Engineering Properties of Manganese-Treated Asphalt Mixtures

Transcription

1 56 Transportation Researh Reord 134 Engineering Properties of Manganese-Treated Asphalt Mixtures THOMAS W. KENNEDY and JON EPPS ABSTRACT An experimental program as onduted to evaluate the engineering properties and moisture suseptibility harateristis of manganese-treated asphalt mixtures over a range of temperatures. The experimental program involved three aggregates, to asphalt soures, three grades of asphalt ement, three levels of manganese treatment, and to air void ontents. Tests ere onduted at 32 F, 75 F, 14 F, and 14 F. The mixtures ere ured 28 days at 14 F; hoever, resilient moduli ere measured at various times during the 28-day uring period. Test methods ere the stati and repeated-load indiret tensile test, Marshall stability test, and Hveem stability test. Properties evaluated ere tensile strength, resilient modulus of elastiity, Marshall stability and flo, and Hveem stability. n addition, the ratios of dry and et tensile strengths and moduli ere evaluated ith respet to moisture suseptibility. On the basis of the results and onditions of this test program, it appears that the temperature suseptibility of the treated asphalt ement as redued. Thus softer grades of asphalt ement treated ith the manganese additive produed a mixture ith less stiffness and strength at 32 F, higher strengths and stiffnesses at l4 F, and higher stabilities at 14 F ompared to the untreated ontrol mixtures ontaining a more visous grade of asphalt ement. This should redue the tendeny for raking at lo temperatures and improve or maintain stability at higher temperatures. Stiffness inreased ith time during the uring period but appeared to be approahing a onstant value after 28 days. An analysis of tensile strength or resilient modulus indiated no signifiant improvement in moisture or stripping resistane. Chemkrete Tehnologies, n., produes an additive (CT 11), an oil-based soap ontaining soluble manganese, that hen mixed ith asphalt ement and alloed to ure in thin films in the presene of oxygen modifies the asphalt ausing inreased visosity and in some ases redued temperature suseptibility as indiated by a flatter temperature-visosity relationship. This suggests that, by using softer asphalts treated ith the additive, adequate stabilities may be ahieved at higher temperatures and more flexible and less brittle mixtures an be obtained at loer temperatures. Greater flexibility at the loer temperatures may inrease resistane to refletion raking and fatigue raking in thinner pavement setions. t is also possible that inreased visosity ould improve resistane to stripping or moisture damage. The study summarized in this paper as part of a researh program that as onduted at the University of Texas at Austin and the University of Nevada-Reno in order to evaluate and define needed improvements of the produt. Before August 1982 a similar produt had been used in field trials that often involved asphalts treated at high levels. Th tiff =:!t!e te=tet!ee! produed mixtures ith high stabilities but also mixtures that tended to be brittle. Beginning in August 1982, at the time the tehnology as aquired by the Lubrizol Company, hanges ere made in the additive and softer asphalts, treated at loer dosage levels, have been used. To date, minimal raking, exept for refletion raking, has been reported (see paper by Moulthrop and Higgins in this Reord). The objetive of the study as to evaluate the engineering properties and stripping or moisture suseptibility harater is tis of manganese-treated asphalt mixtures and the effet of treatment levels using different types and grades of asphalt. The 'test results and a detailed analysis are available elsehere (1,2). Other portions of the total researh program ere onduted at Pennsylvania State University, the Western Researh nstitute, and the University of Waterloo in Canada. TEST PROGRAM The test program onsisted of three aggregates, to asphalt soures, three grades of asphalt ement, three levels of treatment, and to air void ontents. Mixtures ere evaluated over a range of temperatures and in both the dry and et ondition. Aggregates The aggregates are identified as Eagle Lake, Watsonville, and Helms. The Eagle Lake as a siliious river gravel and sand from Texas. Previous use and eva.luation or tnis aggregate inaiatei that it is highly moisture suseptible. The Watsonville as a rushed granite from California and the Helms as a partly rushed river gravel and sand from Nevada. All three aggregates ere dense graded <!.,. >. Asphalt Cements To asphalt soures (Cosden Big Spring and Shell Wood River) ere used. Three grades of asphalt e-

