Sulfur: New Sources and Uses - ACS Publications - American

price and supply problems if crude oil imports again suffer severe disruptions. ..... 1. 6.2. 4. Binde r. Uni t. Weight. ,. 161. 5. 156. 0. 161. 5. 16...
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13 Road Construction Using Sulfur G E R A L D D. L O V E and E D W A R D T. H A R R I G A N

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U.S. Department of Transportation, Federal Highway Administration, Offices of Research and Development, Washington, D C 20590

Elemental sulfur has been modified I n an exothermic r e a c t i o n w i t h commercially a v a i l a b l e hydrocarbon compounds t o produce a pavement binder m a t e r i a l that has been s u c c e s s f u l l y utilized to c o n s t r u c t s e v e r a l experimental pavement s e c t i o n s on p u b l i c highways. The engineering p r o p e r t i e s , the f o r m u l a t i o n , and the methodology f o r producing and utilizing this chemically modified sulfur pavement b i n d e r , intended as a s u b s t i t u t e for asphalt cement, are d i s c u s s e d .

The worldwide d i s r u p t i o n s in crude oil supply in 1973-74, 1978-79 and 1980 have i l l u s t r a t e d the tenuous nature of imported crude oil s u p p l i e s . The United agates annually consumes a p p r o x i mately 30 m i l l i o n tons (2.7 X 10 kg) of asphalt cement r e f i n e d from crude oil; 93 percent of the t o t a l mileage of surfaced highways and s t r e e t s , or c l o s e t o 1.6 m i l l i o n miles (2.6 m i l l i o n km), has been constructed w i t h asphalt m a t e r i a l s . Thus, the highway i n d u s t r y is very v u l n e r a b l e t o asphalt p r i c e and supply problems i f crude oil imports again s u f f e r severe d i s r u p t i o n s . Changing technology a l s o promises t o have a s i g n i f i c a n t impact on asphalt production in the coming decade. F i r s t , modern r e f i n i n g technology is aimed a t the processing of the r e s i d u a l f r a c t i o n s of crude oil t o l i g h t products, t o the detriment of asphalt p r o d u c t i o n . Second, the government is committed t o s w i t c h i n g the nation's energy dependence from petroleum t o a broader base in which c o a l , both as a b o i l e r f u e l and as a feedstock f o r s y n t h e t i c f u e l s and chemicals, p l a y s a p r i n c i p a l r o l e . The p o t e n t i a l f o r bitumen production from s y n t h e t i c f u e l r e s i d u a l s is l a r g e l y unassessed.

This chapter not subject to U.S. copyright. Published 1982 American Chemical Society

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

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Asphalt Extenders and Replacements The oil embargo of 1973-74 caused the Federal Highway A d m i n i s t r a t i o n (FHWA) t o e s t a b l i s h an R&D program to i n v e s t i g a t e the production of asphalt replacements and extenders from e s s e n t i a l l y non-petroleum sources. Since i t s i n c e p t i o n , t h i s program has examined in d e t a i l the use of: sulfur in elemental and c h e m i c a l l y modified form; binders derived from c e l l u l o s i c m a t e r i a l s such as wood wastes and animal manure (I); and l i g n i n s produced as by products of the paper and pulp i n d u s t r i e s (2) · Both c e l l u l o s i c wastes and l i g n i n s were found to have only l i m i t e d a p p l i c a b i l i t y t o the problem at hand. S u l f u r , however, has been shown to be a very u s e f u l m a t e r i a l f o r t h i s purpose. Elemental sulfur may be used t o extend a s p h a l t , as in sulfur extended asphalt (SEA) b i n d e r s , o r chemically modified s u l f u r s may completely r e p l a c e asphalt in paving mixtures. Complementing the t e c h n i c a l f u n c t i o n a l i t y of sulfur f o r pavement c o n s t r u c t i o n , U.S. sulfur p r o d u c t i o n , w h i l e geographi c a l l y l o c a l i z e d , is favored w i t h a nationwide d i s t r i b u t i o n system. S u l f u r is i n v o l u n t a r i l y produced from oil and n a t u r a l gas, and the s w i t c h t o c o a l promise t o produce a d d i t i o n a l l a r g e U.S. surpluses of sulfur in the coming decades. Voluntary production is f l e x i b l e so that the i n t r o d u c t i o n of a major new sulfur use could be phased in without undue s t r e s s in the present supply and demand s i t u a t i o n . The development and e v a l u a t i o n of SEA binders has i n v o l v e d many p u b l i c and p r i v a t e o r g a n i z a t i o n s i n c l u d i n g FHWA, and the wealth of i n f o r m a t i o n in t h i s area w i l l not be reviewed here (see, e.g. J3, 4^ 5). FHWA has pursued the development of c h e m i c a l l y modified (or p l a s t i c i z e d ) sulfur as a replacement f o r asphalt in f l e x i b l e paving mixtures from a rudimentary l e v e l . This development program began in 1975 w i t h the award of a c o n t r a c t t o Southwest Research I n s t i t u t e t o i n v e s t i g a t e mater i a l s and techniques t o improve the engineering p r o p e r i t e s of elemental sulfur. From t h i s c o n t r a c t has come the Sulphlex paving b i n d e r s , a f a m i l y of chemically modified sulfur binders designed as asphalt s u b s t i t u t e s f o r highway pavement construct i o n . These Sulphlex m a t e r i a l s w i l l be discussed in d e t a i l in t h i s paper. Development of Sulphlex Binders The engineering p r o p e r t i e s of aggregate mixtures employing elemental sulfur as a binder are not s u i t a b l e f o r highway pavement a p p l i c a t i o n s ; such mixtures possess adequate compress i v e s t r e n g t h , but are extremely b r i t t l e and l a c k s a t i s f a c t o r y f a t i g u e behavior t o r e s i s t r e p e t i t i v e t r a f f i c l o a d i n g . R a p i d l y quenched, pure elemental sulfur is extremely p l a s t i c (6)· This p l a s t i c sulfur w i t h i t s polymeric s t r u c t u r e has t e n s i l e q u a l i t i e s l a c k i n g in the c r y s t a l l i n e form, but

