The Parking garage problem

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The Parking garage problem

Litvan, G. G.

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The Parking

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Reprinted from

Proceedings Fourth Canadian Building Congress

Learning from Experience/Avoiding Failures

Ottawa, Ontario. 6

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8 October 1985

Session 7, p. 214

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218 (IRC Paper No. 1465)

Price $3.00

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THE PARKING GARAGE PROBLEM

G.G. Litvan, Division of Building Research, National Research Council Canada, Ottawa

Although estimates are not accurate, it is clear that over $3 billion will have to be spent to restore deteriorated parking garages. By examining the mechanism of corrosion of the reinforcing steel

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the chief cause of deterioration

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practical means to avoid or at least retard the galvanic reaction can be identified. The use of salt as deicer has benefits but at a very considerable cost. A description of what has and is being done in an organizational way to aid users and the industry will be given. Beyond the technical aspects the question arises why the parking garage problem was not avoided and what built-in safeguards are in place which will identify the emergence of a potentially costly problem at an early stage.

Malgre l'absence d'estimations pr€cises, il est clair que plus de 3 milliards de dollars devront Stre depenses pour reparer les garages de stationnement. En etudiant le mecanisme de la corrosion de l'acier d'armature (cause principale de la deterioration des garages), des moyens pratiques pour gviter ou du moins pour retarder l'action galvanique peuvent ltre determines. L'utilisation des sels de degivrage comporte certains avantages mais l un coat tr8s eleve. Cette communication traitera des mesures prises par certains organismes pour venir en aide a w utilisateurs et B llindustrie. Au-dell des problemes techniques, on tentera d'expliquer pourquoi la deterioration des garages de stationnement n'a pu ltre Bvitee, et on indiquera les moyens de protection qui existent l llheure actuelle et qui permettent de deceler les premiers signes de desordres qui pourraient s'avgrer coateux.

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THE PARKING GARAGE PROBLEM

G.G. U t v a n

D i v i s i o n of Building Research, National Research Council of Canada

INTRODUCTION Once c o r r o s i o n b e g i n s , t h e i n c r e a s e d volume of t h e r u s t and o t h e r e f f e c t s w i l l cause t h e c o n c r e t e The d e t e r i o r a t i o n of p a r k i n g g a r a g e s , p a r t i c u l a r l y envelope t o c r a c k and t o spa11 and i n t h e

t h o s e underground, became widespread i n t h e so--created p o t h o l e t h e s t e e l i s exposed t o m o i s t u r e mid-1970's. The i n c i d e n c e s were not due t o unique and oxygen. As c o r r o s i o n proceeds t h e bond between circumstances but r a t h e r were m a n i f e s t a t i o n s of a t h e s t e e l and c o n c r e t e f a i l s p r o g r e s s i v e l y , l e a d i n g problem t h a t would sooner o r l a t e r a f f e c t almost p o t e n t i a l l y t o s t r u c t u r a l impairment.

every such garage i n e x i s t e n c e .

Considerable p r o g r e s s h a s been made i n t h e p a s t e i g h t o r t e n y e a r s t o f o r m u l a t e d e s i g n and

c o n s t r u c t i o n p r a c t i c e s f o r newly b u i l t g a r a g e s and t o d e v i s e means t o d e a l w i t h t h o s e t h a t have d e t e r i o r a t e d . Although some important q u e s t i o n s a r e s t i l l unresolved, a survey of t h e p r e s e n t s i t u a t i o n and a review of t h e h i s t o r y of e v e n t s i s u s e f u l a t t h i s time.

It i s w e l l worth examining how t h e p a r k i n g garage problem developed i n s e a r c h i n g f o r an answer t o t h e important q u e s t i o n : Why d i d t h e s a f e g u a r d s t o p r e v e n t adoption of i n a d e q u a t e p r a c t i c e s f a i l ? The l e s s o n l e a r n e d from t h i s e x e r c i s e i s of more t h a n academic i n t e r e s t ; i f problems a r o s e once, s i m i l a r expensive o r dangerous ones may develop a g a i a .

