturecontent, maximum dry density, and maximum strength gain fordesign and construction testing purposes. Since most stabiliza-tion applications with self-cementing fly ash rely on the fly ashas stabilizing agent, the test and design procedures shouldadd
38、ress the rapid rate at which the fly ash hydrates uponexposure to water. Ash hydration can significantly alter thecompaction characteristics of materials treated with self-cementing fly ash.6.2 Hydration RateSelf-cementing ash hydrates at a muchmore rapid rate than Portland cement, a 2-h delay in co
39、mpac-tion may decrease the maximum density and reduce strength.A1- to 2-h compaction delay should be achievable in situ andshould be stated in the project specifications. The specifiedmaximum compaction delay time in the project specification ismeasured from the time the self-cementing fly ash is in
40、corpo-rated into the materials being stabilized and has been exposedto water. Laboratory tests conducted to establish constructionand design parameters should be based on the properties of thestabilized materials compacted at the specified maximumallowable delay time.6.3 Moisture Content for Stabili
41、zationFor a given com-pactive energy, an optimum moisture content exists at whichmaximum strength is achieved. This optimum moisture contentfor maximum strength is generally 1 to 8 % below optimummoisture content for maximum density, depending on miner-alogy of the self-cementing fly ash and the typ
42、e of materialbeing stabilized. Construction specifications that specify mois-ture ranges based solely upon compaction characteristics canproduce stabilized materials having strengths 50 % or less ofthe maximum potential strength, greatly reducing the benefitsachieved through the stabilization operat
43、ion. The allowablerange in moisture content must be specified and monitoredduring construction to ensure that the moisture content of thestabilized section is near the optimum maximum strength.6.4 Mix Design ProcedureThe procedure herein followsACAA manual, Soil Stabilization and Pavement Recyclingw
44、ith Self-Cementing Coal Fly Ash, for determining moisture-density and moisture-strength relationships of the fly ashstabilized materials. Standard size compaction molds with adiameter of 100 mm (4 in.) or 150 mm (6 in.) depending onmaximum particle size of the material to be stabilized can beused wi
45、th standard Proctor or modified Proctor compactiveenergy. Use of split molds (metal or polyvinyl chloridereinforced with clamps) is desirable for the ease of specimenremoval after compaction. After blending of the soil, fly ash,and water, specimens are compacted using the specified com-paction delay
46、 A minimum of five test specimens, compactedover a wide range of moisture contents, should be prepared foreach test series to define both moisture-strength and moisture-density relationships. After extruding the specimens and seal-ing with plastic wrap, they should be cured for a minimum of7 days i
47、n a curing room with near 100 % relative humidity atroom temperature (23 6 20 C (73 6 40 F) prior tocompression testing. The standard compaction specimens pre-pared in 102 mm molds have a height-to-diameter ratio of 1.15;therefore, unconfined compressive strengths determined usingTest Methods D5102
48、provide a relative measure of strength andallow determination of optimum moisture content for maxi-mum strength. For specimens that need to be compacted usinga 150-mm (6-in.) diameter mold because of coarse particles,CBR tests in accordance with Test Method D1883 can beperformed on compacted specime
49、ns after curing to determinethe optimum moisture content for maximum CBR as a measureof relative strength. For a rigorous measure of unconfinedcompressive strength, specimens compacted to the maximumrelative density at the optimum moisture content for strengthgain and having a height-to-diameter ratio of 2 have to beprepared, cured, and tested.6.4.1 An alternative mix design procedure for the moisture-density and moisture-strength relationships of the self-cementing fly ash stabilized fine-grained soils uses combinedcompaction-unconfined compression tests using Harvar
