Sulfur: New Sources and Uses - ACS Publications - American

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

Downloaded by CORNELL UNIV on May 25, 2017 | http://pubs.acs.org Publication Date: March 29, 1982 | doi: 10.1021/bk-1982-0183.ch013

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.

SULFUR: NEW SOURCES A N D USES

210


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



13.

LOVE AND HARRIGAN

Road Construction Using Sulfur

211

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 .


SULFUR: NEW SOURCES AND USES


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 .


13.

LOVE AND HARRIGAN

213


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


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)


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;


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



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 :


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


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 .



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


3/


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 ) .



13.

LOVE AND

HARRIGAN


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.



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 ;



13.

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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



222

SULFUR:

Figure 1.

NEW

SOURCES

AND

USES

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


13.

LOVE AND HARRIGAN


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 .


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.


224 5.

6. 7. 8.


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.


Sulfur: New Sources and Uses - ACS Publications - American

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