DEFENSIVE STRATEGIES

Although c h l o r i d e i o n s a r e t h e p r e r e q u i s i t e t o c o r r o s i o n of r e i n f o r c i n g s t e e l , t o ban c h l o r i d e - based d e i c e r s i s beyond t h e powers of b u i l d i n g r e g u l a t o r y a u t h o r i t i e s . The chances of persuading p r o v i n c i a l and municipal governments t o p r o h i b i t t h e u s e of c h l o r i d e d e i c e r s a r e s l i m , a s no

s u i t a b l e a l t e r n a t e e x i s t s . They a r e l i k e l y h e r e t o s t a y , a t l e a s t f o r t h e time being, and i f damage i s t o be avoided t h e b u i l t environment h a s t o be p r o t e c t e d a g a i n s t t h e i r harmful e f f e c t s .

CORROSION PROCESS

Corrosion i s an e l e c t r o c h e m i c a l process t h a t can TECHNICAL BACKGROUND b e s t be d e s c r i b e d by c o n s i d e r i n g a simple model of

a g a l v a n i c c e l l a s shown i n Figure 1. I n t h i s Cracking, break-up and s p a l l i n g of suspended example t h e c e l l c o n s i s t s of i r o n (Fe) and copper c o n c r e t e s l a b s l e a d i n g t o l e a k i n g c e i l i n g s i n (Cu) e l e c t r o d e s p a r t l y immersed i n an aqueous indoor garages a r e caused, w i t h very few s o l u t i o n of some s a l t .

e x c e p t i o n s , by c o r r o s i o n of t h e embedded s t e e l . Mature, f u l l y cured p o r t l a n d cement c o n c r e t e c o n t a i n s l a r g e q u a n t i t i e s of lime t h a t r e n d e r s i t

s t r o n g l y a l k a l i n e (pH between 12 and 131, an environment i n which steel a c q u i r e s p a s s i v i t y , i.e., i t does n o t corrode. I f t h e c o n c r e t e i s d e p l e t e d of l i m e , t h e s t e e l becomes d e p a s s i v a t e d and c o r r o s i o n can t a k e place. But even i f h i g h a l k a l i n i t y is maintained, i n t h e presence of c h l o r i d e i o n s t h e p r o t e c t i v e p a s s i v e l a y e r on t h e

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s u r f a c e of t h e s t e e l does become d e s t r o y e d , and should m o i s t u r e and oxygen become a v a i l a b l e ,

L c o r r o s i o n w i l l occur. The chemicals co~mnonly used

a s d e i c i n g a g e n t s a r e c h l o r i d e s a l t s of sodium and calcium which, mixed w i t h snow, a r e c a r r i e d by v e h i c l e s i n t o t h e garage. Thawing produces a b r i n e t h a t w i l l p e n e t r a t e u n p r o t e c t e d c o n c r e t e , r a i s i n g t h e c h l o r i d e c o n c e n t r a t i o n around t h e s t e e l t o h i g h l e v e l s . i \ IRON

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F I G U R E 1 S C H E M A T I C D I A G R A M OF G A L V A N I C C E L L

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M e t a l l i c i r o n i n t h e presence of m o i s t u r e and oxygen t e n d s t o r e v e r t t o i r o n o x i d e , i t s s t a b l e s t a t e . I n t h e f i r s t s t e p of t h i s p r o c e s s , t h e m e t a l l i c i r o n goes i n t o s o l u t i o n ( a n o d i c r e a c t i o n ) i n t h e form of p o s i t i v e l y charged f e r r o u s i o n (Feu). The two e l e c t r o n s c a r r y i n g t h e n e g a t i v e c h a r g e s a r e s e p a r a t e d and remain i n t h e metal:

Accumulation of t h e n e g a t i v e c h a r g e s i n t h e m e t a l p r e v e n t s f u r t h e r d i s s o l u t i o n of t h e i r o n a s f e r r o u s i o n s . I n t h e p r e s e n c e of a second e l e c t r o d e s u c h a s copper, a g a l v a n i c c e l l i s formed i n which e l e c t r o n s a r e consumed by t h e f o l l o w i n g r e a c t i o n :

This r e a c t i o n c o n v e r t s oxygen and w a t e r i n t o hydroxyl i o n s , which i n t u r n r e a c t w i t h t h e f e r r o u s i o n s and form a f e r r o u s hydroxide p r e c i p i t a t e ; i n t h e presence of oxygen t h i s i s converted t o f e r r i c hydroxide, t h e f a m i l i a r r e d d i s h brown r u s t .