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

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13.

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it q u i c k l y r e v e r t s back to the c r y s t a l l i n e form which is thermodynamically favored under o r d i n a r y c o n d i t i o n s . However, it may be s t a b i l i z e d by the a d d i t i o n of chemical m o d i f i e r s , f o r example, hydrocarbons such as d i c y c l o p e n t a d i e n e . I t has been demonstrated (_7, 8) that such m o d i f i e r s w i l l apparently s t a b i l i z e the p o l y meric, p l a s t i c sulfur i n d e f i n i t e l y i f they are present in sufficient quantities. Southwest Research I n s t i t u t e (SWRI) undertook a program to screen a l a r g e number of p o t e n t i a l chemical m o d i f i e r s f o r t h e i r a b i l i t y to produce a s p h a l t - l i k e m o d i f i e d s u l f u r s . S e l e c t i o n of the m o d i f i e r s to be screened was based on s e v e r a l f a c t o r s , most important being a c t u a l or p o t e n t i a l a v a i l a b i l i t y from raw m a t e r i a l s other than petroleum; as low a p r i c e as p o s s i b l e (no more than $.40 a pound in 1976); and c u r r e n t a v a i l a b i l i t y in l a r g e q u a n t i t i e s . The l a t t e r two f a c t o r s d i c t a t e d that the m o d i f i e r s would be used in r e a d i l y a v a i l a b l e , commercial grades of p u r i t y . SWRI screened 80 d i f f e r e n t m o d i f i e r s in i t s i n i t i a l program, and produced more than 450 f o r m u l a t i o n s in bench-scale batches (9)· The f o r m u l a t i o n s were screened by measurement of t h e i r physicochemical and r h e o l o g i c a l p r o p e r t i e s , and t h e i r s t a b i l i t y . Of the 450 f o r m u l a t i o n s , 21 were considered promising enough f o r f u r t h e r t e s t i n g . P r o p e r t i e s of these m a t e r i a l s in aggregate mixtures were determined, in p a r t i c u l a r s t r e s s - d e f o r mation behavior. E x t e n s i v e t e s t i n g was conducted on j u s t three f o r m u l a t i o n s , designated Sulphlex-233, -126, and -230 (Table I ) . Table I I n i t i a l Compositions - Sulphlex Formulation

-233, -126, and

-230

Component Percentage By Weight Sulfur

Vinyl Toluene

Dipentene

D i c y c l o - Coal Pentadiene Tar

233

70

8

10

12

-

126

61

13

-

13

13

230

70

-

15

15

-

Sulphlex-233 y i e l d s f l e x i b l e mixtures w i t h aggregates, s i m i l a r in behavior to a s p h a l t i c c o n c r e t e s . Sulphlex-230 y i e l d s mixtures which are handled l i k e a s p h a l t i c c o n c r e t e s , but which r a p i d l y develop p r o p e r t i e s c h a r a c t e r i s t i c of r i g i d mixtures such as p o r t l a n d cement c o n c r e t e . Sulphlex-126 has p r o p e r t i e s intermediate between the other two, though experience shows it tends more to the f l e x i b l e end of the s c a l e .

