concrete paper

8/13/2019 Concrete Paper

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73TECHNIQUES FOR THE UTILIZATION OF FLY ASH

S G . S c h a f f e r a n d R . W . NobleDuquesne L igh t Company, P i t t sb u r gh , P ennsy lvan i a

S i n ce th e i n t r o d u c t i o n of p u lv e r i ze d - c o al b o i l e r s i n t h e 1920-1930d e c a d e , t h e p. roble m o f f l y a s h c o l l e c t i o n a n d d i s p o s a l h a s b e e n a ma j or . p ro bl emt o t he e l e c t r i c u t i l i t y i n d u s t r y . T he q u a n t i t y o f f l y a s h p r od u c ed a n d w hi ch i sn ot c o l l e c t e d i s becoming a n i n c r e a s i n g l y g r e a t e r a i r p o l l u t i o n p ro bl em , s u b j e c tt o c o n t r o l by m u n i c i p a l i t i e s , s t a t e s an d t h e F e d e r a l G ov er nm en t. E v er y e m ph a si si s t h e r e f o r e b e i n g made t o r e d u c e t h e amount o f f l y a s h e s c a p i n g t o t h e a t mo s ph e reby t h e i n s t a l l a t i o n of f l y a s h c o l l e c t i n g e qu ip me nt , wh er e i t d oe s n o t e x i s t , a nd

?\ by i n c r e a s i n g t h e c o l l e c t i o n e f f i c i e n c y of equipment where i t i s a l r e a d y i n s t a l l e d .T h is r e d u ct i on i n a i r p o l l u t i o n , however, a g g r a v a t e s t h e a l r e a d y d i f f i c u l t p roblemof d i s p o s a l of t h e c o l l e c t e d f l y a s h . A t Duquesne L ig ht Company t h e r e a r e twenty .p u l v er i z e d -c o a l b o i l e r s , a n d i n 1964 t h e y p r o d u c e d n e a r l y 500,000 t on s of f l y a s h .; I n t h e Un it ed S t a t e s i n 1962, m or e t h a n e l e v e n m i l l i o n t o n s o f f l y a s h were c o l -l e c t e d ; a n d i t i s e s t i m a t e d t h a t by 1980, t h e r e w i l l b e t w e nt y - f i v e m i l l i o n t o n sp r o d u c e d a n n u a l l y . A t Duquesne L ig h t Company t he f l y a s h p roduced was co l l ec t e dby m e c h a ni c a l c o l l e c t o r s a n d e l e c t r o s t a t i c p r e c i p i t a t o r s , s om et im es i n c om bi na ti on .

One method i s t o t r a n s -' p o r t i t f ro m t h e c o l l e c t i o n h o p pe r s t o a s i l o i n a d r y s t a t e a n d, a f t e r pa s si n g' t h r o u g h a w e t t i n g pu g m i l l , i t i s l. oade d o n t r u c k s a n d h a u l e d t o t h e a s h d i s p o s a la r e a . A second. method i s to remove t h e f l y a s h f r om t h e h o p p e r s , mix i t w i t h

1 w a t e r a nd s l u i c e i t t o an a s h pond. When t h e pond becomes f u l l and ha s been de-\ , w at e r ed b y d r a i n a g e a nd e v a p o r a t i o n , i t i s dug wi t h power equipment and hau led

\ Th e c o l l e c t e d f l y as h- i s g e n e r a l l y h a n d l e d i n t wo w ay s.

\ t o t h e a s h d i s p o s a l a r e a .D uq ue sn e h a s b e en d i s p o s i n g of f l y a s h i n t h e s e w ays f o r mo re t h a n

twenty years and h a s fo un d t h a t t h e y a r e w a s t e f u l a n d r e p r e s e n t a c o n t i n u i n gexpense , f rom which no b e n e f i t s c a n b e r e a l i z e d . The dump a r e a s , a t b e s t , a r eu n s i g h t l y a n d a r e a s o u r c e o f s e co nd a ry f l y a s h e n t r a in m e n t . T h e , u n si g h t li n e s s .

\ a n d t h e d u s t s o u r c e of t h e dump a r e a s a r e a n a n no y an c e t o t h e n e a r b y p o p u l a c e ,: a n d i n some l o c a t i o n s t h i s a n no y an c e ha s c a u s e d a c o n s i d e r a b l e am ou nt o f i l l

' f e e l i n g t oward t h e Company. T h e r e h a ve b ee n a c t s of h a r a s s me n t b y t h e p u b l i ca nd l e g i s l a t i v e a c t i o n by c e r t a i n m u n i c i p a l i t i e s t o pr e v e n t t h e dumping of f l ya s h . F o r t h e s e r e a s o n s , i t h a s be en i n c r e a s i n g l y d i f f i c u l t t o l o c a t e an d o b t a i nnew dum ping a r ea s wh ich a r e l oc a t ed a t r e a s o n a b l e d i s t a n c e s f r om a g e n e r a t i n gs t a t i o n . A l l p r a c t i c a l an d re a s o n ab l e me th od s t o f i n d s o l u t i o n s t o t h e s e pr ob -l e m s , a n d t h e r e b y p l a c a t e t h e n e i g h b o r s , h a v e b e en t r i e d by D uq ue s ne , b u t m o st l y' w i t h o u t , t o o much s u c c e s s . T h i s i s e s p e c i a l l y t r u e i f t h e dump a r e a i s s t i l l, b e i n g u se d . F o r dumps n o l o ng e r i n u s e , a m ethod wh ich has been used succ es s -f u l l y t o e l i m i n a t e s e c o n d a r y f l y a s h e n t r a i n m e nt h a s b e en t o c o v e r t h e dump a r e aw i t h t o p s o i l a nd p l a n t wi t h g r a s s seed. I n many l o c a t i o n s , t h e s e a r e a s h av e. b ee n