The presence of copper i s n o t n e c e s s a r y f o r t h e c o r r o s i o n process. I n c o n c r e t e decks g a l v a n i c c e l l s form u s u a l l y between two a r e a s with d i f f e r e n t e l e c t r o c h e m i c a l p r o p e r t i e s of t h e r e i n f o r c i n g s t e e l ( F i g u r e 2). These d i f f e r e n c e s m y be due t o composition, p h y s i c a l (e.g., d i f f e r e n t l e v e l s of stress a s a r e s u l t of s h a p i n g ) o r environmental (e.g., d i f f e r e n t c o n c e n t r a t i o n s of c h l o r i d e s , o t h e r s a l t s o r oxygen) f a c t o r s . A N O D I C L C A T H O D I C AREA AREA F I G U R E 2 S C H E M A T I C D I A G R A M O F G A L V A N I C C E L L F O R M A T I O N I N A R E I N F O R C E D C O N C R E T E D E C K PREVENTIVE METHODS To i n t e r c e p t t h e f u n c t i o n i n g of t h e g a l v a n i c c e l l , t h u s t h e c o r r o s i o n p r o c e s s , a t l e a s t one of t h e f o l l o w i n g e s s e n t i a l elements h a s t o be made u n a v a i l a b l e i n t h e c o n c r e t e s l a b :

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t h e anode and cathode ( o r a n o d i c and c a t h o d i c a r e a s )

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e l e c t r i c a l c o n t i n u i t y between t h e anode and cathode

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e l e c t r i c a l c o n t i n u i t y i n t h e medium surrounding t h e m e t a l s

-

moisture

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oxygen

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c h l o r i d e i o n s . Because complete c o n t r o l of t h e e l e c t r o c h e m i c a l p r o p e r t i e s of a l l embedded metals is not p o s s i b l e ,

t h e v i a b l e o p t i o n s f o r p r o t e c t i o n a r e e l e c t r i c a l l y i s o l a t i n g t h e s t e e l ( u s u a l l y w i t h epoxy) o r

p r e v e n t i n g c h l o r i d e i o n s from r e a c h i n g t h e s t e e l . This means making t h e c o n c r e t e a s impervious a s p o s s i b l e by:

-

u s i n g a low water/cement r a t i o

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c u r i n g w e l l

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i n c r e a s i n g t h e t h i c k n e s s of cover and

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a p p l y i n g a s u r f a c e s e a l e r , o r

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i n s t a l l i n g a w a t e r p r o o f i n g membrane, o r

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i n s t a l l i n g an impervious l a t e x cement topping. Two o t h e r s p e c i a l measures a r e c a t h o d i c p r o t e c t i o n and c o r r o s i o n - i n h i b i t i n g admixtures. The l a t t e r method c o n s i s t s of adding a n admixture t o t h e p l a s t i c c o n c r e t e mix. I n h i b i t o r s , such a s calcium n i t r a t e , i n s u f f i c i e n t c o n c e n t r a t i o n have been

found t o prevent o r g r e a t l y minimize c o r r o s i o n of s t e e l . The main drawback of t h i s method i s t h a t because t h e admixture i s consumed by t h e p r o t e c t i v e a c t i o n , i n t i m e i t s i n h i b i t i v e a c t i o n is d e c r e a s e d i f t h e i n t e n s i t y of t h e c o r r o s i v e a c t i o n is underestimated a t t h e time of c o n s t r u c t i o n . Cathodic p r o t e c t i o n a r r e s t s c o r r o s i o n by p r o v i d i n g h i g h l y n e g a t i v e p o t e n t i a l t o t h e s t e e l , r e n d e r i n g i t t h e cathode with r e s p e c t t o an i n e r t e l e c t r o d e . This method h a s been used w i t h g r e a t s u c c e s s f o r t h e p r o t e c t i o n of p i p e l i n e s and s h i p s . For parking g a r a g e s i t s e f f e c t i v e n e s s depends on t h e s o l u t i o n of t h e p r a c t i c a l problems of t h e given

i n s t a l l a t i o n .

