US 3162101 A
Description (OCR text may contain errors)
1954 F. s. ROSTLER 3,162,101
METHODS FOR IMPROVEMENT OF ASPHALTS AND OIL EMULSIONS USEFUL THEREIN Filed April 19, 1963 5 Sheets-Shet 1 l 3 11 0 l O A 3 O U I O O 3 w (col-41.2w .la-nad) s50; NOISVHQV asvazmv INVENTOR. 1 2/12, 6. ROST'LER pg 44M- ATTORNEY.
1964 F. s. ROSTLER 3,162,
METHODS FOR IMPROVEMENT OF ASPHALTS AND on EMULSIONS USEFUL THEREIN Filed April 19, 1963 5 Sheets-Sheet 2 FQ/TZ .5. 12051152 ATTORN EV Dec. 22, 1964 F. s. ROSTLER 3,162,101
METHODS FOR IMPROVEMENT OF ASPHALTS AND OIL EMULSIONS USEFUL THEREIN Filed April 19, 1963 5 Sheets-Sheet 3 9 l4 ABRASION Loss AFTER 5ooHQs.WE.ATHE|z|NG-GMs LOSS/(O00 6MS.$HOT
(ouvzl) INVENTOR. 572/72 5. ROSTLEQ ATTORNEY.
Dec. 22, 1964 Filed April 19, 1965 70 L055 PELLET TEST (cuRvE'D ONLY) EMULSIONS USEFUL THEREIN 5 Sheets-Sheet 4 SAM PLES 3o Go 3 4 5 6 7 89m ABRASION Loss AFTER 50o HRS. WEATHERIHG GMS.L.OSS/IOQO GMS. SHOT 00000 O o am wm v m a nvr-ldsv IVHIQIUO NI SNlzL-JVBVd /o JNVENTOR.
1'2/ T2 5. Ros 1151? ATTORNEY Dec. 22, 1964 s, os 3,162,101
METHODS FOR IMPROVEMENT OF ASPHALTS AND OIL EMULSIONS USEFUL. THEREIN Filed April 19, 1963 5 Sheets-Sheet 5 a a N ES to CURVE DEFO MAT 0 INCH x A 48 PEN. ASPHALT WEATHERED l4-DAV5 4s PEN. ASPHALT UNWEATHERED jk/TZ S- HOS /-52 INVENTOR. EMUlION AND WEATHEQED l4 DAVS 2200-300 PEN. ASPHALT UNWEATHEIZED BY 48 PEN. ASPHALT TREATED WITH MALTENES IN KEROSENE. AND WEATHERED l4 DAYS.
C. 46 PEN.ASPHALT TREATED WITH MALTENES United States Patent 3,162,101 METHODS FER Eli/L E RUVEMENT SF ASPHALTS AND Gill. EMULSIGNS USEFUL THEREEN Fritz S. Rustler, Bakersfield, Calif assignor, by means assignments, to Witco Chemical Company, l'no, New
York, N.Y., a corporation of Delaware Filed Apr. 19, 1963, Ser. No. 274,193 47 Claims. (Cl. 94-23) This invention relates to methods for improving the durability of asphalts, both weathered and unweathered, by adjusting the components of the asphalt other than the asphaltenes content, to provide a favorable balance of the concentrations of these several components other than asphaltenes, and to improve the bonding power of the asphalt and the abrasion resistance of asphaltic compositions formed of asphalt and mineral aggregates, for example, sand and rock.
This invention is a result of extensive and continuing research into the chemical constitution of asphalts and into the chemistry of the weathering process of asphaltic pavements and other asphaltic compositions.
This application is a continuation-in-part of application 254,399, filed January 28, 1963, now abandoned and i of application Serial No. 45,023, filed July 25, 1960, now abandoned, which in turn is a continuation in part of application 497,397, filed March 28, 1955, now abandoned.
Asphalts are generally understood to comprise nondistillable and high-boiling residues of petroleum fractions, consisting of asphaltenes, that is, components which are insoluble in n-pentane and of maltenes, i.e., fractions soluble in n-pentane.
Asphalts also include natural asphalts found as such, as deposits in the earth or produced from petroleum crude oils by distillation, or from cracked petroleum fractions. Asphalts are also produced by blending such residues with liquid petroleum oil fractions and also by blending such peroleum oil fractions with residues precipitatfid from the above asphalts by solvents, such as liquid propane.
Asphalts come in various grades, classified according to their penetration values, as is well known in the asphalt art. Paving grade asphalts are understood to include those asphalts usually produced by reduction of petroleum fractions, by steam distillation or vacuum distillation, or blending oils with natural, precipitated or reduced asphalts from petroleum oils, which have a penetration value of 32 or more, for example 200-300 (5", 100 gms.) [Test T49-49, American Association of State Highway Officials].
I Other grades include roofing asphalts and other well recognized grades ofasphalts derived from petroleum or from similar natural deposits.
The pentane soluble components, i.e., maltenes, have been identified and named as follows: The nitrogen bases, symbolized by the letter N; the Group I unsaturates, called first acidaflins, identified by the symbol A the Group II unsaturates, also known as second acidaffins, identified by the symbol A and the saturated fraction, also known as the parafiins fraction, identified by the letter P. The asphaltenes are identified by the letter A.
The method of analysis by which each one of these groups may be determined is described in Compounding Rubber with Petroleum Products, by Rostler and Sternberg, published in Industrial and Engineering Chemistry, vol. 41, at pages 598-608, of March, 1949. The method has been further described in Composition and Changes in Composition of Highway Asphalts, 85-100 Penetration Grade, published in proceedings of Association of Asphalt Paving Technologists, vol. 31, January 1962, at pages 72-79. This method of analysis and the terminology have been adopted in governmental specificasity of Akron, Ohio, in the article entitled, Oil Types in the Program for Oil Extended Rubbers, by Taft, et al., Industrial and Engineering Chemistry, 1955, vol. 47, pages 1077-1090. The method has further been adopted as an A.S.T.M. Procedure under the designation D- 2006-;62T.
The discussion of the method is also described in the article entitled, Influence of Chemical Composition of Asphalts on Performance and Particularly Durability, by Rostler and White, in the American Society for Testing Materials Special Publication No. 277, at pages 64-88.
This method identifies the components of asphalts and petroleum fractions having an initial boiling point not lower than C., at 10 mm. Hg absolute pressure, previously described: asphaltenes, nitrogen bases, first acidafiins, second acidaflins and parafiins.
Throughout this application, wherever the terms asphaltenes, nitrogen bases, first and second acidafifins, also identified as Group I or Group II unsaturates, and parafiins are used, it will be understood that they refer to the fractions as determined by the above analytical procedure.
In application Serial No. 497,397, I grouped the nitrogen bases and the Group I and Group II unsaturates in the term resinous components of the asphalt.
Application Serial No. 497,397 reports the discovery that the weathering produces an increase in the asphaltenes content, and that the total percentage of the resinous components decreases. The change appears explainable by the fact that the Group I unsaturates and nitrogen bases change into asphaltenes with a reduction in the bonding power of the asphalt. The result of weathering is to cause an unbalance as between the saturated frac tions, on the one hand, and the resinous components, on the other hand. The application also describes the discovery that weathered asphalts may be rejuvenated by establishing the proper balance between the resinous components and the parafiins in the rejuvenated asphalt.
The process of the above application rejuvenated the Weathered asphalt by reestablishing the balance of components, as it existed in the original asphalt before weathering. This is accomplished by adding fractions of maltenes which modify the composition of the weathered asphalt by the addition of sufiicient resinous material to raise the content of the resinous component of the weathered asphalt so that the balance of components found in the original asphalt may be re-established. The maltenes added contain the resinous components, that is, the nitrogen bases, and first and second acidafiins, in amounts of at least 50% by weight of the maltenes. The added maltenes may also contain saturated components, i.e., the parafiins.
The maltenes are preferably added to the weathered asphalt in emulsion form. The amount of maltenes added to the weathered asphalt is suificient to materially improve the properties of the asphalt which, by weathering, has had its usefulness markedly reduced, as evidenced by the low penetration value and brittleness of the weathered asphalt. The maltenes added to the weathered asphaltic pavement may be in amounts to bring the asphalt content of the pavement up to 1.3 to 1.4 times the amount specified for that pavement, for example, about 4% to 8% by weight of the asphaltic aggregate composition constituting the pavement.
The aforesaid application is herewith incorporated by this reference.
Subsequent to the filing of the above application, my continued research into the subject developed further dis coveries, including the efiect of the composition on the durability of asphalts, as indicated by the abrasion resistance, using test procedures adopted by the Materials and which the asphalt is deficient. Such fractionsmaybe V duced from petroleum oils by removing asphaltenes and Research Department of. the California Division of Highways, as described by F. N. Hveem in the Proceedings of the Association of Asphalt Paving Technologists, Technical Section, December 1, 1943, vol. 15, page 111, et seq.; and by John B. Skog, A.S.T.M. Special Technical Publication 212, page 1, et seq. The test consists of mixing two parts of asphalt with 160 parts of Ottawa sand at various temperatures and determining the abrasion loss by impinging a stream of steel shot against a compacted specimen. Additional samples are made in the same manner and exposed in a weathering machine to infrared heat for various times, and'weathered samples withdrawn at various intervals and likewise tested. The parameter reported is grams loss per 1,000 gram shot. This test is herein referred to as the ShotAbrasion Test. Experience with this test has shown that the higher the abrasion loss by this test, after weathering, the inferior is the life expectancy of the road produced from these asphalts. (See the Sltog article, page 8.) It is thus a measure of the durability of the asphalt, i.e., its resistance to loss of bonding properties and other characteristics which are useful in pavements.
Discoveries made in connection with this continued research are disclosed in my a plication, Serial No. 45,023. Data are reported as a result of this continued investigation by .the applicant upon 200 to 360 penetration grade asphalt produced from California crude oils derived from the Los Angeles basin, Valley and Santa Maria fields in California. Thirteen such asphalts are reported in the aforesaid application. Additional data are reported for asphalts produced from California crude oils and from blends produced from Gilsonite and various oil fractions. The asphale blends had penetration values in the range of 200-300, and the Gilsonite asphalts had penetrations ranging from 85 to 257.
