BI TUMEN-RUBBER IN THE UNIT ED STAT ES ITS ORIGI N, COST EFFECTIVENESS , DURABILITY AND NEW USES

prepared for present ation at the

PYHRN AUTOBAHN AG INTERNATIONAL CONFERENCE

Graz , Austria 15-16 March, 1988

By

Donald L. Niel sen, Consultant Nielsen Ent erprises, Inc . Phoenix. Arizona U.S.A.

SUMMARY

BITUMEN-RUBBER IN THE UN ITED STATES ITS ORIGIN, COST EFFECTIVENESS, DURAB ILITY AND NEW USES

Donald L. Nielsen Consultant , Phoenix, Arizona U.S.A.

The origin and history of bitumen-rubber will be presented . Since it has been used in the U.S. since 196B, we have a 20-year history. This long period of use has enabled us to prove that the product is cost effective , even at times on a first-cost basis. There are also side benefits , such as reducing fuel consump­tion needed for construction and consuming old tires, an environmental problem , as well as the fact that the product has proven to be much more durable than regular bitumens.

In addition , the author will present other uses of bitumen-rubber in the U.S . that might be different than those in Europe. These uses are:

1. Three-layer system 2. Cape seals 3. Crack sealers and fillers 4. Highway embankment protection and pavement subsealing 5. Bridge deck membra nes 6. Hydraulic structures (reservoirs, ponds. dikes , canals, etc . ) 7. Waste dumps B. Roofing

BACKGROUND AND OR IGIN OF BITUMEN-RUBBER

Bitumen-rubber was developed in Phoenix, Arizona , U.S.A. , by Cha rl ie McDonald, materials eng ineer for the City of Phoenix, He was seek ing an elastomeric bitu­men that would perform better than the standard bitumens . After doing some labor­atory testing in 1963-64. on such materials as raw unvulcanized rubbers. vulcan­ized rubbers. partially depolymerized rubbers , soluble rubbers, rubber latexes. ground whole-tire rubber, synthetiC and natural rubber, he chose granulated used­tire rubber . His original concept was to make pre-formed panels that would be placed over bad ly cracked pavements . Some of the panels were cut into strips! like "Bandaids," and placed over cracks . These products performed well in tests but were costly, and used a great deal of manpower for placement. These original panels conta ined 33% rubber and 67% bitumen .

Next he tried to determine if he could mix the rubber and bitumen at jobsite and apply it directly to the road . He used a modified slurry machine for this but had only limited success . They then tried to spray-apply the product from a distributor truck. but even though it was heated to a high temperature. it was too viscous to spray . A compromise was made by reducing the rubber content to 25% and spraying this blend through larger spray tips and increaSing the truck pump pressure. The first successful commercial application with this spray application was made in 1968, so there is now 20 years of experience with bitumen­rubber in the U.S. My patent, the product containing a smaller percentage of rubber along with extender oil was introduced to the market in 1975 . The first use of bitumen-rubber as a binder in hot mix also occurred in 1975. Bitumen­rubber was introduced to Europe in Belgium in 1981.

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With this longer history in the U.S .• we have been able to develop some cost effectiveness and durability data that I wi sh t o share with you . Bitumen-rubber is being used for purposes that I believe are different than your practices in Europe and I will discuss those briefly.

COST EffECTIVENESS

Experience over a 15-year period in the City of Phoenix shows that a bitumen­rubber SAM will be maintenance free for 10 to 12 years, and the product has been used only on the most heavily travelled streets . The study also Includes some of the ea rly applications before the system and quality cont rol were perfected . Normal surface treatments using a bitumen similar to 60-70 lasted only six to eight years with some maintenance. Therefore,ane can expect almost a doub l ing of the life of a su rface treatment by using bitumen-rubber, and even longer life can be obtained if there is some timely minor maintenance. The effect on the long· range costs Is shown in Figure 1.