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

SULFUR: NEW SOURCES AND USES

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212

Sulphlex binders share c e r t a i n physicochemical p r o p e r t i e s in common. T h e i r t e m p e r a t u r e - v i s c o s i t y curves a r e s i m i l a r t o a s p h a l t , and very u n l i k e the behavior of elemental sulfur. T h e i r p e n e t r a t i o n decreases w i t h age, but a t a c o n s i d e r a b l y f a s t e r r a t e than experienced w i t h asphalt cements. U n l i k e a s p h a l t , which hardens p r i m a r i l y through o x i d a t i o n , Sulphlex binders can under c e r t a i n circumstances be brought back t o near t h e i r o r i g i n a l p e n e t r a t i o n s by heating t o approximately 120C. F i n a l l y , due t o t h e i r high sulfur content, Sulphlex binders have a specific g r a v i t y near 1.5 as compared t o approximately 1.0 f o r asphalt cements. Therefore, i f a Sulphlex binder is s u b s t i t u t e d by weight f o r asphalt in a paving mixture, t h e volume of Sulphlex binder present is only about two-thirds of the volume of a s p h a l t it r e p l a c e s . Based on o r i g i n a l r e s u l t s (_9), p a r t i c u l a r l y M a r s h a l l s t a b i l i t y and compressive s t r e n g t h d a t a , it appeared that Sulphlex binders could r e p l a c e a s p h a l t in mixtures on an equal weight b a s i s . This view has been tempered s i g n i f i c a n t l y by r e s u l t s discussed in the next s e c t i o n . D e t a i l e d T e s t i n g of Sulphlex-233

Binder

The f l e x i b l e b i n d e r , Sulphlex-233, was chosen f o r use in Sulphlex experimental pavement c o n s t r u c t i o n in 1980 and 1981. This choice e n t a i l e d a comprehensive t e s t i n g program by FHWA t o develop t e n t a t i v e mixture design procedures f o r use w i t h the Sulphlex-233 b i n d e r . The r e s u l t s of t h i s program are contained in reference (10)· Table I I presents a comparison of the s e l e c t e d physicochemical p r o p e r t i e s of Sulphlex-233 and an AC-20 grade a s p h a l t cement used in the FHWA study. The t a b l e i n d i c a t e s that t h e i r propert i e s a r e g e n e r a l l y q u i t e d i f f e r e n t , p a r t i c u l a r l y the specific g r a v i t y , p e n e t r a t i o n , v i s c o s i t i e s , and f l a s h and f i r e p o i n t s . However, from a p r a c t i c a l s t a n d p o i n t , as the m a t e r i a l s are used in the f i e l d , these d i f f e r e n c e s are not h i g h l y s i g n i f i c a n t . The t h i n - f i l m oven t e s t (AASHTO T-179) is used t o evaluate the s u s c e p t i b i l i t y of a s p h a l t t o u n d e s i r a b l e hardening during production of hot-mix. Table I I I compares the behavior of the Sulphlex-233 and the AC-20 asphalt cement a f t e r the t h i n f i l m oven t e s t . The Sulphlex-233 binder s u f f e r s almost a f o u r f o l d l o s s of weight compared t o the asphalt cement and t h i s is r e f l e c t e d in the severe p e n e t r a t i o n l o s s . This t e s t was conducted a t 275F (135C) f o r the Sulphlex-233 (as opposed t o 325F (163C) f o r the standard t e s t ) t o avoid p o s s i b l e t o x i c gas g e n e r a t i o n . This p e n e t r a t i o n l o s s is i r r e v e r s i b l e , r e s u l t i n g f o r the most p a r t as it does from a l o s s of v o l a t i l i z e d m a t e r i a l .

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

13.

LOVE AND HARRIGAN

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Road Construction Using Sulfur

Table I I Comparison of Binder P r o p e r t i e s Sulphlex-. » A s p h a l t / Cement — 233 2

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Tests S p e c i f i c G r a v i t y , 25/25C (77/77F) AASHTO T-228

1.032

1.538

P e n e t r a t i o n , 25C(77F), 100g; 5 s e c , AASHTO T-49

172

94

1042

2071

261

457

F l a s h P o i n t r^COC, F

355

505

Fire Point^COC, F

375

560

V i s c o s i t y , Absolute, 60C(140F), AASHTO T-202, poises V i s c o s i t y , Kinematic, AASHTO T-201, cSt

135C(275F),

S o l u b i l i t y in T r i c h l o r o e t h y l e i i e , AASHTO T-44, Weight %

1. 2. 3.

68.1

99.8

Produced by SWRI in 150 g a l l o n (567.8 1) r e a c t i o n v e s s e l in October 1979; see reference 10, Appendix D. Steam-reduced AMOCO AC-20 (Boscan). Performed using AASHTO T-48, modified f o r the Sulphlex binder t o use a hot-sand bath f o r h e a t i n g . This m o d i f i c a t i o n prevented foaming of the Sulphlex m a t e r i a l below the flash point.

1 p o i s e - 0.1 p a s c a l second

—6 2 1 cSt » 10~ metre /second

°C - (°F-32)(5/9)

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

SULFUR: NEW

214

SOURCES A N D

USES

Table I I I Comparison of Binder P r o p e r t i e s A f t e r T h i n - F i l m Oven Test (AASHTO T-179) Sulphlex-, » 233 @275F

Property

Loss, weight percent Penetration, 25C(77F), 100g;

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0.73

2.64 5 sec,

% Penetration Retained

51

50

29.7

53.2

V i s c o s i t y , Absolute, 60C(140F), p o i s e

5712

V i s c o s i t y , Kinematic, 135C(275F), cSt

551

1.

Asphalt, , Cement — @325F

7428 830

See Table I I f o r sources of m a t e r i a l s .

