12 A n Industrial Application of Sulfur Concrete R. H . F U N K E , J R . Asarco Incorporated, Baltimore, MD 21207 W. C. M C B E E U.S. Department of the Interior, Bureau of Mines, Boulder City, NV 89005
In cooperation with the U. S. Department of the Interior Bureau of Mines and The Sulphur Institute, Asarco tested components of sulfur concrete, both precast and poured in place, in corrosive environ ments of sulfuric acid. Favorable endurance of these samples led to a full-scale cooperative dem onstration project. The project selected was the rehabilitation of an electrolytic zinc cellhouse basement floor of approximately 21,000 square feet. Sulfur concrete u t i l i z i n g an aggregate gradation of minus 3/8-inch and minus 1/8-inch materials was pro duced in a portable asphalt patch mix plant. Mixing and placing operations were conducted without prob lems. Economics of sulfur concrete versus portland cement concrete are highly variable. Total costs were approximately 15 pct higher than for portland concrete. Potential uses are electrolytic c e l l s , holding tanks and vats, and floor and basin areas exposed to acidic environments. Asarco, a major refiner of nonferrous metals and producer of byproduct sulfuric acid, has many areas where acidic damage to floor surfaces can occur. Even though different protective coating systems were used, routine replacement of concrete dam aged by exposure to corrosive conditions has been accepted as the response to the problem. Accordingly, in 1977 Asarco wel comed an invitation from The Sulphur Institute, in conjunction with the Bureau of Mines, for f i e l d testing of sulfur concrete in a corrosive environment. The development of sulfur concrete ma terials was reported by McBee and Sullivan (_1, 2) . In early 1978, precast sulfur concrete slabs measuring 24- χ 24- χ 2%inches, prepared by the Bureau of Mines at i t s Boulder City En gineering Laboratory, were l a i d at selected floor locations at the Corpus Christi, Tex. zinc refinery and the Amarillo, Tex. copper refinery. Table 1 indicates the sulfur concrete corrosion 0097-6156/82/0183-0195S05.00/0 © 1982 American Chemical Society
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Table I . Location Corpus C h r i s t i
Amarillo
Τ a coma
East Helena E l Paso Columbus
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S u l f u r concrete c o r r o s i o n t e s t components in Asarco p l a n t s Components and environment I n s t a l l a t i o n date Slabs, e l e c t r o l y t i c z i n c r e Feb. 1978 finery floors. May Sump, catch b a s i n under z i n c 1978 e l e c t r o l y t e c o o l i n g tower. Nov. Sump, z i n c e l e c t r o l y t e 1979 pumping c i r c u i t . June Floor, e l e c t r o l y t i c zinc r e 1980 finery. Slabs, e l e c t r o l y t i c copper March 1978 r e f i n e r y sump. March 1980 Slabs, n i c k e l s u l f a t e p l a n t floor. Sept. 1980 Floor, nickel sulfate plant. May F l o o r patch, e l e c t r o l y t i c 1978 copper r e f i n e r y f l o o r . May 1978 Pump foundation, s u l f u r i c a c i d pump. Slabs, s u l f u r i c a c i d p l a n t , June 1979 l e a d smelter. Nov. C y l i n d e r s in a c i d p l a n t 1979 complex. April Sump, s u l f u r i c a c i d l o a d i n g 1980 area in ZnO p l a n t . T i l e , l i n e r f o r acid drain Oct. 1980 channel.