R e h a b i l i t a t i o n of d e t e r i o r a t e d g a r a g e s and t h e d e s i g n i n g of new ones a r e covered i n o t h e r papers i n t h i s s e s s i o n and t h e r e f o r e a r e n o t d i s c u s s e d h e r e i n f u r t h e r d e t a i l .

REVIEW OF THE ORGANIZATIONAL MEASURES

Since t h e r e c o g n i t i o n of t h e p a r k i n g g a r a g e problem i n t h e 1970's, t h e f i r s t t a s k was t o e s t a b l i s h t h e magnitude of t h e c o s t of r e p a i r . Because of l a c k of d a t a on t h e number of parking g a r a g e s i n Canada, t h e i r t o t a l f l o o r a r e a and t h e degree of d e t e r i o r a t i o n , it was n o t p o s s i b l e t o e s t i m a t e r e l i a b l y t h e d o l l a r v a l u e of t h e damage. It i s c l e a r , however, t h a t t h e c o s t of r e p a i r i s of t h e magnitude of s e v e r a l b i l l i o n d o l l a r s and t h u s a major e f f o r t towards f i n d i n g a s o l u t i o n t o t h e problem i s w e l l j u s t i f i s d . Answers t o two q u e s t i o n s were r e q u i r e d u r g e n t l y :

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How does one r e p a i r d e t e r i o r a t e d g a r a g e s ?

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How does one d e s i g n and b u i l d new g a r a g e s t h a t w i l l l a s t a s l o n g a s t h e b u i l d i n g t h e y

s e r v e ? I

The f o r m u l a t i o n of r e p a i r s t r a t e g i e s and t h e 1

e s t a b l i s h m e n t of new d e s i g n g u i d e l i n e s a r e made d i f f i c u l t by t h e d e a r t h of examples of g a r a g e s t h a t a r e performing w e l l . Most d u r a b i l i t y problems, such a s damage due t o f r e e z i n g and thawing, a r e t h e r e s u l t of d e v i a t i o n from t h e s t a n d a r d p r a c t i c e o r o u t r i g h t d i s r e g a r d of proven p r i n c i p l e s . The

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p a r k i n g garage problem was somewhat d i f f e r e n t , i n t h a t t h e s t a n d a r d p r a c t i c e f o r d e s i g n and

c o n s t r u c t i o n was i n a d e q u a t e . The s i t u a t i o n was t h a t b e f o r e t h e q u e s t i o n a s t o how t o b u i l d a d u r a b l e garage could be answered, i t had t o be e s t a b l i s h e d whether i t was indeed p o s s i b l e t o b u i l d a garage t h a t would perform w e l l f o r decades. The c o n t r i b u t i o n of t h e O n t a r i o Chapter of t h e American Concrete I n s t i t u t e has t o be recognized. It formed a n ad hoc committee (under t h e

chairmanship of J. _{B i c k l e y ) t h a t prepared an} i n t e r i m g u i d e l i n e f o r t h e i n v e s t i g a t i o n , r e p a i r , d e s i g n and c o n s t r u c t i o n of p a r k i n g s t r u c t u r e s ( O n t a r i o Chapter Committee on P a r k i n g S t r u c t u r e s , 1981). I n t h e same y e a r t h e D i v i s i o n of B u i l d i n g Research (DBR) of NRC commissioned a r e p o r t

"Parking S t r u c t u r e D e t e r i o r a t i o n : Information and Analysis" (Trow Ltd., 1981) and Canada Mortgage and Housing C o r p o r a t i o n (CMHC) f i n a n c e d a s t u d y t h e next y e a r on "Nature, E x t e n t and Impact of