Professor Monlsmith of the University of California Issued a research report in 1978 that indi cated a bi tumen-rubber SAMI covered with 2.5 cm of regu lar dense­graded aspha lt as an overlay wou ld resist reflective crack ing as well as 10 cm or more of regular dense-graded asphalt without a SAMI . If the dense-graded asphalt had bitumen-rubber as a binder , the difference wou ld be even more. On a 1983 project In Californ ia. the over lay design indicated that a regu lar dense­graded asphalt over lay would have t o be 21 cm thick to stop ref lective cracking . However, because of budget constraints. they placed only 15 cm of dense-graded asphalt containing 5' regula r bitumen . Reflective cracks came through this secti on within two years . On a nearbY2section . they first applied a bitumen­rubber SAMI at a rate of 2.26 litres/m . The dense-graded asphalt contained 6.8S bitumen-rubber binder and was placed in thicknesses of 4.6 cm and 7.6 cm over t he SAMI . Neither of these secti ons have any cracking . The costs in U.S. dollars on this project were:

15 em of dense-graded asphalt overlay 21 em of dense-graded asphalt overlay 4.6 cm of rubberized mix over SAMJ 7.6 em of rubberized mix over SAMJ

S/M2 ~ 16 .73 (extrapolated) 8. 23

12 . 45

The 4.6 cm-thlck rubberized dense-graded mix over a SAMI provided an initial cost savings of 45S. versus 15 em of regu lar dense-graded aspha lt and 103' of the 21cm design . The thinner rubber ized section is stil l outperforming the 15 em regu lar mix sect ion .

Another favorable factor for t he rubber ized dense-g raded asphalt is that i t re­s ists tire chain wear better . thus reducing long-range costs . Laboratory ab ra­sion tests gave the rollowing resu lts :

Rubberized dense-graded aspha lt Regular dense-graded asphalt

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Loss per 10cm-dia . Core 17 grams 41 grams

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Some other features about the rubberized mix is that energy can be reduced during construction and old tires are consumed. easing an environmental prob­lem . Estimated energy savings and t ire consumption on this same 1983 Califor­nia project are:

Estimated litres of diesel fuel saved by constructing a bitumen-rubber SAMI, covered with 4. 6 cm of rubberized dense-graded mix versus

15 cm of regular dense-graded asphalt

Per 50 ,000 m2

(as built) . . . . . .. .. . .. .. . .. .. . .. ... ...... . 167.763 21 crn of regular dense-graded asphalt

(design) . ... . . ....... . . . . .. . ... . ... . ... . .. 275 , 053 Number of automobile tires consumed with above bitumen-rubber construction . . ... . ... . . ... . . 19.005

OURABILI TV

Bi t umen-rubber in itself is more durable than standard bitumens because

1. The anti-oxidants in the rubber impart a beneficial effect on the bitumen . 2. Rubber extender oil is present in the tires and is often added to the l,lix­

ture . Such oils are similar to pavement rejuvenators. 3. Carbon blacks in the rubber improve life. 4. The particles of undissolved rubber act as a screen to filter out the

harmful ultraviolet rays .

In addition . bitumen-rubber. being more ~iSCOUS than reg~la r bitumens. can be spray-applied in thicker films : 2.94 11m versus 0.9 11m for regular bitumens . The thicker f ilms last longer. When used as a binder in asphalt mixes, the binder contents are usually about 20% higher than with regular bitumens . which aga in results in thicker, longer-lasting films.

As mentioned ea rl ier. the City of Phoenix is getting 10 to 12 years of l ife from bitumen-rubber SAMs versus six to eight years from regular bitumen. This life. however, is more concerned with the appearance of reflective cracking . There is still plenty of l ife left in the bitumen- rubber after 12 years . When bitumen-rubber has been used as a binder in a mi x, the pavement remains much darker and livelier than adjacent mixes made with regular bitumen . indicating a longer life. This was Quite dramatic on a 13-year old project near Phoenix where we have sunshine 86% of the year and summer temperatures exceed 38°C for 100 days or more .