These asphalts were subjected to the above tests, and the data showed that the abrasion resistance measured by the Shot Abrasion Test increases with an increase in the paraflins content (P) of the asphalt in a regular manner. The results of these experiments showed that, in order to obtain an asphalt of penetration from, about 36 to about 360, having a loss of under 3 grams in the above Shot Abrasion Test after 500 hours weathering, the percent parafiins in the asphalt should be above about and up to about 50%; and the higher the percentage in this range, the more abrasion resistant the asphalt. The effects of weathering have been shown in application Serial No. 45,023 to result from an unbalance in the asphaltenes and saturated fractions on the one hand, and the unsaturated and nitrogen bases components on the other. The effect of unbalanceis the lesser, the greater the percentage of saturated'fractions in the asphalt originally employed.
The application Serial No. 45,823 taught that asphalts may be rejuvenated by adding the paraffins fractions to obtain the required balance to produce an asphalt of desirable properties. The percent of resinous iractionshas, however, to be high enough to prevent syneresis. It is to be observed that maltenes employed may also contain the unsaturated fractions and may also contain nitrogen bases.
With some weathered asphalts, which are relatively uncommon, which are unusually high in. peptizing fractions, to wit, the nitrogen bases and other resinous fractions, to wit: first and second acidaifins, the maltenes may be substantially all paraffins, i.e.', higher than 85% and even 100%.' In the cases which are normally encountered, I found that a weathered asphalt which has deteriorated may be suitable for the purpose of the structure in which it is used, if the 'weatheredasphalt is replasticized by adding thereto the selected fractions of maltenes, containing a suitable concentration of the components in prowax of the oil, ifthe oil is awaxy oil, to produce fractions containing about 20% to saturated components, the
remainder being reactive components, to Wit: nitrogen bases and first and second acidafilns.
The application, Serial No. 45,023, further discloses data which show that the durability of rejuvenated asphalt is the greater the greater the percent parafilns (P), and that by increasing the paraffins content of the original asphalt employed in the road construction, the durability, as measured by the Shot Abrasion Test, at various stages of weathering was above that of the original asphalt, the abrasion loss being markedly reduced.
The results of the discoveries as reported in application Serial No. 45,(l23, therefore, showed that the addition of maltenes containing sufficient parafhns fractions (P), in amount sufilcient to raise the paralfins content of a weathered asphalt, could produce an asphalt of bonding power and durability even better than that of the unweathered, original asphalt.
As disclosed in the said application, Serial No. 45,023, the fractions of maltenes are used in emulsion form, preferably as a cationic emulsion, and preferably also as a balanced emulsion containing both cationic and ncnionic emulsifiers.
The aforesaid application, Serial No. 45,023, is herewith incorporated by this reference.
Continued research and investigation in this field resulted from the opportunity afforded applicant to investigate 119 asphalts obtained from crude oils produced in various states or" the United States and in Venezuela, in Canada and in Mexico, and produced by various meth ods, including steam distillation, air blowing, blending, propane fractionation, and fluxing with heavy oils. The details of the test data upon these various asphalts and their origins are given in Public Roads of August 1959, vol. 30, No. 9, issued by the Department of Commerce, United States Government, pages 197-207, and also in the Proceedings of the Association of Asphalt Paving Technologists, vol. 28, January 1959, pp. 242-279.
Samples of these asphalts were secured, and the samples were analyzed according to the analytical procedures given in the above method by Rustler and Sternberg and by a Weathering and abrasion test method reported in the article entitled influence of Chemical Composition of Asphalts on Performance, Particularly Durability, by Rostler and White, published in American Society for Testing Materials, Special Technical Publication No. 277, pages 64-88, 1959. This abrasion test method, which, as shown in the article (see infra) Composition and Changes in Composition of Highway Asphalts, 85-100 Penetration Grade, correlates with the Shot Test, will herein be referred to as the Pellet Test.
This investigation confirmed the results reported in application Serial No. 45,023, and showed that, as a general rule, the asphalts show greater abrasion resistance and durability to Weathering, the higher the parafilns content, provided the paraifins content is not so high as to destroy the suitability of the asphalt as a bonding agent. It also explains and reconciles the results of the two previous applications, and shows that while in each case an improvement in the asphalt is obtained by following the procedures of the aforesaid applications, they are each a special case of a more general principle which makes it possible to improve the durability of asphalts, both weathcred and unweathered.
The reason that this is so, as now appears from my further investigation, is that, as the parafiins content (P) of the asphalt increases, so is there an increase in the sum or". the paraiiins and second acidtiiins (A and that the controlling factor is the ratio of the sum of the nitrogen bases and the first acidaflins (N +14 to the sum of the paraiiins and the second acidafifins (D+A2), expressed as the ratio of the percentages present in the asphalt. It thus appears that the reason that the asphalts of higher parafiinic content showa greater abrasion resistance and increased durability is that, this ratio decreases as the concentration of p mflins increases. However, the paraffins content is not as sensitive an indicator for durability of many asphalts with parafiins contents in excess of about to The above maltenes composition ratio 1 P+Azi s thu a better and o sensitive index of the durability of the asphalt than the content of the component P.
rhel s n es i ated by m ans. of he Pellet Test, clud ng he 119 a phalts and two ot e a ph of 85 to 100 penetration grade (Samples No. 19 and of Table III) which were blended to have an excessively low ratio, showed that the asphalts vary in their maltenes composition ratio from about .3 to above 2, and have abrasion losses by the above Pellet Tests ranging from no loss, or zero loss, to about 100%. These asphalts may be classified into various groups, according to their loss on abrasion by the above Pellet Tests, taken as the average of the abrasion loss before and after aging, as shown in Table I.
6 characteristics. On top of FIGURE 1 is indicated the boundaries of the groups corresponding to values of the ratio for each group, plotted as abscissa.
Line D on FIGURE 4 and the same data plotted as a curve on FIGURE 2 plot the paraffins content of the groups of Table I against the same average abrasion loss.
The above tests show that, for the 85-100 penetration asphalts produced by various procedures from'petroleum ru e oi s of a ou ype nd diverse geographic origins, the following conclusions may be drawni v For asphalts with parafiins' content ranging from about 7% to about and aphaltenes content ranging from about 11% to 36%, the abrasion loss is a funtion of the ratio of N+A /P+A as well asof the parafiins content. It also appears that, for abrasion loss in excess of about 20%, the above ratio is a much more sensitive index gt the durability of the asphalt than is the percent paraf- TABLE I N+ .i* P+A2 1 emgc; A D b'l't R t Durabilit Grou ereen verag ura 1 1 y a ing y p Paraflins Abrasion Range Average 0. 4 0.28 39.8 Decreasing durability with decreasing parameter value. 0.4 to 1.0 0. 82 13. 8 5. 7 Superior. 1 to 1. 2 1.09 11.5 8.9 Good." 1. 2 to 1. 5 1. 34 9. 9 29. 6 Satisfactory. 1. 5 to '1. 7 1. 5S 8. 9 45.4 Fair.
1. 7 1. 34 9. 0 52. 7 Inferior.
* Composition of original (nonaged) asphalt.
** Average of percent abrasion (Pellet Method) before and after 7 days aging.
FIGURES 1-5 are plots of data given in this specification.
FIGURE 1 shows the average abrasion loss by the Pellet Test plotted against the composition ratio N +A /P+A of the original unaged asphalt. The average abrasion loss is calculated as the average of the abrasion loss of the unaged mixture of Ottawa sand and asphalt, and the same mix, after aging seven days as described in the above article by Rostler and White in the article in vol. 31 of the Proceeedings of the Association of Asphalt Technologists, supra and A.S;T.M. Special Technical Publication'No. 27-7.
The solid curve is drawn as a best fit to the data obtained from the above 85-100 penetration grade asphalts, and the dotted line gives the trend line for asphalts of composition ratios in the various groups.
The marked points where the ratio is .4 and less are for asphalts sample Nos. 10 and 20, ab above. All other points are averages as given in Table I. The asphalts fall into six groups. Group 0, with composition ratios less than 0.4, represents compositions which are of consistency of a chessy and putty-like character rather than asphalts. At about 0.4 the compositions attain the desirable characteristic of paving grade asphalts.
The asphalts of Groups I to V may be rated as stated in the table, based on their durability. The lower the abrasion loss initially, and also the less abrasion loss after aging, the better is the asphalt, i.e., the lower the above average, the better the asphalt in its weathering The following asphalts had the values expressive of. composition given in the following Table 11:
TABLE II Initial Composition Sample No. N+A1I Abrasion Percent Percent P+Ag Loss* Par. (P) Asphaltcnes 16. 6 8.8 1. 16 8 16, 2 9. 2 1. 22 6 16.2 26. 6 1. 3 6 9 15. 5 10. 5 1.23 0 1 5 1 11.6 1. 17, 12 15 12. 4 1. 58 16 14. 7 9. 5 1.33 9 14. 3 21. 7 1. 41 10 13. 4 17 1. 61 2O 12. 5 25. 7 1. 41 15 12. 4 l4. 9 1. 12 12.2 24. 6 1. 48 15 11.6 25.6 v 1. 77 20 21. 3 9. 2 1. 14 4 ,19. 1 7. 2 1. 24 5 11.9 8. 4 1. 48 8 10.4 4.0 1. 35 8 *Determined by the Shot Abrasion Test on Samples after weathering for 500 hours in the weathering machine.