2 Kennedy and Epps 57 ment ere obtained from these soures. The asphalts ere treated ith 4, 6.25, and 1 perent of the manganese additive, hih orresponds to.8,.125, and.2 perent manganese, respetively. For the Eagle Lake mixtures all three manganese ontents ere used. Untreated asphalts ere used as ontrols for omparison purposes. The asphalts for the Watsonville and Helms mixtures ontained.125 perent manganese. Both the treated and the untreated asphalt ements ere supplied by the manufaturer. The basi ombinations are given in Table l. TABLE l Perentage Manganese-Cosden Big Spring and Shell Wood River Cosden Big Spring Shell Wood River O" o AC-3 x x x x AC-5 x x x x x x x x AC-2 x x x x x x x x 8 Untreated asphalt ement (ontrol). Mixture Design The Texas gyratory mixture design method as used to establish the optimum asphalt ontrol for the Eagle Lake aggregate mixtures (1,) The SO-blo Marshall design proedure as used for the Watsonville and Helms mixtures (4). All mixture designs ere based on the use of the-untreated Cosden AC-2. The resulting asphalt ontents ere 4.6, 6.3, and 7.5 perent by eight of the dry aggregate for the Eagle Lake, Watsonville, and Helms mixtures, respetively. These values ere used for all mixtures and defined the binder ontent (asphalt ement plus additive). Thus, in the speimens ontaining treated asphalts, 4, 6.25, or 1 perent of the asphalt ement, depending on manganese ontent, as replaed ith the additive. Sample Preparation Different proedures ere used to prepare and ompat the various asphalt-aggregate mixtures. Eagle Lake Mixtures The aggregates and asphalt ement ere preheated to 275 F before mixing. The asphalt ement and aggregate ere mixed at 275 F for approximately 3 min in a Hobart mixer and ere ompated at 25 F using the Texas Gyratory Shear Compator (1,). All samples ere nominally 2 in. high and 4 in. in diameter. To ompation proedures ere used to obtain approximately 3 and 7 perent air voids: the standard proedure speified by the Texas Department of Highays and Publi Transportation, hih normally ould produe about 3 perent air voids in the design mixture ontaining the untreated AC-2, and a modified proedure ith redued ompative effort, hih produed 7 perent air voids in the untreated AC-2 mixture. No orretion to ompation proedure as made for mixtures ontaining either treated or lees visous grades of asphalt ement. Thus the samples ontaining less visous asphalts probably had slightly loer air void ontents. Watsonville and Helms Mixtures The aggregates and asphalt ements ere mixed at 3 F and ompated at 28 F based on an analysis of the temperature-visosity relationship for the Cosden AC-2. The to ompation proedures involved a Marshall ompation hammer using a variable number of blos. The standard 5 blos per side produed approximately 4 perent air voids for both aggregates. Tenty-five and 2 blos per side ere used ith the Watsonville and the Helms mixtures, respetively, to produe approximately 8 perent air voids. Curing and Conditioning After ompation all samples ere oven ured at 14 F for 28 days. Air as irulated in the oven throghout the uring period. After 28 days the samples to be tested dry ere alloed to ool to room temperature and ere then plaed in hambers at the appropriate testing temperature for a period of 24 hr. Speimens to be tested et ere onditioned by vauum saturating the speimens for 3 min using a vauum equal to 26 in. of merury and then soaking for an additional 3 min at room temperature. The speimens ere then subjeted to one freeze-tha yle onsisting of 15 hr in ater at 1 F and 24 hr (dry) at 14 F and subsequently soaked for 2 hr at 75 F before