A side benefit to bitumen-rubber SAMs or SAMIs is the protection it affords to the under lying bitumen pavement . It literally stops further weathering t o the old pavement . A 13-year monitoring program of a pavement at the Phoenix Airport studied the hardening of the old pavement with and without a SAMI . The results were dramatiC . as shown in Figure 2.

OTHER USES FOR BITUMEN-RUBBER IN THE UNITED STATES

Bitumen-rubber is being used for several mayor may not be applicable to Eu rope .

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specialized purposes in the U. S. that I will briefly cover some of these .

THREE-LAYER SYSTEM: This is similar t o the SAM! plus open-graded asphalt over­lay approaCh that is being applied in Europe , except that there is a third layer . Many of ou r rigid, Portland cement pavements are bad ly cracked and such cracks and old joints are rough riding . Prior to placing the SAM!, a levelling course of approx imate ly 2.5 cm of conventional open-graded asphalt is placed first . The bitumen- rUbber SAM I is placed on t op of that. Next comes the top overlay of about 2.5 cm of regular open-graded aspha lt . We should be us ing bitumen-rubber as a binder in that top course as you are dOing , but as yet that is not done . A good portion of the motorway going through Phoenix has been overlaid in this fashion , a part of which is now nine years old . The main pa rt is three years old .

CAPE SEALS: This type of sea l coat was devel oped in the Cape Province of South AfrIca several years ago, and thus the name "Cape Sea l . " It consists of placing a normal ch ip seal, brooming off the excess chips and then covering that with a s lur ry seal . In the U.S., the ch ip seal that is placed first is often a bltumen­rubber SAM. . Reguzar slurry seals arebeingpiaced over2that at a slightly higher rate of 8. 75 kg/m versus a normal rate of about 7kg/m . Slurry seals contain­ing po lymers are st i l l quite ra re in the U.S. , but I believe a product like the German "Ralumac" wou ld make this a superb system.

Natura l ly, Cape Sea ls are not intended for heavy highway use, but they are very suitable on large parki ng areas, residential streets and very low-trafficked country roads . I expect this system to grow rapidly in the U.S.

FILLERS: Bitumen-rubber is used to fill and sea l cracks in U.S. Bitumen-rubber with small amounts of new poly­

to fill and seal cracks and jOints in Portland cement pavements . mod ifications are also made in the bitumen-rubber blend to pro-duce a product that will perform better in co ld climate areas .

The bi tumen-rubber blend i s made at a centra l plant and then poured into boxes lined with plastic sacks . These boxes are 13.6 and 27 .2 kg in size. Special heating units , using indirect hot oi l heating, are used in the field t o heat and soften the crack fil ler to a pouring cons istency. usua l ly around 163°C . Bitumen­rubber and plastic sack are placed in the kett le together. so the hand ling is easy .

Cracks can be routed to widen them and t o present a cleaner crack wall system. But some believe that it is better t o leave the crack alone because the rough­crack interior wall s do a better job of retaining the fi l ler once it has set . In either case. the cracks should be blown clean with compressed air . If it is quite cold., the cracks shou ld be heated with a hot-air lance . The molten sealer shou ld be placed up to the su rface of the crack. but if an over lay Is planned . the sealer may overfl ow the crack t ip and then be smoothed wi th a small squeegee . The sealer will set in a short time and the pavement should then be broomed clean .

There are many locations so ils that expand and

contract due to the presence of moisture . Bitumen-rubber has been used to con­trol that moistu re by sp raying it direct ly on the soil under a new pavement t o

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leave a tough impermeable membrane . That membrane nonmally extends on over the shou lders and embankments as well to keep water from entering the sides.

Bitumen-rubber can also be sprayed over an existing pavement prior to an overlay . In this case , the shou lders and embankments are sprayed as well . The bltumen­rubber membrane is subsequently covered with about 20 em of soil on the embank­ments to protect it against physical damage . This system has worked better than any other to cont rol clay soil action .