The asphalts of Samples 1-13 were all 200-300 penetration grade asphalt. The table gives thepercent parafiins (P), and the percent asphaltenes (A), and the ratio N+A /P+A Samples 14-l8 were all made by blending 32 penetration asphalt'with various oil fractions to give a 200-300 penetration asphalt as follows:
The oil employed in Sample 14 was 50SAE heavy.
raflinate which had the following composition:
Nitrogen bases percent 3.4 First acidaffins do 6.5 Second acidaffins do 28.0 Paraffins do 62.1 N+A /P+A .11
It had the following distillation range at mm. Hg
Initial boiling point C 244 50% point C 322 End point 2 C 385 The blended asphalt had the following composition:
Asphaltenes "percent" 9.2 Nitrogen bases do 36.7 First acidafiins do 11.7 Second acidafiins do 21.1 Parafiins do 21.3 N+A /P+A 1.14
Sample was formed using S.R. stock, 154 Universal Saybolt Seconds at 210 F.
The S3. stock had the following composition:
Nitrogen bases percent 14.6 First acidafiins do 14.3 Second acidaflins d0 35.4 Paraflins d0 35.7 N+A /P+A 0.41
It had substantially the same distillation range as the S.A..E. 50 used in Sample 14.
The asphalt composition of the asphalt in Sample 15 was:
Asphaltenes percent 7.2 Nitrogen bases do 37.4 First acidafiins 1 ;d0 14.0 Second acidatfins .r. .'do 22.3 Parafiins do 19.1. -N+A /P+A 2 1 1.24
Sample 16 was made using 27 Medium Lubricating-Y Extract having the following composition:
Nitrogen bases percent 17.3 First acidatfins 1 do 17.3 Second acidafiins do 53.0 'Paraflins do '12.4 N+A /P+A .53 Ithad the following distillation range at 10mm. Hg pressure: 7 i r lnitial boiling point 205 50% point 1 263 Endpoint The blended asphalt in Sample 16 had the following composition:
Asphaltenes "percent" 8.4 Nitrogen bases do 35.2 First acidaflins do 19.5 Second acidafiins do 25.0 N+A /P+A 1.48 Parafiins percent 11.9
Sample 17 was made using 55% Heavy Lubricating Oil Extract having the following composition:
Nitrogen bases percent 28.7 First acidaifins do 21.2 Second acidaffins do 41.3 Paraflins do 8.8 N+A /P+A 0.99
It had substantially the same distillation range as the SAE. 50 used in Sample 14.
The blended asphalt in Sample 17 had the following composition:
Asphaltenes percent 4.0 Nitrogen bases do 35.4 First acidaiiins do 18.7 Second acidafiins do 305 Paratlins do 10.4 N+A /P+A 1.35
Sample 18 was made by blending with a concentrate of nitrogen bases having the following composition:
Nitrogen bases percent 84.6 First acidamns do 7.3 Second acidaffins do 6.7 Parafins do 1.4 I\ +A /P+A2 The blended asphalt had the following composition:
Asphaltenes percent 1.5 itrogen bases do 77 First acidafiins do 7.8 Second acidaftins do 9.1 Paraifins do 4.6 N+A /P+A 6.12
The above distillation range and boiling points are determined by A.S.T.M. Test 13-4160.
FIGURE 4 shows, in addition to line D discussed above, the relation of percent parafiins to abrasion loss given in Table 11 for the asphalt Samples 1 to 13 and also for Samples 14 to 18. The lines are given only to indicate the trend of the dependence of abrasion resistance on percent parafiins and are not intended to imply a mathematical law.
FIGURE 3 shows the relation of the composition ratios V or the asphalts of Table 11 to the abrasion loss by the Shotv Abrasion Test after Weathering for 500 hours.
As in the case of 85400 penetration grade asphalts,
' whose averages are plotted on FIGURE 1, the asphalts of 200-300 penetration grade also show the dependence ot a rasion loss on the composition ratio. Notwithstanding the differences in the methods of testing the abrasion loss g and resis.ance to weathering, both tests show that an increase in the ratio N +A /P+A results in a decrease in the durability of the asphalt as measured by either test.
Asphalts produced by blending Gilsonite with an oil also show a reduction in abrasion loss with increasing paraiiins content and decreasing N +A /P+A composition ratio. They illustrate, however, the additional fact that an excessively low ratio; substantially below a ratio g; of about 0.4, indicating an excessively high concentration of paraffins and second acidafiins, reduces the bonding power and results in a relatively high abrasion loss. The following table illustrates this phenomenon:
so 300 penetration grade also gave abrasion loss of under 50 grams.
Thus, asphalts of superior abrasion resistance are those whose composition ratios are more than about 0.4, and
TABLE I11 Composition, percent by Wt. Abrasion Loss Sam is p -ll Penetra- Shot Pellet Gilsonite Oil P A tion Abrasion Average 2 Test 1 l Specimen aged in weathering machine before test. 2 Average of percent abrasion before and after 7 days aging.
The data confirm the observations discussed above that for unweathered asphalts (asphalts containing 40% or less of paraffins and having ratios of 0.4 or higher), the durability, as measured by either the Shot Abrasion Test or the Pellet Test, as abrasion loss, increases with increase in the percent parafi'ins, and that asphalts With ratios of from 0.4 to 1.15 have abrasion losses by the Pellet Test of under 10%, and the abrasion loss increases rapidly with increase of ratio beyond 1.15.
The data show that, as a conservative measure, until further research fixes the eflect of paraflins content in excess of 40% and ratios N +A /P+A of less than 0.4, the desirable composition of unweathered asphalts to give superior durability, I conclude, are those having parafiins content of less than about 40% and ratios N +A /P+A of more than about 0.4, andthe asphalts of ratios from about 0.4 to about 1.5 will all have satisfactory durability. Asphalts of the 85-100 penetration grade with ratios above about 1.5 rapidly lose in abrasion resistance as the ratio increases.
It is, therefore, one object of my invention to improve asphalts, which are produced from a petroleum crude or a fraction thereof by distillation or blending an asphalt of relatively low penetration with maltenes, and which asphalts show a high abrasion loss and low durability, by adding to the asphalt a petroleum fraction which will adjust its ratio of N+A /P-|-A to be within the desirable range. For asphalts of lower than about 100 penetration, the said desirable range is above 0.4 and less than its original ratio, if above about 1.5.
Experience has shown that, for 85-100 penetration paving grade asphalt, it is desirable for superior performance in the field that the abrasion loss by the Shot Abrasion Test be not over 50 grams/ 1,000 grams of shot after weathering for 500 hours, and preferably should be much lower; and that the lower the abrasion loss by this test, the more durable is the asphalt. Pavements made of asphalt of grams loss or less will last longer than those which show grams loss or higher, since the bonding power of the asphalts of 30 grams loss appear impaired as compared with the asphalt of 20 grams loss.
As will appear from FIG. 3, for 200-300 penetration grade asphalts, asphalts of ratio less than 1.35 will have an abrasion loss of less than 10 grams for the Shot Abrasion Test after aging for 500 hours, and asphalts of ratio less than 1.7 will have an abrasion loss of less than 20 grams by the Shot Abrasion Test after aging for 500 hours. From Table H (see Sample 18) the ratio may be substantially higher and give abrasion losses under grams, and, as Will be seen in the case of the Gilsonite blends of Table III, ratios of as high as 11 for the 200 the upper limit of ratio for asphalts with good abrasion resistance depends on the penetration grade of the asphalt. For asphalts of or less penetration, the upper limit is suitably about 1.5, and for softer asphalts the ratio may be higher. Thus, in the penetration grade 200..300, the ratio is suitably less than 10. Also, the parafiins content is preferably below about 40% of the asphalt.
The abrasion loss of asphalts may be improved by incorporating, into the asphalt of relatively high ratio and relatively high abrasion loss, fractions in quantity and amount to adjust the ratio to the desired value. Since this will cause some increase in the penetration value of the asphalt, it may be necessary, if the attained penetration is undesirable, to either start with a low penetration asphalt, or employ as the blending oil an oil which has a high value of its P+A fraction, minimizing the total amount of maltenes which is introduced.
The following illustrates the effect of the concentration of the above fractions in the asphalt to .be improved and of the oil used for the improvement.
If N+A and P+A are the concentrations of these fractions in the asphalt to be improved, and R is their ratio N+A /P+A And N'+A' and P'+A' are the concentrations of these fractions in the oil to be added, and R is their ratio N'+A /P+A' in the oil employed;
R is the desired ratio which is to be attained for the asphalt to be improved.
Z is the ratio of the weight of the oil to be employed to the weight of asphalt to be treated.
' above tests.
, be added may be calculated, if the composition of the asphalt to be improved and the composition of the maltenes to be added are known, and the desired. value of R is specified.
It is an object of my invention to shift the composition ratio to a value closer to 0.4 than the value of the asphalt to be improved, which should be sufliciently reduced or raised in value to result in a substantial increase in the abrasion resistance.
Where the asphalt to be improved has a ratio substantially less than 0.4, I employ an oil having a ratio sub stantially higher than the ratio of the asphalt, preferably a ratio of 0.4 or higher. Where the asphalt to be improved has an excessively high ratio, I employ an oil having asubstantially lower ratio.
By using maltenes of a ratio of about 0.4, I may improve asphalts of-higher or lower ratio Without first determining the ratio of the asphalt, since if the ratio of I the asphalt is in excess of 0.4, the oil will reduce the ratio but not to or below 0.4. In treating asphalts of excessively low ratios, the 0.4 ratio maltenes will raise the ratio of the asphalt towards 0.4v and thus also im prove the asphalt.
TABLE IV 32 Pan. M altenes Improved Asphalt 7 Asphalt Sample Composition Composition Composition Shot Abrasion Test, Loss After P R. P Rn P R 500 hrs.
