1、Designation: D 6276 99a (Reapproved 2006)Standard Test Method forUsing pH to Estimate the Soil-Lime Proportion Requirementfor Soil Stabilization1This standard is issued under the fixed designation D 6276; the number immediately following the designation indicates the year oforiginal adoption or, in
2、the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method provides a means for estimating thesoil-lime proportion requireme
3、nt for stabilization of a soil. Thistest method is performed on soil passing the 425-m (No. 40)sieve. The optimum soil-lime proportion for soil stabilization isdetermined by tests of specific characteristics of stabilized soilsuch as unconfined compressive strength or plasticity index.1.2 Some highl
4、y alkaline by-products (lime kiln dust, ce-ment kiln dust, and so forth) have been successfully used tostabilize soil. This test method is not intended for thesematerials and any such product would need to be tested forspecific characteristics as indicated in 1.1.1.3 This test method is used to dete
5、rmine the lowestpercentage of lime that results in a soil-lime pH of 12.4.1.4 Lime is not an effective stabilizing agent for all soils.Some soil components such as sulfates, phosphates, organics,and so forth can adversely affect soil-lime reactions and mayproduce erroneous results using this test me
6、thod.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with 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.2. Referen
7、ced Documents2.1 ASTM Standards:2C51 Terminology Relating to Lime and Limestone (as usedby the Industry)C 977 Specification for Quicklime and Hydrated Lime forSoil StabilizationD 421 Practice for Dry Preparation of Soil Samples forParticle-Size Analysis and Determination of Soil Con-stantsD 653 Term
8、inology Relating to Soil, Rock, and ContainedFluidsD 1193 Specification for Reagent WaterD 1293 Test Methods for pH of WaterD 2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testin
9、g and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4753 Guide for Evaluating, Selecting, and SpecifyingBalances and Standard Masses for Use in Soil, Rock, andConstruction Materials TestingE11 Specification for Wire Cloth and Sieves for TestingPurposesE 145 Specificat
10、ion for Gravity-Convection And Forced-Ventilation Ovens3. Terminology3.1 Definitions:3.2 Refer to Terminology C51 for definitions of termsrelating to lime.3.3 Refer to Terminology D 653 for terms relating to soil.3.4 Definitions of Terms Specific to This Standard:3.4.1 buffer solutiona solution of s
11、pecific pH value usedto calibrate the pH meter.3.4.2 free limelime in a soil-lime mixture that has notdissociated into calcium and hydroxyl ions.3.4.3 hydrated limelime that is predominately calciumhydroxide (Ca(OH)2) or a mixture of calcium hydroxide andmagnesium oxide (MgO) or magnesium hydroxide(
12、Mg(OH)2).3.4.4 limea general term which, for the purpose of thistest method, includes hydrated lime and quicklime.3.4.5 lime contentthe ratio expressed as a percentage ofthe mass of lime to the dry mass of soil.3.4.6 lime stabilizationaddition of lime to a soil in suffi-cient quantities to promote l
13、ong-term pozzolanic reactions thatresult in strength gain and permanent improvement in stability.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.15 on Stabilization andAdmixtures.Current edition approved May 1, 200
14、6. Published June 2006. Originallyapproved in 1998. Last previous edition approved in 1999 as D 6276 99a.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standar
15、ds Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Textural improvement alone, such as reduced plasticity, isoften referred to
16、 as “modification.” Modification can be ef-fected by lime addition rates less than those required forstabilization and may not be permanent.3.4.7 pHthe negative logarithm of the effective hydrogen-ion concentration or hydrogen-ion activity, in gram equivalentsper litre. The pH values range from 0 to
17、 14; where pH 7represents neutrality, pH values less than 7 indicate increasingacidity, and pH values greater than 7 indicate increasingalkalinity.3.4.8 quicklimelime that is predominately calcium oxide(CaO) or calcium oxide in association with magnesium oxide(MgO).3.4.9 stabilizationa process to im
18、prove the engineeringproperties of soils at a site.4. Summary of Test Method4.1 A series of specimens is prepared containing a range ofpercentages of lime content in soil. Measurements of pH aremade on slurries of the specimens to determine the minimumlime content of the soil-lime mixture to obtain
19、a pH of at least12.4.4.2 The pH of at least 12.4 achieved in this test methodresults from free lime remaining in the soil-lime mixture.Normally, the pH of the specific lime being used for soilstabilization should be determined and used as the indicatorpH.5. Significance and Use5.1 The soil-lime pH t