BRIDGE DECK MEMBRANES: Damage to steel bridge decks and to steel reinforcing bar in cement deckS has been extensive in t he colder regions of the U.S. due to water and salt-brine Intrusion . Bitumen-rUbber is now being used to seal such decks p~ior to applying a thin overlay. The normal procedure is to app ly about 3.4 11m by the hot-spray method . A plast ic woven or non-woven mat is then placed over that to provide a surface that subsequent construction equipment can run on without tearing up the membrane. Our State of Washington, which has a very high rainfall and cold winter temperatures, has sealed several hundred bridges with this system with excellent results.

HYDRAULIC STRUCTURES: Bi t umen-rubber has been used to seal hydraulic st ructures (reserVOirs, ponds , dikes, cana ls, ~each ing pads, etc.) since 1981 in the U.S. The largest project wa s a 971,000 m waste-water reservoir at a nuclear power plant west of Phoenix, Arizona .

For such structures , the underlying soil is first smoothed and compacted . All rocks and sharp breaks in the surface shou ld be eliminated . If the soil is too rocky, then non-rocky so il or sand is imported to app ly a thin plate over the soil . A prime coat Of a light MC cutback bitumen should then be applied at a rate of about 1. 1 11m . This was not always done on the early reservoirs and troubles occurred as a resu lt. Af2er the Me has cured, the bitumen-rubber is applied at a rate of about 6.8 11m in two or mo re spray applications. Thi s is done from a special side spray bar extended from the back of the dist ri butor truck . The resu ltant membrane is about 0.6 em thick . Regular bitumen-rubber i s norma lly suitable for s lopes up to 4-to-1 . The formulation is modified to raise the softening point for steeper slopes . For very steep s lopes , a woven plastiC fabric is sometimes used on top of the first spray application and covered by the second application of bitumen-rubber . In all cases, the bitumen-rubber should be covered with 20 to 30 em of soil, sand or grave l to provide physical protection .

Bitumen-rubber has also been used to seal old Portland ceme2t or bitumen-l ined reservoirs . The bitumen-rubber is spray-applied at 3.4 11m or more direct ly on the old surface and then covered with chips and rolled .

WASTE DUMPS: Environmentalists have become quite concerned about poisons and toxic wastes leach ing into ou r underground water systems from waste dumps. To min imize that problem , old dumps have had bitumen-rubber spray-app li ed over the smoothed covering soil after the soil has been stabilized to support the weight of construction equipment . Sometimes it is planned to use the old dump

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site surface as property for new factories or for storage , which is another reason to stabilize the soil. The bitumen-rubber is then covered with chips as with a SAM. This provides a waterproof membrane to stop rainwater from seeping down into the old dump .

On a new dump site, the soil can be first smoothed and compacted as with a re­servoir and then sealed with bitumen-rubber in the same manner . A cover of soil, sand or gravel should be placed over that membrane . This will assure that water and wastes carried with it will not leach out .

ROOFING: Bitumen-rubber is being used to coat level and near-level roofs. On new roofs, it is spray-applied or squeegeed over the roofing felts as with a normal flood coat placed with conventional roofing bitumen. On older roofs. patching may first be necessary and then the bitumen-rubber is applied directly to the old surface. In all cases, the bitumen-rubber should be covered with small gravel for protection .

Flat roofs have posed problems for many years . Shear stresses are tremendous on these decks. and when regular air-refined roofing bitumen is used, it shrinks and becomes brittle in winter , causing leaks at parapet walls. chimneys, pipes, etc . Bitumen-rubber stretches and remains flexible at cold temperatures, and it recovers to its original shape which solves most of these problems. I re­did the roof on my own home in Phoenix three years ago and el iminated all water leaks . Many of my neighbors have had their roofs redone with regular bitumen and with plastic foam, and are still experiencing leaks .

OTHER USES: Recently, bitumen-rubber has been substituted for regular bitumen In the manufacture of bitumen roofing shingles and rolled roofing . So far. these products are performing well.

CONCLUSION

After 20 years of use in the United States, bitumen-rubber has proven it is superior to regular bitumens in performance . In addition , it is cost effective and is more durable . Some side benefits with the use of bitumen-rubber are a savings in diesel fuel consumption during construction because of the thinner sections that are permitted . Mixes are more resistant to tire chain wear and last but not least, old tires are consumed , thus relieving an env i ronmental problem.