The above Table IV illustrates the effect of the R value of-the oil. It is apparent that the oil should have an R value less than that of the asphalt to be improved, and preferably the lower this value the better; but the amount employed, and the parafiinic content, and the R value of the oil should not raise the paraiiinic content and lower the R value'to undesirable limits, as stated above. 2
The oils should also be relatively high boiling petroleum fractions and substantially freeof fractions boiling below about 160 C. at 10 mm. Hg absolute pressure, and preferably should have a distillation range Whose initial value is about 200 C, at 10 mm. Hg absolute pressure (A.S.T.M. Test D4160). It has been found that em- I ploying the lower boiling oils (notwithstanding they be of composition and be used in amounts to produce the desirable paraffins content, R ratio and penetration) pro duces asphalts of inferior durability according to the This is iilustratedby the following data. Sample 28 wasmade by blending the 32 penetration asphalt used in producing Samples 14-18. It was blended with a light spray oil extract in the following ratiosby weight: 87.5% of the asphalt and 12.5%; of the light spray oil extract. ing composition Second acidatlinsunue do The spray oil extract had the follow- Paralii-ns do 20.7 N-l-A /P-l-A 0.258
The oil had the following distillation range:
Initial C 170 50% C 229 End point C 253 The blended asphalt had the following composition and properties Asphaltenes percent ll Nitrogen bases do 38.7 First a'cidaffins d0 15.6 Second aeidafiins do 21.5 Paraflins do 13.2
N+A /P+A 1.5 6 Abrasion loss, Shot Abrasion Test 41.8
This may be compared with Sample 16 above, in which a medium lubricating oil extract was employed to give an asphalt of similar composition, both as to paraifihs content as well as R value, and both having a ratio of about 1.5.
A similar result is obtained by employing a technical white oil (98% unsulfonated residue) of 180 Saybolt Se"- onds at F.
Sample 29 was produced by blending 89% by weight of the above 32 penetration asphalt with 11% by weight of the above technical White oil.
The white oil had the following composition:
Nitrogen bases percent 0 First acidaffins do 01 Second acidafiins do 5.3 Parafiin-s do 94.6 N-l-A /P-l-A 0.01
The distillation range Was the same as for the spray oil extract of Sample 28.
The resultant asphalt had the following composition and abrasion loss by the Shot Abrasion Test:
Asphaltenes percent 10.4 Nitrogen bases do- 38.4 First acidafiins do 12.7 Second acidafiins do 18.2 Paraffins do 20.3 N+A /P+A 1.33 Abrasion loss 23.5
This may be compared with Sample 15, which resulted in an asphalt of similar composition, both in paraflins content and ratio. These results are tabulated below.
TABLE V Maltenes Asphalt hot Abra Sample Composition Distillation Range l Composition sion Test Loss R Initial, 50% E.P., P R
1 At 10 mm. (Hg) absolute pressure.
7 obtain the desired R ratio in the blended asphalt and give Nitrogen bases; upercent 5.9 First acidafiins ClO; 1 14.6
. the desired penetration, it will not achieve the same low value of the abrasion loss it it contains volatile components so that its initial boiling point in the above tests is substantially below 160 (1., at 10 mm. Hg pressure absolute. It should be preferably substantially free of fractions boiling below about 2%" C. at such pressure. By substantially 5.3 free, as used in this connection in the specification and claims, I means that the oil should not contain fractions boiling below about 200, in amounts sufficient to result in an undesirable increase in abrasion loss.
The above observations were all related to the effect of the chemical composition of unweathered asphalts on the properties of the asphalt, particularly their durability when exposed to weathering as measured by the test procedures described above.
Studies in the behavior of asphalts during weathering and the changes which occur in chemical composition, and the beneficial effects of blending weathered asphalts with maltenes, have produced the following surprising results.
Two asphalts, identified as Asphalt A (same as Sample 18) and Asphalt B (same as Sample 16) were weathered, and the weathered asphalt was blended each with two different maltenes having different compositions.
The asphalt, after being subjected to weathering for 650 hours in the weathering machine, was tested for abrasion loss by the Shot Abrasion Test and analyzed. The weathered asphalt from A is given below as A, and the weathered asphalt from B is B.
One portion was treated with an aqueous emulsion of maltenes containing 60% by weight of maltenes a (Method I), and another by a different maltenes b (Method II). This gave four asphalts. Asphalt A'a is the weathered A asphalt treated with the maltenes a (Method 1); A'b is the weathered A asphalt treated with the maltenes b (Method 11) Ba is the weathered B asphalt treated with the maltenes a (Method I); B'b is the B asphalt treated with the maltenes 12 (Method II). The asp-halts so treated were again aged for 650 hours in the weathering machine and tested by the Shot Abrasion Test.
The composition of maltenes a employed in Method I and the maltenes b employed in Method 11 are given in the following table:
TABLE VI 1, 2, R percent percent percent percent Maltenes a (Method 1) 17 17 54 12 0.52 Maltenes b (Method II) 3. 6. 5 28 62 0. 11
The emulsifier was a fatty quaternary ammonium salt 0.7% by weight (cationic emulsifier) and a non-ionic emulsifier (alkylphenylethylene oxide condensation product)- 0.5% by weight of the emulsion.
The results are tabulated below.
l Weathered for 650 hours, Shot Abrasion Test. 2 Aged an additional 650 hours after treatment.
' Comparing Asphalt A, which on aging had an abrasion loss of 37 by the Shot method, with the Asphalt B, which showed 8, reveals the influence ofthe paraffins content and the R ratio, as previously explained.
This is also revealed by comparing the percent parafiins 14 and the R ratio of the asphalts A'a, A'b, B'a and Bb with their abrasion values. It also reveals that the asphalt with the higher R ratio and lower paraflins content shows the higher abrasion.
The low values of the abrasion losses for Ab, Ba and Bb are surprising. Thus, the improvement obtained employing maltenes b (Asphalt A'b) gave an asphalt with an abrasion value of 4. The increase in the durability of the asphalt reflects the increase in the paraffins content and reduction in the-R ratio, although the increase in the durability is in excess of what would be expected for an unweathered asphalt. The same phenomenon appears with the B series.- The reclaimed asphalts B'a and B'b both have relatively low values of R and show lower abrasion loss, the treated asphalt showing a better durability, i.e., lower abrasion loss, after treatment compared with the original asphalt.
I may rejuvenate weathered asphalts by incorporating into the asphalt petroleum fractions of such composition and amount as to reduce the R ratio of the asphalt, and can thus rejuvenate a weathered road and obtain a pavement having an even greater durability than when the road was freshly laid.
Field experience confirms this result. A road which had been weathered for two years was divided into three sections; one was as is, the second was treated with 0.11 gallon/square yard with the cationic maltenes emulsion described below, and the third was treated with 0.22 gallon/square yard of the same emulsion.- The untreated section and the treated sections were cored to a depth, i.e.; top or surface section; a second core was taken to a further depth of about 1, i.e., the middle section of the road. The cores were then extracted by the following procedure.
A sample of asphaltic paving material is first heated to a temperature of approximately F. by any convenient means, as in an oven or overa steam plate. At this temperature most samples can be crumbled by hand. Extremely hard samples may require the use of pliers or a hammer. The sample should be reduced to about /4 pieces or to the size of the largest pieces of aggregate, whichever is larger, Care should be taken not to break up the rocks and stones of the aggregate, so that the grading of the aggregate can be determined by sieve analysis on the sample after extraction.
The crumbled material is first weighed and then is placed into extraction thimbles of a Soxhlet extraction apparatus and covered with a loose plug of absorbent cotton to retain the aggregate. A thimble found suitable is a Whatman single thickness 43 x 123 mm. thimble. The asphalt is extracted in the Soxhlet apparatus with benzol until the benzol in the extraction chamber is colorless. The benzol extract is filtered as some of the finer aggregate passes through the single-thickness extraction thimbles. One may employ a 6-inch funnel using Whatman #1, 24 cm. filter paper many other suitable filter. The benzol is distilled off from the extracted asphalt by heating the flask of the distilling apparatus in an electrically heated wax bath or oil bath at C. Last traces of benzol are removed by carefully applying vacuum to the V distilling apparatus while continuing to heat the flask in ethoxy ethanol, Pronon 280, Process Chemical Co.), and
the balance water. This emulsion was employed in the tests hereinafter referred to, unless otherwise specified.
The results are tabulated in Table VIII.
TABLE VIII Untreated Treated Treated Core Identification (0.11 gsy) (0.22 gsy) Section Top Middle Top Middle Top Middle Asphalt content, by Soxhlet Extraction, percent aggregate weight 3. 8 4.4 5. 2 4. 9 5. 5. 0 Viscosity, megapoises 37. 3 14. 3 14. 0 24. 3 2. 7 22. O Penetration Value, 0.1 mm 17 26 26 2O 56 22 Chemical Composition (Rostler Method), Percent by Weight:
Asphaltenes 25. 8 20. 6 25. 21. 9 24. 9 22.8 Nitrogen Bases--- 31. 9 35. 3 29. 7 34.. 6 28.1 34. 7 First Ae1datfins 10v 2 12.8 10. 9 12.7 10. 4 l1. 9 Second Acidaffius- 18. 3 17. 2 18. 7 16.7 19. 9 16. 2 For us 13.8 14. 1 16. 2 14.1 16.7 14.4 Pellet Abrasion Test, Percent Loss in Weight:
As Recovered 64 27 8 42 1 42 Aged 1 100 72 39 88 4 90 Ratio (R): N-l-Ai/P- 1.31 1. 54 1.20 1. 5i 1. 05 1.52
l I.e., after weathering as reported in Rustler and White article.
The road surface after treatment was in excellent live condition.
The road test confirms the above results that va weathered asphalt may be improved and a weathered asphaltic structure may be reclaimed by adding petroleum fractions to increase the parafiins content, and particularly by adjusting the R ratio of the bonding asphalt.
It is thus an object of my invention to improve the weathering resistance of asphalts, Whether originally weathered or unweathered, by treating the asphalt with a petroleum fraction to adjust the R ratio of the asphalt to reduce the R ratio ii the R ratio is excessively high, for example, substantially above 1.5, or inorease the R ratio if it is less than about 0.4, to a value in the range of about 0.4 to about 1.5.
The improvement attained in the road described above resulted from the reduction in R ratio by the treatment.
Where a weathered road contains weathered asphalt of excessively low R patio, it may be reclaimed by treating the road by the application of a maltencs emulsion of a higher R ratio than that of thc wcathered asphalt. A road so treated was successfully reclaimed by this process, as illustrated by Example 6 given below.
As a rule, parafiins content is also increased by the treatment, but should not exceed about 40% of the asphalt.