1 p o i s e - 0·1 p a s c a l second

1 cSt » 10"^ metre ^/second

°C - (°F-32)(5/9)

As noted above, Sulphlex-233 stored in bulk at ambient c o n d i t i o n s g r a d u a l l y l o s e s p e n e t r a t i o n , but t h i s l o s s is essent i a l l y r e v e r s i b l e upon h e a t i n g . This p e n e t r a t i o n l o s s apparently i n v o l v e s c r y s t a l l i z a t i o n of f r e e sulfur in the m a t e r i a l , and occurs regardless of whether the Sulphlex-233 is stored under a i r , n i t r o g e n , oxygen or water. These r e s u l t s accentuate the d i f f e r e n c e s between Sulphlex233 and the AC-20 asphalt cement, and the r e a l i z a t i o n that Sulphlex-233 is not a s t r i c t l y one-for-one replacement f o r a s p h a l t . F a i l u r e to keep the d i f f e r e n c e s in mind could have s e r i o u s consequences in f i e l d use of the Sulphlex m a t e r i a l . Sulphlex-233 Mixture P r o p e r t i e s The M a r s h a l l design method (AASHTO T-245) in concert with the Immersion-Compression t e s t (AASHTO T-165 and T-167) were s e l e c t e d by FHWA f o r the design of Sulphlex-233 paving mixtures (10). A traprock (diabase) aggregate used in Northern V i r g i n i a f o r road c o n s t r u c t i o n and having a past h i s t o r y of s a t i s f a c t o r y s e r v i c e in a s p h a l t i c mixtures was chosen f o r study. Table IV presents a comparison of the M a r s h a l l design parameters f o r mixtures of Sulphlex-233 and AC-20 asphalt cement under three c o n d i t i o n s : 1) equal weight percents, 2) equal

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

43.5

20.0

10

1450

11.0

156.0

3.97

6.1

79.0

17.4

10

2550

4.0

161.5

5.91

6.1

73.5

19.1

12

1825

4.8

162.6

5.91

9.09

Equal Volumes Sulphlex AC-20 233

6.24

9.6

gravity

78.0

18.7

13

1850

4.0

163.8

specific

79.0

17.4

10

2550

4.0

161.5

5.91

6.1

AC-20

(4%) A i r Voids Sulphlex 233

^

/

l p c f - 16.018 kg/m 1 l b » 4.448 Ν 1 in - 25.4 mm

75-85

16+

8 - 18

500+

3 - 5 -^•

Typical Marshall Criteria for Asphalt Concrete

and AC-20 Asphalt Cement

Equal

Table IV Sulphlex-233

By weight of t o t a l mixture Weight percent of binder d i v i d e d by binder Reference (11). Reference (12).

79.0

Percent VMAFilled

1/ 21 3/ 47

17.4

Percent VMA

Notes:

10

Flow, 1/100"

2550

4.0

Percent A i r Voids

Stability, Lbs.

161.5

5.91

Vol. P e r c e n t ^ Binder

Unit Weight, pcf

6.1

Wt.Percent^ Binder

Equal Weights Sulphlex AC-20 233

M a r s h a l l Design R e s u l t s :

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3

216

SULFUR.

NEW

SOURCES

AND

USES

volume p e r c e n t s , and 3) equal a i r v o i d contents. The Sulphlex233 mixtures meet a l l the t y p i c a l M a r s h a l l design c r i t e r i a f o r a s p h a l t i c concretes except in the case of equal weight r e p l a c e ment where the percent a i r v o i d and percent V M A - f i l l e d c r i t e r i a are u n s a t i s f i e d . Table V presents the "optimum" binder content f o r the Sulphlex-233 and the AC-20 a s p h a l t cement and s e l e c t e d mixture p r o p e r t i e s obtained a t these optimum v a l u e s .

Table V

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Optimum M a r s h a l l Binder Contents: Sulphlex-233 and AC-20 Asphalt Cement With a Well-Graded Diabase Aggregate AC-20 6.4 6.2

Optimum (Wt. %) Optimum ( V o l %)

Sulphlex-233 10.3 6.7

Mixtures P r o p e r t i e s a t These "Optimum" Values Percent A i r Voids Stability, lbs. Flow, 1/100" Percent VMA Percent VMA-Filled 1 l b . - 4.448N

3.1 2600 12 17.0 83.5

3.0 1850 15 18.6 84.0

1 in. « 25.4mm

These data are d e r i v e d from the M a r s h a l l design curves (10); the "optimum" contents meet a l l the c r i t e r i a e s t a b l i s h e d f o r a s p h a l t i c mixtures. The optimum Sulphlex-233 content is a t a s l i g h t l y higher than equal volume replacement of the optimum AC-20 content. Reference (10) presents a f u l l e r d i s c u s s i o n of this topic. The M a r s h a l l design method contains no p r o v i s i o n f o r determining water damage s u s c e p t i b i l i t y . The FHWA employs the Immersion-Compression t e s t f o r t h i s purpose. This t e s t measures the r e t a i n e d unconfined compressive s t r e n g t h of a compacted mixture a f t e r soaking in a 140F (60C) water bath. The t e s t data f o r the Sulphlex-233 and AC-20 asphalt cement are contained in Table V I . I t is evident t h a t w i t h diabase aggregate, water damage is a p o t e n t i a l problem w i t h Sulphlex-233. The use of common a n t i - s t r i p a d d i t i v e s employed w i t h a s p h a l t , such as amines and t a l l oil, s i g n i f i c a n t l y improve the water damage r e s i s t a n c e of the Sulphlex-233 m i x t u r e s .