Several new uses for bitumen-rubber highway maintenance, hydraulic structures and roof surfac ing brings out the versatility of this product . I am sure that other new uses will be found for this remarkable product as time goes by . We believe it has the potential t o solve many problems, and at a lower cost.

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1.60 -'0 ~

~ 1 1.50 -, ~ 1 1.40-co 6-1 1.30-(f)

'-I 1 20-(j) .

(L

~I 1.10-(j')

° °1 1 00 -

.90 -

.80 -

.70 -

.60 -

COST COMPARISON CHART

'l>' Standard Se a \ GO

co (j) (f) , (j)

a:

I -

Asphalt-Rubber SAM

Standard S e'i> \

'l>' GO

o 1 2 3 4 5 6 7 8 9 10 11 12 131415 16 1718

Years

~ ~ , ~

~

14 0

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• o " 6 0

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20

ABS. VISCOSITY vs. TIME {or

PHOENIX SKY HARBOR A IRPORT

ASPHALTS

WI THOUT RU3BER

• 20Q,OOOJ

74 76 78 80 82 84 85

YEAR

Absolute Viscoslly 'IS Time for Phoenix Sky Harbor Airport Asphalts

Figure 2

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REFERENCES

1. "Fifteen Year Pavement Condition History of Asphalt- Rubber Membranes in Phoenix , Ar izona" - Russel l Howard Schnormeler, P.E .• Engineering Super­visor Materials, City of Phoenix, Arizona; 1985

2. "An Analytical Study of the Applicability of a Rubber Asphalt Membrane to Minimize Reflection Cracking in Asphalt Concrete Overlay Pavements" -N. F. Coetzee and Professor C. l . Honismlth. Department of Civil Engineering. University of California, Berkeley. California; June 1978

3. "Effectiveness of Rubberized Asphalt In Stopping Reflection Cracking" (Interim Report) - Raymond A. Forsythe, P. D., Chief, Office of Transpor­tation Laboratory. State of California. Department of Transportation. Sacramento, California; January 1985

4. "Proceedings - Nati onal Seminar on Asphalt-Rubber" - San Antonio, Texas Federal Highway Administration, Demonstration Projects Division , Washington, O. C. ; October 1981

5. Arrn-R-Shield, Asphalt-Rubber ~Iaterproofing Membrane Brochure - Arizona Refining Company , Phoenix. Arizona; 1982

6. "Energy Requirements for Roadway Pavements" - The Asphalt Institute. (MISC-75-3) College Park. Maryland; April 1985

7. "Design and Installation of a Spray-On Type Lining at a Nuclear Generating Facility" - J . R. Bagley. Arizona Refining Company. Phoenix, Arizona ; B. M. Ghadlali, Senior Engineer, Bechtel Power Corporation, Norwalk, Ca li­fornia; and W. L. Hurst. Civil Engineer . Supervisor, Arizona Publ ic Service Company. Phoenix, Arizona; 1982

8. "Finite Element Analysis of Arizona's Three-layer Overlay System of Rigid Pavements to Prevent Reflective Cracking" - Nan Jim Chen . P. E . • PhD; Joseph A. DiVito, P. D.; and Gene R. Morris. P. E. ; Arizona Transportation Research Center, Arizona Department of Transportation. Phoenix, Arizona; Association of Asphalt Paving Technologists Meeting in Kansas City. Missouri February 1982 .

PYHRN AUTOBAHN, AUSTRIA - 10TH ANNIVERSARY IN'fERNAT IONAL CONFERENCE _________ -"G"RA"'Z"-,L-.!A"U"'S"T.!2R"I"-'A, b'IARCH 16 ~_.1.9B8

(Notes taken by Do n Nielsen during presentation of some of the papers)

E, NAKKEL , Prof , and Pr esident of the Technical Committee "Asphal tstras en" of A,I ,P, C, R., Bonn , Germany,

Drainasphalt is a great innovation . For roads, the first consideration is safety and the second is noise abatement.

