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NATIONAL RESEARCH COUNCIL CANADA
TFSTING STJRFACZ WATERPROOFERS FOR CONCRETE by
E.W. Neumann and E.G. Swenson
ANALYZED R e s e a m h R e p o r t No. 1 9 o f t h e D i v i s i o n o f B u i l d i n g Research O t t a w a A p r i l
1953
TESTING SUR FACX WATERPROOFERS -.
FOR
CONCRETE
by E. W. 1.Jsumann and E.G. Swenson
As a r e s u l t o f i n q u i r i e s s u b m i t t e d t o t h e D i v i s i o n of B u i l d i n g Re s e a r c h by Centrs.1. Mortgage and Housing C o r p o r a t i o n , an i n v e s t i g a t i o n h a s been s t a r t e d t o develop r a t i n g t e s t s f o r b o t h s u r f a c e and i n t e g r a l w a t e r p r o o f e r s f o r c o n c r e t e . Large-
s c a l e t e s t s have been mads by o t h e r l a b o r a t o r i e s f o r e v a l u a t i n g such m a t e r i a l s b u t complete i n f o r m a t i o n i s o f t e n l a c k i n g a s t o t e s t i n g c o n d i t i o n s , and p r o c e d u r e s . I d e n t i f i c a t i o n of p r o p r i e - t a r y m a t e r i a l s i n p u b l i s h e d d a t a i s n o t always e a s y and s u c h d a t a ore of t e n out of d n t e i n a s h o r t time due t o f r e q u e n t f o r m u l a changes.
T h i s r e p o r t d e s c r i b e s a method of t e s t i n g developed f o r r a t i n g s u r f a c e w a t e r p r o o f e r s which a r e t o be a p p l i e d t o t h e
i n s i d e s u r f a c e s of l e a k y c o n c r e t e basements or s i m i l a r
s t r u c t u r e s . I t a l s o g i v e s p r e l i m i n a r y r a t i n g s f o r - t h r e e p r o p r i e - t a r y m a t e r i a l s a s determined by t h i s method. The m a t e r i a l s
t e s t e d a r e r e f e r r e d t o by l e t t e r only, a s A , B, and C. Problems Involved i n T e s t i n g W a t e r p r o o f e r s
For convenience w a t e r p r o o f i n g m a t e r i a l s may be d i v i d e d i n t o t h e f o l l o w i n g c a t e g o r 2 . e ~ :
A. Surf aco Waterpleoofers:
1. O u t s i d e , below-srade bituminous a p p l i c a t i o n s s u c h a s out s i d e a s y h a l t c o a t i n g s on basement w a l l s .
2, Gv.i,side, .s1.t)ove-grade cement-base p a i n t s , o i l - b a s e p a l n k s , s i l i c o n e t r e a t m e n t s , s o l u t i o n s of t r a n s p a r e n t waxes
m d s t e a r a t e s , e t c .
3 .
I n s i d e x a t e r ~ r ooi'srs or dampproofers-
cement-basem a t e r l i a l s and o t h e r s . B. I n t e g r a l
-
W a t e r p r o o f e r ~ : 1, Calcic:.m = k l . o r i c ? ~ base. 2. liatsr--i:spo3.lent b a s e , s u c h a s s t e a r a t e s . ii s a t l s f a c t o l n y t e s t f o p a w a t e r p r o o f e r must s i m u l a t e f i e l d condit;fons a s n e a r l y 6 : : p o s s i b l e . I t i s e v i d e n t from t h e abovs g r a u b i a g t h a - t s 2 p a r a t o t e s t s would be r e q u i r e d f o r e a c h t y p e of m a t e r i a l and :?see A cement-base p a i n t f o r o u t s i d e above- grade a p p l i c a t i o n mas.'; be t e v t e d f o r w e a t h e r i n g r e s i s t a n c e a s w e l l a s w a t e r p r o o f i n g c l i a r a c t e r i s t i c s. I n s i d e w a t e r p r o o f e r s do n o t r e q u i r e w e a t h e r i n g t e s t s . I n t e g r a l waterproof e r s must bet e s t e d f o r t h e i r e f f ' o c t s o n t h e p r o p e r t i e s of c o n c r e t e and m o r t a r , a s \ : d l 1 a s f o r t h e < = . e f ? i c i s n c y a s w a t e r p r o o f e r a .