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

4/

6.10 6.10

5.91 5.91 5

7

7

_ι Oil-

AASHTO T-165, T-167 Average of 4 specimens, except as noted. 3/ Average of 2 specimens 4/ Based on t o t a l mixture 5J Added t o the b i n d e r , percent by weight o f b i n d e r . 6/ Aggregate temperature used was 300F, r a t h e r than 325F as s p e c i f i e d .

II 2/

None

4.03

3.91

None _ ι 1% Amine -

None 1% T a l l

9.09 9.09

5.91 5.91

7

3/

WetU

7

351 381

1.4 1.0 5.3 5.4

1 p s i - 6895 p a s c a l

No t e s t , specimens p a r t i a l l y f e l l apart in water b a t h . No t e s t , specimens completely f e l l apart in water b a t h . Weight percent binder d i v i d e d by binder specific g r a v i t y .

76.9 78.5

4.0

NT*/ 0.7

NT— 4.8 2.0

Absorbed

Percent Water

11.4

6.4 4.4

NT^ 70.2

48.1

12.4 12.2 11.2

Voids

Percent Air

NT— 46.4 42.5

Strength

Percent Retained

°C - (°F-32)(5/9)

9/

8/

Jj

270 299

AC-20 A s p h a l t Cement 335 161

NT* 478

657 681

NT

326 301

744 702 708

Z/

Sulphlex - 2 3 3 ^

Dry

Compressive Strength p s i @25C (77F)

None ^. 1% Amine— _ , 1% T a l l Oil-

Additives

6.10 6.10 6.10

Binder -

Weight Percent

3.97 3.97 3.97

Volume Percent 9/ Binder^'

Immersion - Compression Data-lil/

Table V I

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3/

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218

SULFUR:

NEW

SOURCES AND

USES

No p r e c i s e c o r r e l a t i o n is a v a i l a b l e between the immersioncompression t e s t and r e s u l t s t o be expected from pavements in the f i e l d . The t e s t provides comparative guidance on water damage s u s c e p t i b i l i t y . For the diabase aggregate, the Sulphlex233 mixtures measured dry, and a f t e r immersign in the case of wet specimens, exceed the 300 ρsi (2.07 χ 10 p a s c a l ) minimum compressive s t r e n g t h u s u a l l y considered necessary f o r acceptable mixture performance in the f i e l d . Retained strengths g e n e r a l l y f a l l below the 70 percent c r i t e r i o n considered acceptable f o r a s p h a l t i c mixtures. Examination of Sulphlex-233 mixtures w i t h other types of aggregates g e n e r a l l y have confirmed the r e s u l t s presented here. Sulphlex-233 mixtures can meet or exceed most M a r s h a l l design and compressive s t r e n g t h c r i t e r i a at e i t h e r equal volume o r equal weight replacement of asphalt cement, but "optimum" mixtures are obtained a t or near the equal volume replacement l e v e l . The Sulphlex-233 mixtures are in many cases s u s c e p t i b l e to water damage, and the use of t a l l oil as an a n t i - s t r i p a d d i t i v e has been recommended where i n d i c a t e d . C o n s t r u c t i o n Operation w i t h Sulphlex Binders The success of SWRI in f o r m u l a t i n g Sulphlex binders w t i h promising l a b o r a t o r y p r o p e r t i e s prompted FHWA t o c o n s t r u c t a s m a l l pavement s e c t i o n t o evaluate the use of such m a t e r i a l s w i t h conventional asphalt c o n s t r u c t i o n equipment and p r a c t i c e s . The goal was t o determine i f the Sulphlex binders might present unrecognized problems which would argue against t h e i r f u r t h e r development· The c o n s t r u c t i o n was accomplished by SWRI on a low-volume road a t i t s San Antonio facility in December, 1979. The t o t a l pavement is 645 f e e t (197 m) l o n g , 24 f e e t (7.3m) wide, and i n c l u d e s ten Sulphlex s e c t i o n s in a d d i t i o n t o p o r t l a n d cement concrete and an a s p h a l t i c concrete c o n t r o l s e c t i o n s . Three d i f f e r e n t Sulphlex b i n d e r s , numbers -233, -126, and -230, were employed in the c o n s t r u c t i o n ; besides the binder type, v a r i a b l e s i n c l u d e the binder content, the pavement t h i c k n e s s , and the number of l i f t s used in the c o n s t r u c t i o n . The c o n s t r u c t i o n r e q u i r e d the production of 7.5 tons (6.8 tonnes) of each of the three Sulphlex b i n d e r s . Scale-up t o these q u a n t i t i e s was r e q u i r e d from l a b o r a t o r y batch s i z e without b e n e f i t of i n v e s t i g a t i n g intermediate batch p r o d u c t i o n . (Refer to (9) and (10) f o r d i s c u s s i o n of Sulphlex manufacture in l a b o r a t o r y and p i l o t - s c a l e batches.) For the c o n s t r u c t i o n , the Sulphlex binders were produced in nominal 7500 l b (3400 kg) batches in r e c t a n g u l a r metal v e s s e l s w i t h l o o s e l y f i t t e d plywood covers. Two batches of each f o r m u l a t i o n were r e q u i r e d . D e t a i l s of the production of the binders and of the pavement c o n s t r u c t i o n have been reported elsewhere ( 9 ) .