Noise abatement - Automobile manufacturers have gone about as far as they can to reduce noise , So , engineers have sought ways to make quieter roads with sound screens , barriers , dams, et c . There a r e 1 , 000 km (620 miles) of autobahns in West Germany with such screens and barriers. These are expensive. Translated to the adjacent pavement, they ave r age about 120 DM/~~ (about2$79/Yd) . New PCC pavement costs are about 30 D~VM(- (about $15/yd). There are objections to the sc reens. They arc not pretty and motorists complain they wreck the view of the countryside . One a lternative i~ trees but noise absorption is difficult to measure , They have tried some different types of pavement . An increase of ) decibles of noise l evel at a regular traffic noise level is equivalent ~ o doubling the traffic. Drainasphalt has given them a reduction of B to 10 decibles. This is equival ent to reducing th e traffic down t o l/Bth. In the Netherlands , their policy is to provide noise abatement for all motorways that carry )5,000 vehic l es or more per day.

Safety - In the Ne therlands , Dr ainasphal t has provided a reduction of 20 to JO~ in traff ic casualties. The cost of such casual ties would more than pay for Urainasphalt .

Other - Draina~phalt also redu ces tire rolling r esistance so there is a fuel savings to the motorist . They est i mate that if their entire i'iest German autobahn system were cove r ed with Drainasphalt . motorists would save 20 , 000,000 gallons (should this be liters?) of fuel per year.

HELrWT PRAGER , Engineer in Cha r ge of Highways and Bridges , Austria , Vienna , Austria . (No . 2 man in Highway Minis try)

Phyrn Autobahn carries 2B , OOO vehicles per day , J,OOO to 5 , 000 of which are truck~. In ur ban areas whe re speed is Bo km (50 OCPH), barriers will provide adequate noise reduction. vlhere speed is 160 km (lOa mph) , dams are needed . 'rhe~e are costZy and not acceptable to the motorist. 'rhey have one J , 000 ~.f D , 588 yd ) test section of Drainasphalt , ) CM (1.1B ") thi ck . They need 4 eM (1.58" to 5 Cb'l (1.97") thickness to provide complete sur face drainage in high rainfall areas . Their goal is reduce traffic noise to 60 decibles during the day and 50 decibles during the night, They were worried that the good surface dr ainage provided by Drainasphalt would increase the demands for de-icing salts , but this has not happened . Sand must not be applied because it will choke off the voids which will hurt both noise abatement and sur face drainage, They do not have an answe r to service life yet , but positive reports f rom other countries will increase their cons ideration of Drainasphal t.

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NOTES FROM CONFERENCE AT G RA Z I AUSTRIA J/16/88 , CON ' T .

MI CHEL AfIlILHAT , Dir . General of Society of Autoroutes the East of france , Paris , France

of the North and

Mr. Amilhat represents a private au tobahn. 'l'hey have plac ed 156 Km (97 miles) of Vrainasphalt . They plan a 35 Km (22 mile) stretch in a more difficult area . They l ooked at Dr ainasphalt in the lab in 1985. In 1987 , they placed 70 Km (43.4 miles ). Drainasphalt is placed one lane at a time as an overlay so they can keep adjacent lanes open to traffic. But the joints have gi ven them some problems. Drainasphalt costs abou t JO~ mo re than conventional asphalts . but accidents are 5 times higher on regular asphalt pavements when it rains, which is often. The y have concluded that the additional cos t will be amortized by 199J. Th eir trial cou rse cover s ascending , level and deocendine stretches. Pavement had 20t ' voids when built. J years later. 90% of the voids were still there. Friction coeficient on a wet Drainasphalt was the same as on a dry Drainasphalt. (Note : 'l'hese pavements were built by the largest French contractor , Beug,net who cal l the product "Drainochape " .

