60

Traffic Paint Tests

W. G. VANNOY, Pigments Department, E. I. du Pont de Nemours and Company, Newport, Delaware

SYNOPSIS TRAFFIC-paint-testing procedures are reviewed in an attempt to determine which tests might be considered as standard. Although there is no official set of standard tests for traffic paints, those in use by a large percentage of consumers and those established by ASTM are considered as standard. Certain laboratory control tests together with small scale road tests are given as the most effective means available at the present time for evaluating candidate traffic paints. Laboratory tests as used to predict traffic paint durability are considered unreliable without further testing details and clarification. Current ASTM efforts to establish accelerated laboratory traffic-paint tests for dur• ability and suspension are reviewed. The need for such accelerated tests is emphasized in order to permit performance rather than compositional specifications.

• SUITABLE testsfor traffic paint com• Although there is no official set of stand• positions are problems of major impor• ard tests for traffic paint, the tests in tance. These problems are faced by use by a large percentage of consumers every state highway department in writing might be considered as standard. Fur• reliable traffic paint specifications. Fur• ther, certain standards and standard ther, the manufacturers, as well as the methods of test have been established by consumers, are faced with these same the American Society for Testing Mate• problems because various compositions rials and insofar as possible such gen• must be evaluated and the more promis• erally accepted and established testing ing candidates selected. For the most procedures should be used. part, laboratory and road tests are used in order to determine the compositions Laboratory Control Tests which offer most promise. Although actual road tests are believed to be the Laboratory control tests which are safest testing procedure to follow, such widely used include composition, consist• procedures, of course, require consider• ency and drying time. Other tests which able time and do not give the consumer are reasonably well established and which adequate protection against faulty com• might be included for control purposes positions. Obviously it is important, that are bleeding and suspension. Since these reliable, accelerated laboratory testing tests are described in considerable detail procedures be developed. Many ac• in the literature already published, perti• celerated testing procedures have been nent references are supplied and such tried and are being tried. At present, details omitted from this paper. however, there is little agreement re• Compositional determinations should garding a preferred accelerated testing cover such possible variables as gallon procedure for traffic paint. weight, percent pigment, percent ve• hicle and total solids (2). Under some STANDARD TESTS conditions it may be desirable to carry the analysis further to determine the type In the evaluation of candidate traffic and amount of pigment present also the paints, laboratory control tests and small type and amount of resin or oils or both scale road tests are commonly used (1). used m the binder. Obviously the amount 61 of such analytical work will depend to a in order to insure that these suspension considerable extent on the degree of limits are met. control desired. The above-mentioned laboratory control Consistency (2) measurements are im• tests listed as standard because of common portant because such information serves usage should not be considered as a com• as an effective control and is helpful in pleted list. It IS certain that additional judging application characteristics. Con• standard tests, many of which are in use sistency limits should be set for the by various consumers, are desirable. In particular paint and application procedure most instances, however, additional in• which IS to be used. Consistency changes formation IS needed either on reliability on aging are an indication of poor can or testing procedure in order to encourage stability which in turn may result in poor general adoption. durability. Drying Time' is a very important Small-Scale Road Tests characteristic of traffic paint because the traffic line when applied must be Small-scale road tests are used widely protected during the dry to no-pick-up to obtain practical drying time, dura• period. The emphasis on shorter drying bility and visibility comparisons. The times is increasing. This becomes method of making such small scale road doubly important where spray applica• tests is well established. * In this con• tions are made at the rate of some 15 nection, however, the location and type mph. (3). Obviously under such con• of road is an important consideration (4) ditions a slow dry to no-pick-up time as wide differences in performance can would require a very considerable num• result from such variables. In general, ber of flags in order to insure adequate paints show better durability on a bi• protection from traffic throughout the tuminous surface (rock asphalt) than on drying period. In some instances a cement concrete (2c). sacrifice in durability is accepted in order Drying time as determined from small to'obtain improved drying characteristics. scale road tests may vary considerably Bleeding is defined as the relative from the rating obtained in the laboratory condition of discoloration manifested in under more constant conditions. Ob• traffic paint when applied to tar or asphalt- viously, the weather, especially tem• ic roads. Accordingly, paints designed perature and humidity, the manner of ap• for tar or asphaltic roads should be plication and the amount, as well as type , examined carefully by means of control of paint applied are factors in the drying bleeding tests. Further, the laboratory times obtained from actual road tests. bleeding test as developed by ASTM is an Drying times under adverse conditions can easy test to run and is sometimes helpful be an important consideration. Accord• in detecting unsuspected compositional ingly, an opportumty to obtain such in• changes. formation should not be overlooked. Suspension^ tests on traffic paints are Durability is one of the prime con• desirable and helpful. The tendency to siderations in traffic-paint evaluations include coarse particles in the pigmenta• (5). The type of failure most frequently tion of traffic paint compositions in order encountered is chipping. ' Sometimes , to obtain improved night visibility serves however, erosion failure' is observed. to increase the possibility of poor sus• The relative durability of traffic paints can pension. Obviously, suitable suspension be rated satisfactorily by tlie use of limits should be set and control tests used transverse lines. This is pa;rticularly