testing. Testing Speimens ere tested using the stati and repeatedload indiret tensile tests (5), the Marshall stability test (ASTM D 1559), and the Hveem stability test (3). Properties measured ere tensile strength, resilient modulus, Marshall stability and flo, and Hveem stability, Test Program Design The experimental program onsisted of full fatorial designs ith 2 or 3 repliate speimens per ell or test ondition. All asphalts and treatment levels ere oded and all tests ere onduted blind. Subsequently the various ombinations ere identified and the final analysis of the results as onduted. DSCUSSON OF RESULTS The primary objetives of this study ere to (a) evaluate the engineering properties of asphalt mixtures ontaining manganese additive and (b) determine the effet of treatment levels over a range of temperatures for mixtures ontaining approximately 3 and 7 perent air voids. Typial results are shon in the figures and are disussed next. A detailed analysis of all the data and a summary of test values are available elsehere (.!,, ). Tensile Strength Tensile strengths ere analyzed to determine the effet of temperature and manganese or additive ontent. effet of Temperature Typial relationships beteen tensile strength and temperature for modified ompated speimens (7 per-

3 58 Transportation Researh Reord 134 ent air voids) are shon in Figures l-4. t is evident that the tensile strength dereased ith inreased temperature and that the slope of these relationships varied. Although a diret omparison is not provided, the strengths of the modified ompated speimens ere signifiantly less than the strengths of the standard ompated speimens (3 perent air voids). n most ases there as a rossover beteen the treated and untreated (ontrol) asphalt mixtures. Thus the strength of the mixtures ontaining the treated asphalt often as less than the strength of the untreated asphalt ement at 32 F hile the reverse as true at l4 F. Effet of Manganese Content The relationships beteen tensile strength and mangane se ontent for the standard and modified omp ated Eagle Lake mixtures ontaining Shell and Cosden asphalts are shon in Figure 5. t should be noted that the additive ontent also inreased ith inreased manganese ontent. At higher temperatures there appeared to be a manganese or additive ontent for maximum tensile strength. The optimum is ell defined at 75 F. At l4 F the trend is not as evident. At 32 F, hoever, the relationships are varied, hih suggests the possibility that strength dereased ith inreased manganese or additive ontent. Similar behavior also ourred for the modified ompated speimens (7 perent air voids), although the trends ere not as pronouned exept at 32 F, at hih temperature strength dereased ith inreased manganese ontent. Resilient Modulus Resilient moduli ere analyzed ith respet to testing temperature, manganese or additive ontent, and uring time. Effet of Temperature Typial relationships beteen resilient modulus of elastiity and temperature for the modified ompated Eagle Lake mixtures ith manganese ontents of.8 and.125 perent are shon in Figures 6 and 7. As did tensile strength, the resilient modulus dereased ith inreased temperature and the slope of these relationships varied and there as a rossover beteen the treated and untreated (ontrol) asphalt mixtures. Thus the resilient modulus or stiffness of the mixtures ontaining the treated asphalt ements often as less than that of the untreated asphalt ements at 32 F and greater at 14 F. n addition, the resil i ent moduli of the modified ompated speimens ere signifiantly less than the moduli of the standard ompated speimens (3 perent air voids). Effet of Manganese Content The relationships beteen resilient modulus and manganese or additive ontent for Eagle Lake mixtures ontaining Shell and Cosden asphalts are shon in Figure 8. A manganese or additive ontent for maximum stiffness ourred at about.125 perent manganese 5 Modified Compation Shell Wood River Asphalt -.8% Manganese AC-5 AC-2 ll Q. Test Temperature, F F1GURE 1 Relatiomhips beteen tensile strength and test temperature for Eagle Lake mixtures ith untreated and treated (.8% Mn) Shell asphalts.

