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New approaches to building materials
Ramachandran, V. S.
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ANALYZED
Reprinted from
3CIB 83
The 9th. CIB Congress, Stockholm, Sweden
Building Materials and Components, Vol. 4
p.
23
-
34
DBR Paper No. 1203
Division of Building Research
Title of the paper
NEW APPROACHES TO BUILDING MATERIALSAuthor
V.S. RamachandranOrganizationIEnterprise
D i v i s i o n of B u i l d i n g Research, N a t i o n a l R e s e a r c h C o u n c i l CanadaK ~ Y
words
c h a r a c t e r i z a t i o n , w a s t e s . by-products, p a t e r i a l s development, d u r a b i l i t y , t e s t s , a i r q u a l i t y , environment.The paper d i s c u s s e s some i m p o r t a n t a s p e c t e of b u i l d i n g m a t e r i a l s r e s e a r c h t h a t s h o u l d r e c e i v e more a t t e n t i o n i n t h e colaing y e a r s .
T o a p r e d i c t t h e behaviour of m a t e r i a l s , i t is e s s e n t i a l t o c h a r a c t e r i z e t h e i r components u s i n g physico-chemical t e c h n i q u e s .
Resource c o n s e r v a t i o n and concern f o r t h e environment w i l l encourage
u ' t i l i z a t i o n of w a s t e s and by-products and r e c y c l i n g o f , m a t e r i a l s . An
u n d e r s t a n d i n g of t h e i r p r o p e r t i e s and p r o c e s s i n g r e q u i r e m e n t s and o v e r a l l
econony is n e c e s s a r y b e f o r e t h e y c a n be u t i l i z e d .
The demand is i n c r e a s i n g f o r products' w i t h improved p r o p e r t i e s and s p e c i a l
a p p l i c a t i o n s . New composite o r g a n i c and i n o r g a n i c m a t e r i a l s c o n t a i n i n g f i b r e s
o f f e r c e r t a i n a d v a n t a g e s o v e r o t h e r s .
To p r e d i c t d u r a b i l i t y w i t h c o n f i d e n c e . t h e b a s i c p r o c e s s e s t h a t o c c u r d u r i n g exposure and t h e micro-environmental f a c t o r s w i t h i n a m a t e r i a l must be
understood.
S t a n d a r d t e s t i n g tnethods adopted on t h e b a s i s of r e s e a r c h e x p e r i e n c e .
s i m p l i c i t y , economy, a v a i l a b l e equipment and e a s e of measurement have g e n e r a l l y
proven t o be s a t i s f a c t o r y . Sonre c a s e s . h w e v e r , r e q u i r e s p e c i a l i z e d
t e c h n i q u e s .
The long-term e f f e c t a of man-made p o l l u t a n t s on b u i l d i n g s a r e l a r g e l y unknown. Techniques t o measure t h e chemical c o n s t i t u e n t s of p o l l u t a n t s and t h e
development of a c c e l e r a t e d methods would be needed t o p r e d i c t t h e i r e f f e c t on b u i l d i n g s .
Reducing s i r i n f i l t r a t i o n i n t o b u i l d i n g s s a v e s e n e r e y b u t c a n a l s o c r e a t e
h e a l t h h a z a r d s by c o n c e n t r a t i n g i n d o o r a i r p o l l u t a n t s . To f o r m u l a t e s t a n d a r d s
CIB 83
24Titre du teXte
e0NCEPTIONS NOIJVELLES DES MATERIAIJX DE CONSTRUCTIONAuteur
V.S. RamachandranOrganisation/Entrepriw
Division des recherche6 en bltiloent, Conseil national de recherche8 CanadaM o ~ o - c ~ ~ s
caract€ristiquee, d€chete, eoue-produite, d6veloppement des matsriaux, durabilits, eeaaie, qualit6 de l'sir, environnementSommaire
Cette note traite de quelques aapects importanta de la recherche sur lee matLriaux de constmktion qui devraient attirer davantage l'attention dans lee
ann6es B venir.
Pour pr6voir le comportelpent dea mat€riaux, il faut connattre lea
caract6ristiques de leurs composante B l'aide de techniques phyaico-chimiques.
La conservation des reasourcea naturellea et la prLaervation de l'environne- ment entratneront l'utilisation dee d6chets et des aous-produits ainai que le recyclage dea mat€riaux. Leur utiliaation depend de la bonne connaissance de leure propri€t€s, de leur traltement et de leur coat d'utilisation global.
I1 y a une demande croissante pour lea produits ayant dea propriSt6a
am€lior€es et des applications ap6cialea. Les nouveaux mat6riaux composites B
base de produits organiques ou inorganiques contenant dea fibres offrent certaina avantages par rapport aux autree.
Pour pr6dire la durabilitE avec certitude, on doit connaltre lea ph6nodnea ext6rieure qui agiaaent sur un mat6riau ainsi que lea effets des facteure micro- environnementaux.