I may employ any petroleum oil fraction, substantially free of asphaltenes, containing parailins and containing members chosen from the group of the nitrogen bases, first 'acidafiins, and second acidaifi'ns; that is, with or without the presence of one or more than one of the following: first acidafins, second acidafiins or nitrogen I may also employ oils containing second acidaffins with or Without parafiins, first acidaflins or nitrogen As a practical matter, petroleum oils will usually contain both parafiins and second aoidaffins, and may also contain nitrogen bases and first acidaffins or one of the latter two members.
Such maltenes fnactions maybe produced from petroleum oils by removing the asphaltenosand Wax of'the oil (it the oil is a waxy oil) from the oil thereof to producc fractions which have about 5% to about 95% of parafiins components; with or Without second acidaifins, the remainder being the more reactive components, to
-wit, thenitrogcn bases and the first acidaffins, and having :a R ratio of from less than 0.01 to about 19. Since the purpose of my invention is to add components chosen from the group of parafiins and second acidafiu's and, if
I necessary, enough of the more reactive components, to wit,
components chosen from the group of the nitrogen bases Nitrogen basesNot more than about 20% by Weight; First acidalhns-Not more than about 20% by Weight; Parailins-Frorn about 20% to by Weight; Second acidarlins-Balance to make up Another example of a suitable oil is one containing:
Nitrogen basesNot more than about 35% by weight;
Paraffinic fractionsl rom about 20% to 85% by weight;
First and second acidaffins-Balmce to make up 100% by Weight.
Another example of a suitable oil is one having:
Nitrogen bases and first acidaflins-Not more than about 35% by weight;
Paraffinic and second acidaffins-Balance to make up 100% by weight; provided that the parafiinic fraction is in the range of about 20% to 85% by weight of the oil.
Another example of a suitable oil is one containing:
Nitrogen b ases and first a-cidallins-Not more than 20% by weight;
Paraffins and second acidafins-More than 80% by 'weight, the total forming 100%, provided the paralfinic fraction is within the range of 20% to 80% by weight.
Other suitable oils are as follows:
TABLE 1X Specific Gravity,60 F./60 F. 1.015 997 1. 028 6 957 Viscosity cP at 90 C 29. 9 12. 7 171 47. 2- l6. 3 Initial Bolling PL, 375 360 k 432 432 380 Asphaltenes 0 0 0 0 0 Parallins (P) .1 11. 4 11. 9 7. 6 35. 7 40. 7 Second Acidathns (A2) 52. 9 61. 4t 40. 7 g 35. 4 37. 2 Ratio N-i-al r-l-az .55 .as l 1. 1 S .41 .23
and first aoidafiins, to pcptize and. dissolve the asphaltencs; I prefer to cmploy,jas described above, a petroleum fr ac- 7 tion which has the required concentrations of these co ponents.
1 At atmospheric pressure.
As a convenient rule of thumb, the boiling point at atmospheric pressure may be assumed to be C. above that at 10 mm. (Hg) pressure absolute.
The R value of the oil may thus range from about 0.01 to about 10, the ratio R chosen depending on the ratio ,of .the asphalt to be improved and on the ratio sought to be obtained. The ratio of the oil to the asphalt will depend on the penetration grade of the asphalt to be improved and the penetration of the improved asphalt 17 which is desired. Thus, if R, of the asphalt to be improved is known, and R is chosen, and the ratio Z is established, the equation:
2) a 2) iwill establish the R of :the oil which may be used.
The addition of the maltenes to the asphalt will reduce the penetration of the asphalt, and thus the ratio Z is dependent on the penetration of the asphalt and on the penetration desired for the improved asphalt.
In the usual case, this ratio Z will be such as to establish the required penetration grade, to wit, usually, for paving asphalts, in the 85-100 grade or 200 300 grade. However, where special asphalts are desired, other penetrations may be required, and the value of Z is suitably adjusted.
A further observation is that, if the asphalt to be improved has a ratio R in excess of 4, the value of R is taken as less than R,,; and if the vmue of R be less than If the pavement is badlyweathered and cracked, the emulsion will penetrate to the region of weather damage and rejuvenate the weathered asphalt portion of the asphaltic structure.
The preferred practice is to use an amount of emulsion of the above concentration, i.e., about 40% oil phase, in at least an amount per square yard which the road will absorb in about fifteen minutes. In cases where early resumption of traflic is not a requirement, larger amounts may be used.
This phenomenon is not entirely a viscosity effect, although viscosity doe-s aifect the penetration through the pores of the structure. The viscosity of the emulsion, which is substantially that of water, does not control the absorption of the maltenes from the emulsion phase by the asphalt phase of the structure.
The following Table X illustrates the effect of the emulsion type on the absorption of the maltenes into the asphalt as it enters the asphaltic structure. the difference in the effect of other fluids, as named in .4, the value of R should be greater than R Column 2 of the table.
TABLE X Treating Fluid Time for permoation of 10 t Time of penetration for 10 Depth of penetration of ml. Aerosol OT Viscosity ml. of treating fluid treating fluid in inches solution into Description i G treated briquet 1 Control..- 12 sec.
Cationic oil emulsion, cone 71 4 H1111. 60- 18 min. Cationic oil emulsion, diluted 2:1 13 sec- 1 m Cationic oil emulsion, diluted 1:1. 10 30 ee 0. 89 18 min. Anionic oil emulsion, diluted 2:1 10 2 8 ec Ran through briquet and 19 min.
out bottom. Nonionic oil emulsion diluted 2:1 1 51 Se 0v 90. 22 min. $54 asphalt emulsion, diluted 2:1- 13 Dried at rf ce forming None 48 min.
membrane. 1, 62-0 0. 45
Straight oil 2, 660 4 0. 83 8 min, Kerosene 5 3 ec." 0.97. 2min. Oilin kerosenea- 13 2 mm. 3 Sec 0. 84 4 min. Tap water 1 16 hrs Not measurable 21 sec.
1 Treating fluid in these tests have same diluent concentration.
2 Briquet collapsed alter 11 to 12 hrs., before complete penetration of fluid.
In treating roads or other asphaltic structures, it is desirable to employ the maltenes in an emulsion form, as will be described below.
The significant importance of an emulsion form of a reclaiming agent for weathered asphaltic pavement arises from the elfect of the emulsifier to condition the asphaltic structure and the asphalt phase of the structure, as Well as the oil phase of the emulsion, to permit the incorporation of the maltenes phase into the asphalt.
Two different phenomena are to be distinguished. One is the flow of the emulsion fluid through the pores of the asphaltic concrete, i.e., the voids between the aggregate particles bonded by the asphalt, and the other the absorption of the maltenes phase from the emulsion into the asphalt phase to change the chemical composition of the asphalt.
One of the controlling factors is that the emulsion penetrates the surface of the asphaltic structure and passes into the pores of the asphaltic structure but not through the structure before the emulsified maltenes are stripped by the asphalt from the emulsion.
In treating road surfaces for purposes of economy, it is desired to treat the top weathered surface so that its plasticity may be restored. The surface, on rolling either by rollers or by traffic, is thus ironed out and cracks sealed. This preserves the underneath structure. It is undesirable and wasteful to use a treatment which either makes a superficial glaze or runs through the road structure from top to the base. Usually it is suificient to rejuvenate about the first to 1 inch of the road surface. This effectively rejuvenates the road and does not waste the emulsion.
The specimens used in the tests summarized in Table X were molded briquets, 2.5 inches in diameter, 1.6 inches high, with a 2-inch diameter, 0.318-inch deep reservoir pressed into the top side. The mixture used to form the briquets consisted of parts by weight of 20-30 mesh Ottawa sand (ASTM C-l09, 10 parts Portland cement, and 7.5 parts asphalt of 48-penetration.
The cationic emulsion was formed using the cationic and nonionic emulsifiers as described above. (See Table X.) The nonionic emulsions were formed using only the nonionic emulsifier (.8% by weight). The anionic emulsions were formed using only anionic emulsifier (1.2% by weight of a sodium petroleum sulfonate).
The test procedure employed was to place the test fluid in the reservoir on the top of the briquet and to split the briquet after 24 hours, to determine the depth of penetration by inspection under ultra-violet light. The portions of the briquct reached by the treating agent fiuoresce when illuminated with ultra-violet light.
It is evident from the test results reported in Table X that a relatively rapid rate of penetration was obtained with all forms of emulsion systems, except the asphalt emulsion (grade SS1, diluted 2:1 with water), which did not penetrate but formed an asphalt skin at the surface when the water phase evaporated. This notwithstanding that the asphalt emulsion had the same viscosity as the oil emulsions. Further, the anionic emulsion penetrated so easily that it ran through the briquet, and thus the contained oil was not utilized. This is in contradistinction to the cationic and nonionic emulsions.
The fact that viscosity is of minor consecuence for penetration may further be seen by comparing 11 with It also shows 7 aged treated briquet was 21 minutes.
p 3, in that both fluids had the same viscosity and depth of penetration, but the kerosene-oil mixture penetrated much more slowly. v
The oils or cut-back asphalts which are not diluted but are used directly are also not suitable in such form for rejuvenating of weathered roads, since their penetration into the asphalt structure is limited. The same may be said of asphalt emulsion. At best they act merely as a surface coating in the form of a paint. This is illustrated by 7 and 9.
For purposes of comparisi'on, results are also given for kerosene by itself MC70 liquid asphalt cutback, and tap water.
It is interesting to'note that the briquets were relatively impervious to plain tap water but that, with the wetting agent added, water penetrated the briquets readily. The water with the Wetting agent even penetrated the briquets thatw'ere treated, but at a much slower rate. This serves as a measure of the relative eifect on pavement permeability of the various listed treatments, as shown in the last column in Table X.