4 59 5 Modified Compation Shell Wood River Asphalt-.125% Manganese --+- AC-5 AC- 2 4 f/ Q Cl>. -(/) Cl> f/ Cl> t Test Temperature, F F1GURE 2 Relationships beteen tensile strength and test temperature for Eagle Lake mixtures ith untreated and treated (.125% Mn) Shell asphalts. 5 4 Modified Compation Cosden Asphalt -.8% Mango nese AC AC-5 AC ,._- "" ro '--.._. -, -::--. '. "-...,,.. _, '..oa_ _ -8o/,.._ Oo/, ,, =:_ :::::_.!._ ::: ':':" --- Test Temperature, F F1GURE 3 Relationships beteen tensile strength and test temperature for Eagle Lake mixtures ith untreated and treated (.8% Mn) Cosden asphalts. 11

5 6 5 4 Modified Compation Cosden Asphalt-125% Manganese AC AC-5 AC-2..,.. (/) so Ttst Temperature, F FGURE 4 Relatiomhipe beteen teruile mength and teat temperature for Eagle Lake mixture ith lllltreated and treated (.125% Mn) Co.den uphalta. Shell Wood River Aephalt Standard Campatlon - Ory AC AC :! - AC-2 Coeden A1phalt 5 Shell Wood River A1phall Modif ied Compation -Dry. AC AC 5 - AC-2 Co eden Aspha t 4 : i f 2'5 u; 1 o Man9ane11, perent ;; 3 2:5 Ui.! r l ; / /.-."' 1. f.-::- --- o --- 1r f Man9oneee, perent FGURE 5 Relatioruihipt beteen teruile strength and mangane&e ontent for Eagle Lake mixtures.

6 61 Modified Compation- Dry Shell Wood River Asphalt -.8% Manganese U a AC AC-2 Modified Compation - Dry Shell Woad River Asphalt -.125% Manganese AC AC-2 a ll'. >. -U) U :> 'C.!!! G> er ll'. -U) iii - U) :> :; 'C ::!: -.'!! "' G> a:: J.O.1.., _, _. _., Test Temperature, F '-----'------' ioo 12 Test Temperature, F FGURE 6 Relationships beteen resilient modulus and test temperature for Eagle Lake mixtures ith untreated and treated Shell asphalts. 4.C - 3. a. O Q ll'. >. - "' Modified Compation - Dry Cosden Aspha t -. 8 % Manganese AC AC-5 AC- 2 a. CQ Modified Compation - Dry Cosden Asphalt % Manganese AC AC AC-2 - U) :> 'C ::!: - G> G> er Test Temperature, "F.1.. '., Test Temperature, F FGURE 7 Relationships beteen resilient modulus and test temperature for Eagle Lake mixtures ith untreated and treated Cosden asphalts.

7 62 Transportation Researh Reord Standard Compation - Ory AC AC 5 - AC- 2 Shell Wood River Asphalt Cosden Asphalt Modif ied Compation - Ory ---r-- AC-3 _,,. AC AC Shel Wood River Asphalt Cosden Asphalt 3. -./ 32 F{ 't::.> 'Q 2. ' y { { />----::::.:i ;; 75 F / '- 75 F / /t.- ; : -.,.,.,,,, ". /.8 /.7.6 -; 'O.5 :!.4 :.3 Q:.2 /--. f "'.- r -"' 14 F / /! i. -; " 'O :! 'E - Q: " ,3.1. _., _, Mon;onese, perent ' Mongon oso, pe rent FGURE 8 Relationehips beteen resilient modulus and manganese ontent for Eagle Lake mixtures ith Shell and Cosden asphalts. for test temperatures of 75 F and 14 F. At 32 F the relationships ere not as onsistent and errati behavior indiated that the effet of manganese as qui te small. Unlike tensile strength, there as no indiation that stiffness dereased ith inreased manganese ontent. Effet of Curing Time The relationships beteen resilient modulus and time for the Watsonville and Helms mixtures made ith AC-2 untreated and treated asphalts are shon in Figure 9. At 77 F the treated mixtures initially had loer resilient moduli (stiffness) than the untreated mixtures. After uring, hoever, the stiffness of the treated mixtures exeeded the stiffness of the untreated mixtures. n addition, it appears that, although the stiffness of both mixtures ontinues to inrease after 28 days, the rate of inrease is relatively small. Treated samples ith higher void ontents exhibited a higher rate of stiffness inrease. For Watsonville aggregate mixtures, the rossover beteen treated and untreated asphalt ourred after about 5 to 8 days of uring hereas for the Helms mixtures, -'- 1 - '- '-- -.!, ""' _,_ !:1-.tt- WU.