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50-FMC Draft Recommendat ion

D e t e r m i n a t i o n o f t h e f r a c t u r e e n e r g y o f m o r t a ra n d c o n c r e t e b y m e a n s o f t h r e e p o i n t b e n d t e s t s o n n o t c h e d b e a m s

C O N T E N T S

1 . S c o p e .

2 . S p e c i m e n s .

3 . C o n d i t i o n s o f s t o r a g e .

4 . A p p a r a t u s .

5 . P rocedure .

6. Test resul ts .

7 . Tes t r epor t .

1 . S C O P E

T h i s R e c o m m e n d a t i o n s p e c if ie s a m e t h o d f o r t h ed e t e r m i n a t i o n o f t h e fr a c t u re e n e r g y G F ) o f m o r t a r a n dc o n c r e t e b y m e a n s o f s t a b le t h r e e - p o i n t b e n d t e s t s o nn o t c h e d b e a m s . T h e f r a c t u r e e n e rg y i s d e f i n e d a s t h ea m o u n t o f e n e r g y n e c e ss a ry t o c r e a t e o n e u n i t a r e a o f ac r a c k . T h e a r e a o f a c ra c k is d e f i n e d a s t h e p r o j e c t e d a r e ao n a p l a n e p a r a l l e l t o t h e m a i n c r a c k d i r e c t i o n .

T h i s te s t m e t h o d is n o t r e c o m m e n d e d f o r f i b r e - r e in f o r -c e d c o n c r e t e .

Horizontal ,~urfaceat castinq

l~notch dep th

L

Fig. 1

r e c o m m e n d e d t o m a k e t h e i n se r t in t h e m o u l d w e d g e -s h a p e d w i t h a n a n g l e o f 1 0 - 1 5 ~ in o r d e r t o m a k e i t p o s s i b let o l o o s e n t h e m o u l d w i t h o u t d a m a g i n g t h e b ea m . I f t h en o t c h is c a st t h e b e a m m u s t b e h a n d l e d v e r y c a r e f u l l yd u r i n g d e m o u l d i n g .

T h e n o t c h w i d t h a t t h e t i p s h o u l d b e le s s t h a n 1 0 m m .

I f t h e f r a c t u r e e n e rg y o f c o n c r e t e o f a n e x i s t i n g s t r u c t u r eh a s t o b e d e t e r m i n e d , i t i s s u g g e s t e d t h a t s u i t a b l e s p e c i -m e n s a r e c u t f r o m d r i l l e d co r e s . A n o t c h h a s t o b e s a w na n d m e t a l o r c o n c r e t e a r m s h a v e t o b e g l u e d t o t h e s p e c i -m e n , s o t h a t t h e t o t a l s p e c i m e n f u l f i l s t h e g e o m e t r i c a lc o n d i t i o n s g i v e n i n t a b l e I. T h e d i a m e t e r o f t h e c o r e h a s

t o b e a d j u st e d t o t h e m a x i m u m a g g r e g a t e s iz e .

2 . S P E C I M E N S

T h e s p e c i m e n s s h a l l b e b e a m s w i t h a c e n t r a l n o t c ha c c o r d i n g t o f i g u r e 1 . T h e d e p t h o f t h e b e a m a s t e s t e ds h a l l b e h o r i z o n t a l d u r i n g c a s t i n g . T h e s iz e o f t h e b e a ms h a l l d e p e n d o n t h e m a x i m u m s i z e o f t h e a g g r e g a t e , Dm ax ,a c c o r d i n g t o t a b l e I .