The duplicate briquets, each separately treated as in the above series, were weathered for 7 days as for the Pellet Abrasion Test. The test method employed consisted of placing the 10 milliliters of the Aerosol OT solution '(dioctyl ester of sodium sulfo succinic acid) into the reservoir on top of the briquet and measuring the time for the penetration of the liquid into the briquet. The results reported in Table X show that all emulsion systems tested are more effective in decreasing the permeability of a weathered asphalt-aggregate mixture to the water containing the OT surfactant than are the kerosene cutbacks. Moreover, although the SS1 asphalt emulsion formed a membrane, Water still managed to permeate the structure. a
Control 1 is untreated. The permeability of the briquet to the fluid is evidenced by the time of penetration of the fluid through the briquet. Thus, for the untreated briquet (1) the penetration time was 12 seconds, using the aerosol OT water solution. The briquet treated with water required 21 seconds. The time for the weathered asphalt treated with the oil emulsions varied from 16 to 22 seconds, that for the nonionic emulsions being slower than the cationic emulsion containing also the nonionic emulsifier.
In addition to the tests reported in Table X, a number of other fluids were tested to check on the importance of the emulsification system. One of these tests was the use of a straight cationic emulsion, i.e., an emulsion the same as used in test 3 but not containing a nonionic emulsifier, only the catonic. The viscosity was substantially the same (14 centipoises), but the time of penetration for 10 ml. of the treating fluid into the briquet was 162 seconds. The depth of penetration was 0.81 inch. The time of permeation of 10 ml. of Aerosol OT solution in the A comparison of these figures with those shown in Table X for test 3 demonstrates the difference between a cationic-nonionic 'emulsification system and a straight cationic. Depth of penetration was slightly less for the straight cationic system, but the time of penetration was about 3 times that of the nonionic-cationic system. The slower permeation of the Aerosol OT solution into the briquet treated with the straight cationic emulsion can be explained by the more efiicient stripping of the maltenes from the emulsion by the asphalt, as evidenced by the lower depth of penetration into the briquet' and thus increased density of the treated portion of the briquet.
The above data is further evidenced that the effect of the oil emulsion on asphaltic concrete is not a viscosity effect, but is strongly affected by the nature of the systems, the oil emulsion system showing a markedly different and more rapid penetration than do other systems of similar viscosity, resulting in less permeable structures.
This effect is further demonstrated by actual field test experience. A weathered road was treated with a cationic emulsion containing additionally a nonionic emulsifier Similar to that employed in the tests shown in Table X.
A weathered asphaltic road was treated in sections with a 2:1 dilution of a cationic maltenes emulsion containing nonionic emulsifier, such as described in connection with Table X, employing 0.06 gallon/square yard, 0.14 gallon per square yard, and an excess quantity, approximately 0.25 gallon per square yard. Another section was treated with conventional asphalt emulsion SS1h (slow setting emulsion containing 60 penetration asphalt), with a dilution of approximately 3:2 at the rate or" 0.1 gallon per square yard. A section was left untreated.
From visual observations during application, it was evident that the diluted maltenes emulsion penetrated into the five-year-old pavement quite readily, with complete penetration being accomplished within five to twenty minutes, depending on the rate of spread. Since this pavement had not previously been sealed, and since there were no accumulations of grease drippings, no sanding was required. On the other hand, the asphalt emulsion did not penetrate, and sanding was required for safety reasons and to prevent pick-up of the asphalt by trathc.
Two months after application, cores were taken from the various sections and cut horizontally at /z-inch intervals. Viscosities of the asphalt recovered from each slice were then determined using the sliding plate microviscorneter, manufactured by Hallikainen Instruments, Berkeley, California. See articles by Labout and Van Ort in Anal. Chem, vol. 28, 1147-1151 (1956) and Griilen et al., in Road and Paving Materials (A.S.T.M.) Special Technical Publication 212 (1957), pages 3650. Table X1 is a tabulation of the viscosities measured and the penetration (given in parentheses) derived from the viscosities. (See Pfeifier, The Properties of Asphaltic Bitumens, published by Elsevier, New York, 1950, p.
TABLE XI Viscosity of Recovered Asphalt, Megapoises Norm-Numbersin parenthesis are penetration values of asphalts obtained by conver sion. See
It is quite apparent from Table XI that the treatment with the maltenes emulsion has caused a significant change in asphalt viscosity present in the pavement to a depth of at least /2 inch, with a possible effect of the added maltenes to a depth of 1% inches of the heavier treatments. Since these results were from cores taken relatively soon after application (approximately two months), it is possible that the maltenes had not yet had sufiicient time to reach a state of equilibrium with the asphalt. In the case of the asphalt emulsion of substantially the same viscosity, no such efiect is observed.
The cationic emulsion of the maltenes produces asphaltic structures of improved cohesiveness as compared to other dilution systems. They have improved loadpenetration characteristics. Tests were run on the same type of briquet used in comparing rates and depths of liquid-penetration. (See Table X.) An apparatus was used which would apply load to the treated end of the briquet through a 1.128-in. diameter (1.0 sq. in.) piston at a strain rate of 0.25-in. per minute to a total deformation of 0.250-in. The data obtained from this test are relative but valid for the series of briquets tested. Resulting load vs. deformation diagrams were obtained and are shown in FIG. 5.
In order to establish reference points on the chart,
two load-deformation curves are shown for freshly mixed briquets made with 7 /2 percent by weight of 48 penetration and 200-300 penetration asphalts. All other curves represent various treatments of a reference briquet made with 48 penetration asphalt at various states of aging. The aging of the briquets was accomplished in the infrared oven described in the article by Rostler and \Vhite, supra. The oven is automatically controlled so that the temperature within the briquets themselves is maintained at 140 F. during the specified aging time.
From FIG. it is evident that kerosene used as a carrier destroys the cohesiveness of asphalt binder and that proper cohesion cannot be regained even after 14 days of exposure at 140 F. in the infra-red oven because the kerosene has dislocated that asphalt cement located between the points of aggregate contact. In contrast, the emulsion system used for introducing the maltenes does not displace the asphalt providing the bonds between aggregate particles in the briquets, as evidenced by the fact that in all cases the briquets have resistance to load penetration exceeding that of 200300 penetration asphalt, although the consistency of the binder (asphalt) has been lowered.
From laboratory studies similar to those described above and from field experience in applying various emulsions to pavements, it has been concluded that the best method for incorporating the maltenes into the weathered asphalt concrete, as in road pavement, is in the form of a fine particle size, cationic emulsion, containing a nonionic emulsifier, as described. Although a dilution rate of two parts of emulsion concentrate to one part of water (40% oil content) is preferred to get the best combination of penetration rate and economy, the dilution rate to fit each particular job should be chosen on the basic of job conditions.
The importance of the emulsion system as affecting the particle charge is shown by the following.
One series of tests was designed to determine the importance of particle charge, as related to the adhesion characteristics of the asphalt=aggregate system. The test consisted of placing 2-g pellets made by mixing l00'parts Ottawa sand and two parts 85400 penetration asphalt,
aged for seven days in the infra-red oven at 140 E, into beakers containing 50ml. distilled water and heating the water to. the boiling-point. For this. test several. pellets were prepared and tested after treatment with 0.06-g. of the maltenes. The oil was applied as a. cationic-nonionic emulsion, described above, and as a nonionic emulsion, undiluted, andas a solution in kerosene. The pellets, after aging, for seven days in the infra-red oven at 140..
22 F., were immersed in milliliters of water, the water heated to boiling, and the contents of the beaker filtered through a No. l Whatman filter paper. The stripping effect was evaluated by observing the amount of asphalt floating at the water surface and clinging to the beaker walls, as well as by noting the area of exposed aggregate surfaces on the Ottawa sand at the bottom of the beaker.
The relative effect of the test on stripping of the asphalt could be readily observed visually. Most of the asphalt was stripped off the sand grains in the untreated control pellet aud all of the other treated pellets, except the one treated with the cationic emulsion of the maltenes, where very little stripping was noted. The stripping that was observed in the cationic sample was due to asphalt stripped from the bottom of the pellet where the treatment did not reach.
Another test consisted in examining under a microscope fragments of the treated pellets in order to observe the etfect of the treatment and aging procedure on the asphalt cementing the sand grains in the pellets. Improvement in the bonding accomplished by the cationic emulsificaiton system, which causes the oil to wet preferentially the asphalt portion of the asphalt-sand mixture, was readily observable.
This microscopic examination showed that the nonionic emulsion system does little to increase the bond because there is no preferential wetting of the asphalt portion. The undiluted maltenes result in droplets of uncombined oily material attached to the sand grains.
With kerosene as a carrier for the oil, the asphalt films are washed from the sand grains and are accumulated in the voids between them, resulting in loss of bond at the points of contact.
The advantageous results obtained from using the above combination of emulsifiers is additionally shown in the following tests.
Abrasion tests pellets were prepared in accordance with the Pellet Test procedure referred to above, using a 48- penetration asphalt and 20-30 mesh Ottawa sand. Duplicate pellets without treatment, and also duplicate pellets treated with aqueous emulsions of the maltenes in the same concentration of maltenes but differing only in the emulsion system, were subjected to the following tests. The cationic emulsion was that previously described containing nonionic emulsifier. The nonionic emulsion was made from the nonionic emulsifier alone, and the anionic emulsion contained only an anionic emulsifier. The pellets were then aged in the infra-red cabinet for seven days (see Rostler and White, supra). After exposure in the infra-red oven employed in the above procedure, the weathered pellets were subjected to an abrasion test by tumbling them in a 16-oz. French sl quirre bottle for 500 revolutions, as. in the above Pellet I Table XII summarizes the results obtained in this abrasion test.
TABLE XII Pellet Abrasion Test Results Abrasion Loss, Percent (aver-ago of duplicate specimens), 7-day Aging Treatment:
Untreated Control 34 Cationic Emulsion 13 Naniouic Emulsion 1 19;
Anionic Emulsion 21 The efiect of the maltenes in the cationic-nonionie emulsion form in modifying the asphaltic phase of an asphaltic pavement is further illustrated by Table XHI, showing the effect of this treatment on the permeability of the road pavement to water.
The emulsion is stable in the sense that it Will not break when stored for long periods in clean, closed containers at ordinary atmospheric temperature above freezing. Additional water may be introduced into the emulsion prior to time of application.