Lea dthodea d'esaai normalis€es, adopt€'es pour raieons d9exp0risnce dans la
recherche, de simplicit€, d'bconomie, de disponibilit6 de l'appareiliage d'eesai et de la rapidit6 des d t h o d e s de mesure sont, en g6n6ra1, aatisfaiarntes. Pour
certains can, cependant, il faut avoir recoura
il
dea techniques pluc. complexes.Lea effets B long terme des polluants d6vere6s dans la nature par I'homme sur
lea 610ments de conatruction sont g6nkralement ma1 connus. 11 faut d6velopper dea techniques de mesure de conatituante chimiques et des J t h o d e s acc616r6ea pour pr6dire ces effete.
La r6duction de l'infiltration de l'air dans lea bati~oents 6conomiae l96nergie
maia peut nuire B la aant6 en augmentant la concentration des polluants. Des
mBthodes de recherche et de reduction de la pollution doivent 8tre misea au point pour €laborer dee normes de qualit6 de l'air.
25
NFM APPROACHFX T O RUTI,DINC: MA'PERJALS
V.S. Ramachandran, Canada
INTRODUCTION
M a t e r i a l s form a s u b s t a n t i a l p e r c e n t a g e of t h e t o t a l v a l u e of c o n s t r u c t i o n . I n
1981 t h e t o t a l v a l u e of a l l m a t e r i a l s used i n c o n s t r u c t i o n i n Canada amounted t o
$20 b i l l i o n . The r e p a i r problelns a s s o c i a t e d w i t h some of t h e s e m a t e r i a l e a r e
commensurate w i t h t h e i r widespread use. Consequently t h e theme "New Approaches
t o B u i l d i n g M a t e r i a l s " is t i m e l y , b u t complex.
The a u t h o r h a s a t t e m p t e d t o p r e s e n t a s h o r t review, based on h i s own accumulated e x p e r i e n c e , some i m p o r t a n t a s p e c t s of b u i l d i n g m a t e r i a l s r e s e a r c h
t h a t s h o u l d r e c e i v e more a t t e n t i o n i n the coming y e a r s : c h a r a c t e r i z i n g
m a t e r i a l s , u t i l i z i n g w a s t e s and by-products, d e v e l o p i n g new b u i l d i n g m a t e r i a l e , ' c o r r e c t l y a s s e s s i n g d u r a b i l i t y c h a r a c t e r i s t i c s , f o r m u l a t i n g r e a l i s t i c s t a n d a r d s ,
s t u d y i n g p o l l u t i o n e f f e c t s o n b u i l d i n g s and e v a l u a t i n g a i r q u a l i t y i n b u i l d i n g s .
CHARAmERIZATION
Two r a v m a t e r i a l s a p p a r e n t l y i d e n t i c a l i n a 1 1 r e s p e c t s may show d i v e r g e n t p h y s i c a l and mechanical b e h a v i o u r s once t h e y a r e p r o c e s s e d under s i m i l a r
c o n d i t i o n s t o produce t h e same t y p e of b u i l d i n g m a t e r i a l . T h i s o b s e r v a t i o n
p o i n t s o u t t h e i n a d e q u a t e knowledge a t p r e s e n t of t h e i m p o r t a n t f a c t o r s t h a t d e t e r m i n e t h e p r o p e r t i e s of a m a t e r i a l and t h e l i m i t a t i o n s of t e c h n i q u e s used t o
i d e n t i f y the p r o p e r t i e s .
S u r f a c e a r e a v a l u e s of cement g e n e r a l l y i n d i c a t e t h e r a t e a t which it w i l l
h y d r a t e . The B l a i n e a i r p e r m e a b i l i t y method, p r e s c r i b e d by ASTM f o r measuring
s u r f a c e a r e a s , is p r a c t i c a l b u t h a s limitations. T a b l e I showe t h a t s u r f a c e
a r e a determined f o r t h e same cement depends on t h e method used ( I ) .
Even u e i n g t h e same t y p e of cement i n c o n c r e t e d o e s n o t mean t h a t s i m i l a r
s t r e n g t h s w i l l be o b t a i n e d , e s p e c i a l l y i n combination w i t h admixtures. Using
t h e same cement t y p e and amount, a i r c o n t e n t end p e r c e n t a g e of c a l c i m c h l o r i d e a d m i x t u r e and producing mixes w i t h t h e same slump d o e s n o t e n s u r e t h a t t h e i n f l u e n c e of c a l c i u m c h l o r i d e on s t r e n g t h w i l l be t h e same f o r e a c h batch.