'made u s e f u l t o m u n i c i p a l i t i e s f o r r e c r e a t i o n a l a c t i v i t i e s . However, i t i s n o tp o s s i b l e t o u se t h e s e f i l l e d a r e a s f o r h eavy b u i l di n g s b e ca us e f l y a s h w i l l n o t, s u p p o r t h ea vy l o a d s , t h e i n h e r e n t t en de nc y b e i n g t o " fl ow " when s u b j e c t e d t o

) g r e a t p r e s s u r e s o r e x c e s s i v e m o i s t u r e . T ak in g a l l f a c t s i n t o c o n s id e r a t i o n , i tcan be conc luded t ha t t he p re se n t p roc edure o f dum ping i s a v e r y u n d e s i r a b l em et ho d of d i s p o s i n g o f f l y a s h .

C onf ro n t ed wi th t h es e co nd i t i o ns , t h e Duquesne L ig h t C ompany has beenb c t i v e l y e n ga g ed , f o r m or e t h a n f i f t . e e n y e a r s , i n s e a r c h i n g f o r o t h e r m et ho dsl f o r t h e d i s p o s a l of f l y a s h i n a n e co n om i c' m an n er . D uq ue sn e h a s f i n a n c e d , b ot hp r i v a t e l y a nd j o i n t l y w i t h o t h e r c o mp an ie s, r e s e a r c h p r o j e c t s t o d e te r mi n e t h e{ e a s i b i l i t y o f new m eth od s f o r t h e u t i l i z a t i o n of f l y a s h . I n a d d i t i o n , i t hasit I


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74w ork ed c l o s e l y w i t h n a t i o n a l o r g a n i z a t i o n s s u c h a s t h e E d is o n E l e c t r i c I n s t i t u t ew h ic h , o f c o u r s e , a l s o r e c o gn i z e s t h a t w i t h t h e i n c r e a s e i n pu l ve r i z ed -c o alb o i l e r s , t h e d i s p o s a l of f l y a s h . i s b ecoming a more a c u t e p ro bl em .

S e v e r a l wo r t hw h i le u s e s h a v e b ee n f ou n d f o r f l y a s h , o n e o f . w h i c h i si n t h e c o n s t r u c t i o n o f a s p h a l t ro ad wa ys . F l y a s h h a s p r ov e n t o b e v e r y e f f e c t i v ea s a " ch ok in g" m a t e r i a l f o r t h e l a r g e , h ea vy s l a g b a s e c o u r s e s , b e c a u s e o f i t sf l u i d i t y , a n d a s a r e p la c em e n t f o r l i m e s t o n e d u s t i n t h e s u r f a c e c o u r s e . I n 1953,w o r k i n g i n c o n j u n c t i o n w i t h B i tu m in o us C o a l R e s e a r c h , I n c . , D uq ue sn e L i g h t Companyc o n s t r u c t e d a s p e c i a l a s p h a l t roadway a t i t s P h i l l i p s Power S t a t i o n n e a r Al iq u ip pa ,P e n ns y l v an i a , f o r t h e p u r p o s e o f d e t er m i ni n g t h e e f f e c t on t h e d u r a b i l i t y of t h i st y p e of r oa dw ay when f l y a s h i s s u b s t i t u t e d f o r o t h e r m a t e r i a l s . The r oa d i sa p p r o x i m a t e l y 170 f e e t l o n g a nd r u n s fro m a p a s s i n g h i g h w a y t o t h e s t a t i o n c oa lt r u c k s c a l e . The r o a d , o v e r wh i ch a l l of t h e s t a t i o n t r u c ke d c o a l p a s s es , i sc o n s i d e r e d t o be a v e r y h e a vy o n e a n d h a n d l e s a n a v e r a g e o f 1 6 0 t r u c k s p e r d a yf o r a f ive -day week a t a n a v e r a g e l o a de d w e i g ht o f a t l e a s t 25 t o n s . V a r i o u sc o m b i n a t i on s o f s t a n d a r d a n d f l y - a s h - c o n t a i n i n g s u r f a c e s a n d b a s e s were i n s t a l l e dt o co mp ar e t h e d i f f e r e n t t y p e s of c o n s t r u c t i o n . The r o a d , a s c o n s t r u c t e d , c o n -s i s t s o f a 1 - i n ch s a n d b a s e , t wo 6 - i n c h l a r g e s l a g b a s e s , a 2 - i n c h b i n d e r c o u r s ea n d a 1 - i n c h s u r f a c e c o u r s e . F l y a s h w a s u s ed f o r f i l l i n g ( "c ho ki ng ") b et we ent h e l a r g e s l a g of t h e b a s e s a n d a s a s u b s t i t u t e f o r l i m es t o ne du s t i n t h e s u r fa c ec o ur se . The r oad i s s t i l l i n u s e a n d d i d n o t r e q u i r e r e p a i r u n t i l May 1 96 5, whenv e r y m in o r r e p a i r s were made. The r e s u l t s of t h e t e s t i n d i c a t e t h a t t h o s e p or -t i o n s o f t h e ro ad wh i ch were c o n s t r u c t ed u s i n g f l y a s h , a s p r e v i o u s l y d e s c r i b e d ,ha ve . pe r f o r m e d a s w e l l , i f n o t b e t t e r , t ha n t h e p o r t i o n s u s i n g r e g u l a r c o ns t ru c -t i o n m a t e r i a l s w i t h r e s p e c t t o s u r f a c e wear a n d g e n e r a l r o a d u p k e e p . I t was duem o s t l y . t o t h e r e s u l t s of t h i s t e s t r o a d t h a t t h e P e n n sy l v a ni a S t a t e HighwayD ep ar tm en t a c c e p t e d f l y a s h a s a s u i t a b l e m a t e r i a l i n t h e i r a s p h a l t r oa d spec i-f i c a t i o n s . W it h t h e p r o s p e c t of h a v in g a m a r k e t f o r i t s f l y a s h , t h e D uquesneL i g h t Company i n s t a l l e d f l y a s h b ag gi ng f a c i l i t i e s a t i t s P h i l l i p s S t a t i o n . Thef l y a s h i s m a r ke t e d by a l o c a l c o n t r a c t o r u n d er t h e name of " D u r o si l " . T h e re h a s ,howe ver , ne ve r be e n a ny r e a l demand f o r t h e p r o d u c t i n t h i s area ' .