TABLE XIII Water Permeability, Mls. Min. Station OWT BW'l IW'I Test Section: Section treated with cat-ionie-nonionic-maltenes emulsion. Rolling same as control section. Section 1.
Control Section: Rolling consisted of breakdown with 12 T tandem 3 coverages with 26 T pneumatic ollovged with 8 '1 tandem. See
Total Ave OW'I =out er wheel tracks. BWT=between wheel tracks. IWT =inner Wheel tracks.
Tests were made by treating 'a road to ascertain the effect of the emulsion on the Water permeability of a is an extremely important feature of the maltenes emulsion treatment, particularly when one considers the cornpaction efiort required to reduce the permeability to a similar degree. Moreover, the decrease in permeability has been achieved in a finite depth of the pavement, and not by a skin coating which can readily be worn away by weather and trafiic.
The superiority of the balanced emulsions containing the blend of the cationic emulsifier and the nonionic emulsifier, as shown by the above tests, is confirmed by actual field experience. I
These cationic emulsions have the additional superiority that they are stable and may be mixed with hard water and even sea water without breaking the emulsion.
I have found that, for the purposes of my invention, the emulsionrshould preferably have the following characteristics: It should be free-flowing, preferably 'Within the range of 57 to 63 parts of the oily component by weight, and Water as the continuous phase not less than about 25 parts by weight and preferably in the range of 37 to'43 parts by Weight, and also an emulsifier. Water employed may be distilled Water, or ordinary soft or hard waters.
I have found that the best results are obtained by using a balanced type emulsion, as described above. The emulsifiers to be employed are preferably surfactants which are stable under the conditions employed in making the emulsion, and which will not break immediately when applied to the road or other asphaltic structure being reclaimed, so as to penetrate the asphalt and release the oil phase, i.e., the maltenes, within the asphalt structure, to become incorporated into the weathered asphalt.
The surfactant compounds having properties previously described are listed in standard textbooks in this art, for example, the Encyclopedia of Surface Active Agents, by Sisley and WVood, published by the Chemical Publishing Company, Inc, New York. The cationic emulsifying agents employed may be, for example, Cetylpyridinium chloride, or other quaternary ammonium salts and other cationic surfactants listed in the above publication and other standard books on the subject. These include the aliphatic fatty amines and their derivatives, the homologues of the aromatic amines having fatty chains (see pages 35, etc., 95405, of the 1952 edition of the above publication). Nonionic emulsifying agents such as are described above, and others which have the properties previously described, may be employed, such as are listed in the above text book, at pages 119-123 and page 163, etc.
Suitable nonionic emulsifiers which have been employed are nonionic surfactant sold by Process Chemical Company as Pronon 280, and as Oronite NI-W by the Oronite Chemical Company, and believed to be dodecyl phenol polyethoxyethanol. Suitable cationic eulsifiers are the fatty quaternary ammonium salts, fatty amide-aminoamine salts of the lower fatty acids sold by Process Chemical Company as Promine 2118, and believed to he a fatty amido-aminoamine acetate, and also the propionate salt sold as Promine 2115.
This list is not intended to be exhaustive, and is but suggestive of the emulsifying agents which may be employed. Many agents useful for emulsifying petroleum oils are effective in various concentrations.
In addition to the emulsifying agent, stabilizers may be used to stabilize the emulsion against electrolytes which may be present in the water used for making or diluting the emulsion.
The emulsion has the surprising result discussed above, in that it causes a rapid penetration of the reclaiming agent into the weathered structure, such as a weathered road. The rate of penetration depends also on the porosity of the road. This depends on the density, i.e., the compaction of the road when laid down, the grading of the aggregate, the original asphalt content of the road and the degree of weathering. Depending on these factors, the emulsified maltenes of my invention will be absorbed from almost instantaneously up to about 2 days, depending upon the volume per unit area of road. Unemulsified maltenes applied in equivalent volume rate calculated as oil, on a like road surface, will, experience has shown, take from several hours to a week or more, and in some cases will not be absorbed at all. During all this period the road is slick and unsafe for traffic.
Highway regulations in California require two lanes to be opened by sun-down, and for many roads this is not possible, using unemulsified oil; whereas with an emulsion used according to my invention, such penetration is achieved.
When using an emulsion made with a nonionic emulsitication system on processed roads which had a large amount of dirt and dust incorporated by the breaking up process, the emulsion appeared to preferentially wet the unoiled aggregate and dirt and acted as a dust-layer and did not penetrate the asphalt very well. When the emulsion is made with a cationic emulsifier, the weathered asphalt-coated surfaces are preferentially wetted, but a mixed cationic-nonionic emulsification system is preferred because it provides a balance of desirable properties, to Wit: ease of emulsification; stability in storage and application; rapid penetration; preferential Wetting of asphalt rather than of aggregate; and a water-repellent surface on the reclaimed structure.
I have found that materially improved results may be obtained by employing a balanced emulsion. By a balanced emulsion I mean an oil and water emulsion stable against electrolytes present in hard water and containing nonionic surfactants and cationic surfactants in amounts sufiicient to form an emulsion of cationic character, i.e., one in which the oil phase will deposit on the negative electrode if the emulsion is subjected to electrophoresis. Thus, the preferred emulsion will contain in parts by weight, based upon the oil phase of the emulsion, nonionic surfactants from 0.5% to 2% and cationic surfactants from 0.5% to 1.5%. Preferably the surfactant should be employed in the emulsion in an amount, based upon the oilphase, such that the nonionic surfactants are preferably about 0.7% or more by weight and cationic surfactants of 0.5% or more. Such an emulsion system will wet the asphalt portion of the road surface preferentially over the wetting of the aggregate and penetrate into the capillaries of the wetted asphalt at a more rapid rate than if no nonionic surfactant were employed.
For the purpose of convenience, I prepare the emulsion in the above concentrations. Before applying the emulsion to the road, I- may dilute the emulsion, for example, With an equal amount of water, although higher or lower dilutions may be employed.
The amount of maltenes to be added to the weathered asphalt depends on the nature of the Weathered asphalt. In the case of an asphaltic pavement, the amount of the maltenes to be added should be not so great as to make the pavement unstable and should not exceed the safe asphalt content of the road, nor be used in an amount such as to cause syneresis, i.e., oil exudation. Additionally, the amounts added should be suificient to improve the quality of the road or other asphaltic structure above that of the weathered road or structure, but not in such large quantity as to exceed, in the case of a road or other asphaltic structure, the capacity of the road or other structure to, absorb the fluid applied, as will be described below. The amount of the total asphalt should not exceed the safe holding power of the aggregate. If it is exceeded, the asphalt will exude as a'separate phase and not be incorporated into the asphaltie structure. Various authorities specify the particular composition of asphalt pavement, and thus determine the quantity of asphalt to be contained in. the asphalt pavement.
Standard Specifications issued by theDivision. of Highways, Department of Public Works, State of California, dated August 1954, gives at page 321, etc'., the properties of various asphalts which were acceptable to the State of California. See also Asphalts and Allied Substances, by Abraham, 5th. Ed, vol. 1, page 643, published by D. Van Nostrand & Co. The particular penetration grade asphalt found acceptable for any specific road job is usually specified by the engineer on the job or by contract. Thus, the required penetration grade for a good structure acceptable to the owner may be determined.
The concentration and amount of emulsion to be applied to the road surface is further controlled by the requirement that the emulsion be absorbed into the road surface without wasteful run-off. The quantity of emulsion to be employed on the road depends thus also on the permeability of the road. Road permeability, measured 'as milliliters of Water absorbed per minute by the road, may be determined by the test procedure California 341-A, issued January 1960, by the Materials and Research Department, Division of Highways, Department of Public Works, State of California. To de termine the rate of application of the emulsion to the road in treating either freshly laid or Weathered roads, the following modification of the above California 341-A procedure, known as the grease ring test, may be used.
The above emulsion concentrate, diluted with half its volume of water, is applied to the road within the six-inch diameter grease ring, formed as described in California Test 341-A. The time to absorb measured incremental. volumes of the diluted emulsion is measured. This is continued until, as in the California test, the surface remains wetted after prolonged standing. From this data the volume applied per square yard of the top surface of the road, required to be absorbed in a given time, e.g., 15 minutes, is determined.
In addition to rejuvenating weathered asphaltic roads, it has been found that the treatment also acts as a seal in depth. After penetrating into an asphalt pavement, it combines with and expands the asphalt. Permeability of the pavement to water is reduced. In some, instances, where initial shrinkage cracks had developed, the treat ment reverses the shrinkage process and closes the cracks. Moreover, when placed between successive layers of asphalt pavement, it provides an excellent bond by promoting a fusing of the asphalt layers at the interface.
Because of its ability to act as an asphalt replasticizer, as a seal in depth and as a bonding agent, the maltenes emulsion described can be used on all types of asphalt paved surfaces not only in preventive and corrective maintenance but also in construction and reconstruction operations.
In preventive maintenance, the emulsion is applied to a structurally sound asphalt pavement as soon as it begins to show signs of aging or brittleness through the the symptoms of dryness, surface pitting, ravelling or shrinkage cracking. Generally, these conditions develop in a period of two to ten years after construction, de-
2?? pending on such factors as mix design, asphalt durability, pavement permeability and climatic conditions. Here the abject is to penetrate the asphalt pavement and replasticize the asphalt before deterioration of the pavement due to brittleness has progressed too far.
Pavements that have developed a traffic glaze from high density traffic and grease drippings sometimes require removal of this seal to facilitate penetration.
In corrective maintenance, the oil emulsion is used in conjunction with other procedures to improve an asphalt pavement which is structurally sound but is extensively pitted or badly cracked. Usually the surface requiring treatment must be scraped or loosened in some convenient Way and the loose material discarded or sprayed and recompacted. It may also be desirable to incorporate a new mixture of sand and asphalt in the loosened treated surface, in order to provide a proper balance of aggregate and asphalt.