R e s i d e n t i a l P a r k i n g S t r u c t u r e D e t e r i o r a t i o n " (Trow Ltd., 1982). A review of i n f o r m a t i o n a v a i l a b l e a t t h e time was p u b l i s h e d by DBR i n i t s Canadian B u i l d i n g Digest S e r i e s i n 1982

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No. 224,

" D e t e r i o r a t i o n of Indoor Parking Garages" ( L i t v a n , 1982a) and No. 225, "Evaluation and Repair of D e t e r i o r a t e d Garage F l o o r s " ( L i t v a n , 1982b). A d e m o n s t r a t i o n p r o j e c t t o e v a l u a t e t h e f e a s i b i l i t y of c a t h o d i c p r o t e c t i o n i n p a r k i n g garages was j o i n t l y sponsored by DBR and P u b l i c Works Canada

(PWC) i n 1984. A major i n v e s t i g a t i o n i n v o l v i n g t h e survey of 300 g a r a g e s was a l s o j o i n t l y f i n a n c e d by CHHC, NRC, PWC and Supply and S e r v i c e s Canada, and was completed r e c e n t l y (Trow Ltd., 1985).

Based on t h e s e s t u d i e s and e x p e r i e n c e g a i n e d , i t i s g e n e r a l l y recognized t h a t d u r a b l e p a r k i n g g a r a g e s can be b u i l t and o n l y t h e l e v e l of p r o t e c t i o n r e q u i r e d t o a c h i e v e t h i s o b j e c t i v e need be b e t t e r d e f i n e d , r e s u l t i n g , i t i s hoped, i n a s i m p l i f i e d c o n s t r u c t i o n method and a s a v i n g i n o v e r a l l c o s t . At p r e s e n t , a c c o r d i n g t o t h e consensus, m u l t i l e v e l p r o t e c t i o n i s thought t o be n e c e s s a r y ; no s i n g l e p r o t e c t i o n measure s u c h a s t h e i n s t a l l a t i o n of a w a t e r p r o o f i n g membrane o r u t i l i z a t i o n of epoxy- c o a t e d r e i n f o r c i n g b a r s i s , i n i t s e l f , deemed t o be s u f f i c i e n t . T h i s approach is o u t l i n e d i n T e c h n i c a l B u i l d e r ' s B u l l e t i n No. 7 of CMHC ( r e v i s e d e d i t i o n t o appear s h o r t l y ) and i n t h e Standard on Durable Parking Garages being p r e p a r e d by t h e Canadian Standards A s s o c i a t i o n .

S i g n i f i c a n t p r o g r e s s h a s t h u s been made r e g a r d i n g t h e proper d e s i g n and c o n s t r u c t i o n of d u r a b l e p a r k i n g g a r a g e s ; h e l p f u l g u i d e l i n e s a r e a l r e a d y a v a i l a b l e o r w i l l be very soon. Guidance f o r s e l e c t i n g a w a t e r p r o o f i n g membrane o r a s u r f a c e s e a l a n t i s s t i l l n o t a v a i l a b l e . A committee of t h e Canadian General S t a n d a r d s Board h a s been formed t o p r e p a r e a s t a n d a r d f o r w a t e r p r o o f i n g membranes but i t s p u b l i c a t i o n may t a k e some time. I n t h e meantime, s e l e c t i o n must be based on f i e l d performance. A s i n g l e r e p a i r t e c h n i q u e f o r e x i s t i n g d e t e r i o r a t e d g a r a g e s c a n n o t , of c o u r s e , a c h i e v e l a s t i n g d u r a b i l i t y . I f c o n c r e t e i s l a r g e l y contaminated w i t h d e i c i n g s a l t i t cannot be r e s t o r e d f u l l y t o g i v e t r o u b l e - f r e e s e r v i c e over s e v e r a l decades. The o b j e c t i v e of t h e r e p a i r i s t o r e s t o r e s t r u c t u r a l i n t e g r i t y s o t h a t t h e s e r v i c e l i f e of t h e g a r a g e can be extended a s much a s p o s s i b l e . It

i s almost c e r t a i n t h a t f u r t h e r r e p a i r s d u r i n g t h e l i f e t i m e of t h e s t r u c t u r e w i l l be r e q u i r e d but i t

i s hoped t h a t t h e u s e f u l l i f e of d e t e r i o r a t e d g a r a g e s can be extended t o e q u a l t h a t of t h e b u i l d i n g s t h e y s e r v e .