B..QGEJLCA;IG~.I;: , Direct or of Roads , Minister of Public ~'iorks . Brussels , Belgium

First trial of Drainasphalt was on the E-J Motorway south of Ghent in 1981. (Note: this was when I introduced this concept to Belgium and I supervised the test.) 'fhis was over a cracked , deteriorating PCC pavement. This first tri al corrected the problem. They placed a layer 2.5 CM (1") thick of pervious mix with 20J' voids and 7% asphalt-rubber binder content . This was I KM ( . 0 miles) long . Stability and se rvice life have been good. There are 35 , 000 vehicles per day on this portion of the E-J , JOfo of whi ch are heavy trucks with 1J ton (14.56 short ton) axle loads . With this good success , they next laid a similar , longer section in 1982 on the Ring of Brussels where traffic noise was a problem in the met ropolitan area with positive results. They obtained a noise reduction of 4 to 6 dec ibles vs. the PCC pavement that was there. This section carries 60 , 000 vehicles per day . Noise level was so high that they reduced the maximum spee d to 80 Km (50 mph) . They were able to raise the limit back up to 120 Km (75 mph) after the drainasphalt was placed. The pavement is still in perfect cond ition today.

Be l g ian autobahns were built in the 1960s to be safe at 160 Km (100 mph). The coefi cient of friction was high as they built rough (laterally g r ooved) surfaces on the PCC and noise was not a consideration. Objections to the traffic noise arose in the 1970s. When Drainasphalt appeared on the market , they did not want to take years to '>'latch the results and do more experimentation because of the flood of complaints from cit~zen s . So , they have plunged ahead and now have 1.500,000 r.; (1 , 794 , 000 yd ) in place , most of it in the Brusse ls area. After 7 years , they have the following oberser~ationsl

1. There has been a considerable noise reduction . 2. There is very little hydroplaning . J. Surface remains black - it does not tu rn g rey like normal asphalt. 4. There i s a reduction of oncoming headlight glare. 5 . ? (I missed this one) 6. There are ha r dly any ruts even though the surfacing remains very

live as compa red to a normal asphalt mix. 7. Costs have been J to 5 ~ above traditional overlays . 8 . Salt consumption has increased . 9 . Single sized rock must be of higher quality .

10. Compocition of various ingredients requires much care.

l"age J .

NOTES FROM CONPERENCE AT GRAZ, AUSTRIA )/16/88, CON ' T.

11. Have increased the thickness of Drainasphalt to 4 CM (1. 6") to obtain better drainage .

They are so satisfied with Drainasphalt that they now look to overlay their entire autobahn system as well as many heavily travelled surface streets. (Note I I learned later that they are currently surveying the noise levels on their entire system to set up a list of job priorities . Also, they have noted a big drop of noise within tunnels and plan to put Dr a inasphalt in all of them).

E. HEINISCH - Technical Director of the Autobahn , Budapest , Hungary .

Their pec autobahn pavements are 2) years old and are badly cracked and abraidcd. Traffic safety is a problem . They have been overlaying with a total of 1.5 CM (6") of regular asphalt concrete but this ties up the roadway too long . And , cracks soon re-appear in the travel lane but the fast lane is still g ood. They tried some thin overlays including Drainasphalt. Cos ts have been increased but it has been successful. They now have 160 KM (100 miles) buil t .

PROf'. DR. GERHARD STEHNO - Uni versi t y Professor , Civil Engineer and 'fechnician 01' Physics , Igls (Innsbr uck) , Austria.

The first application of Drainasphalt on the autobahn in Austria was in 1984. In addition to the instruments showing a noise reduction , people living closeby verbally told them they noticed the roduction . This pavement cu~~ noise frequency in the range of 1 , 000 to 3,000 hertz the best and there is little reduction of lower frequency noises . They found a .5 to 9 decible reduction in some places and ) to .5 decible reductions in others . Noise measurement was 2.5 meters (82 ft . ) away. Higher f requencies from 640 to ) , 000 he rtz are annoying to humans . Drainasphat reduced these. Lower frequencies of 80 to 6)0 he rtz were not reduced but this level is not disturbing to humans . For some reason , this lower fronquency range increased when measured 3 KM (1.9 miles) away .