&.Vll uau alua.luqillc:.j:f "' C:&.YC:lli UV&.C vv o, ""'uo rossover ourred after about 3 days (Figure 1) Figure 11 shos a typial relationship beteen mixtures ontaining AC-2 untreated asphalt and AC-5 treated asphalt. The mixtures ontaining the treated AC-5 asphalt had loer initial resilient modulus as measured at 77 F. Within 28 days the resilient modulus of the mixture ontaining the treated AC-5 asphalt approahed or exeeded the modulus value of mixtures ontaining the untreated AC-2 asphalt ement. 1 a.o.126' ,, 'i 7. a ll. 3. :!::. iii 2. Marshall Compation.i Teat Temperature 77 F 'Cl " 1. :: o.a.6 Cosden Big Spring AC-2 :!.7 Weteonvllle Aggregate 'i.6 a:.6 Shall Wood River AC-2 Helms Aggregate Curing Time, daye FG URE 9 Relationships beteen resilient modulus and uring time for mixtures ith untreated and treated asphalts. Marshall Stability and Flo Relationships beteen Marshall properties at 14 F and manganese ontent for standard ompated Eagle Lake mixtures are shon in Figure 12. Marshall stabilities inreased ith inreased manganese or additive ontent ith many of the relationships for the

8 Kennedy and Epps 63. a.., ri UJ g "' iii. 2. "' -; ",, :! :! a: Marshall Compation Test Temperature 77 F 15 Curing Time, days Cosden Asphalt AC-5 Watsonville Aggregate Cosden Big Spring AC-5 Helms Aggregate FGURE 1 Relationships beteen resilient modulus and uring time for treated asphalt mixture ith 4 and 8 perent air. 1 - / 9. / / B.O / 7. / 'iii 6. / a. /., 5.. e" -()'!,/ ri 4. UJ r"'-a.,,./ 3.!' "' " /,f " i iii 2..ii O' "' /J' Marshall Compation Test,, -;! Helms Aggregate 1. :.9 Temperature = 77 F 1!, O.B " Cosden Big Spring AC-5 and AC-2 :!.7 - i 'iii a:.6 ;.5 j.4 i J Curing Time, Daye FGURE 11 Relationships beteen resilient modulus and uring time for Hehn mixtures ith treated AC-5 and untreated AC-2 Cosden asphalts. standard ompated mixtures indiating a manganese ontent for maximum stability. Stabilities ere substantially greater for the standard ompated speimens. t is also evident that the stability of mixtures ith. 8 perent manganese as greater than that of the ontrol (no manganese) asphalt mixtures ontaining the next grade of asphalt. For the Cosden asphalts,.125 perent manganese as required for the AC-3 to ahieve a stability greater than the stability of the ontrol AC-2 mixture. u: ::;; : 3 Ui 2 ::;; 1 Standard Compation -- - AC AC-5 - AC-2 Shell Wood River Asphalt Cosden Asphalt ---- o ,,,, ---.1,2!'., ": -. / 1 {/ o Manganese, perent FGURE 12 Relationships beteen Marshall properties and manganese ontent for standard ompated Eagle Lake mixtures ith Shell and Cosden asphalts. Flo values did not exhibit onsistent relationships although flo values may have inreased slightly ith inreased manganese ontents. Nevertheless, the differene for the various mixtures as small. n addition, there ere essentially no differenes beteen the standard and the modified ompated mixtures. Hveem Stability Relationships beteen Hveem stability and manganese or additive ontent for standard ompated Eagle Lake mixtures are shon in Figure 13. There ere no onsistent relationships. For the modified ompated mixtures, stability inreased ith inreased manganese or additive ontent. t should also be noted, hoever, that the stabilities of the treated asphalt ement mixtures generally ere equal to or greater than the stability of the ontrol ith no manganese. For the Cosden asphalts, the AC-2 (ontrol) had higher stabilities than the mixtures ith treated AC-3 asphalt. The small effets produed by the additive probably are not unexpeted beause the Hveem stabilities, unlike the Marshall stabilities, are relatively insensitive to the binder. Moisture Suseptibility The tensile strength ratios and the resilient modulus ratios for Eagle Lake mixtures ith various manganese ontents indiated a substantial loss in strength and modulus. Only about 15 to 25 perent of the dry tensile strength and 1 perent of the dry resilient modulus ere retained and ere essentially