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

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219

The e n t i r e c o n s t r u c t i o n was accomplished without i n c i d e n t ; the conventional equipment and techniques worked as w e l l as w i t h Sulphlex binders as w i t h a s p h a l t . A f t e r 2.5 years s e r v i c e , at a t r a f f i c volume of 1000 ADT (10 percent t r u c k s ) , d i s t r e s s is evident in a number of s e c t i o n s . In g e n e r a l , the d i s t r e s s has been p r i m a r i l y a t t r i b u t e d to poor subgrade drainage; placement of c e r t a i n s e c t i o n s w i t h mix at extremely low temperature (below 65C (150F)); r a v e l l i n g of dry mixtures; and l a t e r a l s h i f t i n g of l i f t s due to the absence of adequate tack between them. None of the d i s t r e s s is uniquely r e l a t e d to the use of Sulphlex binders in l i e u of asphalt cement in the pavement. The success of t h i s pavement c o n s t r u c t i o n prompted development of a program to b u i l d l a r g e r Sulphlex pavement s e c t i o n s on p u b l i c highways in a v a r i e t y of c l i m a t e s and t r a f f i c l o a d i n g s . Based on i n t e r e s t by the State highway agencies, seven s i t e s were chosen f o r c o n s t r u c t i o n in 1980 and 1981. The goals of t h i s program are to o b t a i n l i m i t e d data on the performance and d u r a b i l i t y of Sulphlex pavements and to f u r t h e r evaluate standard c o n s t r u c t i o n operations w i t h Sulphlex. The d e c i s i o n was made to l i m i t the Sulphlex binder used in t h i s program to Sulphlex-233. Arrangements were made w i t h Chemical E n t e r p r i s e s , I n c . (CEI) of Houston, Texas f o r production of the Sulphlex-233 at i t s p l a n t in Odessa, Texas. A t o t a l of 187 tons (170 tonnes) of Sulphlex-233/A binder were produced (NOTE: A shortage of one commercial grade of dipentene used p r e v i o u s l y n e c e s s i t a t e d i t s replacement by another source and minor r e f o r m u l a t i o n of the Sulphlex-233 from the composition in Table I ; the reformulated b i n d e r , having e s s e n t i a l l y the same physicochemical p r o p e r t i e s as noted in Table I , is designated Sulphlex-233/A). CEI produced the Sulphlex-233/A in 7.5 ton (6.8 tonne) batches; the r e a c t i o n v e s s e l has a nominal 9 ton (8.2 tonne) c a p a c i t y , is steam heated, and is equipped w i t h a wet scrubber system to c o n t r o l p o t e n t i a l hydrogen s u l f i d e emissions. Since no c o o l i n g c a p a b i l i t y was a v a i l a b l e , the r e a c t i o n exotherm was c o n t r o l l e d by the r a t e at which the preblended chemical m o d i f i e r s were added to the r e a c t i o n mass. The seven States s e l e c t e d f o r the Sulphlex c o n s t r u c t i o n p r o j e c t s and d e t a i l s of the p r o j e c t s are presented in Table V I I . The San Antonio, Texas, c o n s t r u c t i o n is the l a r g e s t job planned f o r the program, and i t s f e a t u r e s w i l l be discussed in some detail. The Sulphlex-233/A binder m a t e r i a l was shipped from the production p o i n t in Odessa, Texas to the McDonough Brothers hot-mix p l a n t north of San Antonio, Texas, in three asphalt t r a i l e r s c o n t a i n i n g approximately 20 tons (18.1 tonnes) each. The t r a i l e r s were steam heated to a l l o w the binder to be t r a n s f e r r e d i n t o an empty asphalt storage tank.

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

900

TR 405, Montgomery

1-75, Gainesville

PENNSYLVANIA

FLORIDA

MICHIGAN

ARIZONA

1. 2. 3.