I f t h e m a x i m u m a g g r e g a t e s i ze e x ce e d s 6 4 m m t h e d e p t ha n d w i d t h s h a l l b e in c r e a s e d p r o p o r t i o n a l t o t h i s s iz e a n d

t h e l e n g t h a n d s p a n i n c re a s e d p r o p o r t i o n a l t o t h e s q u a r eroo t o f th i s s i ze .T h e n o t c h s h a ll a l w a y s h a v e a d e p t h w h i c h is e q u a l t o

h a l f t h e b e a m d e p t h -I- 5 m m . I t is r e c o m m e n d e d t h a t i tis s a w n u n d e r w e t c o n d i t i o n s a t l e as t o n e d a y b e f o r e t h et e s t. I t m a y a l s o b e c a s t b u t t h i s i s o n l y r e c o m m e n d e d i f as u i t a b l e s a w i s n o t a v a i l a b l e . If t h e n o t c h i s c a s t i t is

~ ) m a x__ mm)

I 1 - 1 6 .I 16.1-32 lI : 3 2 . 11 - 4 8 9

1 6 4 I

TABLE IS I Z E S O F S P E C I M E N S .

Depth dmm)

100 • 5200 • 5300 • 5400 • 5

Width b Length Lmm) mm)

100 • 5 840 • 10100 • 5 1 ,190 • 1 0150 • 5 1 ,450 • 10200 • 5 1 ,640 • 10

S p a n /m m )

800 + 51,130 -t- 51,385 + 51,600 -t- 5

3 . C O N D I T I O N S O F S T O R A G E

D u r i n g t h e p e r i o d o f c u r i n g t h e a m b i e n t t e m p e r a t u r esh all be 2 0 ___ 2~

T h e s p e c i m e n s h a l l re m a i n i n t h e m o u l d , p r o t e c t e d f r o ms h o c k , v i b r a t i o n s a n d d r y i n g , f o r a t l e as t 1 6 h o u r s .

A f t e r r e m o v a l f ro m t h e m o u l d , t h e s p e c i m e n s h a l l b es t o r e d i n l i m e - s a t u r a t e d w a t e r u n t i l l es s t h a n 3 0 m i n u t e sb e f o r e t e s t in g .

4 . A P PA R AT U S

4 . 1 . T e s t i n g m a c h i n e

T h e t e s t in g m a c h i n e h a s t o b e s t if f e n o u g h o r f u r n is h e dw i t h a c l o s e d - l o o p s e rv e c o n t r o l i n o r d e r t o m a k e i t p o s s i-b l e t o p e r f o r m s t a b l e t e s ts . A t e s t c a n b e r e g a r d e d a s s t a b l ei n t h e l o a d a n d t h e d e f o r m a t i o n c h a n g e s l o w l y d u r i n g t h ew h o l e t es t, i . e . w i t h o u t a n y s u d d e n ju m p . U n l e s s t h ec o m p l e t e l o a d - t i m e c u r v e i s r e c o r d e d th e c h e c k o f s t a b i l it ym u s t b e m a d e v i s u a l l y d u r in g t h e t e s t , as th e l o a d - d e f o r m a -t i o n c u r v e d o e s n o t a l w a y s r e v e a l a n i n s t a b i l it y.

I f th e t e s t in g m a c h i n e h a s n o c l o s e d - l o o p s e r v e c o n t r o lt h e r e q u i r e d s t if f ne s s i s a b o u t 1 0 k N / m m f o r t h e s m a l l e sts t a n d a r d b e a m . T h e c o r r e s p o n d i n g s t if f n e s s e s o f t h e l a rg e r

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Vol. 18 - N~ 106 - Ma t~riaux et Constructions

L e s r i g i d i t ~ s c o r r e s p o n d a n t a u x p l u s g r a n d e s d e s p o u -t r e s - ty p e s o n t r e s p e c t i v e m e n t d e I ' o rd r e d e 2 5 , 7 0 e t1 5 0 k N / m m . C e s n o m b r e s n ' i n d i q u e n t q u e I ' o rd r e d e g r a n -d e u r d e s r i g i d i t ~ s r e q u i s e s , d ' i m p o r t a n t e s v a r i a t i o n s p o u -v a n t s e p r o d u i r e s e l o n l e s p r o p r i ~ t 6 s d e s b ~ t o n s ~ t u d i ~ s .

C h a q u e f o i s q u ' o n r e n c o n t r e ra d e s d i ff i c u lt ~ s d a n s I ' o b -t en t ion de l a s t ab i l i t6 de I ' e s sa i , i l f aud ra u t i l i se r l e d~p lac e -m e n t d ' o u v e r t u r e d e s I ~ v r e s d e l a f i s s u r e c o m m e v a l e u r d ec o n t r6 1 e d u t a u x d e d ( ~ f o r m a t i o n .