A lt ho u gh s u b s e q u e n t l y t h e r e h a v e b ee n r o a d s i n o t h e r a r e a s s i m i l a r l yc o n s t r u c t e d , there h a s n o t been any r e a l w i d e -s p r ea d u s e of f l y ash f o r t h i sp ur po se . E l e c t r i c u t i l i t i e s , whose p ri ma ry i n t e r e s t i s g e n e r a t i n g e l e c t r i c power,h a v e , p e r h a p s , n o t a t t e m p t e d t o p us h g r e a t l y t h e u s e s of f l y a s h f o r r o ad c on-s t r u c t i o n . T h is m et ho d of u t i l i z a t i o n a l s o w ou ld no t n e a r l y a pp ro ac h t h e t o t a lamo unt o f f l y a s h p r o d uc e d e a c h y e a r b y t h e e l e c t r i c i n d u s t r y , a n d i t s s e a s o n a ldemand would p r odu c e p r ob le m s o f s to r a g e or i n t e r m i t t e n t d i s p o s a l .

Due to i t s p o zz o la n ic p r o p e r t i e s , a n o t h er u s e f o r f l y a s h i s a s ac o n c r e t e a d d i t i v e s u b s t i t u t e d f o r c em en t. A lt ho ug h f l y a s h ca n n ot b e w ho ll ys u b s t i t u t e d f o r ce me nt , i t h a s b e e n shown t o b e e f f e c t i v e when u s e d a s a r e p l a c e -men t i n q u a n t i t i e s up t o 2 5 -3 0 p e r c e n t of t h e c em en t us e d i n b u l k c o n c r e t e a n dc o n c r e t e b l oc k : Much r e s e a r c h h a s b ee n d on e by t h e e l e c t r i c u t i l i t y i n d u s t r y ,a s w e l l a s many o t h e r i n t e r e s t e d o r g a n i z a t i o n s , t o d e t er m i ne t h e e f f e c t s ofs u b s t i t u t i n g f l y a s h f o r ce me nt i n t h e p r e p a r a t i o n of c o n c r e t e . The B a t t e l l eMemorial I n s t i t u t e h a s been eng aged f o r s e v e r a l y e a r s i n r e s e a r c h f o r t h eE di so n E l e c t r i c I n s t i t u t e f o r t h e p u r p o s e of d e t e r m i n i n g c e m e n t i t i o u s c h a r a c -t e r i s t i c s of f l y a s h a n d t h e e f f e c t o f v a r i a t i o n s i n c h em i ca l c o mp o si t i o n ofd i E f e r e n t a s h e s . A s l o n g a g o a s 1 9 5 2 , Duquesne Lig ht Company engag ed t h eP i t t s b ur , q h T e s t i n g L a b o r a t o ry t o p er f o rm t e s t s on c o n c r e t e c o n t a i n i n g f l y a sh .U s in g b a s i c 1:2:3 and 1 : 2 : 4 c o n c r e t e m i xe s , f l y a s h was s u b s t i t u t e d f o r c ementin a m oun t s o f 10 , 20 and 3 p e r c e n t . The c o n c r e t e s a m p le s were t h e n u s e d t oc o n du c t c om p re s si v e an d f r a c t u r e t e s t s . I n 1954 Duquesne L ig h t Company, wheni n s t a l l i n g a new c o n c r e t e r o a t a t i t s E lrama S t a t i o n , u s e d f l y a s h i n 10, 20a n d 25 p e r ce n t q u a n t i t i e s i n c e r t a i n t e s t s e c t i o n s o f t h e r o a d. C o n cr e tes am pl es t a k en a t t h a t t i m e were a l s o t e s t e d by P i t t s b u r g h T e s t i n g L a b or a t or y .