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t e s t components in Asarco p l a n t s . A few months l a t e r , s e v e r a l small o n - s i t e sulfur concrete pours u t i l i z i n g equipment from the Bureau of Mines were made at the Tacoma, Wash, p l a n t in both the e l e c t r o l y t i c tankhouse basement and a pumping facility handling 93 pct s u l f u r i c a c i d . In the s p r i n g of 1978, a precast sump prepared by the Bureau of Mines was i n s t a l l e d in a drainage b a s i n under the z i n c e l e c t r o l y t e c o o l i n g towers erected as new cons t r u c t i o n in the ongoing modernization of the Corpus C h r i s t i z i n c r e f i n e r y . In June 1979, t e s t slabs were placed in the s u l f u r i c a c i d p l a n t in the East Helena, Mont, l e a d smelter. In l a t e 1979, an a d d i t i o n a l sulfur concrete sump, as shown in f i g u r e 1, was precast by the Bureau of Mines and i n s t a l l e d in the z i n c e l e c t r o l y t e pumping c i r c u i t at Corpus C h r i s t i . In November 1979, a s e r i e s of t e s t samples were put in the a c i d p l a n t complex at the E l Paso, Tex. p l a n t . In 1980, a precast sump was placed in the s u l f u r i c a c i d t r u c k - l o a d i n g area at the Columbus z i n c oxide p l a n t . A l l of the i n s t a l l a t i o n s have e x h i b i t e d e s s e n t i a l l y no d e t e r i o r a t i o n in t h e sulfur concrete i n s t a l l a t i o n s , except f o r one s l a b at East Helena. Examination of t h i s sample showed that the sulfur binder had been melted. The replacement s l a b remains i n t a c t a f t e r more than a year's exposure. A f t e r 1-% years, the p o r t l a n d cement concrete c o n t r o l samp l e s at Corpus C h r i s t i that were i n s t a l l e d contiguous to and intermixed w i t h the sulfur concrete t e s t samples showed t o t a l d i s i n t e g r a t i o n , whereas the sulfur concrete e x h i b i t e d no i d e n t i f i able a t t a c k ( f i g u r e 2). In the summer of 1979, the ongoing maintenance needs at the Corpus C h r i s t i p l a n t placed r e h a b i l i t a t i o n of a cellhouse basement f l o o r in a p r i o r i t y p o s i t i o n . The opportunity to perform the r e p a i r work on a f u l l - s c a l e b a s i s , u t i l i z i n g Bureau of Mines technology f o r sulfur concrete in l i e u of p o r t l a n d cement concrete, was accomplished by an agreement f o r a demonstration p r o j e c t executed between the Bureau of Mines and Asarco. Demonstration P r o j e c t A modified Wylie Model PM-830 Patchmobile owned by the Bureau of Mines was assigned to the p r o j e c t . The Bureau of Mines had p r e v i o u s l y s t u d i e d the a v a i l a b l e aggregates in the Corpus C h r i s t i area and designed a s u i t a b l e mix. The Patchmobile is a small p o r t a b l e asphalt patch p l a n t , propane-fired f o r heating and gasoline-powered f o r r o t a t i n g motions and other a u x i l i a r i e s . Because it is designed to be towed on the highway, i t s d e l i v e r y p o i n t is at a conveniently low e l e v a t i o n f o r s h o v e l i n g mixed patch m a t e r i a l , but was too low f o r u t i l i z a t i o n on t h i s p r o j e c t . The machine was cribbed up to a s u i t a b l e e l e v a t i o n to permit handling of r e c e p t a c l e containers under the d e l i v e r y p o i n t . This elevated p o s i t i o n , in a d d i t i o n to a l a r g e r volume aggregate b i n f i t t e d to the machine by the Bureau of Mines, r e q u i r e d the use of an e l e v a t i n g b e l t conveyor f o r d e l i v e r y of aggregates to the b i n .
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Figure 1.
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Sulfur concrete sumpfor installationinthe zinc electrolyte pumping circuit.
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Figure 2. Sulfur concrete and control portlandcementconcrete(4-test sections eachjin thefloor area of the electrolytic zinc refinery. After 28 months, no corrosive attackisseen on thesulfurconcrete sections, although the control samples were severely attacked.