4 . 2 . A p p u i s e t d i s p o s i t i f d e r a is e e n c h a r g e

L e s a p p u i s e t l e d i s p o s i t i f d e m i s e e n c h a rg e d o i v e n t~ t re t e ls q u e l e s y s t ~ m e m ~ c a n i q u e s o i t i s o s t a t i q u e ,c o n f o r m 6 m e n t ~ la f i g u r e 2 .

L ' (~nerg ie de ru p tu re se ra d~ du i t e de I ' (~qua t ion :

GF= Wo+m gSo)/Aiig[ N / m ( J i m 2 ) ] ,

Art icu la t ionsp~riclue

* 4

Fig, 2

4 . 3 . M e s u r e d e s d e f o r m a t i o n s

L a f l ~ c h e a u c e n t r e d e l a p o u t r e s e r a d 6 t e r m i n ~ e p a rr a p p o r t ~ u n e l i g n e d 6 f i n i e p a r d e u x p o i n t s d e l a p o u t r e

s i tu 6 s a u - d e s s u s d e s a p p u i s .L e d e p l a c e m e n t d u p o i n t d ' a p p l i c a t i o n d e la c h a r g e p e u t

~ g a l e m e n t ~ tr e m e s u r ~ p a r r a p p o r t & la l i g n e d ' a p p u i s i led i s p o s i t i f d ' a p p l i c a t i o n d e l a c h a rg e e t l e s a p p u i s s o n tc o n ? u s d e t e l le s o r t e q u ' e n c e s p o i n t s l e s d ~ f o r m a t i o n snon 61as t iques r es t en t in f~r ieures ~ 0 ,01 mm.

L e s d 6 p l a c e m e n t s s e r o n t m e s u r ~ s a v e c u n e p r e c i s i o n d e0 , 0 1 m m a u m o i n s .

avec :

W o = a i r e l i m i t 6 e p ar l a c o u r b e ( F, 6 ) , cf , f i g u r e 3 ( N m ) ;m = m l + 2 m 2 ( k g ) ;

r n t = m a s s e p r o p r e d e l a p o u t r e e n t r e a p p u i s , c a l c u l 6 ec o m m e la m a s s e t o t a l e m u l t i p l i 6 e p a r l e ra p p o r tIlL;

m 2 = m a s s e d e l a p a rt ie d u d i s p o s i t i f d e c h a r g e m e n t n o ns o l i d a i r e d e l a m a c h i n e d ' e s s a i s , m a i s s u i v a n t l a p o u t r ed a n s sa d 6 f o r m a t i o n ju s q u ' ~ l a r u p t u r e ;

g = a c c ~ l ( ~ r a t i o n d e l a p e s a n t e u r, 9 , 8 1 m / s 2 ;

5 o = f l ~ c h e I o r s d e l a r u p t u r e t o t a l e d e l a p o u t r e ( m ) ;

A i i g = a i r e d u l i g a m e n t , d ~ f i n i e p l u s h a u t ( m 2 ).

5 . P R O C E D U R E E X P E R I M E N T A L E

L ' e ss a i e s t e f fe c t u ~ & u n e v it e s s e d e d 6 f o r m a t i o n a p p r o x i -m a t i v e m e n t c o n s t a n t e , c h o i s ie d e t e l l e s o r te q u e l e m a x i -m u m d e c h a rg e s o i t a t t e i n t 3 0 ,~ 6 0 s e c o n d e s e n v i r o n a p r ~ sle d~bu t de I ' e s sa i . La f l~che au cen t re de l a pou t re e t l av a l e u r c o r r e s p o n d a n t e d e l a c h a rg e s o n t e n r e g i s tr ~ e s ju s -q u ' ~ c e q u e la p o u t r e s o i t c o m p l ~ t e m e n t p a r t a g ~ e e n d e u x .