20、est is performed as a test to indicatethe soil-lime proportion needed to maintain the elevated pHnecessary for sustaining the reactions required to stabilize asoil. The test derives from Eades and Grim.35.2 Performance tests are normally conducted in a labora-tory to verify the results of this test
21、method.5.3 This test method will not provide reliable informationrelative to the potential reactivity of a particular soil, nor willit provide information on the magnitude of increased strengthto be realized upon treatment of this soil with the indicatedpercentage of lime.5.4 This test method can be
22、 used to estimate the percentageof lime as hydrated lime or quicklime needed to stabilize soil.5.5 Agricultural lime (crushed limestone) will not stabilizesoil.NOTE 1Notwithstanding the statements on precision and bias con-tained in this test method: The precision of this test method is dependenton
23、the competence of the personnel performing it and the suitability of theequipment and facilities used. Agencies that meet the criteria of PracticeD 3740 are generally considered capable of competent and objectivetesting. Users of this test method are cautioned that compliance withPractice D 3740 doe
24、s not itself ensure reliable testing. Reliable testingdepends on several factors; Practice D 3740 provides a means of evalu-ating some of those factors.6. Apparatus6.1 Balance or Scale:6.1.1 A balance or scale for determining the mass of soiland lime having a minimum capacity of 600 g and meeting th
25、erequirements of Specification D 4753 for a balance or scale of0.01 g readability.6.2 SieveA 425-m (No. 40) sieve, conforming to therequirements of Specification E11.6.3 Plastic BottlesSix 150-mL (or larger) plastic bottleswith tight-fitting screw caps.6.4 A pH MeterA pH meter equipped with referenc
26、eelectrode and low-sodium error glass pH-sensitive electrodes(or combination electrode) and a meter capable of displaying0.01 units pH at 0.2 pH accuracy over a range from 0 to 14.6.5 Drying OvenOven conforming to requirements ofSpecification E 145.6.6 Miscellaneous EquipmentAn airtight, moisture-pr
27、oofcontainer for preserving the moisture content of the soil;mixing tools and scoops for use in preparing test specimens.7. Reagents and Materials7.1 WaterReference to water shall be understood to meanType II reagent water conforming to Specification D 1193.Store the water in a tightly capped contai
28、ner; boil and cool thewater immediately before use.NOTE 2If the pH of the site water to be used is highly acidic (9) test results should be checked against a specimen madeup with site water rather than Type II water.7.2 Buffer SolutionUse a buffer solution having a pH of12, either commercially avail
29、able or prepared in accordancewith Test Methods D 1293.7.3 Hydrated LimeOnly fresh lime meeting the require-ments of Specification C 977 may be used.7.4 QuicklimeOnly fresh lime meeting the requirementsof Specification C 977 may be used.8. Safety Hazards8.1 Quicklime becomes hot when mixed with wate
30、r. Useprotective gloves when handling containers of soil-quicklime-water mixtures.8.2 Hydrated lime and quicklime are strong caustics andmay cause severe irritation of skin, eyes, and mucous mem-branes. Appropriate safety equipment such as heavy rubbergloves, protective eye wear, and a plastic apron
31、 should be wornwhen handling lime. Ensure that adequate ventilation (or arespirator) is provided.9. Technical Hazards9.1 Lime readily absorbs water and carbon dioxide from theair, therefore, store lime in tightly closed containers.9.2 The soil-lime-water mixture is alkaline and will reactwith metal
32、and glass; therefore, use plastic bottles and beakers.10. Specimens10.1 Prepare a representative sample of air-dried soil inaccordance with Practice D 421. Soil may be oven-dried at atemperature # 60C.10.2 Pass 350 g of material through the 425-m (No. 40)sieve.10.3 Thoroughly mix the material passin
33、g the 425-m (No.40) sieve.3Eades, J.L., and Grim, R.E.,AQuick Test to Determine Lime Requirements forLime Stabilization,Highway Research Record No. 3, 1996, National Academy ofSciences, National Research Council, Highway Research Board, Washington, DC.D 6276 99a (2006)210.4 Determine the water conte
34、nt, in accordance with TestMethod D 2216, of a representative specimen of the materialobtained in 10.3. Place the remaining material obtained in 10.3in an airtight container to preserve the moisture content untilthe procedure described in Section 12 is performed.11. Calibration and Standardization11