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The r e s u l t s o f t h e s e t e s t s , a s w e l l a s t e s t s by many o t h e r o r g a n i z a t i o n s , i n d i c a t et h a t f l y a s h c a n be s u b s t i t u t e d s u c c e s s f u l l y f o r c em ent i n c o n c r e t e up t o 25-30p e r Cent rep lacement and s t i l l produ ce a c o n c r e t e which exc eeds t h e minimum com-\ p r e s s i v e s t r e n g t h .

w i t h v a r i o u s p e r c en t ag e s o f f l y a s h s u b s t i t u t e d f o r P o r t l a n d ce me nt .was ta ken f rom t e s t s per fo rm ed by t h e Na t i on a l R eady-Mixed C on cre t e Asso c i a t i on .The f o l l o w i n g t a b l e s hows t h e c o m pr e s s iv e s t r e n g t h o f c o n c r e t e

The data

C o mp re s si ve S t r e n g t h , p s iCement Replacedr\ Per Cent 7 days 28 days 3 months

' c a l c i u m h y d r o x i d e , w hi ch i s w a t e r s o l u b l e , w i l l l e a c h o u t w i t h t i m e , l e a v i n g v o i d sin t h e c o n c r e t e . Leach ing beg ins soon a f t e r t h e c on c re t e i s p l a c e d a nd c o n t i n u e sf o r i t s l i f e t i m e . The f r e e c a l c i um h y d r o xi d e i s a t t a c k e d by v a r i o u s s u l f a t e s a nd

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76o t h e r co mp ou nds , i n c r e a s i n g t h e p e r m e a b i l i t y o f t h e c o n c r e t e a n d t h e r e by l e a d i n gt o d e t e r i o r a t i o n an d d e c r e a s e i n d u r a b i l i t y . T h e r e f or e , c o n c r e t e s h ou ld c o n t a ina minimum o f c a l c i u m h y d r o x i d e i n o r d e r t o i n c r e a s e i t s d u r a b i l i t y a n d de c re a sei t s p e r m e a bi l i t y . By u s i n g f l y a s h i n c o n c r e t e , t h e f l y a s h t a k e s ad v an ta g e oft h e h y d r a te d lime f r e e d i n t h e c e me n t- wa te r r e a c t i o n by c om bi ni ng w i t h i tc h e m i c a l r e a c t i o n b e t w e e n t h e h y d r a t e d l i m e a n d t h e s i l i c o n a n d alu min um o x i d e si n t h e f l y a s h p r o d u c e s i n s o l u b l e c e m e n t i n g c om po un ds . T h e se a i d t h e h a rd e ne dp a r t i c l e s i n t h e r e ma i ni ng ce me nt m i x tu r e t o make f l y a s h c o n c r e t e s u p e r i o r t oo r d i n a r y c o n c r e t e i n s t r e n g t h , d u r a b i l i t y , w a t e r t ig h t n es s and r e s i s t a n c e t o v a r i -o us a c i d s , a l k a l i e s a nd s u l f a t e s . A s w ou ld b e e x p e c t e d , t h e f l y - a s h - c o n t a i n i n gc o n c r e t e d o es n o t h a r d e n a s r a p i d l y a s r e g u l a r c o n c r e t e ; h ow ev er , t h e f l y a s hc o n c r e t e w i l l i n t i me , become s t r o n g e r t h a n t h e r e g u l a r c o n c r e t e . I t can bes e e n o n F i g u r e 1 t h a t f o r t h e p a r t i c u l a r f l y as h- ce me nt c om bi na ti on u se d (2 0 perc e n t f l y a s h , 80 p e r c e n t P o r t l a n d c e m e n t) , t h e f l y a s h c o n c r e t e becomes h a r de ra f t e r a b o ut 100 d a y s .

T h i s same l i m e - f l y a s h c h em i ca l r e a c t i o n t h a t t a k e s p l a c e i n c o nc r e t ea l s o o c c u r s when m i xi ng f l y a s h w i t h l i m e a n d a g g r e g a t e - a c o m b i n a t i o n w hi ch h a sb ee n u s ed t o b u i l d low c o s t t em po ra ry r o a d s , a i r p o r t ru nw ay s a nd p a r k i n g l o t s .A c t u a l l y , t h e Romans u s e d a s i m i l a r c om bi na ti on f o r r o a d b u i l d i n g n e a r l y 2 , 0 0 0, e a r s a g o , e x c e p t v o l c a n i c a s h was u se d i n p l a c e of f l y a s h . I t i s f r o m t h i sa n c i e n t u s e t h a t t h e word " p o zz o l an i c " i s d e r i v e d .