D a n s l e c a s o e l a d ~ f o r m a t i o n n ' e s t p a s m e s u r ~ e d ir e c t e -m e n t s u r I ' ~ c h a n t i l l o n , i l e s t r e c o m m a n d ~ q u ' a v a n t I ' e n r e -g i s t re m e n t d e l a c o u r b e e f f o r t - d ~ f o r m a t i o n , l a c h a r g e s o i tc y c l ~ e t r o i s f o i s e n t r e 5 e t 2 5 d e la c h a rg e m a x i m a l ee s c o m p t ~ e .

L a c h a rg e d e v r a ~ t r e m e s u r ~ e a v e c u n e p r e c i s i o n d ' a um o i n s 2 d e l a v a l e u r m a x i m a l e e n r e g i s t r ~ e e n c o u r sd ' e s sa i .

D a n s l e c a d r e d e I ' e s s a i , l e p o i d s d e l a p o u t r e , d ' u n ep a r t , e t , d ' a u t r e p a r t , c e l u i d u d i s p o s i t i f d ' a p p l i c a t i o n d e l ac h a rg e n o n s o l i d a i r e d e l a m a c h i n e d ' e s s a i , s e r o n t d ~ t e r m i -n@s.

L ' a i re d u l i g a m e n t , A l i g s e r a 6 g a l e m e n t m e s u r ~ e . C e t t ea i r e e s t d 6 f i n i e c o m m e l a p r o j e c t i o n d e l a z o n e d e r u p t u r es u r u n p l a n p e r p e n d i c u l a i r e ~ la l ig n e m o y e n n e d e l ap o u t r e .

L a I o n g u e u r L d e la p o u t r e , t o u t c o m m e s a p o r t ~ e / ,s e r o n t m e s u r ~ e s a v e c u n e p r 6 c i s i o n d e 1 m m a u m o i n s .

6 . R E S U LTAT S

L a c o u r b e e f f o r t - d 6 f o r m a t i o n s e ra c o r r ig ~ e d e s ~ v e n t u e l -l es n o n l in ( } a ri t6 s a u x f a i b l e s c h a rg e s , c o m m e l e m o n t r e l af igu re 3 ( tr ac(~ en t i r e t s ) . L '~nerg ie W0, r ep r6sen t6ep a rI ' a ir e l i m i t ~ e p a r l a c o u r b e F - 6 , a i n s i q u e l a v a l e u r u l t i m ed e l a fl ~ c h e 6 0 l o t s d e l a r u p t u r e c o m p l e t e , s e r o n t m e s u r 6 e s .

2 8 8

7 . C O M P T E R E N D U D ' E S S A I

7 . 1 . I n f o r m a t i o n s i n d i s p e n s a b l e s & m e n t i o n n e rs y s -t ~ m a t i q u e m e n t d a n s l e c o r n p t e r e n d u d e s s a i

- - n u m 6 r o d ' i d e n t i f i c a t i o n d e I ' @ c h a n t i l lo n ;- d im en s ion s de 1 '6ch an t i l lon : b , d , L, / , A l ig ;- m ~ t h o d e d e f a b r i c a t io n d e I 'e n c o c h e ;- p o i d s d e I ' ~ c h a n t i l l o n ;- m a s s e m l ;- masse m2;- W 0 ;- 50;

- F m a x = c h a r g e m a x i m a l e a p p l i q u ~ e , m 2 n o n c o m p r i s e ;- p r e c i s i o n d e la m e s u r e d e s d ~ p l a c e m e n t s ;- m o y e n d e c o n t r b l e d e l a s t a b i l it ~ d e I ' e ss a i ;

F(char~e)

Fig. 3

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standard beams are about 25, 70, and 150 kN/ mm respecti-vely. These figures only indicate the order of magnitudeof t he required stiffnesses, and large variations may occurdepe ndin g on the properties of the tested concrete. Whene-ver there are problems in running the test in a stable way,crack mouth opening displacement shall be used as thecontrol value for deformation rate.

4.2. Supports a n d lo a d i n g a r r a n g e m e n t

The supports and loading arrangements shall be suchthat the forces acting on the beam are statically determi-nate, e. g. according to figure 2.