SOME REFLECTIONS ON THE DEVELOPMENT OF THE PARKING GARAGE PROBLEM

The a n a l y s i s of t h e c i r c u m s t a n c e s t h a t l e d t o t h e b i l l i o n d o l l a r problem of p a r k i n g g a r a g e s i s of more t h a n h i s t o r i c i n t e r e s t . Another s i m i l a r l y c o s t l y problem may d e v e l o p u n l e s s s a f e g u a r d s a r e p u t i n place.

The N a t i o n a l B u i l d i n g Code concerns i t s e l f mainly w i t h s a f e t y and h e a l t h - r e l a t e d a s p e c t s of d e s i g n .

It has not p r e v e n t e d , and i s n o t expected t o p r e v e n t , t h e emergence of problems such a s t h e d e t e r i o r a t i o n of g a r a g e s . Market f o r c e s a r e t h u s t h e s o l e d e f e n c e a g a i n s t making c o s t l y m i s t a k e s . Obviously owners and d e v e l o p e r s w i l l n o t p a t r o n i z e t h o s e who do n o t d e s i g n d u r a b l e b u i l d i n g s . But t h i s f o r c e p r o t e c t s o n l y a g a i n s t obvious

s u b s t a n d a r d d e s i g n and workmanship. Once a f a u l t y approach becomes t h e norm, almost insurmountable d i f f i c u l t i e s f a c e t h o s e who would a d v o c a t e a b e t t e r q u a l i t y and more expensive design. The owner and t h e d e s i g n e r want c l e a r e v i d e n c e t h a t t h e more economical d e s i g n w i l l f a i l . A more expensive o p t i o n w i l l be s e l e c t e d o n l y when i t i s proven beyond doubt t h a t t h e more economical d e s i g n w i l l f a i l . I n a d d i t i o n , t h e f a c t t h a t subsequent r e p a i r c o s t s w i l l be o f f s e t by s a v i n g s i n i n t e r e s t c h a r g e s due t o t h e reduced c a p i t a l e x p e n d i t u r e , by t a x advantages and, i n c a s e of r e n t a l p r o p e r t y , by maintenance c o s t s c h a r g e a b l e t o t h e t e n a n t s , can be a n i m p o r t a n t c o n s i d e r a t i o n . It t a k e s s e v e r a l y e a r s t o prove t h e inadequacy of a p a r t i c u l a r d e s i g n . I n t h e c a s e of t h e r a t h e r r a p i d p a r k i n g garage d e t e r i o r a t i o n , t h e f i r s t symptoms may n o t be o b s e r v a b l e i n t h e f i r s t t h r e e t o f i v e y e a r s of s e r v i c e . P r o c e s s e s of d e t e r i o r a t i o n can be m c h s l o w e r , e x t e n d i n g t o 20 o r 30 y e a r s , y e t t h e l i f e span of most b u i l d i n g s i s much l o n g e r than t h a t . Obviously, performance i n such c a s e s i s

d i f f i c u l t t o p r e d i c t . A c u r r e n t concern

i l l u s t r a t e s t h i s p o i n t . It i s n o t known whether c o n c r e t e c o n t a i n i n g secondary cementing m a t e r i a l s s u c h a s f l y a s h , s l a g o r s i l i c a fume w i l l , a f t e r 20, 30 o r 40 y e a r s of exposure t o carbon d i o x i d e , have enough lime t o p r o t e c t t h e embedded

r e i n f o r c e m e n t from c o r r o s i o n . We know t h a t c o n c r e t e made from blended cement c o n t a i n s l e s s lime t h a n t h a t made from o r d i n a r y p o r t l a n d cement and t h a t i t is l e s s permeable ( a t l e a s t a t e a r l y a g e s ) t h a n c o n v e n t i o n a l c o n c r e t e . A s d i s c u s s e d e a r l i e r , h i g h lime c o n t e n t i s e s s e n t i a l f o r t h e development of p a s s i v i t y of s t e e l and f o r p r o t e c t i o n a g a i n s t c o r r o s i o n of t h e metal. We hope t h a t lower p e r m e a b i l i t y w i l l compensate f o r t h e reduced lime c o n t e n t but t h i s i s not y e t proven.