F i g u r e 1 shows t h e e f f e c t of c a l c i u m c h l o r i d e on t h e compressive s t r e n g t h s of 13
cements (2) ( e l l ASTM Type I ) c u r e d f o r 7 o r 28 daya. Calcium c h l o r i d e c a u s e s a
s l i g h t t o moderate i n c r e a s e i n t h e 7-day compressive s t r e n g t h s of I1 o u t of 13
cements. At 2 8 d a y s t h e compressive e t r e n g t h s of 9 o u t of 13 cements c o n t a i n i n g
calcium c h l o r i d e a r e l e s s t h a n t h e compressive s t r e n g t h s of t h e i r c o r r e s p o n d i n g
r e f e r e n c e mixes. These r e s u l t s show t h a t c h a r a c t e r i z i n g cements a c c o r d i n g t o
t h e s t a n d a r d s l a y n o t a d e q u a t e l y p r e d i c t t h e i r behaviour.
Attempts have been made t o c h a r a c t e r i z e b u i l d i n g m a t e r i a l s a s a b a s i s f o r
p r e d i c t i n g t h e i r mechanical p r o p e r t i e s . C h a r a c t e r i z a t i o n based on s u r f a c e a r e a ,
p o t o s i t y , p o r e e i z e , d i s t r i b u t i o n , d e n s i t y , m i c r o s t r u c t u r e and c h e m i c a l
26
WASTES AND BY-PRODUCTS
C o n s e r v a t i o n of r e s o u r c e s , e n v i r o n m e n t a l q u a l i t y s t a n d a r d s and j u d i c i o u s u s e of energy w i l l c r e a t e a n i n t e r e s t i n u t i l i z i n g w a s t e s and b y - p r o d k t s and r e c y c l i n g m a t e r i a l s . Some p o t e n t i a l m a t e r i a l s a r e : f l y a s h , b l a s t f u r n a c e s l a g and o t h e r s l a g s , r i c e husk, mica, w a s t e g l a s s , condensed s i l i c a fumes, waste gypsum, w a s t e rubber, l i m e s t o n e powder w a s t e , s u l p h u r , l i g n i n and d e m o l i t i o n waste.
S i n c e c o n c r e t e made w i t h p o r t l a n d cement, w a t e r and a g g r e g a t e s c o n s t i t u t e s t h e g r e a t e s t p o r t i o n of a l l man-made m a t e r i a l s , a t t e m p t s w i l l be made t o i n c o r p o r a t e w a s t e s i n t o i t . Some of t h e m a t e r i a l s d e s c r i b e d i n t h e examples g i v e n below and o t h e r s may a l s o be u t i l i z e d t o f a b r i c a t e i n o r g a n i c and o r g a n i c b u i l d i n g
m a t e r i a l s not based on p o r t l a n d cement.
A w a s t e o r by-product may be used a s a raw m a t e r i a l f o r t h e p r o d u c t i o n of p o r t l a n d cement c l i n k e r , a s a supplementary m a t e r i a l i n blended cements, o r a s a s u b s t i t u t e f o r chemical gypsum ( a n i m p o r t a n t i n g r e d i e n t of p o r t l a n d cement), admixture and a g g r e g a t e .
I n t h e p r o d u c t i o n of p o r t l a n d cement, of a t o t a l energy of 6.06 x lo6 JIKg, c l i n k e r f o r m a t i o n a c c o u n t s f o r 4.89 x 106 J/Kg (4). T h i s e n e r g y can be s u b s t i t u t e d o r d e c r e a s e d by u s i n g w a s t e o i l s o r m n i c i p a l w a s t e s o r by a d d i n g c e r t a i n i n g r e d i e n t s t o t h e raw mix. For example, by u s i n g phosphogypaum ( a by- p r o d u c t of p h o s p h o r i c a c i d ) o r f l u o r o g y p s m a s a m i n e r a l i z e r . t h e c l i n k e r i n g t e m p e r a t u r e c a n be reduced by 200'C. P o s s i b l e a d v e r s e e f f e c t s of t h i s method o n s e t t i n g and s t r e n g t h w i l l need t o be examined.