I n t e g r a l wn-krproof e r s pose a s p e c i a l problem, a s t h e i r e f f i c i e n c y i s based on r i g i d conformity t o s p e c i f i c a t i o n s I n making and p l a c i n g c o n c r e t e and m o r t a r s , Since p r o p e r l y made conczaete ?.s i t s e l f zs::.entially waterproof, t h e r e should be no need f o r such admixtures e x c e p t i n s p e c i a l c a s e s where imperme- a b i l i t y t o w a t e r a t an e a r l y age i s r e q u i r e d . I n such c a s e s the use of a small q u a n t i t y of' calcium c h l o r i d e i n t h e c o n c r e t e mix a c c e l e r a t e s t h e h y d r a t i o n l ~ i " cement and t h e r e b y p r o v i d e s e a r l y irn;;erme2bi?-ity. However, s p e c i a l p r e c a u t i o n s must be t a k e n i n i t s use.
S e l e c t i n ? a S u i t a b l e T e s t f o r I n s i d e Waterproofers
I n s i d e s u r f ace w a t e r p r o o f e r s a r e i n t e n d e d f o r a p p l l c a - tion. 0 2 ccricrete s u r f a c d s which e x h i b i t v a r i o u s d e g r e e s of
dampness o r water-seepage due t o f a u l t y c o n s t r u c t i o n , Normally, t h e s e p r o p r i e t a r y m a t e r i a l s are mixed t o a creamy c o n s i s t e n c y and a p p l i e d by brush. For severe c a s e s of seepage, t h e P o r t l a n d Cement A s s o c i a t i o n recommends a p p l i c a t i o n of two c o a t s of m o r t a r , e a c h
1/4
i n c h t h i c k . The National Bureau of S t a n d a r d s recommends two c o a t s , e a c h 3/8 i n c h t h i c k , u s i n g one p a r t cement t o two o r t h r e e p a r t s s a n d &For mild c a s e s of seepage o r dampness, Fishburn of t h e N a t i o n a l Bureau of S t a n d a r d s has r e p o r t e d t h a t t h e a p p l i c a t i o n of two o r t h r e e c o a t s of cement-sand g r o u t of t h i c k cream
c o n s i s t e n c y i s e f f e c t i v e . M r , Mshburn used one p a r t cement
t o
one p a r t f i n e sand ( p a s s i n g No, 30 s i e v e ) and found t h i s
t o
bemore e f f e c t i v e t h a n s t 1 tiight cement-water p a i n t i n r e d u c i n g leakage and c a p i l l a r y p e n e t r a t i o n ,
I n t h e t e s t i n g procedure developed by t h e D i v i s i o n
of
B u i l d i n g Research the r e f e r e n c e m a t e r i a l s e l e c t e d wae p o r t l a n d cement-water p a s t e because
i t
i s c o n s i d e r e d t h e l e a s t e f f e c t i v eof t h e recommended procedure s ,
The more common p r o p r i e t a r y m a t e r i a l s
can
be compared o n l y w i t h t h e brush-on cement-paste or g r o u t , For v e r y mild c o n d i t i o n s of seepage where b o t h t h e cement-paste t r e a t m e n t and t h e p r o p r i e t a r y w a t e r p r o o f e r a r e e f f e c t i v e remedies, no compara- t i v e a p p r a i s a l can be made except on a c o s t b a s i s , T h i swould,
i n every c a s e , f a v o w t h e cement-paste. Only where seepage
i s
s t r o n g enough t o r e s i s t complete stoppage of flow, would
i t
be p o s s i b l e t o compare t h e e f f e c t i v e n e s s of t h e s e m a t e r i a l s . T h i st h e n is t h e b a s i s f o r t h e method of comparative t e s t i n g developed i n our l a b o r a t o r y m d d e s c r i b e d i n t h i s r e p o r t .
The t e s t prl;cedur,r+ a d o p t e d does n o t i n c l u d e w e a t h e r i n g r c s i s t m c e as t h e s e condit.l.ons a r e n o t a p p l i c a b l e . The d u r a b i l i t y of thy v;i1i 3 u s i.r::t? rpl-oc-f e r o , p a r t i c u l a r l y t h e r e s i s t ance t o
! i .,.i. <, .. 2 2 lng ' 2: . , r i t k i n g
e~1.e
t o s h r i n k a g e , i s n o t t a k e n i n c oa c c o u ~ t S y the: t e s t s i n c e t h e o r i g i n a l cause of dampness o r
seej;rse ~ o u l d p r o v i d e a c c n t i n u o u s s u p p l y of m o i s t u r e t o p r e v e n t c o m p l ~ . t e d r y i ~ g o u t sf tllc m a t e r i a l .