35、.1 Calibrate the pH meter in accordance with the manu-facturers instructions using a pH 12 buffer solution at 25 61C. The calcium hydroxide reference buffer solution de-scribed in 11.1.2 of Test Methods D 1293 may also be used asa calibration standard.12. Procedure12.1 Specimen Preparation:12.1.1 Us
36、ing the air-dried sample in accordance with Sec-tion 10, obtain five specimens, each equivalent to 25.0 g ofoven-dried soil. Splitting or other appropriate means should beused to obtain each of the five specimens.12.1.2 Determine the mass of each air-dried soil specimenequivalent to 25.0 g of oven-d
37、ry soil as follows:Ma5 25 3 1.0 1 W/100! (1)where:Ma= mass of air-dried soil specimen, andW = water content, %, of air-dried sample determined in10.4.12.1.3 Place each specimen into dry plastic bottles and captightly.12.1.4 Obtain six representative specimens of lime meetingthe requirements of Speci
38、fication C 977. Five specimens arerepresentative of 2, 3, 4, 5, and6%oftheequivalent 25-goven-dried soil mass. The sixth specimen of 2.0 g of limerepresents a saturated lime solution. Place the 2.0 g of lime intoa dry plastic bottle and cap tightly.NOTE 3The range of lime percentages for soil-lime m
39、ixtures may beadjusted to meet the requirements of Section 13.NOTE 4The appendix of Specification C 977 notes that if quicklime isused, rapidly crush to pass a 3.35-mm (No. 6) sieve.12.1.5 Add one of the first five lime specimens to one of thesoil specimens in plastic bottles, cap tightly, mark the
40、percent-age on the bottle, and mix thoroughly by shaking. Repeat thisprocedure for the remaining four lime and soil specimens.12.1.6 Add 100 mL of water to each of the soil-limemixtures and to the bottle containing 2.0 g lime.12.1.7 Cap the bottles and shake each of the soil-lime-waterand lime-water
41、 mixtures for a minimum of 30 s or until thespecimens are thoroughly mixed. Continue to shake the speci-mens for 30 s every 10 min for 1 h.12.2 If necessary, heat or cool the specimen as needed tobring the temperature of the specimen to 25 6 1C.12.3 Within 15 min of the end of the 1-h shaking period
42、,determine the pH of each soil-lime-water and the lime-watermixture of 0.01 pH units. Maintain the temperature of themixture at 25 6 1C when determining pH.12.4 Record the pH value for each soil-lime-water mixtureand for the lime-water mixture.13. Soil-Lime Proportion and pH Relationship13.1 The low
43、est percentage of lime in soil that gives a pH of12.4 is the approximate lime percentage for stabilizing the soil.There may be some soils in which the pH is greater than 12.4.If this occurs, select the lowest percentage of lime where thehigher pH value does not rise for at least two successive tests
44、amples at increasing lime percentages.13.2 If the highest measured pH is 12.3 or less, thenadditional test samples using higher percentages of lime shouldbe prepared and tested.NOTE 5There may be some soils where the pH of the soil-limemixture will not go above 12.3. This phenomenon is thought to oc
45、cur withsoil (that is, clays) that are holding univalent ions such as sodium inexchange positions. As these ions are exchanged with calcium ions fromlime, the pH electrode becomes sensitive to the sodium ions as well as thehydrogen ions.13.3 If the highest measured pH is 12.3 and at least twosuccess
46、ive specimens at increasing lime percentages yieldvalues of 12.3, the lowest percentage of lime to give a pH of12.3 is the approximate optimum lime percentage for stabiliz-ing the soil.13.4 If the highest measured pH is less than 12.3, the test isinvalid due to equipment or material error or due to
47、insufficientlime having been added. Check the pH electrode in the pH 12buffer solution and the lime-water solution for possible equip-ment error or repeat the test using higher percentages of lime,or both.14. Calculation14.1 Convert percentage of lime as hydrated limeCa(OH)2 to percentage of lime as
48、 quicklime (CaO) asfollows:LQ5 LH3 56/74 (2)where:LQ= percentage of quicklime, %,LH= percentage of hydrated lime, %,56 = molecular weight CaO, and74 = molecular weight Ca(OH)2.14.2 Convert percentage of lime as quicklime (CaO) topercentage of lime as hydrated lime Ca(OH)2 as follows:LH5 LQ3 74/56 (3
49、)where:LH= percentage of hydrated lime, %,LQ= percentage of quicklime, %,74 = molecular weight Ca(OH)2, and56 = molecular weight CaO.15. Report15.1 Report the following information:15.1.1 The estimated lime percentage required for stabiliza-tion to the nearest 1 % and the lime percentage and measuredpH of each of the soil-lime-water mixtures tested.15.1.2 The type of lime used to determine the estimatedlime content for soil stabilization.D 6276 99a (2006)316. Precision and Bias16.1 PrecisionThe precision of this test method is beingdetermined
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