F l y a s h o r b l a s t f u r n a c e s l a g can be blended w i t h p o r t l s n d cement d u r i n g g r i n d i n g t o r e d u c e t h e energy consumed i n making c o n c r e t e . They may a l s o be added t o t h e c o n c r e t e mix a s s e p a r a t e l y dry-batched compounds o r mixed a s a w a t e r s l u r r y w i t h p o r t l a n d cement and a g g r e g a t e when b a t c h i n g c o n c r e t e . The r e s u l t i n g c o n c r e t e p o s s e s s e s c e r t a i n a d v a n t a g e s o v e r normal c o n c r e t e : reduced a l k a l i - a g g r e g a t e e x p a n s i o n , b e t t e r e u l p h a t e r e s i s t a n c e . reduced s e g r e g a t i o n and b l e e d i n g , and b e t t e r w o r k a b i l i t y . F i g u r e 2 shows how a d d i n g d i f f e r e n t amounts of f l y a s h c a n reduce t h e e x p a n s i o n due t o a l k a l i a g g r e g a t e r e a c t i o n ( 5 ) . Although f l y a s h o r b l a s t f u r n a c e s l a g can be used i n c o n c r e t e , c e r t a i n problems a r i s e . A l l f l y a s h e s and s l a g s a r e n o t e q u a l l y a c t i v e w i t h r e s p e c t t o s t r e n g t h development. F a c t o r s r e s p o n s i b l e f o r t h i s a r e n o t c o m p l e t e l y known. The r e l a t i v e r o l e s of p h y s i c a l s t r u c t u r e ( c r y s t a l l i n i t y o r g l a s s y n a t u r e ) , chemical composition, pore s t r u c t u r e , s u r f a c e a r e a , p a r t i c l e s i z e and s h a p e , d e n s i t y and w e i g h t l o s s on i g n i t i o n have y e t t o be c l a r i f i e d . A good a c c e l e r a t o r t o i n c r e a s e t h e r a t e of s t r e n g t h development i n blended cement h a s s t i l l t o be d i s c o v e r e d . The dosage of a i r - e n t r a i n i n g a g e n t r e q u i r e d t o a t t a i n a known amount of a i r i n c o n c r e t e i s n o t e a s y t o p r e d i c t when f l y a s h i s used.
Normal p o r t l a n d cement c o n t a i n s a b o u t 4 t o 5% gypsum. Waste gypsum from v a r i o u s i n d u s t r i e s i n t h e form of phosphogypsum, fluorogypsum o r organogypeum
c a n be s u b s t i t u t e d f o r normal m i n e r a l gypsum, b u t t h e i r v a r i a b l e c o m p o s i t i o n makes it d i f f i c u l t t o o b t a i n c o n s i s t e n t behaviour. The d e l e t e r i o u s i n g r e d i e n t s i n t h e s e m a t e r i a l s s h o u l d be removed.
U t i l i z i n g w a s t e s o r by-products i n c o n c r e t e t o r e p l a c e normal a g g r e g a t e s . which comprise 75% of t h e volume of c o n c r e t e , h a s g r e a t p o t e n t i a l . Waste m a t e r i a l s a r e c l a s s e d i n t o 3 g r o u p s ( s e e T a b l e 2 ) baaed on t h e i r p o t e n t i a l f o r
I
u s e a s a g g r e g a t e s (6). Croup I h a s t h e h i g h e s t p o t e n t i a l . The d e m o l i t i o n w a s t e s c o n t a i n i n g c o n c r e t e belong t o t h i s c l a s s . C o n c r e t e b e i n g t h e major c o n s t r u c t i o n m a t e r i a l . i t s h o u l d a c c o u n t f o r most of t h e d e m o l i t i o n waste. I n f a c t , i t s p r o d u c t i o n i n t h e USA, UK, J a p a n , Canada and Sweden i s e s t i m a t e d a t
2 5 . 21-23. 7 - 1 2 , 3 and 2-5 m i l l i o n t o n s r e s p e c t i v e l y (7). Compressive s t r e n g t h , modulus of e l a s t i c i t y and f l e x u r a l a t r e n g t h s of c o n c r e t e c o n t a i n i n g r e c y c l e d c o n c r e t e a r e lower t h a n i n c o n c r e t e made w i t h normal a g g r e g a t e . The p a r t i a l replacement of normal a g g r e g a t e by w a s t e s , t h e u s e of s u p e r p l a s t i c i z e r s o r o t h e r admixtures, and t h e e f f i c i e n t removal of c o n t a m i n a n t s needs t o be i n v e s t i g a t e d .
Croup 11 s h o u l d be c o n s i d e r e d f o r a p p l i c a t i o n a f t e r f u r t h e r r e s e a r c h and development work. Group 111 m a t e r i a l s do n o t show promise a t p r e s e n t because t h e y need e x t e n s i v e p r o c e s s i n g and have non-uniforn c h a r a c t e r i s t i c s .
V a r i n b l l i t y i n t h e i r p h y s i c a l and chemical p r o p e r t i e s and t r a n s p o r t a t i o n d i f f t c u l t i e s may i n h i b i t t h e i r widespread use. The long-tern d u r a b i l i t y of c o n c r e t e c o n t a i n i n g t h e s e m a t e r i a l s needs t o be s t u d i e d i n g r e a t e r d e t a i l .