Tiid fh31'iowirg t e s t h a s been developed on t h e b a s i s o f t h e assumptions o u t l i n e d i n t h e p r e v i o u s p a r a g r a p h s , and i s , l i k e a l l test,.,
,
312b j32t t o c e r t a i n l i m i t a t i o n s . I n g e n e r a l , it c o n s i s t s of a p p l y i ~ g the: w a t e r p r o o f i n g m h t e i 2 i a l , a c c o r d i n g t o t h e d i r e c t i o n s s p e c i f i e d , t o the outsir3e s u r f a c e of a hollow c o n t a i n e r made of a u n i f o r m l y poroua concrc t e n o r t a r . The c o n t a i n e r i s f i l l e d w i t h w a t e r and a small head of w a t e r i s a p p l i e d t o p r o v i d e a s t e a d yseepage t h r o u g h t h e w a l l s of t h e c o n t a i n e r , The r a t e of f l o w i s t h e n measured and comparison i s made between d i f f e r e n t m a t e r i a l s . D u p l i c a t e samples and d u p l i c a t e s e r i e s a r e made t o e n s u r e
rzprodu.cib: l i t y ,
F ~ b r i c a t i o n d' T e s t C e l l s
---
A s ~ l . t a b l y po, ous c o n c r e t e m o r t a r i s made from a mix c o n s i s t i n g o f one p a r t cement t o e i g h t p a r t s w e l l - g r a d e d sand by we i g h t , and a w a t e r - c e m e n t r r a t . i o of
1.14,
The u n i f o r m l y g r a d e d sand i s r o o ; ; l - d r i e d i n t h e 1z.Soratory b e f o r e use.I t
was found t h a t i t s mo!.stul-o c o n t e n t val-led from 0.1 t o 0.4 p e r c e n t . Thesame k i n d of c e ~ e n t i ? ' 3 3 t : < j.-i a l l mixes.
S t a n a a r d
6-
12.-inch c a r d b o a r d c y l i n d e r moulds a r e c u t down t o a h e i c h t of6
i n c h e s and a l a v e r of t h e m o r t a r about 2 i n c h e s deep i s c a r e f u l l y tr:.lped i n t o e a c h mould. A s m a l l e r c a r d b o z r d c y l i n d e r 4-1/2 iriches i n d i a m e t e r i s t h e n c e n t r e d on t h i s bottcii I n y c r and lnortj nort tar i s v e r y c a r e f u l l y tamped between t h s c y l i n d s , . 1.511:3, The bra11 %hFckne s s of t h e p o r o u s c o n c r e t em o r t a r i s
7/8
i n c h . S p e c i a l c a r e i s r e q u i r e d i n t h i s o p e r a t i o n t o o b t a i c r e p r o d u c i b i l i t y i n w a t e r seepage when t h e m o r t a r h a s hardene d.The moulds a r e removed af'ter 20 t o 2 4 h o u r s and t h e cups a r e immediately p l a c e d i n an oven and d r i e d a t 130°F. f o r
2 1 ~ h31:~: t o p r e v e n t r a p i d h y d r a t i o n of t h e cement.
Caps f o r t h e cups a r e f a b r i c a t e d from t h e same m a t e r i a l s b u t u s i n g a n i x c o n s i s t i n g of one p a r t cement t o 2-1/2 p a r t s
g r a d e d sand by weight, and a water-cement r a t i o of 0.42, The cups a r e 2 i n c h e s t h l c k and a r e p e n e t r a t e d by two 1/4-inch copper t u b e s , The c a p s a r e cured f o r 24 h o u r s and s e a l e d on t h e cups by means of a r i c h mortar c o n s i s t i n g of one p a r t cement t o one p a r t g r a d e d sand by w e i g h t and a water-cement r a t i o n of 0.48, The r i m s of t h e cups are f i r s t sanded t o e n s u r e a smooth f i t . Four h o u r s
a f t e r capping, the r i n g of m o r t a r i s c o a t e d w i t h a p r o p r i e t a r y m a t e r i a l n p s d f o r stopp?;.:; w a t e r flow. A f i n a l c o a t of aluminum
''Sprayp~?:" 1.3 ;1 >~?!.?ced o v e r t h e cap and s e a l . The completed
c e l l ( F i g . l a ) i s allowed t o s t a n d f o r 20 t o 24 hours b e f o r e t h e w a t e r p r o u f e r i s a p p l i e d .