'Method of Test for Dry to No-Plck-Up Time of Traffic Paint ^Method of ConducUng Road Service Tests on Traffic Paint (0 711-48), 1949 Book of ASTM Standards, Part 4, p 388. (D 713-46), 1949 Book of ASTM Standards, Part 4, p 395 'Tentative Method of Laboratory Test for Degree of Resistance "TenUUve Method of Evaluating Degree of Resistance of Traf• of Traffic Paint to Bleeding (D 969-48T), 1949 Book of ASTM fic Paint to Chipping (D 913-47T), 1949 Book of ASTM Stand• Standards, Part 4, p. 382 ards, Part 4, p 384.

"Method of Test for Evaluating Degree of Settling of Traffic 'Method of Evaluating Degree of Resistance of Traffic Paint Paint (D 8S9-48), 1949 Book of ASTM Standards, Part 4, to Abrasion Erosion, or a ComblnaUon of Both, In Road p 397. Service TesU (D 821-47), 1949 Book of ASTM Standards, Part 4, p. 376 62 true when the paints are placed on nar• the test results obtained with the abrasion row pavements and different portions of machine. Also, the correlation between the line are subjected to extreme varia• alkali resistance and road durability is tions in the amount of traffic (2c). rated as negative. Visibility IS without question a perti• It is stated by Skett and Herbert (7) nent requirement for traffic paints. The that actual road tests gave check results most common practice is to judge day and regardless of the type of road, traffic night visibility by eye (1). In some in• count, method of application, and spread• stances, photographic methods are used. ing rate. In general, abrasion tests are Within the last few years portable night- stated to give more reliable information visibility instruments have been made on durability than flexibility tests. No available which are very helpful m mak• one .laboratory test or combination of ing such ratings (6) and a tentative method tests used was sufficient to evaluate of test has been established. ^ correctly the durability of traffic paints. Allen (8), in an ASTM progress report, Tests in Use by Various Consumers states that the adhesion, flexibility, and hardness tests examined show no general Several traffic-paint tests other than correlation with field service behavior. those given as standard are used by However, very close correlation is re• various consumers (1, 2). As listed in ported with field service behavior of the the approximate order of popularity these samples of traffic paint examined by tests cover: the abrasion test developed by Leavitt 1. Flexibility (Maine State Highway Commission) and 2. Water resistance, hot and cold the combined accelerated weathering and 3. Hiding power abrasion tests developed by Hickson (Na• 4. Color stability tional Bureau of Standards) and Werthan 5. Spreading rate (New Jersey Zinc Co.). 6. Abrasion, dry and wet Shuger (2d) stated that paints which 7. Accelerated weathering pass a severe bend test do not neces• 8. Skin resistance sarily give better road performance. 9. Adhesion Further, it is stated that paints which 10. Hardness possess durability exhibit good abrasion 11. Alkali resistance resistance. However, it is possible that 12. Light sensitivity a paint with poor durability can show 13. Daylight reflectance excellent results on an accelerated wear 14. Dilution test test. Accelerated-weathering tests are 15. Stability mentioned as useful in rating comparative No attempt will be made to discuss these chalking and color failure. However, no various tests in detail. Certain con• great progress has been made on accel• clusions are available from published data, erated weathering to secure checking, however, which may be of interestin con• cracking and adhesion failures which are nection with further consideration of some the types most often encountered in traffic of these tests. paints. According to Goetz (2c) the degree of Light sensitivity* of traffic paint is a flexibility as measured by 32 test varia• property which can have a definite bearing tions shows no correlation whatever with on visibility. Accordingly, a test of this road durability on concrete pavements. type can serve as a helpful control. It is stated, however, that the modified Likewise, hiding power, daylight re• wet-abrasion test and the water-resistance flectance, dilution, and stability tests (2a) test show a direct correlation with field can be useful control tests. Under certain durability. The dry-abrasion test gave no limited conditions a skid-resistance test positive correlation between test con• may be of value. Spreading rate generally stants and road performance. Hardness can be varied widely by adjustments m is stated to have an important bearing on consistency and application technique.