T o d a t e , a l i m i t e d a mo un t of f l y a s h h a s b ee n u s ed by t h e b u l k c o n c r e t eu s e r s . The l a r g e s t p r o j e c t t o d a t e which u t i l i z e d f l y a s h a s a s u b s t i t u t e f o rcement was t h e Hungry Hors e Dam i n nor thw es t Montana. Th is dam, which co nt a i ns3 ,086 ,000 c u b i c ya r d s of c o n c r e t e , u s e d 126,000 t on s o f f l y a s h w i t h a r e s u l t a n ts a v i n g o f $ 1 . 5 m i l l i o n . V a r i o u s o t h e r dams a n d b u i l d i n g s t h r o ug h o ut t h e c o u n t r y ,i n c l ud in g Duquesne L i gh t Company' s S h i pp in gp or t A tomic Power S t a t i o n , have beenb u i l t u s i n g f l y - a s h- c o n t a in i n g c o n c r e t e .

I f a l l t h e c o n c r e t e us ed c o n t a i n e d f l y a s h , t h e r e would b e no d i f f i c u l t yi n d i s p os i n g of a l l t h e f l y a s h t h a t i s c u r r e n t l y p r o du c e d . H owe ver , t h e r e a r es e v e r a l f a c t o r s w hic h p r e s e n t l y t e nd t o l i m i t t h e ma r ke t in g of f l y a s h on t h a tl a r g e a s c a l e .

F i r s t , some d e g r e e o f c o n s i s t e n c y , w i t h r e s p e c t t o t h e p r o p e r t i e s off l y a s h , i s n e e d e d b e f o r e i t c a n b e u s ed i n c o n c r e t e . T h es e p r o p e r t i e s v a r y f ro ml o c a t i o n t o l o c a t i o n a nd f ro m t i m e t o t i m e, b ec a us e t h e r e i s n o a t t e m p t Io c o n t r o lt l y a s h p r o p e r t i e s . I t m u s t b e re me mbe red t h a t f l y a s h i s a b y -p r od u ct of e l e c t r i cpower gen er a t i o n and i t s p r o p e r t i e s d e p e n d , t o a l a r g e e x t e n t , on how t h a t genera-t i o n i s performed and a l s o on t h e o r i g i n a l c o m po s i ti o n o f t h e c o a l w hi ch i s burned.F o r i n s t a n c e , a s t a t i o n w hi ch i s b a s e l o a d e d w i l l p ro du ce f l y a s h w i t h a lowerc a r b o n c o n t e n t t h a n a s t a t i o n whose e l e c t r i c a l o u t p u t , a n d t h e r e f o r e c o a l bu rn in gr a t e , c o n t i n u a l l y f l u c t u a t e s .

S e co n d, t h e b a s i c c o m p o s i t i o n o f t h e c o a l b ur n e d may c o n t a i n e x c e s s i v ea mo un ts of u n d e s i r a b l e e l e m e n t s . F o r i n s t a n c e , f l y a s h may c o n t a i n e x c e s s i v e i r o na n d t h e r e f o r e i m pa r t an u n d e s i r a b l y d a r k e r c o l o r o r may r e s u l t i n s t a i n i n g wheni n c o r p o r a t e d i n t o c o n c r e t e b l o c k s o r o t h e r m as on ry p r o d u c t s .

T h i r d , t h e b ul k c o n c r e t e mi x in g p l a n t s a r e n o t a l wa y s c o n v e n i e n t l yl o c a te d t o f l y as h s ou r c e s ; a n d , t h e r e f o r e , t r a n s p o r t a t i o n c an be a p ro ble m o r a tl e a s t c o s t l y enough t o e l i m i n a t e p o s s i b l e s a v i n g s .

F o u r th , t h e h a n d l in g a nd s t o r a g e of f l y a s h c an b e a p ro bl em i f i t i su se d i n l a r g e c o n c re t e p r o j e c t s l i k e d a m s a n d b u i l d i n g s . I n c o n s t r u c t i o n p r o j e c t s ts u ch a s t h e s e , t h e n ee d f o r f l y a s h i s i n t e r m i t t e n t a nd s t o r a g e f a c i l i t i e s would

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F i f t h , t h e e l e c t r i c u t i l i t y i n d u s t r y , a s a w ho le , h a s p ro ba bl y no t p us heds u f f i c i e n t l y ha r d t o d e v el op a m ar ke t f o r t h e m a t e r i a l n o r t o e n l i g h t e n co n cr e teu s e r s s u f f i c i e n t l y . A l l e l e c t r i c u t i l i t y c omp ani es do n o t h a ve f l y a s h d i s p o s a lp r o bl e m s, s i n c e some co m pa n ie s u s e o t h e r f u e l s a n d s t i l l o the r c om pa n ie s ha ve no te xp e r i e nc e d p r ob le m s wi th dumping be c a use o f ge og r a ph ic a l l o c a t i on . However ,e v a l u a t i n g a l l f a c t o r s , i t i s e v i d e n t t h a t , a t l e a s t i n c e r t a i n a r e a s , many pr ob -l e m s e x i s t a nd t h a t much r e s e a r c h i s s t i l l n eed ed i f f l y a s h i s t o be s u b s t i t u t e df o r P o r t l a n d cement i n an y g r e a t q u a n t i t i e s .

F l y a s h h a s be en t r i e d a s a s u b s t i t u t e mater ia l i n v a r i o u s p r o c e s s e s bymany i n d u s t r i e s . T he p r e v i o u s u s e s d i s c u s s e d are known t o be su cc es sf u l ; someo t h e r p r o c e s s e s h av e be en r e a s o n a b l y s u c c e s s f u l an d c a n u s e f l y a s h ; w h i l e s t i l lo t h e r s h a ve f ou nd f l y a s h t o b e an u n s u i t a b l e m a t e r i a l f o r a p a r t i c u l a r u se .

E x p e r i me n t a l w ork h a s b e en d o n e o n u s i n g f l y a s h a s a s u b s t i t u t e f o rc o r e s a n d f o r s t e e l a n d alu min um c a s t i n g s . A lt ho ug h t h e c a s t i n g s u s i n g f l y a s hm ol ds w e re s m oo t he r, t h e y t e n d e d t o d ev e l o p p i t t i n g ; a nd a l s o , t h e r e was t h e e v e rp r e s e n t p r o b l e m of h a nd l in g t h e f l y a s h .

F l y a s h w as t e s t e d a s a n ex t e n d er i n p a i n t a n d a s a f i l l e r i n p ut ty .I t p ro ved t o be of no v a l u e i n p a i n t , an d p a r t i c l e s i z e was t o o l a r g e f o r p u t t y . 1

ib u t h a s b ee n r e j e c t e d f o r f l o o r t i l e be c a use o f i t s d ar k c o l o r . 1

Some f l y a s h i s b e i n g u se d i n a s p h a l t r o o f i n g an d s i d i n g m a t e r i a l s ,

A b u i l d i n g b l o c k was t e s t e d u s i n g l i m e a nd f l y a s h an d c o n t a i n i n g noP or t l a n d c e m en t . The b lo c ks ha d a s mo ot h s u r f a c e w hi ch made t hem d i f f i c u l t t oh a n d l e . A l s o , t h e y were more b r i t t l e , t en de d t o c h i p an d sp a1 1 a f t e r i n s t a l l a t i o na n d w e r e h e a v i e r t h a n r e g u l a r b l o c k . They w e r e r e j e c t e d b e c a u s e t h e y a f f o r d e d noa d v a n t ag e o ve r t h e r e g u l a r b l o c k . I

A n i n v e s t i g a t i o n was made i n t o t h e p o s s i b i l i t y of u s i n g f l y a s h a s ac o n s t i t u e n t i n b r i c k m ak ing . I t was r e j e c t e d b e c a u s e when mi xe d w i t h c l a y , t h em a t e r i a l p ac ke d t o o h a r d , was t o o a b r a s i v e a nd t h e b r i c k s were too b r i t t l e .

F l y a s h was t e s t e d f o r u se i n a so un d d ea de ni ng p l a s t e r , b u t i t s c o l o rwas o b j e c t i o n a b l e .F l y a s h h as b ee n t r i e d a s a n ad mi xt u re t o f e r t i l i z e r , r e p l a c i n g fou ndry

s a n d , b u t was f ou nd t o b e t o o f i n e a n d d u s t y .Some a g r i c u l t u r a l e x p e r i m e n t s h a v e b e en c o n d u ct e d on p o t p l a n t i n g s o f

s oy b ea n s by ad d i n g f l y a s h t o t h e s o i l . The f l y a s h p ro du ce d a s u b s t a n t i a li n c r e a s e i n g r ow t h an d a n i m pr ov em en t i n c o l o r .

l y as h was t r i e d a s a f i l l e r f o r a b r a s iv e so ap , b u t w a s f ound to bei n f e r i o r t o t h e p um ic e w hi ch was b e i n g u s e d . . I t w as a l s o f o un d t o b e u n s u c c e s s f u la s a f i l l e r m a t e r i a l i n p a pe r a nd r ub b er .

F ly a sh wa s t r i e d a s a s ou nd a nd h e a t i n s u l a t o r , b u t was found to packe x c e s s i v e l y an d a b s o r b m o i s t u r e when e x p o s ed t o a i r .

I n s u l a t i n g c em en t h a s b een made c o n t a i n i n g f l y a s h whi ch r e s u l t s i n l e s' shri.nk.age c r a c k s j a n d t h e r e f o r e i s c ons i . de r e d to h e s u p e r i o r t o o t h e r m a t e r i a l s

u s e d .F l y a s h h a s b e e n s u b s t i t u t e d f o r p um ic e i n b u f f i n g compounds a n d f o r

w h i t i n g i n t oo t h p a s t e . I t d i d n o t p r od u ce t h e d e s i r e d p o l i s h e d f i n i s h when u s ef o r b u f f i n g , a nd i t w as t o o h a r d f o r u s e i n t o ot h p a s t e .

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9When f l y a s h was s u b s t i t u t e d f o r c l a y i n ce ra mi c t i l e , t h e r e was noi mp ro ve me nt i n p r o d u c t q u a l i t y a n d i t c o s t more t o m a n uf a c tu r e .

f o r d ia to ma ce ou s e a r t h i n p l a s t i c s , i t r e s u l t e d i n a p r o d u c t o f p o o r e r q u a l i t y .When t r i e d a s a f i l t e r f o r w a te r a nd o i l p u r i f i c a t i o n , r e p l ac i n g s an d

A s a s u b s t i t u t e

' a n d f u l l e r ' s e a r t h , f l y a s h d i d n o t produce d e s i r e d c l a r i f i c a t i o n o f t h e water o ro i l .

The u t i l i z a t i o n o f t h e i n d i v i d u a l c h e m ic a l s of w h ic h f l y a s h i s composedT h e e x t r a c -

may be a p o s s ib l e u s e i n t h e f u t u r e .r em oving t r a ce s o f ge rm an ium wh ich have been found i n some f l y a s he s .The B ureau o f Mines ha s exper im en ted w i t h

' t i o n of o t h e r e l em e nt s a n d compounds may b e f e a s i b l e i n t h e f u t u r e .I t i s e v i d e n t t h a t u s e s f o r f l y a s h h a ve b ee n a t t e m p t e d by many i n d us -

I'd0 n o t u s e f l y a s h i n s u f f i c i e n t q u a n t i t i e s t o c on su me a n y g r e a t p e r c e n t a g e of t h et r i e s , b u t w i th o nl y l i m i t e d s u c c e s s .y e a r l y p r o d u c t i on .

T ho se t h a t h a v e f o un d t h e p r o d u c t u s e f u l

To d a t e , t h e mo st p r o m is i n g m et ho d f o r u t i l i z i n g f l y a s h a pp e a r s t o b e, a s a l i g h t w e i g h t a g g r e g a t e . H owe ve r, t h e f l y ash m us t f i r s t b e s i n t e r e d a nd' c r u s h e d a n d t h e n i t c a n b e u s e d a s a s u b s t i t u t e f o r f i n e o r c o a r s e a g g r e ga t e i nLs The p o s s i b i l i t y of s i n t e r i n g f l y a s h c ame t o l i g h t i n t h e e a r l y 1 95 0' s?hen e f f o r t s w er e made by c e r t a i n co mp an ie s t o s i n t e r f l y a s h w i t h o u t f i r s t p e l -l e t i z i n g . The p r o c e s s was n o t s u c c e s s f u l . I t was f ou nd t h a t p e l l e t i z i n g was

' n e c e s s a r y a nd c o u ld b e a c co mp li sh ed o n l y a f t e r a d d i n g e x p e n si v e b i n d e r s .m e n t a t i o n c o nt i n u e d t o im pr ov e p e l l e t i z i n g e q ui p me n t, m o s t l y i n c o n j u n c t i o n w i t h

r on o r e , s o t h a t by 1 96 0 p e l l e t i z i n g c o u l d b e a cc o mp l is h ed w i t h o u t b i n d e r a d -m i x t u r e s . By 1 96 1, p e l l e t i z i n g a nd s i n t e r i n g t e s t s w it h f l y a s h i n v a r i o us p i l o tp l a n t s d e mo ns tr at ed t h a t f l y a s h s i n t e r i n g p l a n t s o f a commercia l s i z e were nowt e c h n i c a l l y a nd e co no mi ca ll y f e a s i b l e . S i n c e t h a t t i m e , t h r e e f l y a s h s i n t e r i n gp l a n t s h a ve b ee n i n s t a l l e d , o ne e a c h a t C o n s o l i d a t e d E d i s o n Company i n N e w YorkC i t y ; Nia ga ra Mohawk Power Company i n B u ff a lo , New Y or k; a n d a t D e t r o i t E d is on"ompany i n De t r o i t , Mich igan . A l l t h r e e of t h e s e p l a n t s u t i l i z e t h e same b a s i c

e s i g n pro duc ed by t h e McDowell-Wellman Company.d f P i t t s b u r g h , P en n sy l va n ia , a l s o h a s i n s t a l l e d a s m a l l p l a n t n e a r Du qu es ne L i g h t ' s

c o n c r e t e , c o n c r e t e b l o c k , r oa dw ay s a n d a ny w he re e l s e w h e r e a g g r e g a t e s a r e r e q u i r e d .

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The S t i r l i n g S i n t e r i n g Company

x t r u s i o n p r o ce s s . Both of t h e p r o c e s s es th en f e e d t h e p e l l e t s i n t o g a s - f i r e dhe same t i m e s i n t e r e d p e l l e t s a r e f or me d. T he se p e l l e t s c a n b e c r u s h e d t o v ar i o u si z e s t o g i v e e i t h e r a f i n e o r c o a r s e a gg r e ga t e .

Ia t a p p ro x i ma t e ly 2000 F, a nd t h e c ar bo n i n t h e f l y a s h i s b ur ne d w h il e a t

The c h i e f a d v a n ta g e of s i n t e r e d f l y a s h a g g r e g a t e i s i t s l i g h t w e i gh t .h en s i z e d t o c o n c r e t e bl oc k g r a d e , s i n t e r e d f l y a s h w ei gh s 4 8 5 0 l b s . / cu . f t . , wh i l en o t h e r c o m o n b l oc k a g g r e g a t e m a t e r i a l , e xp an de d s l a g , w ei g hs 68-72 l b . / c u . f t . T h i se i g h t d i f f e r e n t i a l ca u se s a r e d u c t i o n i n b lo c k w e i g ht f ro m a p p r o x i m a te l y 35 l b .o 5 l b . T h i s r e d u c t i o n c a n mean a d e c re a s e i n b u i l d i n g s t r u c t u r e c o s t s , h a nd l i ngo s t a nd sh ip p in g c o s t . I n a d d i t i o n t o t h e r e d u c t i o n i n c o s t s r e a l i z e d i n us in gh e b l o ck , t h e b lo ck c o n t a i n i n g f l y a s h a g g r e g a te c a n be pr od uc e d a t a l o w e r c o s t ,i n c e i t has been shown that l e ss P or t l and cem en t i s r e q u i r e d t o p ro du ce a b lock

t h an w i t h r e g u l a r a g g r e g a t e . The ASTM s p e c i -

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8/8

T e s t s h a v e a l s o b ee n p e r fo r m ed o n b u l k c o n c r e t e made u s i n g f l y a s h a s ac o a r s e a n d f i n e a g g r e ga t e .s t r e n g t h t e s t r e q u i r e s 40 0 0 p s i f o r 28 -d ay c u r e d c o n c r e t e , t h e f l y -a s h -c o n t ai n i ngc o n c r e t e was t e s t e d t o 4 9 10 p s i , w hi ch s u r p a s s e s t h e 4800 p s i c o n c r e t e made u s i n ge x p a n d e d s l a g as a n a g g r e g a t e . I t c an r e a d i l y b e s e e n t h a t c o n c r e t e an d c o n c r et eb l o c k u s i n g f l y a s h a g g r e g a t e g r e a t l y e x ce ed t h e minimum e s t a b l i s h e d s t r e n g t hr e q u i r e m e n t s . When u s e d i n r oad way c o n s t r u c t i o n , c o n c r e t e c o n t a i n i n g f l y a sha g g r e g a t e a s a n a d d e d b e n e f i t h a s b ee n shown t o b e more s k i d r e s i s t a n t .

T h e s e t e s t s h a v e sh ow n t h a t w h e r e t h e ASTM compress ive

W it h t h e a d v a n t a g e s p r e v i o u s l y m en t io n ed , t h e m a rk e t f o r f l y ash a g g r e -g a t e a p p e a rs t o b e a l m o s t u n li m i t e d . P r e s e nt s u r v e y s h av e i n d i c a te d t h a t a r e a ldemand c a n be e s t a b l i s h e d , p r o v i d e d a q u a l i t y p r o d u c t c a n c o n s i s t e n t l y b e pr od uc edb y t h e s i n t e r i n g p l a n t . Because f l y a s h s i n t e r i n g i s a r e l a t i v e l y new c o n c e p t ,o p e r a t i o n a l d i f f i c u l t i e s h av e been e n co un te re d by t h e t h r e e u t i l i t i e s p re vi ou s l ym e nt i on e d w hi ch h av e f l y a s h s i n t e r i n g p l a n t s ; h ow ev er , a l l f e e l t h a t mo st of t h ep r o b l e m s t h a t s t i l l e x i s t a r e d u e t o i n e x p e r i e n c e o f o p e r a t i o n a n d n ew ne ss ofequipment des i gn . Duquesne Li ght Company, a t t h e t ime o f p r e p a r at i o n o f t h i sp a p e r , i s p r o ce e d in g w i t h t h e d e s i g n a n d w i l l i n s t a l l a f l y a s h . s i n t e r i n g p la n ta t i t s Elrama S t a t i o n . W it h t h e e x p e c t a t i o n of b e in g a b l e t o t u r n a c o s t l y ex-p e ns e i n t o a p r o f i t - m a k i n g o p e r a t i o n , i t i s a n t i c i p a t e d t h a t m ore co mp an ie s w i l ll i ke w is e i n v e s t i g a t e t h e p o s s i b i l i t i e s o f s i n t e r i n g f l y a s h. I t i s e v e n p o s s i b l et h a t f u t u r e d e si g ns o f p u l v e r i z e d c o a l bu rn i ng s t a t i o n s w i l l i n c o r p o r a t e f l y a s hs i n t e r i n g f a c i l i t i e s a s a n i n t e g r a l p a r t o f t h e s t a t i o n d e s ig n an d o p e ra t i on . [

The e l e c t r i c u t i l i t y i nd u. st ry , a s a whole , i s v e r y e n t h u s i a s t i c o ve rt h e p o s s i b i l i t i e s o f s i n t e r e d f l y a s h , f e e l i n g t h a t p e r ha p s a t l a s t a u se hasbe e n f ound t h a t c a n u t i l i z e a l l o f t he f l y , a s h t h a t i s produced and end once andf o r a l l t h e p ro bl em s p r e s e n t l y e n c o un t er e d i n f l y a s h d i s p o s a l . 1

concrete paper

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