9 64 Transportation Researh Reord Shell Wood River Asphalt Standard Compation ----a---- AC AC-5 - AC-2 Cosden Asphalt equal at all levels of manganese, n addition, there ere no apparent benefits relative to the absolute values of strength and modulus. This suggests that the treatment did not improve the moisture suseptibility of these mixtures. Similar results are shon for the Watsonville and Helms mixtures (Figures 14 and 15). The ratios for the Watsonville mixture, although not aeptable, ere greater for the treated asphalt (Figure 15) Thus, on the basis of these test results, it must be onluded that the use of manganese-treated asphalts did not improve moisture resistane to an aeptable level as measured by the indiret tensile test. Previous testing using the Texas boiling test had shon substantial improvementi the benefits measured by the Texas pedestal test ere questionable (). 1 CONCLUSONS The folloing onlusions are based on the findings of this study and the onditions evaluated..1,2.1 Manganese, perent FGURE 13 Relatiomhips beteen Hveem stability and manganese ontent for standard ompated Eagle Lake mixtures ith Shell and Cosden asphalts..2 Tensile Strength 1. The tensile strengths of the treated mixtures dereased inreased testing temperature. the untreated and signifiantly ith t 1 BO. 6 a: = go 4 Ui.!! 2 Modified Compation - 75 F Test Temperature Helm Aggregate Minimum Aeptane Level Cosden Asphalt Shell Wood River Asphalt AC-5 AC-2 AC-5 AC Manganese, perent FGURE 14 Tensile strength ratios for Helm mixtures ith untreated and treated Shell and Cosden asphalts. 1 BO 6 Modified Compation - 75 F Test Temperature Watsonville Aggregate Cosden Asphalt Shell bod River Aspha t AC-2 AC-5 AC-2 AC-5 Minimum Aeptane Level Manganese, perent FGURE 15 Tensile strength ratios for Watsonville mixtures ith Dltreated and treated Shell and Cosden asphalts.

10 Kennedy and Epps Tensile strengths of treated asphalt mixtures at all temperatures generally ere greater than tensile strengths of untreated asphalt mixtures ontaining the same asphalt type and grade. 3. The effet of temperature on the tensile strengths of treated asphalt mixtures as less than on untreated mixtures (i.e., the slope of the temperature-tensile strength relationship as flatter). 4. Tensile strengths of the treated asphalt mix-. tures ere less at 32 F and greater at 14 F than the tensile strength of the untreated ontrol mixtures that ontained the same type but a higher visosity grade of asphalt. 5. The rossover in strength generally ourred at about 8 F to 9 F. 6. An optimum manganese ontent for maximum tensile strengt h at 75 F and 14 F ourred for both asphalts and void ontents although the optimum as more pronouned for the lo void ontent speimens (standard ompated). Resilient Modul us of Elastiity 1. The resilient moduli of the untreated and the treated mixtures dereased signifiantly ith inreased testing temperature. 2. Resilient moduli of treated asphalt mixtures at all temperatures generally ere greater than moduli of untreated asphalt mixtures ontaining the same asphalt type and grade. 3. The effet of temperature on the resilient moduli of treated asphalt mixtures as less than the effet on that of untreated mixtures. 4. Resilient moduli of the treated asphalt mixtures ere less at 32 F and greater at 14 F than the moduli of the untreated ontrol mixtures that ontained the same type but a higher visosity grade of asphalt. 5. The rossover in moduli generally ourred at about 8 F to 9 F for the Shell Wood River asphalt mixtures but as not as onsistent for the Cosden asphalt mixtures. 6. An optimum manganese ontent for maximum resilient modulus ourred for a fe mixtures at the higher testing tempera tu res 1 hoever, there as no onsistent relationship at 32 F. 7. The resilient moduli of the treated mixtures initially ere loer than those of the untreated mixtures, presumably beause of the inreased amount of additive1 hoever, after uring, the stiffness of the treated mixtures exeeded the stiffness of the untreated mixtures. 