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An a p p r o p r i a t e working p l a t f o r m was b u i l t adjacent to the e l e v a t e d mixer to permit attendance. The mixing o p e r a t i o n was r o u t i n e . Feeding of the d r y i n g drum was accomplished by an i n t e g r a l r e c i p r o c a t i n g feeder d e l i v e r i n g both coarse and f i n e aggregate in c o r r e c t p r o p o r t i o n s . The aggregate, heated to 400° F, was accumulated in a discharge hopper, p e r i d i c a l l y d i s c h a r g i n g to the p u g m i l l when a p r e d e t e r mined volume was obtained. At the time of r e l e a s e of the aggre gate to the m i l l , a p r e v i o u s l y measured volume of m o d i f i e d sulfur and s i l i c a f l o u r was fed to the p u g m i l l . The average d e l i v e r y temperature of the sulfur concrete mixture was 280° F. Mainte nance of the temperature in the p u g m i l l was accomplished by the c i r c u l a t i o n of oil at 300° F through a j a c k e t surrounding the p u g m i l l . D e l i v e r y of sulfur concrete from the p u g m i l l was con tinuous. The p r e p a r a t i o n of sulfur concrete is i l l u s t r a t e d in f i g u r e 3. Approximate p r o p o r t i o n s of the c o n s t i t u e n t s of the mix were 83 p c t aggregate and 17 p c t m o d i f i e d sulfur. The aggregate f r a c t i o n s c o n s i s t e d of 46 p c t minus 3/8-inch pea g r a v e l , 46 pct minus 1/8-inch sand, and 8 pct minus 200-mesh s i l i c a f l o u r . The f r a c t i o n s were blended as shown in f i g u r e 4 and gave a dense-graded aggregate r e q u i r i n g a minimum of sulfur to produce an acceptable sulfur concrete. The sulfur had been p r e v i o u s l y m o d i f i e d w i t h a p l a s t i c i z e r c o n s i s t i n g of d i c y c l o p e n t a d i e n e (DCPD) and oligomer in the amount of 5 wt p c t of the t o t a l sulfur. DCPD-oligomer r a t i o s of 65:35 and 50:50 were employed. The development of t h i s f o r m u l a t i o n is d e s c r i b e d by McBee ( 3 ) . The m o d i f i e d sulfur was prepared in a commercial p l a n t and d e l i v e r e d in bags. The coarse aggregate used was a s i l i c e o u s r i v e r g r a v e l and was s i z e d by screening. The r i v e r g r a v e l was r e l a t i v e l y smooth and round. R e s u l t i n g concrete s t r e n g t h s averaged 3,500 to 4,000 psi. The sharp edges of a crushed g r a v e l would have given h i g h e r s t r e n g t h . S p e c i f i c g r a v i t y of the sulfur concrete was a p p r o x i mately 2.4. P o r o s i t y on t e s t samples i n d i c a t e d a b s o r p t i o n of water of 0.0 p c t to 0.2 p c t . C o r r o s i o n t e s t i n g of the sulfur concrete was done by immersing 3- χ 6-inch compressive s t r e n g t h t e s t c y l i n d e r s in 10 and 20 wt pct s u l f u r i c a c i d s o l u t i o n s f o r 6 months. The c y l i n d e r s were p e r i o d i c a l l y t e s t e d f o r c o r r o s i o n , a b s o r p t i o n , and compressive s t r e n g t h . A gradual i n c r e a s e in the compressive s t r e n g t h of approximately 8 p c t was obtained d u r i n g the t e s t p e r i o d . No c o r r o s i v e a t t a c k on the m a t e r i a l was found, and the a b s o r p t i o n remained constant at 0.04 p c t d u r i n g the 6-month t e s t p e r i o d . Transport of the mixed sulfur concrete was accomplished by motorized wheelbarrows w i t h i n s u l a t e d buckets ( f i g u r e 5 ) . Covers would have a s s i s t e d in r e t a i n i n g the heat of the mix, but were not necessary in the summer months in south Texas. The approximate t o t a l area r e p a i r e d was 21,000 square f e e t , w i t h a nominal t h i c k n e s s of 4 i n c h e s . S i t e p r e p a r a t i o n f o r the r e p a i r r e q u i r e d the establishment of a s u i t a b l e grade, removal of
FUNKE AND MCBEE
Industrial Application of Sulfur Concrete
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Figure 5. Transporting and pouring the hotsulfurconcrete with an insulated motorized concrete buggy.