(8)

There a r e , of course, no easy s o l u t i o n s t o t h e g e n e r a l problem. Regulatory a c t i o n cannot be taken f o r each of t h e perceived problems, and advocating a more expensive s o l u t i o n t o p o t e n t i a l problems without evidence would be i r r e s p o n s i b l e .

One important document t h a t i s a t p r e s e n t unknown i n t h e b u i l d i n g i n d u s t r y i s t h e owner's manual. It i s a c u r i o u s f a c t t h a t w h i l e no i n d u s t r i a l product of any complexity i s s o l d without a manual and o p e r a t i n g i n s t r u c t i o n s , m u l t i m i l l i o n d o l l a r b u i l d i n g s a r e handed over t o t h e owners without a word of i n s t r u c t i o n , c a u t i o n o r advice. More o f t e n t h a n n o t , even t h e drawings a r e of l i m i t e d use because they d e s c r i b e what was designed a t some s t a g e of t h e development and not what was b u i l t . The purchaser of a t o a s t e r r e c e i v e s a

trouble-shooting manual but t h e owner of an

eighty-storey b u i l d i n g r e c e i v e s no such a s s i s t a n c e t o s o l v e problems.

An owner's manual would be h e l p f u l by drawing a t t e n t i o n t o p o t e n t i a l problems, and g i v i n g a t i m e t a b l e f o r p r e v e n t i v e maintenance and a replacement schedule f o r c e r t a i n components. Perhaps j u s t a s important would be t h e b e n e f i t d e r i v e d from f o r c i n g t h e d e s i g n e r t o t h i n k i n terms of d u r a b i l i t y and performance.

U n c e r t a i n t i e s o r doubts about problems, such a s carbonation of c o n c r e t e , could be recorded i n t h e documents with d e t a i l s on frequency and n a t u r e of t e s t i n g . Perhaps t h e parking garage problem would have been l e s s s e r i o u s i f such a monitoring system had been adopted.

This paper i s c o n t r i b u t i o n from t h e M v i s i o n of Building Research, National Research Council of Canada.

REFERENCES

Ontario Chapter Committee on Parking S t r u c t u r e s , 1981. American Concrete I n s t i t u t e , I n t e r i m Guidelines, I n v e s t i g a t i o n , Repair, Design and Construction of Parking S t r u c t u r e s , Toronto. Litvan, G.G., 19829. D e t e r i o r a t i o n of Indoor

Parking Garages, Division of Building Research, National Research Council Canada, Canadian Building Digest No. 224, Ottawa.

Litvan, G.C., 1982b. Evaluation and Repair of

D e t e r i o r a t e d Garage F l o o r s , M v i s i o n of Building Research, National Research Council Canada, Canadian Building M g e s t No. 225, Ottawa.

Trow Ltd., 1981. Parking S t r u c t u r e D e t e r i o r a t i o n :

Information and Analysis, T-2298-C, prepared

f o r National Research Council Canada, Ottawa. Trow Ltd., 1982. Nature, E x t e n t , and Impact of

R e s i d e n t i a l Parking S t r u c t u r e D e t e r i o r a t i o n , T-21734, prepared f o r Canada Mortgage and Housing Corporation, Ottawa.

Trow Ltd., 1985. Parking S t r u c t u r e D e t e r i o r a t i o n : a Survey and Analysis of i t s Extent and I n f l u e n c i n g F a c t o r s , T-40104, prepared f o r Canada Mortgage and Housing Corporation, National Research Council Canada, Public Works Canada and Supply and Services Canada,