A n t i p o l l u t i o n measures have s t i m u l a t e d i n t e r e s t i n t h e r e c y c l i n g o f r e s i d u a l c o n c r e t e and w a t e r from washed'mixes i n ready-mixed c o n c r e t e p l a n t s . and i n p r e c a s t c o n c r e t e o p e r a t i o n s . When used i n c o n c r e t e . s o l i d s i n r e c y c l e d w a t e r r e q u i r e a l a r g e amount of w a t e r ; hence such c o n c r e t e w i l l e x h i b i t l a r g e r d r y i n g s h r l n k a g e , i n c r e a s e d s e t t i n g time and lower a t r e n g t h s . T h i s may be overcome by d e v e l o p i n g machines t o s e p a r a t e t h e p a r t i c l e s and a p p l y i n g c e r t a i n p h y s i c a l and chelntca1 t r e a t m e n t s t o t h e r e c y c l e d m a t e r i a l s .
DEVEI.OPHENT OF NEW MATERIALS
A l t h o t ~ g h many b u i l d i n g m a t e r i a l s perform s a t i s f a c t o r i l y , some have t o be r e p l a c e d w i t h new m a t e r i a l s p o s s e s s i n g b e t t e r d u r a b i l i t y c h a r a c t e r i s t i c s . New m a t e r i a l systems a l s o need t o be developed f o r u s e i n s t r u c t u r e s i n c o r p o r a t i n g new d e s i g n s o r requirements such a s a i r t i g h t n e s s . O l d e r b u i l d i n g s needing r e p a i r s o r r e t r o f i t t i n g may a l s o r e q u i r e new m a t e r i a l s o r systems c o m p a t i b l e w i t h t h e o l d e r m a t e r i a l s . New r o o f i n g m a t e r i a l s . f a s t - s e t t i n g cements. a d m i x t u r e s , cements t o immobilize r a d i o a c t i v e w a s t e s , s e a l a n t s and c o q o s i t e m a t e r i a l s ( s u c h a s f i b r e - r e i n f o r c e d cements and polymer c o n c r e t e s and p l a s t i c s ) a r e examplea of such p r o d u c t s .
While t h e r e a r e s e v e r a l a d v a n t a g e s i n i n s t a l l i n g i n s u l a t i o n o u t s i d e t h e w a l l , t h e s u r f a c e of t h e i n s u l a t i o n must be p r o t e c t e d from t h e d e t r i m e n t a l i n f l u e n c e s
of rain, heat and sechanical forces. One solution is to apply a coating. usually a mortar, compatible with the substrate. Several types of composite mortars containing cement, latex, fibres and others have been proposed.
Several types of precast fibre-reinforced producta have attracted attention in recent years because their high flexural and impact strengths offer several advantages such as post-cracking durability, controlled cracking and economy of size. Since 1960 glass fibre has been investigated as a possible alternative to other fibrea in cements. While aome glass-fibre composites have good resistance to alkali attack, their long-term performance and durability have not yet been
fully ascertained. New formulations in glass fibre and the search, for
alternatives continue. One suggested alternative is mica of a particular aspect ratio. Figure 3 shows hov adjusting the waterlcement ratio and amount of mica flake can increase the modulus of rupture. One advantage in using mica flakes is their resistance to alkali attack (3).
DURABILITY CHARACTERISTICS
Many standard methods used to assess durability during exposure to service may
not be adequate. Materials rejected as "nondurable" have performed
satisfactorily and aome that have passed the tests have shown poor performance. In many instances, understanding the mechanisms of deterioration and the microenvironmental factors to which the materials may be exposed under service conditions ia essential to formulate realistic tests.
I n most studiea only the ambient conditions to which a material is exposed are used to asseae durability and develop accelerated tests. In the context of weathering, external factors such as temperature. moisture (precipitation and relative humidity). solar radiation, wind and pollution are taken into account. However, the condition existing within the material is what determines ite ability to withstand physical and chemical effects. The surface of an aephalt- covered flat roof nray reach a maximum of 88°C on a sunny day in summer and a
black PVC panel, 30 to 45'C, when the ambient temperature ia only 0 to 10°C (8).
Corrosion can occur at a fast rate in an atmosphere at a relative humidity of about 85% although it is assumed that it occurs only in tne presence cf liquid water. Similarly, the surfaces of plastics, protective coatings and roofing membranes can begin to deteriorate when the relative humidity is hig.: or when the surface temperature is lower than the dew point of the air. thus proving
that precipitation need not be a prerequiate for the initiation of
deterioration. The aicroenvironmental conditions play an important role in the deterioration of plastics exposed at different anglee.