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some d e t e r i o r a t e d concrete, and p r e p a r a t i o n of subgrade. I n a d d i t i o n to t h i s r o u t i n e work, a f l o o r underdrain system u t i l i z i n g PVC pipe and a c a s t - i n - p l a c e sump was a l s o i n s t a l l e d . E l e v a t i o n of subgrade was e s t a b l i s h e d by placement of washed sand. F i n i s h grades were d e l i n e a t e d by placement of screed boards. The procedure d i d not d i f f e r from the normal p r e p a r a t i o n for a p o r t l a n d cement pour. The s t r u c t u r a l p i e r p a t t e r n supp o r t i n g the e l e c t r o l y t i c c e l l s and the tankhouse work f l o o r presented an o b s t r u c t i o n to s t r a i g h t - l i n e work. Hence, the f l o o r p a t t e r n was developed as a s e r i e s of panels graded w i t h approp r i a t e p i t c h e s to d r a i n to p e r i o d i c swales i n t e r s e c t i n g the p r e v i o u s l y mentioned underdrain p i p i n g system. At the i n i t i a t i o n of the p r o j e c t in l a t e June 1980, Bureau of Mines personnel were present to c o n s u l t , a s s i s t , and advise. The Asarco Corpus C h r i s t i P l a n t Engineering Department organized and supervised the p r o j e c t a t s t a r t u p and assumed complete cont r o l a f t e r the departure of the Bureau of Mines personnel. The Bureau o f Mines and The Sulphur I n s t i t u t e maintained p e r i o d i c contact by telephone and v i s i t s throughout the work. Panel widths ranged from 8 to 10 f e e t , lengths were 8 to 12 f e e t , and nominal t h i c k n e s s was 4 inches. The d e s i r a b l e approach is to d e l i v e r a f u l l width of mixed m a t e r i a l a t the beg i n n i n g to the panel and s u s t a i n a d e l i v e r y r a t e to maintain f u l l width ahead of the screed. Screeds used were wood equipped w i t h a v i b r a t o r , e i t h e r e l e c t r i c a l or air-powered, the l a t t e r being p r e f e r r e d by these operators. Once the screed s t a r t s , it is p r e f e r a b l e to continue in one s i n g l e sweep to the completion of the panel. F i g u r e 6 shows a f l o o r s e c t i o n a f t e r screeding. S u l f u r concrete freezes l i k e a metal c a s t i n g . The surface forms a skin f i r s t . Once the s k i n is formed, no f u r t h e r work can be accomplished. I t can be reheated w i t h i n l i m i t s by r a d i a n t heat and f u r t h e r worked. A single-sweep method is most e f f e c t i v e . Some puddling can be done p r i o r to the formation of the f r o z e n s k i n . F i n i s h e s on the f l o o r s were screed f i n i s h e s and were rougher than s t e e l t r o w e l f i n i s h e s a t t a i n e d w i t h p o r t l a n d cement concrete. The screed was adequate f o r the s e r v i c e i n s t a l l e d . F i n e r f i n i s h e s can be achieved by i n c l u d i n g e x t e r n a l heat and correspondingly longer f i n i s h i n g o p e r a t i o n s . I n a d d i t i o n to the f l o o r panels poured, r e i n f o r c i n g and p r o t e c t i v e c o l l a r s of sulfur concrete were poured around the support p i e r s . S u l f u r concrete can be v i b r a t e d w i t h conventional concrete probes in forms, and r e i n f o r c i n g can be used as it was in these c o l l a r s , but it was not used in the f l o o r . With respect to smoke and fumes, measurement of S O 2 in the mixing area showed no i n c r e a s e above background, and no hydrogen sulphide was detected. I n the placement areas, there was some odor from the aromatics in the sulfur m o d i f i e r . Pouring c o n d i t i o n s were s i m i l a r to those of an a s p h a l t paving o p e r a t i o n and i n c l u d e d a s i m i l a r odor. No s p e c i a l p r o t e c t i v e equipment was utilized or r e q u i r e d . Operators a t the mixer wore dust masks.
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Although the m a t e r i a l is hot and worked hot, t h i s was not a personnel problem f a c t o r in the placement. There were some problems that were not viewed as being of great magnitude but are worthy of mention. Any moisture in the subgrade generated a s m a l l number of bubbles. T h i s was c o r r e c t e d by pouring onto sheet p o l y e t h y l e n e l a i d on the subgrade. Moisture in the aggregate a l s o caused hangups in the feed hoppers. V i b r a t o r s were placed on the hopper s h e l l s i d e . Close a t t e n t i o n must be paid to the temperature of the heated aggregate, because e x c e s s i v e l y moist aggregate w i l l lower the d e l i v e r y temperature, and correspondingly the temperature of the mix, rendering the mix p o t e n t i a l l y unusable. The p h y s i c a l panel s i z e used r e s u l t e d in more j o i n t s between panels than would have been the case in a p o r t l a n d cement pour, owing to the s u r f a c e f i n i s h i n g w i t h a screed and the continuous o b s t r u c t i o n of the e x i s t i n g support columns. A s p h a l t expansion s t r i p s were placed between panels and were provided w i t h a r e movable top s t r i p which was f i l l e d w i t h a polyurethane compound. Shrinkage of pours in t h i s work was n e g l i g i b l e . Shrinkage in sulfur concrete was p r o p o r t i o n a l to the amount of sulfur b i n d e r used. Economics P o t e n t i a l l y every parameter of cost i n v o l v e d in sulfur conc r e t e is a v a r i a b l e . The cost of sulfur and the cost to modify it, the a v a i l a b i l i t y and c a p a c i t y of mixing equipment and the d a i l y volume of m a t e r i a l mixed, and the l a b o r requirement at the mixing i n s t a l l a t i o n are v a r i a b l e f a c t o r s f o r a specific p r o j e c t . Added to these v a r i a b l e s are the normal parameters of a concrete j o b s i t e p r e p a r a t i o n , form c o n s t r u c t i o n and grade d e l i n e a t i o n , t r a n s p o r t , placement, f i n i s h , j o i n t p r a c t i c e , and other items c o n s t i t u t i n g the t o t a l concrete i n s t a l l a t i o n . F i n a l l y , a cost comparison must be made versus the l o c a l cost of p o r t l a n d cement concrete, which is h i g h l y v a r i a b l e in d i f f e r e n t l o c a t i o n s . Based on t h i s experience and a p p l i e d to a spread of readymix concrete cost of $40 to $80 a yard and extended to a range of q u a n t i t y of sulfur concrete mixed per day, there is an i n d i c a t e d cubic yard comparison, m a t e r i a l s o n l y , of approximately lh to 6 times the cost of p o r t l a n d cement concrete f o r sulfur concrete. Greater volumes per day y i e l d lower u n i t c o s t s . Experience at Corpus C h r i s t i would put the premium cost of sulfur concrete approximately 15 pct more than the cos*- of p o r t l a n d cement concrete L i m i t a t i o n s and P r o j e c t e d Future Use The experience of Asarco was l i m i t e d to exposures in d i f f e r e n t c o n c e n t r a t i o n s of s u l f u r i c a c i d . Researchers s t u d y i n g sulfur concrete i n d i c a t e that it is r e s i s t a n t to many o r g a n i c and i n o r g a n i c compounds, but not to aromatics, strong c a u s t i c
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s o l u t i o n s , or o x i d i z i n g a c i d s , and is not s u i t a b l e at e l e v a t e d temperatures because sulfur melts at about 240° F. S u l f u rinthe concrete can be f l a s h e d o f f when exposed to an open flame, but the concrete w i l l not s u s t a i n combustion. Few data are publ i s h e d on i t s performance under sustained loads. The s t r e n g t h of the m a t e r i a l ranges from 4,000 to 10,000 p s i , depending on aggregate q u a l i t y , g r a d a t i o n s , and amount of sulfur binder used in the mix. For a c i d i c environments at Asarco, s i l i c a g r a v e l is the most s u i t a b l e aggregate m a t e r i a l . Crushed and graded metall u r g i c a l slags could be an acceptable aggregate; however, no inv e s t i g a t i o n of t h i s p o s s i b i l i t y has been made. At the c o n c l u s i o n of the paving work at Corpus C h r i s t i , two e l e c t r o l y t i c c e l l s were cast of sulfur concrete f o r useint h e z i n c r e f i n e r y . Subsequent to the work at Corpus C h r i s t i , a sulfur concrete f l o o r was a p p l i e d in the n i c k e l p l a n t at the Asarco A m a r i l l o copper r e f i n e r y . An i s o l a t i n g b a r r i e r of b i t u mastic m a t e r i a l was mopped on the concrete before the sulfur conc r e t e pour. This f l o o r , a s u b s t a n t i a l l y s m a l l e r area, was overl a i d on a damaged e x i s t i n g f l o o r . S i m i l a r techniques to those described were used in mixing and placement. S u l f u r concrete is not viewed as a s u b s t i t u t e f o r p o r t l a n d cement concrete in general c o n s t r u c t i o n . A u s e f u l f e a t u r e is achievement of s t r e n g t h w i t h i n s e v e r a l hours a f t e r pouring. Placement can be made in a wider range of c l i m a t i c c o n d i t i o n s than can p o r t l a n d cement concrete. S u l f u r concrete o f f e r s advantages in c o r r o s i v e environments of the type t e s t e d and under t e s t i n g at the Asarco p l a n t s and has advantages in f l o o r areas, e i t h e r as a s t r u c t u r a l m a t e r i a l or as a p r o t e c t i v e o v e r l a y f o r s t r u c t u r a l concrete, w i t h an i s o l a t i n g b a r r i e r between the conc r e t e and the sulfur concrete. Precast s l a b s and sumps were prepared f o r i n s t a l l a t i o n at the Tacoma p l a n t in an a c i d - t r u c k l o a d i n g area. The s l a b s are o v e r l a i d on s t r u c t u r a l concrete. S u l f u r concrete has p o t e n t i a l as a m a t e r i a l of c o n s t r u c t i o n f o r e l e c t r o l y t i c c e l l s , f o r l e a c h v a t s , f o r other low temperature a c i d i c containment v e s s e l s , and f o r general areas of f l o o r s and r e t e n t i o n basins in a c i d i c environments. Acknowledgment The review and comments on the t e x t by Messrs. R. S. Jones, P l a n t Engineer, Asarco Corpus C h r i s t i ; H. L. F i k e , V i c e P r e s i dent of The Sulphur I n s t i t u t e ; and T. A. S u l l i v a n , Research Chemist, U. S. Bureau of Mines, Boulder C i t y , Nev. are g r e a t l y appreciated.
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Literature Cited 1. 2. 3.
S u l l i v a n , Τ. Α.; McBee, W. C. "Development and T e s t i n g of Superior S u l f u r Concretes." BuMines RI 8160, 1976, 30 pp. McBee, W. C.; S u l l i v a n , T. A. "Development of S p e c i a l i z e d S u l f u r Concretes." BuMines RI 8346, 1979, 21 pp. McBee, W. C.; S u l l i v a n , Τ. Α.; Jong, B. W. "Modified S u l f u r Cements f o r Use in Concretes, F l e x i b l e Pavings, Coatings, and Grouts." BuMines RI 8545, 1981.
RECEIVED October 5,
1981.