The M a t e r i a l s --. T e s t e d an6 t h e --.-- ,?eating Procedure Followed_:
P r o ~ r i e t a r y M a t e r i a l s A and B a r e made f r o m a cement, a f i l l e r r n a t e r i s l ~ n d p r o b a b l y o t h e r admixtures. M a t e r i a l B i s more f i n e l y divi-dsd, i s I n t e n d e d a s a f i n i s h c o a t , and c a n be
o b t a i n e d i : ~ d i f f e r e n t s o l o u r s . The makers c l a i m t h a t M a t e r i a l
A w i l l w i t h s t a d extreme h y d r o s t a t i c p r e s s u r e when a p p l i e d over belotr-zrade masonry. I t i s d e s c r i b e d a s a slow-set h y d r a u l i c compound. They recommend two c o a t s of A f o r w a t e r p r o o f i n g work. Both t h e s e m a t e r i a l s a r e mixed w i t h water and brushed on the a f f e c t e d s u r f a c e . M a t e r i a l s A and B a r e i n t e n d e d a s complementary m a t e r i a l s when a f i n e f i n i s h
i s r e q u i r e d . The manuf ac t u m r s recommendat i o n s a s t o p r o c e d w e were f o l l o w e d i n the t e s t .
2. Materi:i: C i s desl=?-'bed as a f i n e c o p p e r i z e d cement compound and a s a c k ~ e m i c a l l y b a l a n c e d combinet i o n of i n o r g a n i c m i n e r a l and m e t a l l i - components. The m a n u f a c t u r e r s c l a i m t h a t
it
can : q i t h ~ % a n d severe hydrr,st-."ic p r e s s u r e s e x e r t e d from behind t h e s u r f ace on whi-ch t h e y a:-3 ~ p p l i e d . I t i s a p p l i e d i n e s s e n t i - a l l y t h e 8an:j wasy a s l ~ e t e r i a l A end t h e i n s t r u c t i o n s s u p p l i e d by the r W i ? n ~ f a c t u r c ; F;L;.~ . a r e f u l l y f o l l o w e d i n t h e t e s t .The powciered f or,n c f C c o n ? a i n s a cement, a f i l l e r , and a v e r y s m a l l amount of a copper compound ( p r o b a b l y t h e h i g h e r oxide!. i?ccordir,g .to i)nsurrlers' liesearch,
it
i s about 40 t i m e s P S c o s t l y a3 p o r ~ l a n d cement..
-
3.
Refs;-.-o:lce Ka\e:r;.;l -..-.- s.-
Since t h i s t e s t i s designedt o
g i v e cornpa- r a t i n g s , and s i n c e p o r t l a n d cement p a s t e i s t h e l e a s t e f f e c t i v e of t h e methods f o r dampproofing recommendedby M r . Fishburn o f t h e N a t i o n s 1 Bureau of S t a n d a r d s , i t wab 5dsed a s a r e f e r e n c e m a t e r i a l . It i s mixed w i t h w a t e r ( , \ r / ~ = 0.38) t o a ::rsamy c o n s i s t e n c y and twcj z o a t s a r e a p p l i e d by b r u s h .
A second r e f e r e n c e m a t e r i a l c o n s i s t s of a creamy mi;,ture of sement, l i m e , a r d w a t e r and i s a l s o a p p l i e d by
b r u s h , This mixture i s sometimes used f o r dampproof i n g w a l l s . The f i r s t c o a t c o n t a i n e d 2 p e r c e n t lime and t h e second c o a t
1 0 p e r n s n t ?,ilr;. ( b a s e d c~r, cem??t; c o n t e n t ) . The water-cement
r a t i o u ~ e d was
^-.38.
Companion specimens t h a t were n o t c o a t e d were used "J s~zp;,!-:menl- the r a t i n g t e s t s w i t han
i n d i c a t i o n of t h e e f f i c i e n c y ,,f' t-iLs w a t e r p r o o f e r .A l l t e s t s uere c a r r i e d o u t i n d u p l i c a t e and some samples were repc5at3.j ':;o t e s t r e p r o d u c i b i l i t y .
T e s t i n g Procedure
-
The t e s t c e l l s , 2oated w i t h the v a r i o u s w a t e r p r o o f i n g m a t e r i a l s , were assembled i n l i n e on a metal g r i d over a copper
catch-baqin f Fig. l b j . One copper i n s e r t p i p e from e a c h c e l l
is
connected. by r u b b e r t u b i n g t o a 50 m l . b u r e t t e p l a c e d a t a n e l e v a t i o ~ ~ of
3
f e e t i n o r d e r t o p r o v i d e a small water head. Clamps on the t u b i n g are provided. The second copper i n s e r t p i p e on each c e l l i s connected w i t h a s h o r t r u b b e r tube w i t h cla:,q tc, allow complete f i l l i n g of e a c h c e l l .T e s t i n g b e g i n s by f i l l i n g t h e b u r e t t e s w i t h t a p w a t e r , c o l o u r e d r e d by the a d d i t i o n of 0.1 p e r c e n t s a f r a n i n e dye t o lsrovide v i s u a l a i d i n r e a d i n g t h e b u r e t t e s . When t h e c e l l s a r e f i l l e d t h e o u t l e t t u b e s a r e clamped, and t h e b u r e t t e s r e f i l l e d t o t h e same s t a r t i n g l e v e l .
Water flow i s allowed t o s t a b i l i z e by a p r e l i m i n a r y r u n of
4
t o6
hours t o r e a c h s a t u r a t i o n e q u i l i b r i u m . When t h i sc o n d i t i o n h a s been r e ached, r e a d i n g s a r e t a k e n a t 15-minute i n t e r v a l s .
A t t h e end of each day t h e c e l l s a r e l e f t a s s a t u r a t e d a s p o s s i b i e so t l n t thek.6 i s n o d e l a y i n s t a r t i n g t h e n e x t d a y ' s run. T e s t s a r e continued .tor a s u f f i c i m t l e n g t h of time t o make c e r t a i n t h a t no secondary e f f e c t s a r e p r e s e n t .
f lirnlJ,ed number oP t e c : t c e l l s can be f a b r i c a t e d a t one
time, S j z c e I t i s ex? - e m e i : ~ L i f f i c u l t t o reproduce p o r o s i t y exct;tly frorr or;e bat;?, G O a n o l h e r , each b a t c h i s r e f e r r e d t o a s
a " s e r i e s " . R a t i n g s arp t b s r e f o ~ ~ c : made w i t h i n a s e r i e s a l t h o u g h f a i r l y good r a p r o d u c i b i l i t ~ r i s o b t a i n e d f r o m one s e r i e s t o
a n o t h e r .
The datn. o b t a i n e d a m ehown g r a p h i c a l l y i n F i g s . 2,
3,
*ma
4.
Figure 2 shows t h e r e l a t i v e e f f i c i e n c y of the
w a t e r p m o f i n g m a t e r i a l s used, a s o b t a i n e d i n the f i r s t s e r i e s . Two c o a t s o f n e a t cement p a s t e showed t h e b e s t w a t e r p r q o f i n g e f f 2 c i e n c y i n t h i s t e s t . Two c o a t s of M a t e r i a l A showed up
e f f e c t i v e l y and two c o a t s of M a t e r l a l C was found t o have a much lowe- r a t i n g .
A s shown i n F i g .