In reconstruction, the oil emulsion may be used to replasticize existing asphalt paved surfaces prior to a resurfacing operation or as an aid in breaking up and reworking an old, weathered asphalt paving while simultaneously replasticizing the asphalt in the mix. In the latter case, the treatment may be sufficiently effective to make the mix reusable again as a surface'course In new construction the treatment, which is applied after the asphalt paving has been spread and compacted, serves two purposes. The maltenes penetrate the surface and combine with the asphalt to restore the properties lost in the mixing cycle at the hot plant. The maltenes also combine with the asphalt to cause the asphalt to expand and close the pores of the pavement, thereby sealing the pavement to the depth of genetration of the oil.
By far the simplest method of bringing together the maltenes and the aged asphalt is by spraying a predetermined quantity of emulsion on the pavement surface and 4 allowing it to soak in. This procedure is always effective in preventive maintenance, in new construction seals and in priming and tack coatingoperations. Conventional calibrated asphalt spreader trucks may be used.
It has been found that all newly laid asphalt paving and the majority of weathered asphalt pavements, whether asphalt concrete, plant mix or road mix, are suliiciently permeable to respond to this simple spray and penetrate approach, provided a seal coat has not previously been applied. The grease ring test described above provides a method for determining the amount of the emulsion to be applied in one operation.
If the pavement has had a so-called asphalt emulsion fog seal, there is usually no dificulty in getting penetration, as this type of seal Weathers rapidly and wears off in a short time. a problem calling for special precautions, as the weathered remnants of the fog seal will combine with and hold a certain amount of maltenes at the surface, causing a slippery condition. In such instances, a light sanding is necessary, about 1 to 2 pounds of fine, dry sand per square yard, before traffic can be allowed on the pane ment. It is preferable, however, that sanding not be done before the emulsion has had at least 15 minutes and preferably 45 minutes to penetrate into the pavement.
The California Standard Specifications previously dea scribed give the quantity of asphalt to beappliedto a Examples taken from the California road structure. 7 Standard Specifications will illustrate'thisf,
However, the fog seal does present 233 Thus, at page 143, for Asphalt Concrete requirement is:
avcment the I may add sufiicient maltenes to bring t e total of asphalt, including the added fraction, based on the sample extracted, up to about the maximum percentage permitted by the specification for the road; thus, 6% for the specifications given above. I may, however, exceed this maximum percentage allowed by such specifications by about 2%, increasing the asphalt content to about 8% instead of'6%, i.e., increase the asphalt content to about 1.2 to about 1.3 times the specification requirement, particularly when determining the desirable asphalt content to be established in reclaiming, in place, a weathcred road or asphalt pavement.
Reference may also be had to the manual on Design and Construction of Asphalt Roads and Streets, issued by the Asphalt Institute Pacific Coast Division, page 66, Section H(6e), 1952 Edition, for methods of determining the allowable percentage of asphalt to be present in various asphalt structures.
The formula for the percentage by weight of asphalt to be used in the mixture with the aggregate, in producing a fresh asphaltic pavement mix from asphalt and aggregate, is given by the formula:
P:(R 4+S 7+F 12)C Where P=the percentage by weight of asphalt to be used in the mixture with the aggregate; R=the decimal percentage of rock in the mix; S=the decimal percentage of sand in the mix; F=the decimal percentage of silt in the mix; C :circumstantial factor, which normally is 1.
In order to determine the amount of maltenes to be added, according to the procedures of this invention, I may proceed in the following manner.
A core taken from the weathered road was treated to extract the asphaltic content of the road, and the extract asphalt determined by the method previously described on pages 31-32 of this specification.
The sieve analysis of the recovered aggregate is per formed according to the above Asphalt Institute reference. Due to the fact that the weathered asphalt partakes somewhat of the nature of an oxidized asphalt, I have found that the reclaimed road will tolerate an amount of asphalt up to about 30% in excess of the amount specified according to the above formula, i.e., to a value equal to about P+.3P. Knowing the weight of the asphalt in the core as determined above, and the top surface area of the core, the weight of the maltenes in emulsified form to be added per square yard of the surface of the road may be readily calculated.
Since the addition of maltenes is limited by the amount which the road can tolerate and be stable, i.e., form a homogeneous body without exudation of oil as a separate phase, it has been found that a practical application without a preceding core analysis may be made. This procedure depends on the nature of the surface.
The following examples illustrate the methods applied to the above cases. They are given as illustrations of, and not as limitations of, my invention.
EXAMPLE 2 This procedure for relaying completely deteriorated road surfaces consists of three steps:
(1) Breaking up of the road to give pieces exposing suiiicient fractured surfaces for the emulsion to penetrate the aged asphalt, e.g., pieces with no dimension substantially over 4 inches.
(2 Spraying the broken-up pieces with A to /2 gallon of the emulsion per square yard per inch depth. (In most cases dilution of 4 parts of the above emulsion with 1 part of water before application is recommended to reduce the viscosity of the emulsion and thus to facilitate penetration.)
(3) Regrading and compaction-This operation can be carried out with standard road building equipment. If the asphalt to be reclaimed is from an abandoned pavement, then the product after step (2) can be kept in a stock pile for later use.
The machinery used is (1) a grader equipped with scarifier teeth and a blade; (2) a grader equipped with a set of discs and a blade; and (3 a road oil truck equipped with spreader bar and pump to deliver the emul, sion in required amounts.
The surface is first broken up by means of the scarifier teeth of the grader, then further broken by the discs of the other grader, set to reach down to the base. The blades are used to turn and mix the broken pieces. After running this equipment back and forth several times to break up the road surface, the surface is leveled by the blade. The spreader truck is then driven over the brokenup surface and a suitable dilution of the emulsion is s rayed on the mix; for example, a 1:1 concentrated emulsion-to-water mix, at the rate of 1 /2 gallons per square yard. The emulsion quickly penetrates the brokenup material, coating each individual particle of the mix and depositing a film of the emulsion on the base. The treated mass is then mixed back and forth several times by the blade, and is then graded with a blade. The surface is then compacted by the wheels of the graders. (In some cases a properly graded, reworked surface can be left to automobile and truck traific for compacting.)
Even in cases where the road shows considerable embrittlement and large cracks, it often suffices to scarify the road surface slightly, to spread the required amounts of the emulsion onto the surface and let capillary action carry the reclaiming agent into the pavement. If the surface is uneven and badly cracked, it is advisable to fill the cracks with an asphalt-sand mix and to cover the whole road with a thin layer of this mix in order to form an even surface.
EXAMPLE 3 Procedure of Example 2 is to be used with asphalts which have deteriorated to a stage of embrittlement which needs. drastic measures for repairing the damage. Although much more economical and much more effective than other methods of repairing deteriorated asphaltic pavements, this procedure may be considered to be only a salvaging operation. Considerable more economy can be achieved by revitalizing asphalt pavements in a planned preventive maintenance program consisting of regular inspections of roads and corrections of damage due to natural aging at its onset, by application of the emulsion of this invention in the process of this invention.
Preferably the procedure of Example 3 is started as soon as the road is constructed and should take place not later than when the first stage of hardening is evidenced by the appearance of hair cracks. At this stage of the aging process, spraying of the surface with small amounts, for example, 005' to 0.15 gallon per square yard per inch depth (sometimes followed with a light application of sand), reverses the aging process and gradually restores the asphalt to its original plasticity. It can be expected that such maintenance, started soon after completion of the road and repeated when needed, will prolong the life of flexible pavements far beyond their original life expectancy. This is the type of operation recommended as preventive maintenance.
Many roads are, however, already in existence and in need of maintenance. Some of the existing roads will be in a condition between the two described under- Example 2 and Example 3 and will consequently require maintenance. m asur between. the two me h d su e This is illustrated by Example 4.
EXAMPLE 4 The operation may include scarifying the road surface by means of discs or heater-planers, removing loose dirt, cleaning out larger cracks in the pavement, filling the cracks with repair material (asphalt reclaimed by use of the emulsions described herein, taken from a stock pile, is highly suitable), and spraying the emulsion with a spreader truck onto the surface. The amounts of emulsion to be used are usually between about 0.1 to about 0.2 gallon per square yard per inch depth of pavement.
EXAMPLE 5 The composition of the emulsion described herein has been designed to be usable for all three procedures of Examples 24 and with all asphalts. The difference in degree of aging of different asphalts is taken into account in the recommendation of the amounts of the emulsion to be used. For areas large enough to warrant individual consideration, it is suggested that cores be taken from the pavement, the asphalt extracted and analyzed. From this analytical data a special emulsion and application can be devised.
In designing a revitalizing procedure exactly tailored to fit a particular asphalt, one of the principal precautions to observe is to add the right amount of reclaiming agent, in order not to exceed the total amount of asphalt permissible for the particular mix, i.e., to stay within the stability limits prescribed for the pavement. As shown by laboratory tests and field trials, reclaimed pavements can tolerate (as can constructions made with artificially oxidizedi.e., air blown.asphalt) 20% to 30% more asphalt than aggregate-asphalt mixes made with regular steam reduced asphalts.
The precaution not to exceed the permissible amounts of asphalt in the mix is automatically taken care of, in the procedure of. each of the Examples 2 by addin in small increments, observing the workability of the mix after each addition, and stopping When the desired degree of plasticity has been obtained. The following example is an illustration of a sp cially devised application.
A core taken from a Weathered road was extracted with benzol by the method previously described. The recovered extract asphalt was analyzed to determine its composition. The silt from the filter was combined with the aggregate from the extraction thimble, dried, and sieved to determine the grading of the aggregate. The extraction gave the following results:
Percent by weight of core Recovered extract asphalt 4.6 Recovered aggregates 94.3
Sieve analysis of recovered aggregate (according to procedure given in Design and Construction of Asphalt Roads and Streets, issued by Asphalt Institute, Pacific Coast Division, 1952 Edition, p. 66, Section H (62)):
Percent Rock portion, retained on 4 mesh screen 68.2
Sand portion, passing 4 mesh and retained on 200 mesh Silt ortion, passing 200. mesh screen The formula for maximum allowable asphalt content given in the above reference is applied as follows: