APPLICATION OF SOME WASTE MATERIALS I N H Y D R A U L I C E N G I N E E R I N G

K.W. Pi l a r czyk , Rijkswaterstaat, Road and Hydraul ic Engineer ing d i v i s i o n ,

G.J. Laan, Rijkswaterstaat, Road and Hydraul ic Engineer ing d i v i s i o n ,

H. den Adel, Delft Geotechnics , P.O. Box 69 , 2600 AB DELFT,

P.O. Box 5044, 2600 GA DELFT, The Nether lands

P.O. Box 5044, 2600 GA DELFT, The Nether lands

The Nether lands

1 . INTRODUCTION I n d u s t r i a l waste products o f t e n form a great problem rega rd ing their

s t o r a g e (dumping) and environmental consequences. I n The Nether lands cons ide rab l e exper ience has been gained wi th the a p p l i c a t i o n o f i n d u s t r i a l waste products as a l t e r n a t i v e materials i n h y d r a u l i c eng inee r ing ( i . e . bank and bottom p r o t e c t i o n , f i l t e r c o n s t r u c t i o n s , f i ï ï materiaï o f c ï o s u r e s t r u c t u r e s ) . For t h e greater p a r t t h e gene ra l a p p l i c a t i o n s have been carried ou t based on practica1 exper ience wi thout s c i e n t i f i c research i n t o t h e s t r u c t u r a l and environmental imp l i ca t i ons . Th i s kind of research has r e c e n t l y been s tar ted, mainly as a r e s u l t of t he growing awareness o f environmental impacts o f a p p l i c a t i o n of i n d u s t r i a l waste products . The research is focussed no t on ly on t h e commonly used waste materials, bu t 3lso aims a t i n v e s t i g a t i n g t h e u s e f u l n e s s of o t h e r r e s i d u a l materials. Waste materials t h a t we commonly used are minestone, a e v e r a l k inds o f slags and s i l e x ( a byproduct of t h e cement i n d u s t r y ) . A new development concerns the a p p l i c a t i o n o f t h e so-called "Euroclay" i n d i k e embankments. Euroclay is formed by c o n s o l i d a t i o n under g iven c o n d i t i o n s o f the l i g h t l y p o l l u t e d s i l t from the Rotterdam harbour area. The r e l e v a n t eng inee r ing p r o p e r t i e s o f t h e r e s i d u a l p roduc t s have already been s t u d i e d i n t e n s i v e l y . Th i s has l e d t o t h e d r a f t i n g of requi rements as t o the i r use , and t o t h e concept ion of c o n t r a c t s p e c i f i c a t i o n s f o r q u a l i t y z o n t r o l . The ideal is t o ach i eve a s i t u a t i o n i n which t h e materials w i l l be suppl i ed under ce r t i f i cat e . A s tudy of t h e environmental aspects involved ha3 on ìy r e c e n t l y been taken i n hand. A first r e s u l t of t h i s concerns t h e exc lus ion of lead slags as material i n h y d r a u l i c eng inee r ing s t r u c t u r e s , This s tudy should lead t o special requi rements with regard t o the environment, and t o systems f o r an adequate q u a l i t y assurance . Th i s paper w i l l review the e x i s t i n g knowledge and exper ience on a p p l i c a t i o n o f waste materials i n h y d r a u l i c eng inee r ing i n The Nether lands. Special a t t e n t i o n w i l l be pa id t o d e f i n e t h e environmental requi rements when us ing these materials.

2. DUTCH POLICY ON ALTERNATIVE MATERIALS The endeavour t o i n c r e a s e t h e use o f a l t e r n a t i v e materlals arises from

two g e n e r a l p u b l i c concerns (10) : a. a safe s t o r a g e and p roces s ing of the i n c r e a s i n g amounts of waste

materials ( t ab le 1 ) : t h i s is p r i m a r i l y the r e s p o n s i b i l i t y o f t h e Min i s t e r o f t h e Environment (waste materials p o l i c y ) .

b. reduc ing s t r i p p i n g of s u r f a c e mine ra l s ( table 2 ) ; t h i s is p r i m a r i l y the r e s p o n s i b i l i t y of the Min i s t e r of P u b l i c Works.

waste materials

- b u i l d i n g and

- d r e d g i n g s l u d g e - c o a l f l y- a s h - c o a l e i n d e r s - i n c i n e r a t i o n f l y- a s h - i n c i n e r a t ion s lags - s t ee l s l a g s - phosphor s lags - phosphor ic ac id

d e m o l i t i o n wastes

gypsum

amounts i n 1 0 t o n / y e a r

6 48 (18 d r y )

0.6 0.1 0.07 0.65 0.3 0.6

2.0

m i n e r a l s

- g r a v e l - sand f o r

indus t r i a l purposes

- sand f o r embankment f i ï l i n g - c l a y

- marl

amounts i n î û 6 t o n / y e a r

15

19

33 3 t o 4 2

T a b l e 1 : P roduc t ion of waste materials i n t h e Ne ther lands

Tab le 2: P r o d u c t i o n of s u r f a c e m i n e r a l s i n the N e t h e r l a n d s

S t o r a g e and p r o c e s s i n g of waste materials, and s t r i p p i n g o f s u r f a c e m i n e r a l s cause env i ronmenta l and p l a n o l o g i c a l problems, which can be d imin i shed by r e- u s e of waste materials. Such re- use may also i n f l u e n c e , both p o s i t i v e l y and n e g a t i v e l y , f a c t o r s as e n e r g y consumption, employment, l a b o u r c o n d i t i o n s , and commercial i n t e r e s t s ( i n v e s t m e n t i n i n n o v a t i v e developments) . A basic g u i d e l i n e of a p o l i c y aimed a t s t i m u l a t i n g the u s e of a l t e r n a t i v e materials i n works directed by Rijkswaterstaat, s h o u l d be t h a t when d e c i d i n g whether o r n o t t o use such materials, n o t o n l y p r o j e c t - c o s t s , b u t als0 t h e above-mentioned p u b l i c i n t e r e s t s be t a k e n i n t 0 account . Higher p r o j e c t c o s t s might t h e n i n some i n s t a n c e s be acceptable. Based on t h e fo re- going , Rijkswaterstaat ( R W S ) involvement wi th a l t e r n a t p v e materials has f i v e approaches : a. b. C.

d.

e.

t h e p r o d u c t i o n o f waste materials from construction/maintenance works t h e p o s s i b i l i t y t o use a l t e r n a t i v e materials i n works directed by RWS t h e r e s p o n s i b i l i t y RWS ha3 for the q u a l i t y of s u r f a c e waters; both s t o r a g e and re- use of waste materials may damage t h e q u a l i t y o f s u r f a c e waters t h e part RWS can p l a y towards i n n o v a t i o n ; i n her p o l i c y f o r awarding research and c o n s t r u c t i o n contracts, RWS can c o n t r o l and direct t e c h n o l o g i c a l renewal . For t h i s t o work we11 i t is n e c e s s a r y t h a t t h e needs of both RWS and t h e i n d u s t r y are c l e a r l y f o r m u l a t e d a t a n e a r l y s t a g e so tha t bo th p a r t i e s - c a n a d j u s t themse lves on time; i n close c o n n e c t i o n w i t h b, c and d , the ( c o - ) r e s p o n s i b i l i t y fo r s t i m u l a t i n g , i n close c o o p e r a t i o n wi th i n d u s t r y , research i n s t i t u t e s , e tc . , t h e c o m p i l a t i o n o f g e n e r a l q u a l i t y r e q u i r e m e n t s , s t a n d a r d s and r e g u l a t ions .

From t h e fo re- going it may be concluded t h a t , based on these f i v e approaches, t h e Dutch s t r a t e g y is aimed a t d e f i n i n g what Rijkswaterstaat can do w i t h i n i ts own s e r v i c e s t o i n c r e a s e t h e use o f a l t e r n a t i v e materials. Recommendations t o other p u b l i c a u t h o r i t i e s and i n d u s t r y etc. t o promote t h e use of a l t e r n a t i v e materials are g i v e n , when such i 3 desirable, under t h e ( p r i m a r y ) r e s p o n s i b i l i t y o f t h e M i n i s t e r of T r a n s p o r t and P u b l i c Works, i n n a t i o n a l p o l i c y s t a t e m e n t s r e g a r d i n g borrow p i t s .

.. . .- ". . ... . - . . - .. - .

The r e a l i s a t i o n o f the po l i cy mentioned above is the main task o f t h e Road and Hydraul ic Engineer ing Div i s ion o f Rijkswaterstaat. Many de ta i l ed s t u d i e s on t h e t e c h n o l o g i c a l , environmental and p r a c t i c a 1 a p p l i c a t i o n have been undertaken i n the pas t 15 yea r s . Most s t u d i e s were on the use of concre te- and masonry r u b b l e i n road c o n s t r u c t i o n s and water works, and as aggregate i n conc re t e ; t h e use o f minestone, s t ee l s l a g s and phosphor s l a g s i n t h e same areas; the use o f f l y- ash and c i n d e r s , t h e use of conso l ida t ed dredging s ludge ("Euroc layvt ) , r e c y c l i n g of a s p h a l t , t h e use o f i n c i n e r a t i o n s lags and the p o s s i b i l i t y o f re-use of gypsum waste ( e s p e c i a l l y phosphoric acid gypsum). Recent ly a n a t i o n a l p r o j e c t on a p p l i c a t i o n o f a l t e r n a t i v e materials has been s ta r ted a t the Dutch Cent re f o r C i v i l Engineer ing , Research, Codes and S p e c i f i c a t i o n s ( C . U . R . ) i n coopera t ion w i t h Rijkswaterstaat, research i n s t i t u t e s and i n d u s t r i a l o rgan iza t ions . The aim of t h i s p r o j e c t is t o formula te g e n e r a l l y v a l i d s p e c i f i c a t i o n s ( i nc lud ing environmental a s p e c t s ) f o r v a r i o u s c i v i l eng inee r ing a p p l i c a t i o n s .

3. TECHNOLOGICAL ASPECTS AND DESIGN REQUIREMENTS 3.1 . Genera1

I n d u s t r i a l waste materials have a long r e c o r d of a p p l i c a t i o n i n Dutch h y d r a u l i c eng inee r ing cons t ruc t ion . Practica1 exper ience w i th the p r o p e r t i e s o f these products and t h e i r compe t i t i ve price compared t o n a t u r a l materials s t i m u l a t e d these a p p l i c a t i o n s . Much used materials were g ranu la r materials such as minestone, s l a g s from metal product ion and phosphor product ion. I n r e c e n t years, the environmental aspects of these a p p l i c a t i o n s have been s t u d i e d . Also, t h e eng inee r ing p r o p e r t i e s o f these materials is r e c e i v i n g i n c r e a s i n g a t t e n t i o n , and their a p p l i c a b i l i t y is being increased by op t imiz ing these p r o p e r t i e s and improving the q u a l i t y c o n t r o l .

The experience- based i n t r o d u c t i o n of i n d u s t r i a l waste materials i n h y d r a u l i c eng inee r ing c o n s t r u c t i o n has t h u s g iven way t o concen t r a t ed research i n t 0 new a p p l i c a t i o n s . The inc reased awareness o f t h e need t o re- l o c a t e waste m a t e r i a l a i n a f'ashion n o t harmful t o t he environment, and the i i m i t e d a v a i l a b i l i t y o f n a t u r a l materials has s t i m u l a t e d t h i s research. The research is directed both a t o b t a i n i n g s u i t a b l e eng inee r ing p r o p e r t i e s and a t s o l v i n g the problems associated wi th t h e l each fng of harmful matter from e.g. phosphoric acid gypsum, f l y- ash , i n c i n e r a t i o n s l a g s and contaminated dredged material. Immobil izat ion o f harmful elements i n the waste material, and c r e a t i o n of u s e f u l eng inee r ing e lements may be ach ieved by baking, b ind ing by cement and i s o l a t i o n o f t h e wastes.

Th i s c o n t r i b u t i o n is l i m i t e d t o i n d u s t r i a l waste products , w i th which much exper ience has been acqu i r ed i n Dutch h y d r a u l i c engineer ing .

3.2. A l t e r n a t i v e materials i n d u s t r i a l waste materials re-used i n h y d r a u l i c eng inee r ing c o n s t r u c t i o n

are: minestone, v a r i o u s s l a g s such as LD-slags, phosphor s lags , copper slags and s i l icomanganese slags, si lex, VIuroclay" and demol i t ion rubb le . Minestone was genera ted i n l a r g e q u a n t i t i e s by t h e coal i n d u s t r y i n the Dutch province o f Limburg. After t h i s i n d u s t r y came t o an end, many o f the minestone dumps have been used Por l a n d f i l l i n g and rec lamat ion o f o l d g r a v e l , sand and c l a y borrow p i t s i n Limburg. Minestone used by the h y d r a u l i c c o n s t r u c t i o n i n d u s t r y , about 0.5 m i l l i o n ton8 annua l ly , has been imported e x c l u s i v e l y from the Ruhr area i n West Germany and the Zolder area i n Belgium, t h e t r a n s p o r t costs being r e l a t i v e l y low i n these cases.

P a r t of t h e s lags are produced i n t h e Nether lands. "Hoogovens IJmuiden B.V.?', gene ra t e s about 300,000 t o n s o f LD slags annua l ly ( L D is the a b b r e v i a t i o n o f t h e Linz-Donawitz s t ee l product ion p r o c e s s ) . However, most LD-slags used i n hyd rau l i c c o n s t r u c t i o n , about 0.2 m i l l i o n t o n s , are imported from Belgium and t h e Ruhr area. 0.5 m i l l i o n t o n s of phosphor s lags are genera ted annua l ly i n t h e product ion of phosphor by Hoechst near Flushings. Approximately hal f of t h i s is used i n h y d r a u l i c c o n s t r u c t i o n . Copper slags and s i l icomanganese slags are imported from West Germany and Belgium r e s p e c t i v e l y , i n amounts o f about 35,000 t o n s each. Apar t from the LD process f o r s teel product ion , o t h e r p roces se s used i n t h e Nether lands gene ra t e smal1 amounts o f s lags which are a l s o used i n h y d r a u l i c c o n s t r u c t i o n . In the p a s t a l i t t l e more than 1 m i l l i o n t o n s o f lead s lags have been used i n c o n s t r u c t i o n works. Due t o the unacceptab le l each ing of e s p e c i a l l y lead, bu t also copper and z i n c , these slags are n o t used any longer . S i l e x is a waste material which r e s u l t s from qua r ry ing marl f o r the product ion of cement. Marl is q u a r r i e d i n Belgium and t h e sou th of Limburg, i n annual amounts o f approximately 0.3 and 0.2 m i l l i o n ton3 respectively. "Euroclayff is produced from silt dredged i n t h e Rotterdam harbours . Its a p p l i c a t i o n has been rather l i m i t e d up t o now. Dredging t o main ta in t h e d e p t h o f access waterways and harbours produces some 25 m i l l i o n m 3 s ludge . O f t h i s , 1 4 m i l l i o n m 3 is on ly l i g h t l y p o l l u t e d , and through dewater ing and c o n s o l i d a t i o n can be rendered u s e f u l as c l a y f o r d i k e c o n s t r u c t i o n . Demolit ion r u b b l e has long been used i n h y d r a u l i c engineer ing . Due t o changed c o n s t r u c t i o n methods and t h e development of methods t o upgrade r u b b l e t o make it s u i t a b l e f o r road c o n s t r u c t i o n , use of r u b b l e i n h y d r a u l i c c o n s t r u c t i o n is now i n s i g n i f i c a n t .

3.3. Engineer ing p r o p e r t i e s The eng inee r ing p r o p e r t i e s of t hose i n d u s t r i a l waste materials used t o

date i n hyd rau l i ca1 c o n s t r u c t i o n are o f t e n n o t i n f e r i o r and sometimes even s u p e r i o r t o t h o s e o f t r a d i t i o n a l materials. Th i s is e s p e c i a l l y t r u e of the good f r i c t i o n a l p r o p e r t i e s of slags due t o the i r roughness and a n g u l a r i t y . A number o f s lags possess a h igh d e n s i t y making them very s u i t a b l e t o resist waterf low and wave a c t i o n . Some o f t h e less f avourab le p r o p e r t i e s are the weatherabil i ty and low c rush ing s t r e n g t h of some waste materials (8) . Minestone has a D,, ( a measure f o r t h e theoretica1 s i e v e r e t a i n i n g 50 5 of t h e material) up t o about 65 mm. Its d e n s i t y v a r i e s between 2.4 and 2.6 t / m 3 . Minestone is rather s e n s i t i v e t o c rush ing and weather ing. Under water and i n deep f i l ls it remains i n t a c t . A s long as i t is n o t remoulded, even s t r o n g l y weathered minestone r e t a i n s a pe rmeab i l i t y which is a t least e q u a l t o t h a t of s l i g h t l y s i l t y sand. S lag pieces are g e n e r a l l y rough, angu la r and more o r less cube-shaped. Gradings up t o D,, v a lues o f about 100 mm are feasible. The d e n s i t y of LD slags is between 3.1 and 3.4 t / m ' . The basic s t r e n g t h is high. However, i n d i v i d u a l pieces of s l a g s may c rush rather e a s i l y due t o t h e presence o f c leavage p l anes , l a y e r i n g and i n t e r n a l stresses. A smal1 p ropor t i on of t he slag pieces is u n s t a b l e due t o so -ca l l ed lime p i t t i n g , c o n c e n t r a t i o n s o f pure calcium. The i r o n p re sen t i n s l a g s can aho r t en the s e r v i c e l i f e of polypropene fabr ic , which is used i n h y d r a u l i c eng inee r ing as a f i l t e r fabric beneath a layer o f s t o n e s .

Copper s lags have a d e n s i t y o f 3.9 t / m 3 . I t may be s l i g h t l y u n s t a b l e when t h e minera l k i r s c h s t e i n i t e is p r e s e n t , which swells i n water and t h u s may r e s u l t i n d e s i n t e g r a t i o n . S i l e x , d e n s i t y 2.6 t / m 3 , is a s t r o n g material, Gradings having a D, , v a lue of s l i g h t l y more t h a n 100 mm can be ob t a ined . Contamination by weak and weatherable l imes tone can s t r o n g l y reduce i ts u s e f u l n e s s , vlEuroclayll is equa l i n q u a l i t y t o the t r a d i t i o n a l l y a p p l i e d r i v e r clays and marine clays. A proper product ion p roces s i n t h e so -ca l l ed I lc lay factory ' l is important however. A good q u a l i t y c o n t r o l both of the mechanical- p h y s i c a l p r o p e r t i e s and o f those p r o p e r t i e s important from an environmental viewpoint is neces sa ry t o s t i m u l a t e its use and t o remove u n j u s t i f i e d p re jud i ce . The r e a l i s a t i o n o f a good q u a l i t y c o n t r o l is p r e s e n t l y underway. This is expected t o r e s u l t i n the inc reased a p p l i c a t i o n o f ITEuroclayvT and o t h e r subs t ances i n d ike- s t rengthening p r o j e c t s , f o r which i n t h e coming years annua l ly a few m i l l i o n m 3 is needed. I n g e n e r a l , a good q u a l i t y c o n t r o l can cons ide rab ly i n c r e a s e t h e use o f materials produced from i n d u s t r i a l wastes. I t can e s p e c i a l l y e f f e c t i v e l y counter p r e j u d i c e which ha3 a r i s e n from a j u s t i f i e d a n x i e t y r e g a r d i n g environmental effects o f re- use o f such materials.

3.4 . Environmental a s p e c t s The environmental a s p e c t s o f t he use o f i n d u s t r i a l waste products i n

h y d r a u l i c c o n s t r u c t i o n depend n o t o n l y on the i r chemical composi t ion, but e s p e c i a l l y on their l each ing behaviour . The Researchgroup Development S tandard Leaching Tests I n c i n e r a t i o n Residue (SOSW) has developed tes ts t o s tudy t h i s behaviour . These tests concern, amongst o t h e r s , t h e de t e rmina t ion of t h e con ten t of anorganic micro contaminants , the de t e rmina t ion o f t h e maximum l e a c h a b i l i t y , shaking tes ts and s t a t i c tests. These tests a l l ow t o compare t h e l e a c h a b i l i t y o f d i f f e r e n t materials. To decide on the s u i t a b i l i t y o f a given material f o r use i n h y d r a u l i c c o n s t r u c t i o n , supplementary data are o f t e n r e q u i r e d , which fac i l i t a te the V r a n s l a t ion1' of l a b o r a t o r y r e s u l t s t o i n- s i t u c i rcumstances . The d i f f i c u l t i e s associated wi th apply ing l a b o r a t o r y r e s u l t s t o i n - s i t u c i rcumstances have t o date prevented t h e development of unequivocal s t a n d a r d s fo r j udg ing t h e r e s u l t s of l a b o r a t o r y tests. Models are neces sa ry f o r t h i s , bu t these must s t i l l be developed. These models must c o r r e c t l y account f o r t h e governing parameters such as t h e p a r t i c l e s i z e , the v e l o c i t y o f waterf low p a s t the p a r t i c l e s , t h e t o t a l mass o f t h e material i n r e l a t i o n t o the q u a n t i t y of the s u r f a c e water wi th which it is i n c o n t a c t , e tc . As such unequivocal s t a n d a r d s f o r the i n t e r p r e t a t i o n of l a b o r a t o r y tes ts are s t i l l l a c k i n g , some s u b j e c t i v e n e s s is unavoidable . I n t h e fo l lowing t h e environmental a s p e c t s o f a number of materials w i l l be t reated (51, (61 , (7 ) . Lead slags have been used i n l a r g e q u a n t i t i e s i n h y d r a u l i c c o n s t r u c t i o n i n t h e p a s t , Th i s has now been p r o h i b i t e d due t o an unacceptab ly h igh l e v e l of emission of heavy metals. Regarding p o l l u t i o n and the l e a c h a b i l i t y o f minestone, d i s t i n c t i o n must be made between r e c e n t l y produced minestone and minestone from dumpheaps, as t h e l a t t e r p o s s i b l y con ta in chemical r e f u s e . Moreover, i t is u n l i k e l y tha t PCB'S which are used i n h y d r a u l i c f l u i d s , w i l l appear i n r e c e n t l y produced minestone a s use o f o i l s con ta in ing PCBIS is p r o h i b i t e d s i n c e January lst , 1986. Minestone from dumpheaps y i e l d s on the average twice as much s u l p h a t e on l each ing as r e c e n t l y produced minestone. Su lpha t e con ten t v a r i e s s t r o n g l y ; i n dumpheaps the average is approximately 2000 mg/kg dry matter.

Notwithstanding the above-mentioned d i f f e r e n c e s between r e c e n t l y produced minestone and minestone from dumpheaps, some r e s t r i c t i o n s i n t h e use of t h e former w i l 1 sometimes be necessary . Leachable PAK con ten t i n minestone averages 0.7 mg/kg d r y matter. Also minestone may c o n t a i n leachable a r s e n i c and s t ron t ium. Heavy metals pose no problems i n minestone. App l i ca t i on o f minestone i n s t a g n a n t f r e s h water may r e s u l t i n exceedance of t h e TMP basic q u a l i t y norm f o r s u l p h a t e , and p l ans Por any such a p p l i c a t i o n must be c a r e f u l l y reviewed. I n less s e n s i t i v e waters ( s a l t water o r running water) emiss ion of s u l p h a t e from minestone poses no threat t o water q u a l i t y . The fore- going a l s o a p p l i e s , though less so , t o t h e o t h e r parameters . If PCB'S rnight occur however, use o f such minestone is n o t advised . LD s lags and s i l icomanganese s lags c o n t a i n small amounts o f heavy metals such a s z i n c , copper , chrome and lead. Emission of these metals i n sa l t and fresh water is q u i t e i n s i f n i f i c a n t . On t h e grounds o f l e ach ing tests which y i e l d e d t h i s r e s u l t , and on environmental grounds, no r e s t r i c t i o n s are imposed on t h e use o f these s l a g s i n h y d r a u l i c c o n s t r u c t i o n as y e t , The on ly p o s s i b l e effect phosphor slags could have on t h e environment is through t h e emission of f l u o r i d e . These have a h igh i n i t i a 1 l e v e l of emission and t h u s use of fresh phosphor s l a g s i n a lmos t s t a g n a n t water and i n water catchment areas is u s u a l l y i nadv i sab l e . Th i s a p p l i e s p a r t i c u l a r l y f o r large q u a n t i t i e s of phosphor s l a g s i n s t a g n a n t and r e l a t i v e l y small waters. Copper s l a g s from two l o c a t i o n s have been tested f o r composition and l each ing p r o p e r t i e s . One of these conta ined o n l y small amounts of heavy metals and y e t was found t o leach rather e a s i l y , y i e l d i n g copper , lead and z inc . The o t h e r sample, from t h e Ruhr area had a h igh copper con ten t and y e t i ts leachabi l i ty was no t worse t han t h a t o f LD slags. Fu r the r research is neces sa ry t o confirm whether coppe r s l ags from t h e Ruhr are as acceptable as LD slags. S i l e x c o n s i s t s o f f l i n t s t o n e , p i t g r a v e l and l imestone. There are no environmental r e s t r i c t i o n s a g a i n s t its use i n h y d r a u l i c eng inee r ing , fTEuroclayfv is weak ly contaminated by a range o f m a t e r i a l a which might endanger t h e environment. Fu r the r research must be performed i n t o the environmental e f fec ts o f fTEuroclaytv i n d i k e s . For the time be ing its use is permitted by the a u t h o r i t i e s , as long as i t is covered by a t o p l a y e r of uncontaminated clay.

4 . APPLICATIONS 4 .1 . General a p p l i c a t i o n s

The use of a l t e r n a t i v e materials such as minestone, s l a g s , s i l e x etc. i n Dutch c i v i l eng inee r ing is very common and goes back f o r q u i t e some time. I n t h e scope o f r e c o n s t r u c t i o n work which fol lowed t h e f l ood disaster of 1953, c i v i l e n g i n e e r s began t o r e ly more h e a v i l y on these materials as a c o n s t r u c t i o n material, an the i r use i n h y d r a u l i c eng inee r ing has inc reased e v e r s i n c e . The main r ea sons f o r t h e growing p re fe rence f o r a l t e r n a t i v e materials i n t h e Nether lands are: a. sho r t age o f n a t u r a 1 rocky materials; b , greater r e s i s t a n c e t o c u r r e n t and wave attack as compared t o sand and

roughly equa l t o g r a v e l and l i g h t s o r t i n g s of r o c k f i l l ; c. a v a i l a b i l i t y i n r e l a t i v e l y l a r g e q u a n t i t i e s ; d. r e l a t i v e l y low cost; e. growing problem o f s t o r a g e of these materials.

Dutch

A l t e r n a t i v e materials are used i n h y d r a u l i c eng inee r ing i n s e v e r a l ways (see Fig. 1 ) . They are o f t e n used as re ta in ing- bunds of sand-closure dams (and subsequent ly as part of a p r o t e c t i v e dam s l o p e c o n s t r u c t i o n ) because t h e slopes of these materials both below and above water l e v e l can be b u i l t rnuch steeper than sand s l o p e s , t h u s reduc ing sand l o s s e s du r ing c l o s u r e . Another a p p l i c a t i o n has been a3 c o r e materials i n c l o s u r e dams, breakwaters and g r o i n s . Because o f their scour r e s i s t a n c e a l t e r n a t i v e materials are a l s o used f o r bottom p r o t e c t i o n and f i l l i n g scour h o l e s underneath s t r u c t u r e s and a l o n g r i v e r banks. After f i l l i n g up t h e h o l e s these materials, i f neces sa ry , can be covered by s tone- mat t r e s se s , blockmats o r o t h e r p r o t e c t i v e systems. These a l t e r n a t i v e materials have been app l i ed on a l a r g e scale i n t h e Nether lands as a foundat ion l a y e r f o r roads and under SlOpe p r o t e c t i o n ( d i k e s and r i v e r b a n k s ) , i n t h i s l a t t e r case very o f t e n s u c c e s s f u l l y r e p l a c i n g the expensive and d i f f i c u l t t o rea l i se ( e s p e c i a l l y under water) t r a d i t i o n a l g r anu la r f i l t e r s . Due t o t h i s wide a p p l i c a b i l i t y of a l t e r n a t i v e materials there has been an i n c r e a s i n g need i n r e c e n t y e a r s f o r r e l i ab le informat ion on t h e s t a b i l i t y c r i t e r ia o f these materials exposed t o wave and c u r r e n t a c t i o n . S t r u c t u r a l de s ign places demands on t h e mechanica1 s t a b i l i t y of waste materials. Also, s p e c i f i c demands can be formulated w i th r e s p e c t t o t h e purpose of t h e s t r u c t u r e ; e.g. t h e p r o t e c t i o n o f t h e under lay ing soil a g a i n s t e r o s i o n leads t o requi rements on the character is t ic diameter and d e n s i t y of the material. Other requi rements concern the i n t r i n s i c p r o p e r t i e s o f t h e material, e.g. pe rmeab i l i t y and i n t e r n a l f r i c t i o n . These specif ic demands o r i g i n a t e d by the type and load o f t h e s t r u c t u r e must be compared w i th the p r o p e r t i e s o f the a v a i l a b l e material. I n case of disagreement there are two a l t e r n a t i v e s : a. mod i f i ca t i on o f a given material or s e l e c t i o n o f ano the r waste material; b. mod i f i ca t i on of des ign by u s ing s t a n d a r d , though u s u a l l y more c o s t l y

materials.

I n cons ide r ing the use o f these materials one i n e v i t a b l y comes up a g a i n s t t h e problems o f the expected f l o u ( c u r r e n t ) and wave c o n d i t i o n s and of the s u i t a b i l i t y of t h e v a r i o u s materials under those cond i t i ons . I n o r d e r t o s o l v e these problems v a r i o u s l a b o r a t o r y and i n s i t u (p ro to type ) tests have been carried o u t i n r e c e n t years . Some o f the r e s u l t s of t h i s research w i l 1 be d i s cus sed below. The h y d r a u l i c r e s i s t a n c e o f l o o s e materials can be related t o t h e magnitude o f t h e c r i t i c a l shea r ing stress ( T ~ ~ ) which the c u r r e n t ( c r i t i c a l v e l o c i t y u ) e x e r t s on the bottom. cr

The r e s u l t s o f t h e tes ts i n d i c a t e that minestone has similar va lues o f T as g r a v e l . However, minestone has a l i m i t e d mean s i z e ( i . e . D,, = 0.065 $7 and tha t means, t h a t t h e a p p l i c a t i o n is l imi ted t o i n f r equen t v e l o c i t i e s up t o 2 m / s b u t u s u a l l y n o t more than 1.5 m/s, and waves u s u a l l y n o t h ighe r t h a n 0.5 m. Contrary t o minestone, s l a g s have r e l a t i v e l y h i g h e r h y d r a u l i c s t a b i l i t y t h a n g r a v e l o r even crushed s tone . This is due t o two f a c t o r s : a h ighe r d e n s i t y (depends on type o f s l a g s ) and a h ighe r i n t e r n a l f r i c t i o n - f a c t o r ( i r r e g u l a r angu la r g r a i n s ) . The i n f l u e n c e of d e n s i t y is a l r e a d y t aken i n t o account i n clCr

I n genera1 T (slags) = 1.55 T~~ ( g r a v e l ) o r ucr (s lags) = 1.25 ucr cr ( g r a v e l ) .

and can be c a l c u l a t e d d i r e c t l y .

GRANULAR FILTERS

F o r e s h o r e p r o t e c t i o n

3 0 0 - C l o s u r e d a m

B o n k p r o t e

D i k e p r o t e c t i o n .

F i g . 1 Examples of a p p l i c a t i o n of a l t e r n a t i v e ma te r i a l s i n h y d r a u l i c e n g i n e e r i n g .

FILTER RULES

A GEOTEXTILES THIN TYPES

WOVEN NON- W OVEN

MULTILAYER TYPES FILTER- ANO THICKNESS FUNCTION

COMPOSED FILTERS A - GRANULAR LAYER

FUNCTION GEOTEXTILE

THICKNESS-OAMPING-

FILTER FUNCTION

F i g . 2 F i l t e r s .

1.0

O8

P - :a6 P b 2 0 4

t! C

‘O 1 C a W O

.-

L

- 1 - u, E c u -

0.1 10 50 100

Dtflt.i obos.

F i g . 3 C r i t i c a l g r a d i e n t i n f i l t e r layers.

- - _ _ Minestonc

F i g . 4 C r i t i c a l s o i l g r a d i n g r a n g e s f o r i n t e r n a l s t a b i l i t y .

The l a b o r a t o r y tes ts have been confirmed by i n - s i t u measurements. A s an i n d i c a t i o n , phosphor-slags and LD(s tee1) -s lags w i th D S 0 = 0.07 m have been s u c c e s s f u l l y a p p l i e d i n the Nether lands f o r v e l o c i t i e s up t o 2.5-3 m/s and in f r equen t wave a t tack up t o 1 . 0 m wave-height (some p r o f i l e deformation was al lowed) . The r e s i s t a n c e t o c u r r e n t of a heavy c l ay v a r i e s from 1 t o 1 .5 m/s depending on compaction. However, c l ay covered by a grass-rnat can resist v e l o c i t i e s up t o 3 m/s. The r e c e n t r e s u l t s on the r e s i s t a n c e o f c l a y and grass-mats under c u r r e n t and wave a t tack are summarized i n ( 9 ) . More detai led informat ion on the s u b j e c t s d i s cus sed above can be found i n ( 2 ) and ( 3 ) , and i n v a r i o u s i n t e r n a l r e p o r t s of Rijkswaterstaat.

4.2. A l t e r n a t i v e materials i n f i l t e r p r a c t i c e 4 .2 .1 . What is a f i l t e r ? Granular f i l t e r s are the most common element i n

t h e des ign of h y d r a u l i c s t r u c t u r e s . However, t h e y are u s u a l l y expensive and d i f f i c u l t t o p l ace ( p a r t i c u l a r l y under water) w i th in t h e requirement limits. An a l t e r n a t i v e s o l u t i o n c o n s i s t s of a combination o f a g e o t e x t i l e (which p rov ides the f i l t e r f u n c t i o n ) and a l a y e r of a c e r t a i n t h i c k n e s s of graded s t o n e , which a t t e n u a t e s the i n t e r n a l h y d r a u l i c l oads , see f i g u r e 2. A cheaper but e q u a l l y good s o l u t i o n is t o place a t h i c k layer of broadly graded waste products such as minestone, s lags, s i l e x , e tc . For large h y d r a u l i c l oads , t h i c k n e s s e s i n the o r d e r of 0.5 m are r e q u i r e d , p rope r ly compacted and composed accord ing t o i n t e r n a l s t a b i l i t y c r i t e r i a ( 4 ) . An e x t e n s i v e review o f t h i s s u b j e c t can be found i n ( 1 ) and ( 4 ) . I n t h e des ign o f f i l t e r s , s e v e r a l f a c t o r s are involved. Apart from t h e macroscopic s t a b i l i t y (does the material remain i n p l a c e even under extreme flow c o n d i t i o n s ? ) a l s o the microscopic s t a b i l i t y (does the material i t se l f no t change?) must be ensured. Both problems are ana lysed by p a r t s . F i l t e r - t h e o r y provides a method t o ana lyse macroscopic s t a b i l i t y .

4.2.2. F i l t e r- t h e o r y . A h y d r a u l i c f i l t e r is composed of one o r more l a y e r s o f d i f f e r e n t p a r t i c l e s i z e s . The l a y e r o f f i n e s t material (base) u s u a l l y has t o be p ro t ec t ed a g a i n s t e ros ion . The f i l t e r provides t h i s p r o t e c t i o n . There are two methods, based on d i f f e r e n t p r i n c i p l e s : Geometric: By a s u i t a b l e choice of t h e character is t ic diameter of t h e f i l termaterial , displacement o f t h e f i n e material is prevented. The f i l t e r ac ts as a s i e v e which r e t a i n s the base material, bu t l e t s t h e water pass. This process is governed by t h e r e l a t i v e par t ic le s i z e s i n t h e coa r se layer and the base material. Such f i l t e r s are u s u a l l y stable. H y d r a u l i c : By an adequate choice o f t h e p a r t i c l e s i z e o f the f i l t e r material, t h e water v e l o c i t y between t h e p a r t i c l e s is r egu la t ed . The water e x e r t s a d rag fo rce on the base p a r t i c l e s . Loss of base material is prevented by keeping t h e d rag fo rce below a c r i t i ca l va lue . The f i n e r t h e f i l t e r is, the lower the water v e l o c i t y and t h e d rag fo rce w i l 1 be. The obvious choice o f very f i n e f i l t e r material however, r e s u l t s i n e r o s i o n o f t h e filtermaterial i t se l f . The choice o f f i l t e r t ype depends on the magnitude o f h y d r a u l i c l oad ing , which is o f t e n expressed i n a g r a d i e n t (103s of p r e s s u r e ove r a c e r t a i n d i s t a n c e ) . The c a p a c i t y of a f i l t e r is expressed by i ts c r i t i c a l g r a d i e n t , which is t h e l a r g e s t g r a d i e n t i n t h e f i l t e r a t which base material is no t t r a n s p o r t e d . Large h y d r a u l i c l oads o f t e n r e q u i r e geome t r i ca l l y s table f i l te rs , bu t f o r smaller loads , h y d r a u l i c f i l t e r s are more economical. Cri ter ia have been developed t o s i m p l i f y the des ign of g r anu la r f i l t e rs .

These relate p a r t i c l e s i z e and h y d r a u l i c load t o t h e c r i t i c a l g r a d i e n t . The e a r l i e s t geometr ic f i l t e r c r i t e r i a date from 1922. S ince t hen , o t h e r c r i t e r i a have c o n s t a n t l y been devised f o r a whole range o f s p e c i a l cases. I n t h e e a r l y 1970's a n overview was publ i shed of e x i s t i n g f i l t e r c r i t e r i a and their v a l i d i t y . I n many c r i t e r i a , t h e i n f l u e n c e o f c e r t a i n material parameters is n o t accounted f o r . T h i s and o t h e r overviews of c r i t e r i a may be used t o develop a des ign method ( 4 ) . Much pract ica1 research on f i l t e r p roces se s has been done i n the Nether lands f o r t h e s torm surge barrier i n the E a s t e r n Scheldt . The r e s u l t s of t h i s research have been publ i shed i n condensed form ( 5 ) . Figure 3 i l l u s t r a t e s t he dependence of t h e c r i t i c a l g r a d i e n t on t h e r a t i o o f t h e c h a r a c t e r i s t i c diameters of f i l t e r and base material. I t may be seen that t h e c r i t i c a l g r a d i e n t is markedly smaller i n t h e l a te ra l d i r e c t i o n than i n the perpendicu la r d i r e c t i o n .

4.2.3. I n t e r n a l s t a b i l i t y . Another compl ica t ion arises i n well-graded f i l t e r s wi th a wide range o f par t ic le s izes . This is the case wi th many waste materials such as minestone and v a r i o u s slags. The f i l t e r then cannot r e t a i n i ts own f i n e s when s u b j e c t e d t o h y d r a u l i c load ing . Such a f i l t e r is termed Y n t e r n a l l y uns t ab l e ' . S p e c i a l c r i t e r i a have been developed t o p red ic t i n t e r n a l i n s t a b i l i t y , see f i g u r e 4. Genera l ly speaking , materials w i th a l a r g e p ropor t i on of f i n e s are p o t e n t i a l l y u n s t a b l e i n t e r n a l l y . Unsorted minestone i n p a r t i c u l a r is prone t o large p ropor t i ons of f i n e s , and should then n o t be used. However, r e j e c t i o n o f minestone i n the p a s t probably was no t necessary i n a l 1 cases on h y d r a u l i c grounds. Fu r the r research i n t 0 the h y d r a u l i c c o n d i t i o n s caus ing i n t e r n a l i n s t a b i l i t y may i n c r e a s e t h e a p p l i c a b i l i t y o f waste materials. For t h i s i t is necessary t o c l o s e l y c o n t r o l the product ion p roces s which y i e l d s t h e waste materials.

4.2.4, Material s t a b i l i t y . The expe r i ence acqu i r ed wi th minestone and s t e e l s l a g s i n road c o n s t r u c t i o n and the i r a v a i l a b i l i t y have l e d t o t he i r use i n h y d r a u l i c eng inee r ing as well. Their use i 3 n o t wi thout danger , however. To ensu re t h e long term s a f e t y o f t h e s t r u c t u r e , t h e material must n o t weather or waste. This is p a r t i c u l a r l y impor tan t f o r waste materials such as slags, minestone and s i l e x . These are u s u a l l y s o f t e r t han e.g. g r ave l . Minestone f o r i n s t a n c e is a kind of c l a y s t o n e and slakes when s u b j e c t e d t o a l t e r n a t e c y c l e s o f we t t i ng and dry ing . Should t h i s occur i n a f i l t e r , the material would e v e n t u a l l y become f i n e r , the grad ing would broaden and t h e i n t e r n a l macroscopic s t a b i l i t y w i th r e s p e c t t o the o t h e r layers would be l o s t . Thus material i n s t a b i l i t y would t r i g g e r , through i n t e r n a l i n s t a b i l i t y , a macroscopic i n s t a b i l i t y . S i l e x , a waste product from marl mining, can also e x h i b i t such behaviour. Caution is a l s o neces sa ry wi th s l a g s . It is neces sa ry t o know from which process t h e y o r i g i n a t e d and how t h e y were cooled. Phosphor s l a g s e.g. can be ex t remely b r i t t l e when cooled t o o qu i ck ly , t h u s c rush ing e a s i l y d w i n g t r a n s p o r t and p l ac ing , I n the presence of water (abundant ly p r e s e n t i n h y d r a u l i c s t r u c t u r e s ) s tee l s l a g s may induce cementat ion ( h y d r a u l i c i t y ) . The f i n e s f r a c t i o n , u s i n g water as c a t a l y s t , cements t h e l a r g e r p a r t i c l e s . While t h u s prevent ing washing o f the f i n e s , t h e pe rmeab i l i t y s t r o n g l y decreases and t h e f i l t e r no longer f u n c t i o n s proper ly .

4.2.5. Conclusion. Waste m a t e r i a l a may c e r t a i n l y be u s e f u l i n h y d r a u l i c eng inee r ing c o n s t r u c t i o n , i f on ly t h e i r s p e c i f i c weaknesses are recognized and e f f e c t i v e l y deal t wi th , Some a d d i t i o n a l research is needed t o f i l l i n gaps i n e x i s t i n g knowledge. Rijkswaterstaat p l ans t o i n s t i g a t e t h i s research i n coopera t ion with producers of waste materials, I n f i l t e r des ign , o t h e r t h a n the c r i t e r i a Por t r a d i t i o n a l s table materials must be adopted. N e w r e g u l a t i o n s must t h e r e f o r e be developed. It is expected t h a t ,

given s u f f i c i e n t funding, mater ia l- dependent c r i t e r i a can be developed wi th in a few years, so t h a t a p p l i c a t i o n s of waste materials i n h y d r a u l i c eng inee r ing can be extended f u r t h e r .

4.3. Q u a l i t y c o n t r o l Q u a l i t y c o n t r o l o f materials used i n h y d r a u l i c c o n s t r u c t i o n was g e n e r a l l y

speaking poor ly developed up t o t h e r e c e n t p a s t . The r e c e n t c o n s t r u c t i o n of a number of large h y d r a u l i c s t r u c t u r e s has changed t h i s s i t u a t i o n . Most waste products i n use i n h y d r a u l i c c o n s t r u c t i o n are now covered by c o n t r a c t requi rements r ega rd ing mechanical-physical p r o p e r t i e s and t h e s u p e r v i s i o n of these (21, ( 8 ) . With waste products one wishes t o c o n t r o l no t on ly t h e mechanical- physical p r o p e r t i e s , but a l s o t hose which might a f f ec t t h e environment. This is however hampered by the ea r l i e r mentioned lack o f unequivocal s t a n d a r d s fo r i n t e r p r e t i n g t h e r e s u l t s of l e a c h i n g tests. P re sen t research is p a r t i c u l a r l y aimed a t developing such s t anda rds . I t is expected t h i s w i l l soon r e s u l t i n requirement s t a n d a r d s and d e s c r i p t i o n s of methods of t e s t f o r use i n c o n t r a c t s . The ideal is t o ach ieve q u a l i t y c o n t r o l through t h e d e l i v e r y of materials under cer t i f ica te . I n such a s i t u a t i o n the producer p r i m a r i l y performs the q u a l i t y c o n t r o l . I t is expected such d e l i v e r y under ce r t i f i ca te w i l l g rea t ly i n c r e a s e the e x t e n t of q u a l i t y c o n t r o l o f a l t e r n a t i v e materials i n t h e Nether lands.

5. CONCLUSIONS Dutch exper ience shows, and t h i s is suppor ted by r e s u l t s of r e c e n t

s t u d i e s , t h a t many a l t e r n a t i v e (waste) materials are appl icable i n most c i rcumstances of the h y d r a u l i c eng inee r ing works. Because of t he environmental consequences lead slags should be excluded from t h e common a p p l i c a t i o n s e s p e c i a l l y i n t h e cases o f direct c o n t a c t w i th fresh water. I n g e n e r a l , a p p l i c a t i o n o f lead Slag3 should always be suppor ted by de t a i l ed environmental s t u d i e s . Because of a d d i t i o n a l p r o p e r t i e s some types o f waste materials produce specif ic d i f f i c u l t i e s , which cannot be judged i n their f u l l e x t e n t y e t ( i . e . d i s i n t e g r a t i o n of minestone a t water-air i n t e r f a c e o r conglomerat ion of s lags) . Add i t i ona l research ha3 t o be carried ou t t o q u a n t i f y these d i f f i c u l t i e s , t o determine t h e des ign c r i t e r i a f o r d i f f e r e n t a p p l i c a t i o n s and t o s p e c i f y the q u a l i t y c o n t r o l i n o r d e r t o make t h e waste materials move g e n e r a l l y a p p l i c a b l e i n c i v i l eng inee r ing . The research on these aspects is s t i l l going on i n t h e Nether lands. The f i n a l r e s u l t s , i nc lud ing those waste products no t y e t researched ( i .e . f l y - ash and phosphoric acid gypsum) can be expec ted w i t h i n a few years.

REFERENCES

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Graauw, A. d e , Meulen, T. van der, Does-de Bye M. van der: Design c r i t e r ia f o r g r anu la r f i l t e r s . Delft Hydraul ics p u b l i c a t i o n 287, January 1983 . Laan, G . J . , Westen, J . M . van, B a t t e r i n k , L . : Minestone i n H y d r a u l i c Engineer ing Appl ica t ion , D e t e r i o r a t i o n and Q u a l i t y Cont ro l . Symposium on t h e Reclamation, Treatment and U t i l i s a t i o n o f Coal Mining Wastes, Durham, England, September 1984. Guide t o Concrete Dyke Revetments (1984) . Centre f o r C i v i l Engineer ing Research, Codes and S p e c i f i c a t i o n s ( C U R ) and Technica1 Advisory Committee on Waterdefences, October 1984, The Nether l ands . Adel, H. den: Waste products as f i l t e r material. Delft Geotechnics r e p o r t no. C0-272550/27, September 1985 ( i n Dutch) TAW I n f r a Consul t B.V. : Composition and l e a c h a b i l i t y o f minestone. January 1986 ( i n Dutch). Luin, A.B. van, Gaastra, D.J.: The l e a c h a b i l i t y of metals and s u l p h a t e from basalt and s l a g s . D B W / R I Z A - n o t e no. 86.01 5, Apr i l 1986 ( i n Dutch) . S l o o t H.A. van der, : Environmental eng inee r ing research of phosphor slags. ECN, September 1986 ( i n Dutch). Laan, G . J . , : Q u a l i t y and q u a l i t y c o n t r o l of slags i n h y d r a u l i c engineer ing . Rijkswaterstaat DWW, September 1986 ( i n Dutch). P i l a r c z y k , K.W.: Dutch Guide l ines on D i k e P r o t e c t i o n , 2nd I n t e r n . Conf. on Coas t a l and Po r t Engineer ing i n Developing Coun t r i e s , B e i j i n g , China, 1987. Rijkswaterstaat: P o s s i b i l i t i e s of a p p l i c a t i o n o f a l t e r n a t i v e materials. Rijkswaterstaat-serie, Report no. 4 4 , 1984 ( i n Dutch).