3,
second s e r i e s , two c o a t s of n e a t cement p a s t e a g a i n ge.v? t h e b e s t r e s u l t s , followed by two c o a t s of a mixture o f n e a t cement and lime, Two c o a t s of e a c h ofM a t e r i a l s A and C b o t h showed lower e f f i c i e n c i e s . One c o a t of A followed by one c o a t oP B gave t h e l o w e s t r a t i n g ,
Figure
4
shows the p e r c e n t a g e d e c r e a s e of f l o w w i t h time f o r t h e second s e r i e s . D e s p i t e t h e d e f i n i t e f a l l i n go f f
of flow, t h e i n d i v i d u a l r a t i r . g s were maintained.To i l l u s t r a t e t h e r e p r o d u c i b i l i t y of r e s u l t s w i t h i n
a
s e r i e s comparative d a t a a r e shcwn i n Table 1 f o r t h e f o u r t h day! s run. A p p r a i s a l ,-?f Method of T e s t-
---.-
D u p l i c a t e samples w i t h i n a s e r i e s of t e s t s show remarkably good agreement. T h i s i s a t t r i b u t e d t o t h e s p e c i a l care t a k e n i n t h e f a b r i c a t i o n of t h e c e l l s from a very l e a n mix.Sotn;: v a r i a t i o n o c c u r s between t h e two s e r i e s s i n c e i t i s v i r t u a l l y impossible t o reproduce m a t e r i a l of the n a t u r e used
i n t h e t e s t c e l l s even though i d e n t i c a l p r o p o r t i o n s of the same i n g r e d i e n t s a r e used. It i s t o be noted, however, t h a t t h i s v a r i a t i o n does n o t i n any way a f f e c t t h e r a t i n g s of t h e
w a t e r p r o o f e r s t e s t e d . N e v e r t h e l e s s ,
i t
i s recommended t h a t , f o r e a c h t e s t s e r i e s , a l l t h e c e l l s be f a b r i c a t e d from t h e same b a t c h a t t h e same time.I n t h e s e r i e s o u t l i n e d above, the t e s t s
were
n o tcontinued f o r a s u f f i c i e n t l e n g t h of time t o i n d i c a t e whether a complete stoppage of flow might be achieved. Since a l l t h e
m a t e r i a l s t e s t e d reduce t h e f l o w of w a t e r and would i n mild c a s e s of w a t e r seepage. completely s t o p t h e f l o w , t h i s was considc.:-ed unnecessar;.. It was, t h e r e f o r e , o n l y a m a t t e r of t e s t i n g t h e comparative e f f e c t i v e n e s s of t h e s e m a t e r i a l s .
A Forous concreta mortar was s e l e c t e d a s t h e base f o r t e s t i n g i n o r d e r t o s i m u l a t e a c t u a l c o n d i t i o n s a s n e a r l y a3 p o s s i b l e .
This t e s t d ~ a s n o t t a k e i n t o account the d u r a b i l i t y of t h e w a t e r p r o o f e r . For t h e p a r t i c u l a r c o n d i t i o n s f o r which t h e s e m a t e r i a l s a r e design.?d, t h e r e i s no exposure t o f r e e z i n g , e x t e n s i v e d r y i n g o r o t h e r weather c o n d i t i o n s . A cement-base m a t e r i a l o t t h i s n a t u r e c c u l d n o t be e x p e c t e d t o w i t h s t a n d sul:>hate a c t i o n . A p p r a i s a l of Waterprcofers T e s t e d
-
--
The r e s t : i t s i n b o t h s e r f e s i n d i c a t e c l e a r l y t h a t o r d i n a r y poxstland cement , p a s t e , of a creamy c o n s i s t e n c y , and a p p l i e d byb r u s h i s n more e f f e c t i v e w a t e r p r o o f i n g m a t e r i a l t h a n any one of p r ~ p r i o t a r y X n t e r i ~ l s , A , A
+
B, o r C a p p l i e d i n t h e e x a c t manner r e commended by t h e manufacturers.The d a t a a l s o shcx t h a t a s m a l l a d d i t i o n of lime
t o
t h e n e a t cement-paste sligkibly reduces i t s w a t e r p r o o f i n g e f f i c i e n c y b u t t h i s combination i s s t i l l s u p e r i o r t o t h e p r o p r i e t a r y
m a t e r i a l s t e s t e d .
I n a l l c a s e s , t h e p r o p r i e t a r y w a t e r p r o o f e r s d i d reduce w a t e r flow. I t may be assumed t h a t the d e c r e a s e i n r a t e of f l o w
w i t h time i s d i r e c t l y p r o p o r t i o n a l t o the r a t e of h y d r a t i o n of t h e cement i n g r e d i e n t p r e s e n t i n each c a s e .
There was no i n d i c a t i o n t h a t t h e p r o p r i e t a r y waterproofing m i x t u r e s were i n any way s u p e r i o r t o t h e p o r t l a n d cement-paste
i n w o r k a b i l i t y o r i n e a s e of a p p l i c a t i o n . Where c o n d i t i o n s of m o i s t u r e seepage
can
be e f f e c t i v e l y c o n t r o l l e d by a p p l y i n gbrushed-on c o a t s of cement-base p a s t e s , p o r t l a n d c e m n t appears t o be s u p e r i o r t o t h e o t h e r m a t e r i a l s t e s t e d from b o t h t h e p o i n t of view of e f f i c i e n c y and of c o s t . The e x p e r i e n c e of t h e N a t i o n a l
Bureau of S t a n d a r d s , as r e p o r t e d elsewhere i n t h i s r e p o r t , should be n o t e d ,