8. The resilient moduli of the higher void ontent mixtures inreased more rapidly than did the moduli of the mixtures ith lo voids. Marshall Stability and Flo 1. An optimum manganese or additive ontent for maximum stability ourred for the standard ompated (lo void) mixtures. 2. Stabilities inreased ith inreased manganese ontent for the modified ompated (high void) mixtures. 3. The treated mixtures had higher stabilities than the untreated ontrol mixtures ontaining the same type but a higher visosity grade asphalt. 4. There as no signifiant relationship beteen manganese ontent and flo value although for the modified ompated (high void) mixtures the flo values inreased slightly. Hveem Stability Tnere as no signifiant effet of manganese ontent on Hveem stability. Moisture Suseptibil ity There as no improvement in moisture or stripping resistane of mixtures produed using treated asphalts. All moisture-onditioned Eagle Lake mixtures, both treated and untreated, retained only about 15 to 25 perent of the dry tensile strength and only about 1 perent of the dry resilient modulus. Similar results ourred for the Watsonville and Helms mixtures, although the Watsonville mixtures ith the additive did sho a substantial improvement. Summary On the basis of the results and onditions of this test program, it appears that the temperature suseptibility of the treated asphalt ement is redued. Thus use of the manganese additive ith softer grades of asphalt ement ill produe a mixture ith less stiffness and strength at 32 F, higher strengths and stiffnesses at 14 F, and higher stabilities at 14 F ompared to the untreated ontrol mixtures ontaining a more visous grade of asphalt ement. This should redue the tendeny for raking at lo temperatures and improve or maintain stability at higher temperatures. Additional ork is required to determine the signifiane of the observed behavior in terms of pavement performane. This should involve theoretial estimates of performane as ell as additional field trials. An analysis of tensile strength and resilient modulus indiated that there as no signifiant improvement in moisture or stripping resistane as measured by the retained strength or modulus or the absolute values of et strength and modulus. Hoever, previous evaluations on other mixtures using the boiling test have shon signifiant improvements. Additional ork ill be required to asertain the effet of manganese-treated asphalts on the moisture suseptibility of mixtures. REFERENCES l. T.W. Kennedy and J.N. Anagnos. Engineering Properties and Moisture Suseptibility of Manganese Treated Asphalt Mixtures Researh Report CT-1. Center for Transportation Researh, Bureau of Engineering Researh, The University of Texas at Austin, July Eihhorn, Y.K. Tung, J. Andreae, and J. Epps. Charaterization of Chemkrete Treated Asphalt Mixtures. Department of Civil Engineering, University of Nevada-Reno, June Manual of Testing Proedures, Bituminous Setion, 2-F Series. Texas State Department of Highays and Publi Transportation, Austin, Mix Design Methods for Asphalt Conrete. Manual Series 2. The Asphalt nstitute, College Park, Md., Marh T.. Kennedy and J. N. Anagnos. Proedures for the Stati and Repeated-Load ndiret Tensile Tests. Researh Report Center for Transportation Researh, The university of Texas at Austin, Aug T.W. Kennedy and J.N. Anagnos. Evaluation of the Moisture Suseptibility of Asphalt Mixtures Containing Manganese Treated Asphalt. Researh Report CT-2. Center for Tr anspor ta tion Researh, Bureau of Engineering Researh, The University of Texas at Austin, Sept Publiation of this paper sponsored by Committee on Charateristis of Bituminous Paving Mixtures to Meet Strutural Requirements.