2000

N-66, Valparaiso

NEBRASKA

1 f o o t = 304.8 mm 1 i n c h « 25.4 mm 1 t o n » .9072 tonne

2.25" t h i c k s u r f a c e course Spring 1981 22

U.S. 70, Safford

A l l p r o j e c t s a r e 12 f e e t in w i d t h . ND - not determined a t t h i s time. Approximately 3000 f e e t of 12 f o o t wide chip s e a l was a l s o p l a c e d .

we' Spring 1981

22

5" t h i c k s u r f a c e course overlay

1.5" t h i c k wearing course

2" t h i c k s u r f a c e course

3.5" t h i c k s u r f a c e course

1" t h i c k overlay

Type of Construction

1-75 o f f ramp, Flint

10/27/80

9/19/80

9/18/80

8/26/80

Date Completed or Planned f o r Construction

11/20/80

22

22

13

60

Sulphlex-233/A Requirement (tons)

1980 and 1981

22

1000

1150

U.S. 2 and 52, Minot

NORTH DAKOTA

7920^

Loop 1604, San Antonio

Location

TEXAS

State

i

P r o j e c t Length—1/ (Approximate, Feet)

Table V I I Sulphlex C o n s t r u c t i o n P r o j e c t s ;

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H AR RIG AN

221

A mix design had been developed by the Texas State Depart­ ment of Highways and P u b l i c T r a n s p o r t a t i o n (SDHPT) in c o n j u n c t i o n w i t h the FHWA. The aggregate proposed was composed of the f o l l o w i n g f r a c t i o n s : Νο· 10 limestone, 22·5 percent; limestone s c r e e n i n g s , 7.0 percent; No. 4 sandstone, 43.0 percent; and s i l i c a sand, 27.5 percent. This combination y i e l d s a well-graded b l e n d , and is s i m i l a r to the aggregate g r a d a t i o n used l o c a l l y in a s p h a l t i c concrete and used in the 1978 SWRI c o n s t r u c t i o n . The mix design y i e l d e d a binder content of 7.3 percent by weight as most s a t i s f a c t o r y . In order to assess the e f f e c t of binder content v a r i a t i o n on performance, three s e c t i o n s w i t h b i n d e r contents of 7.0, 7.5 and 8.0 percent were decided upon. One and one-half m i l e s (2.4 km) of e x i s t i n g a s p h a l t i c concrete pavement on Loop 1604 were o v e r l a i d w i t h an i n c h (25.4 mm) t h i c k Sulphlex mixture. The Sulphlex hot-mix was produced in a three ton (2.7 tonne) batch p l a n t , and hauled approximately f i v e m i l e s (8.05 km) in open t r u c k s to the construction s i t e . Weather c o n d i t i o n s during the c o n s t r u c t i o n were hot and d r y , w i t h temperatures near 95F (35C). The c o n s t r u c t i o n oper­ a t i o n s proceeded without s i g n i f i c a n t problems, and t h i s p r o j e c t again demonstrated that the equipment and techniques used f o r a s p h a l t pavement c o n s t r u c t i o n can be a p p l i e d to Sulphlex pavement c o n s t r u c t i o n without m o d i f i c a t i o n . A view of the completed Sulphlex pavement is shown in f i g u r e 1. In c o n j u n c t i o n w i t h the o v e r l a y c o n s t r u c t i o n , approximately 15 tons (13.6 tonnes) of the Sulphlex binder was used in a s e a l coat o p e r a t i o n on Loop 1604 adjacent t o the o v e r l a i d s e c t i o n . The binder^ was appli^ul by a d i s t r i b u t o r t r u c k a t a r a t e of 0.4 g a l . / yd. (1.81 1/m ). Three hundred f e e t (91.4 meters) of 5/8 i n c h (15.87 mm) precoated rock a s p h a l t were dropped on the binder f o l l o w e d by 2700 f e e t (823 meters) of 3/8 i n c h (9.5 mm) sandstone. To date, the performance of both the Sulphlex o v e r l a y and s e a l c o a t is s a t i s f a c t o r y and completely comparable to the a s p h a l t c o n t r o l s e c t i o n s constructed during the same p e r i o d . T r a f f i c volume on t h i s s e c t i o n was measured a t 5630 ADT; due to numerous heavy c o n s t r u c t i o n p r o j e c t s in the a r e a , the percentage of heavy t r u c k s is near 60 percent. The Texas A i r C o n t r o l Board was r e s p o n s i b l e f o r monitoring emissions of hydrogen s u l f i d e and sulfur d i o x i d e during a l l phases of the Sulphlex c o n s t r u c t i o n . The measurements i n d i c a t e d that n e i t h e r gas was present at l e v e l s near those which would pose a s a f e t y or environmental hazard during any phase of the operation. The c o n s t r u c t i o n in Pennsylvania and F l o r i d a (see Table V I I ) a l s o proceeded u n e v e n t f u l l y . However, problems were encountered in North Dakota and Nebraska where drum mixers were used f o r the Sulphlex hot-mix p r o d u c t i o n in c o n t r a s t to the 2

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

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222

SULFUR:

Figure 1.

NEW

SOURCES

AND

USES

Completed Sulphlex pavement (right-hand lane) on Loop 1604, August 1980.