As already stated, some accelerated test methods for assessing durability have not proven satisfactory. One reason is the approach used for developing these tests. In accelerated weathering tests for organic materials, the method has
been t o presuppose i m p o r t a n t e x p o s u r e f a c t o r s i n a g i v e n s e r v i c e and i n c o r p o r a t e a s many of them a s p o s s i b l e i n a t e s t chamber. Each f a c t o r is a l l o t t e d a n e x p o s u r e t i m e and t h e t e s t d e t e r m i n e s i f t h e m a t e r i a l w i l l f a i l w i t h i n t h a t time. I t is more e f f e c t i v e t o d e t e r m i n e f i r s t t h e b a s i c p r o c e s s e s t h a t o c c u r i n t h e d e g r a d a t i o n of a m a t e r l a l and t a i l o r t h e t e s t t o r e p r o d u c e them. Using t h i s approach t o e v a l r ~ a t e c l e a r wood f i n i s h e s (9) l e d t o t h e d i s c o v e r y t h a t t h e d u r a b i l i t y of p h e n o l i c v a r n i s h e s exposed n a t u r a l l y f o r 2 y e a r s i s r e l a t e d t o t h e i r w a t e r a b s o r p t i o n . water vapour p e r m e a b i l i t y and, t o a l e s s e r e x t e n t . t e n s i l e s t r e n g t h . S i m i l a r r e s u l t s o c c u r r e d w i t h a l k y d s .
The same approach was used t o s t u d y t h e f a d i n g of p o l y ( v i n y 1 c h l o r i d e ) (PVC) due t o exposure i n Ottawa. I t was found t h a t a n e p o x i d i z e d soya bean o i l p l a s t i c i z e r , hydrolyzed i n a PVC sample under h o t . humid c o n d i t i o n s i n t h e p r e s e n c e of HCl a r i s i n g from t h e v i n y l r e s i n , m i g r a t e d t o t h e s u r f a c e a s a w h i t e l a y e r . Samples exposed f o r one month t o c o n t r o l l e d changes i n t e m p e r a t u r e and humidity f o r s p e c i f i e d p e r i o d s showed a tendency t o d e v e l o p s u c h a l a y e r ( F i g . 4) (LO).
TEST DEVP,I.OPHENT
G e n e r a l l y , t h e c r l t e r l a f o r a c c e p t i n g or modifying test methods f o r b u i l d i n g m a t e r i a l s a r e based on s i m p l i c i t y . immediate need, economy, r e s e a r c h e x p e r i e n c e , a v a i l a b l e equipment and e a s e of measurement. However, a r e a l i s t i c e v a l u a t i o n of a m a t e r i a l sometimes r e q u i r e s u s i n g complex t e c h n i q u e s t h a t do n o t conform t o t h e above c r i t e r i a . For example, a r e q u i r e m e n t t h a t a b u i l d i n g m a t e r i a l e h o u l d not emit more t h a n a few p a r t s p e r b i l l i o n of a g a s can o n l y be determined u s i n g very s o p h i s t i c a t e d t e c h n i q u e s .
According t o t h e s t a n d a r d l i n e a r t r a v e r s e t e s t , a i r - e n t r a i n e d s u p e r p l a s t i c i z e d c o n c r e t e f a i l s t o a c h i e v e t h e r e q u i r e d s i r c o n t e n t and a i r void s p a c i n g r e q u i r e d f o r f r o s t r e s i s t a n c e . However, o t h e r t e s t s measuring f r o s t r e s i s t a n c e s h w t h a t such c o n c r e t e s have e x c e l l e n t d u r a b i l i t y t o f r o s t a c t i o n . T h i s would s u g g e s t t h a t t h e l i n e a r t r a v e r s e t e s t , e f f e c t i v e i n measuring l a r g e r v o i d s , i s n o t r e l i a b l e f o r a s s e s s i n g a i r - e n t r a i n e d s u p e r p l a s t i c i z e d c o n c r e t e . A r e c e n t i n v e s t i g a t i o n h a s shown t h a t f o r s u c h c o n c r e t e s , and p e r h a p s f o r o t h e r s , d u r a b l l t t y i s determined by t h e volume of p o r e s of s i z e 0 . 3 t o 2 pm (11). Such measurements can o n l y be c a r r i e d o u t by r e a l i s t i c t e c h n i q u e s s u c h a s mercury porosimetry o r i s o t h e r m a l a d s o r p t i o n .
I n t h e s t a n d a r d t e s t f o r f r o s t s u s c e p t i b i l i t y of b r i c k s (12). t h e t e s t based on n a t u r a t l o n c o e f f i c i e n t v a l u e s d o e s n o t y i e l d r e l i a b l e r e s u l t s . However, a more complex t e s t based on s u r f a c e a r e a by N p is c a p a b l e of d i s t i n g u i s h i n g poor from good b r i c k s . I n one e x p e r i m e n t , i t r a t e d t h e v a l u e s f o r b r i c k s t h a t had performed we11 i n t h e f i e l d below l . i l
dlg,
whereas f o r t h o s e te-dWhen new materials such aa single-ply roofing of various types are introduced. there is usually presaure to develop standard methods to evaluate these
materials and their applications. Very careful aasessment of the background information available on these materiale in conjunction with laboratory and field studies should form a basis for formlating standards (13). Otherwise unreallatic standards will result.