'TenUUve Method of Test tor Night VislbiUtyof Trafllc Paints •Method of Test for Light Sensitivity of Traffic Paint (D 71^- (O 1011-49T), 1949 Book of ASTM Standards, Part 4, p 392. 47), 1949 Book of ASTM Standards, Part 4, p. 390. 63

CURRENT INFORMATION ON ASTM details and a clarification of the meaning of the results obtained are needed before Subcommittee IV, ASTM Committee such tests can be used with confidence. D-1 currently is working on accelerated The fact that composition specifications laboratory traffic -paint tests for durability are extensively used is adequate evidence and suspension. Further, consideration that suitable accelerated testing pro• is being given to specifications on glass cedures are not available. In this con• beads as used to improve the night visi• nection reliable accelerated laboratory bility of traffic paints. tests on traffic paints for durability and The work on accelerated traffic-paint for suspension are needed urgently. If tests for durability is being centered accelerated tests could be made available around combined accelerated weathering which would be adequate m predicting and abrasion tests also, combination lab• performance characteristics insofar as oratory tests involving hardness, hot water durability and suspension are concerned resistance and accelerated weathering. then performance specifications could be Cooperative tests are in progress but as used. Such a change in traffic-paint- yet no official reports, beyond the refer• specification practice would be highly ences already given, have been released. desirable from the standpomt of both the Accelerated suspension tests on traf• manufacturer and the consumer. fic paints are in progress. Hot and cold cycles are being used to accelerate settling REFERENCES and an attempt is being made to correlate the accelerated paint settling with normal 1. J. E. Myers, and H. A. Nelson, shelf aging. Consideration is being given "Report on Survey of Traffic Zone Paint as well to a possible correlation of 2- Testing Procedure by Committee on Traf• week and 6-month suspension ratings. fic Zone Paint," Highway Research Ab• In connection with the development of stracts, No. 81, pp. 8-10, June, 1941. suitable accelerated tests on traffic paints 2a. Traffic Paint, Exterior White and for durability and suspension a maximum Yellow, Federal Specification TT-P-115, testing period of two weeks is believed by April 29, 1942. many to be highly desirable. Accordingly, 2b. H. A. Gardner, and G. G. Sward, a 2-week time limit is included as a part "Physical and Chemical Examination of of the goal in the work under way on ac• Paints, Varnishes, Lacquers and Colors," celerated tests. Tenth Edition, p. 538, May, 1946. 2c. W. H. Goetz, "Field and Lab• POSSIBLE VALUE ON TESTS IN USE oratory Investigation of Traffic Paints," Proceedings, Highway Research Board, All of the tests listed here and consid• Vol. 21, pp. 233-259, 1941. ered as standard are beneficial and help• 2d. L. Shuger, "Traffic Paint," Drugs, ful control tests for traffic paint composi• Oils, and Paints, Vol. 54, pp. 343-344, tions. This would include the laboratory 346, 414-416, 418, 420, October, Decem• control tests and the small-scale road ber, 1939; Vol. 55. pp. 12-15. 126, 128- tests. Further, such tests are used 130, 229-232, 378, 380, 382-384, 385, widely and considered important by many January, April, July, November, 1940. consumers. In 1940, Drugs. Oils and Paints became The tests listed as in use by various the Paint Industry Magazine. consumers might be considered as op• 3. H. E. Neal, "Rapid and Economical tional. In certain instances, tests on Traffic Striping," Engineering News Rec- hiding power, color stability, or light ord, Vol. 133, pp. 842-845, December sensitivity, daylight reflectance, dilution, 2S7 194.4. and stability can be helpful controls. The 4. D. H. Dawson and A. Skett, "Ac• possibility of using such tests as flexi• celerated Testing of Traffic Zone Paints," bility, water resistance, abrasion, ac• Proceedings, Highway Research Board. celerated weathering, adhesion, and Vol. 2S, pp. 267-272, 1943. hardness to predict ultimate durability is 5. G. W. Ashman, "Present Prefer• questionable. Certainly, further testing ences for Traffic Paint," Highway Re- 64 search Board Bulletin No. 36, p. 7, No. 159, p. 69, 1949. May, 1951. 7. A. Skett and M. S. Herbert, "Ac• 6a. R. S. Hunter, "Night Reflectance celerated Testing of Traffic Zone Paints," of Traffic Paints and Signs," Traffic Engi• Proceedings, Highway Research Board neering, Vol. 17, p. 466, August, 1947. VoL 21, pp. 223-232, 1941. Sbr~J. M. Hill and H. W. Echer, 8. C. W. Allen, "Tests for Abrasion, "A Direct Reading Portable Photoelectric Adhesion, Flexibility and Hardness of Photometer for Determimng Reflectance Traffic Paints," ASTM Bulletin, No. 130, of Highway Centerlines," ASTM Bulletin pp. 29-36, October, 1944.