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

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223

other States where batch p l a n t s were employed. D i f f i c u l t i e s were met in a c c u r a t e l y metering the Sulphlex binders i n t o the drum mixers, and the binder contents of the hot-mix were s e r i ­ ously d e f i c i e n t , p a r t i c u l a r l y in Nebraska. This problem may be r e l a t e d t o the higher specific g r a v i t y of the Sulphlex binder a f f e c t i n g the operation of the pumps which d e l i v e r the binder t o the drum. The low binder contents have had d e l e t e r i o u s e f f e c t s on the i n t e g r i t y of the pavements. The s i t u a t i o n is most acute in Nebraska. The outlook f o r adequate s e r v i c e in e i t h e r State is p r o b l e m a t i c a l .

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Future Developments The use of Sulphlex in the f u t u r e as an accepted a l t e r n a t i v e to asphalt is p r e d i c a t e d on s e v e r a l f a c t o r s , most i m p o r t a n t l y (1) a vigorous R&D program t o optimize the engineering p r o p e r t i e s of the Sulphlex binders and c h a r a c t e r i z e them f o r use in pavement c o n s t r u c t i o n , (2) evidence of adequate s e r v i c e a b i l i t y of the experimental Sulphlex pavements, (3) c o n t i n u i n g r i s e in crude oil p r i c e and d e c l i n e in assured f o r e i g n crude oil s u p p l i e s , and (4) c o m m e r c i a l i z a t i o n of Sulphlex production a t a r e a l i s t i c u n i t price. The FHWA has planned a comprehensive R&D program aimed a t i d e n t i f y i n g a generation of Sulphlex binders ready f o r commer­ c i a l i z a t i o n in the p e r i o d 1985 t o 1990. The program of pavement c o n s t r u c t i o n underway a t the present time w i l l be followed by a new round of p r o j e c t s u s i n g second or l a t e r generation Sulphlex binders and planned f o r a s t a r t in 1984 or 1985. This round would s t r e s s much l a r g e r pavement s e c t i o n s subjected t o i n t e n ­ s i v e e v a l u a t i o n of performance and d u r a b i l i t y . A necessary adjunct t o t h i s c o n s t r u c t i o n program w i l l be production of the binder m a t e r i a l s in a p i l o t p l a n t s p e c i f i c a l l y designed and constructed f o r maximum e f f i c i e n c y and minimum c o s t . Literature Cited 1.

2.

3.

4.

B u t t e , W. Α.; Kohn, Ε. M.; and S c h e i b e l , E. G.; "Highway Binder M a t e r i a l s from C e l l u l o s e and Related Wastes"; Report FHWA/RD-80/031, May 1980. T e r r e l , R. L.; " E v a l u a t i o n of Wood L i g n i n as a S u b s t i t u t e or Extender of Asphalt"; Report FHWA/RD-80/125, November 1980. P i c k e t t , D. E.; Saylak, D.; L y t t o n , R. L.; Conger, W. E.; Newcomb, D.; Schapery, R. Α.; "Extension and Replacement of Asphalt Cement w i t h S u l f u r . " ; Report FHWA-RD-78-96, March 1978. I z a t t , J. O.; "Sulfur-Extended-Asphalt F i e l d Trials, M-153 Brazos County, Texas, A D e t a i l e d C o n s t r u c t i o n Report"; Report FHWA-TS-80-214, December 1979.

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

224 5.

6. 7. 8.

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9. 10. 11. 12.

SULFUR: NEW SOURCES AND USES

Gallaway, B. M.; Saylak, D.; "Sulfur Extended Asphalt (SEA) Sulphur/Asphalt Mixture Design and Construction Details - Lufkin Field Trials"; Report FHWA-TS-78-203, January 1976 (reprint 1977)· Meyer, Β· "Sulfur, Energy and Environment"; Elsevier Scientific Publishing Co.: New York, 1977; p. 41. Blight, L . ; Currell, B. R.; Xlash, B. J.; Scott, R. A. M.; Stillo, C.; "Preparation and Properties of Modified Sulfur Systems"; ADV. CHEM. SER. 1978, 165, 13. Bordoloi, Β. K.; Pearce, Ε. M.; "Plastic Sulfur Stabili­ zation by Copolymerization of Sulfur with Dicyclopentadiene"; ADV. CHEM. SER. 1978, 165, 31. Ludwig, A. D.; Gerhardt, Β. B.; Dale, J. M.; "Materials and Techniques for Improving the Engineering Properties of Sulfur"; Report FHWA/RD-80/023, June 1980. Lentz, H. L . ; Harrigan, E. T.; "Laboratory Evaluation of Sulphlex-233: Binder Properties and Mix Design"; Report FHWA/RD-80/146, November 1980. "Mix Design Methods for Asphalt Concrete"; Publication MS-2; The Asphalt kInstitute: College Park, MD, 1974. "AASHO Interim Guide for Design of Pavement Structures"; American Association of State Highway Officials: Washington, D.C., 1972.

RECEIVED October 5, 1981.

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.