ENVIRONMENTAL POLLUTION EFFECTS
One of the major concerns of industrialized countries is the pollution of air by effluents resulting from the increased uee of hydro-carbon fuels. Deleterious effluents may alao originate from the raw materials used to produce building materials and other producte. These pollutants, which affect some construction materiale as a result of c o w l e x reactions with water vapour, acidic compounds and salts, may cause surface discoloration or deterioration of the materials to varying degrees of severity. The approximate concentrations of the 5 most common pollutants, comprising about 98% of all emiasiona. are 52% carbon monoxide. 18% sulphur dioxide, 12% hydrocarbons, LOX particulates and 6% nitrogen oxides (8).
Concentration of pollutants in the atmosphere and in rainwater is monitored by varioua agencies, but little attempt has been made to relate this information to material deterioration. It has been reported that high concentrations of locally-generated industrial SO2 are mainly responsible for corroding metals (14.15). Large variations in SO2 concentrations with height, their dependence on season and their effect on corrosion have been studied.
The type of building material and its surface characteristics, and the effect of orientation, shading effecta and other factors interacting in a complex way may determine how severe the effecca of pollution are.
An area that should receive more attention is the repair and restoration of materiale that have already shown signs of distress. Nondestructive techniques to analyae (in situ) the surfaces of materials need to be developed, as well as accelerated laboratory tests that reproduce the behaviour of materiale exposed outdoors for long periods. Preliminary work on some nonstructrrral materials has s h w n that the accelerated testa have potential (16).
Research is alao needed to control the small amounts of kiln effluents, such as hydrogen fluoride, produced during high-temperature reactions of some raw materials.
INDOOR AIR QUALITY
Decreasing air infiltration into building8 saves energy But may adversely affect air quality and pose health hazarda to the occupants. Indoor air pollutants include radon and its decay producte, formaldehyde and other organic
contaminants, a s b e s t o s , g l a s s f i b r e , s i l i c a d u s t and o t h e r forma of d u s t , ozone and s o l v e n t vapors. A few of t h e p o l l u t i o n s o u r c e s a r e consumer p r o d u c t s , c i g a r e t t e smoke, cooking. apace h e a t e r s , and b u i l d i n g m a t e r i a l s .
Radon and i t s a l p h a - e m i t t i n g decay products c o n t r i b u t e most of t h e background r a d i a t i o n i n b u i l d i n g s . S o i l , c o n s t r u c t i o n m a t e r i a l s and ground w a t e r a r e t h e major s o u r c e s of radon. Some waste m a t e r i a l s used f o r making b u i l d i n g m a t e r i a l s may a l s o c o n t a i n r a d i o a c t i v e elements. For example. phosphogypsun produced from sedimentary phosphate may have a r a d i o a c t i v i t y l e v e l of 25 p Ci/g.
Desulphogypsua is a n o t h e r waste m a t e r i a l c o n t a i n i n g r a d i o a c t i v e m a t e r i a l s . Indoor radon c o n c e n t r a t i o n s a r e o f t e n an o r d e r of magnitude g r e a t e r than t h o s e o u t s i d e t h e b u i l d i n g . Determining t h e r a t e of radon emanation from v a r i o u s s o u r c e s w i t h i n a b u i l d i n g w i l l h e l p t o e s t a b l i s h a c c e p t a b l e l e v e l s i n it. Also, inexpensive measuring i n s t r u m e n t s should be developed a s w e l l a s s t r a t e g i e s t o e l i m i n a t e o r reduce unacceptable c o n c e n t r a t i o n s .
Another p o t e n t i a l l y dangerous i n d o o r contamtnant is formaldehyde. It is e m i t t e d by u r e a formaldehyde foam i n s u l a t i o n , plywood, p a r t i c l e board, f a b r i c s . c i g a r e t t e s and indoor combustion products. Formaldehyde can cause t h r o a t , s k i n end eye i r r i t a t i o n s and r e s p i r a t o r y d i s o r d e r s . E f f e c t s of f a c t o r s such a s r e l a t i v e humidity, temperature. chemical composition and wind on t h e r a t e of e v o l u t i o n of f o r m l d e h y d e and t h e i r r e l a t i o n t o h e a l t h - r e l a t e d p r o b l e m should be monitored. A j o i n t e f f o r t by i n o r g a n i c , o r g a n i c a n a l y t i c a l and s u r f a c e chemists, a t a t i a t i c i a n s . e n g i n e e r s , h e a l t h s c i e n t i s t s , computer s c i e n t i s t s and b i o l o g i s t s is needed t o a r r i v e a t some workable s o l u t i o n s .
ACKNOWLEDGEMENT
T h i s paper i s a c o n t r i b u t i o n from t h e D i v i s i o n of B u i l d i n g Research. National Research Council Canada and is published w i t h t h e approval of t h e D i r e c t o r of t h e Divis ion.
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2. ROSSKOPF, P.A., F.J. LINTON and R.B. PEPPLER, E f f e c t of Various A c c e l e r a t i n g Chemical Admixtures on S e t t i n g and S t r e n g t h Development of Concrete. J. T e s t i n g and E v a l u a t i o n
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p. 322-330. 1975.3. WCHANDRAN, V.S., R.P. P B L W . a n d J.J. BEAUDOIN, Concrete S c i e n c e , Heyden 6 Son. London
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UK, p. 427, 1981.4.
EMERY, J. Trends i n Waste U t i l i z a t i o n i n C o n s t r u c t i o n , Prac. V. Mineral Waste U t i l i z a t i o n Symp., Chicago, p. 26-32, A p r i l 1976.5. BRINKYI[, R.H. and J.W. HALSTBAD, S t u d i e s R e l a t i n g t o t h e T e s t i n g of Fly Ash f o r Use i n Concrete, ASM Proc.
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g. 1161-1206, 1956.MILLER, R.H. and P.J. COLLINS, Waste Materiale as Potential Replacements for Highway Aggregates, Trans. Res. Board, Net. Co-op. Highway Res. Pro? Rep. 166, Washington. p. 94, 1976.
WILSON, D.G., P. FOLEY, R. WEISMAN and S. FRONDISTOU-YANNAS, Demolition Debris
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Quantities, Composition and Possibility for Recycling, Proc. 5th Mineral Waste Utilization Symp., Bur. Mines. Chicago, p. 8-15, 1976. ASHTON, H.E. and P.J. SEREDA, Environment, Microenvironment and Durabilit of Building MaterialsL.
p. 49-65. 1982.ASHTON, H.E. Evaluating the Performance of Organic Coatings,
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Tech. Publ. 781, p. 67-85, 1982.BLAGA, A. Long-Term Weathering Can Change the Complexion of PVC, SPE Journal
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Sp. Tech. Publ. 589, p. 123-132, 1975.L M L Y , H.O. and H.E. ASHTON, Methodology and Test Procedures for Evaluati New Materials, 2nd Intl. Symp. on Roofs and Roofing, Vol. 11, Brighton. U.K., p. 23-32. 1981.
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and E.V. GIBBONS, Corrosion Behaviour of Netal-Coated Panels Eight Canadian Locations: Summary of a Fourteen Year Program, National Research Council of Canada, Div. Bldg. Res., NRCC 12230, p. 21, 1971. WALTERS, H.V. and P.B. ADAM, Predicting Beeietance of InorganicArchitectural Elateriale to Appearance Degradation in Natural and Polluted Environments, Bull. her. Car. Soc. p. 1224-1227, 1982.
TABLE 1 : SUBFACE AREA OF CEMENT (sq cm/g)
Andreasen Method Wagner Air
"2
Spherical Cubical Method Permeability Adsorption Cement I 2 310 2 860 1 7902
6007
900 Cement I1 3 110 3 860 2 2704
150 10 OM)TABLE 2: CLASSIFICATION AND PRODUCTION OF WASTE MATERIALS I N THE USA Group I B l a s t f u r n a c e s l a g (30)* Fly a s h (32) Bottom a s h (10) B o i l e r a l a g (5) Reclaimed c o n c r e t e A n t h r a c i t e c o a l r e f u s e (10) Group I1 S t e e l a l a g (10-15) Bituminoua c o a l r e f u s e (100) Phosphate s l a g ( 4 ) S l a t e mining w a s t e Foundry waste (20) T a c o n i t e t a i l i n g s ( 150-200) Group 111 Alumina m d e (5-6) Phosphate s l i m e s ( 2 0 ) S u l p h a t e s l u d g e (5-10) Scrubber sludge Copper t a i l i n g s (200) Dredge s p o i l (300-400) F e l d s p a r t a i l i n g a (0.25- 0.50) I n c i n e r a t o r r e s i d u e I r o n o r e t a i l i n g s ( 10) Lead-zinc t a i l i n g s Waste g l a s s (12) (20-40)
Zinc s m e l t e r waste Nickel t a i l i n g s
(5-10) Rubber t i r e s (3-5)
Building r u b b l e B a t t e r y c a s i n g s (0.5-
(20) 1 .O)
*Figures i n b r a c k e t s r e f e r t o t h e a n n u a l production ( i n
lo6
t o n s ) .F l G U R E 1
' 0 1 ' 2 3 4 1 6 1 VOLUME f R A C l l O N O f FLAKES. S f l C U R t 3 E F f t C I OF A D D I N G M I C A O N 1HE MODULUS OF R U P l U R E OF CEMENT PASTES fLV A S H I N BLEND. S FIGURE 2 E f F t C 1 OF f l l A S H OM THE E X P A l S l O N OF M O R I A R DUE 10 A L K A L I - A C G R t G A l E R E A C I I O N w 1 . 1 ' I
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