4 . 3 . D e f o r m a t i o n m e a s u r e m e n t

The deformation of the center of the beam shall bedetermined with regard to a line between two points onthe beam above the supports.

Alternatively the deformation of the load -poi nt with res-

pect to the support may be measured if the load-applica-tion and supports are arranged in such a way that non-elastic deformat ions at these points are less than 0.01 ram.

The deformation shall be measured with an accuracy ofat least 0.01 mm.

50-FMC Draft Recommendation

A BaJ_/_l

I

Fig. 2

where:

Wo = area according to figure 3 ( N/m) ;m = ml + 2m2 (kg);

ml weig ht of the beam between the supports, calcula-ted as the beam weight multiplied b y// L;

m2 = weight of the part of the loading arrangementwhich is not attached to the machine, but follows thebeam until failure;

g = acceleration due to gravity, 9.81 m/s2;

= deformation at the final failure of the beam (m);Allg = area of the ligam ent as define d above (m2).

5. PROCEDURE

The test is performed with an approximately constantrate of deformation, which is chosen so that the maximumload is reached within about 30-60 seconds after the start

of the test. The deformation of the center of the beam andthe corre sponding load are registered until t he beam iscompletely separated into two halves.

In case the deformation is not measured directly on thespecimen it is recommended that before measuring theload-defo rmation curve the load is cycled 3 times between5 and 25 of the expected maximum load.

The load shall be measured with an accuracy of at least2 of the maximum value in the test.

In connection with the test, the weigh t of the beam andthe weight of the part of the loading arrangement whichis not attached to the t esting machine shall be determined.

The area of t he ligament, AJig, shall be measured. It is

defined as the projection of the fracture zone on a planeperpendic ular to the beam axis.

The length L of the beam as well as the span / duringthe test shall be measured with an accuracy of at least 1mm.

6. TEST RESULTS

The load- deformatio n curve is corrected for eventualnon-l ineari ties at l ow loads, see dashed line in figu re 3.The energy Wo, represented by the area under the curve,is measured as well as the defor matio n 8o at final fracture.

The fracture energy is calculated from the equation:

GF = Wo + mgSo)/Alig [N/m (J/m2)],

7. TEST REPORT

7.1 . Bas ic in format ion , a lways to b e m e n t i o n e d int h e repor t

-identification number of specimen;

- dimensions of the specimen: b, d, L ,/ , Azig;-method of making the notch;-weight of the specimen;- weight /771;- weight m2;

Wo;

o ;

--Fmax = maximu m applie d load, exclud ing m2;

-accuracy of deformation measurements;- how the stabilit y has been checked;

F(toad)

~o

Fig. 3

6(def]

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V01. 18 - N~ 106 - M at6r iaux e t Construct ions

- o b s e r v a t i o n s s u r l a s t a b i l i t ~ d e I e s s a i ;F G .

7 . 2 . I n f o r m a t i o n s a d d i t i o n n e l l e s

- N a t u r e d u b ~ t o n ;

- N a t u r e d e s g r a n u l a t s ;

- Q u a n t i t 6 d e c im e n t e t c o m p o s i t i o n d u b 6 t o n ;- A g e d u b d t o n a u j o u r d e I e s s a i;

- R ~ s i s ta n c e ~ l a c o m p r e s s i o n , a v e c i n d i c a t i o n d e l am ~ t h o d e d (~ v a l u a ti o n d e c e t t e r 6 s i s ta n c e ;

- R 6 s i s t a n c e ~ la tr a c t io n , a v e c i n d i c a t i o n d e l am ~ t h o d e d ~ v a l u a t i o n d e c e t t e r ~ s i st a n c e ;

- M o d u l e d ~ l a s t i c it 6 I o n g i t u d i n a l e , a v e c i n d i c a t i o n d el a m 6 t h o d e d ~ v a l u a t i o n ;

- Dens i t6 ;

- To u t e c a r a c t ~ r i s t i q u e p a r t i c u l i~ r e o u o b s e r v a t i o n i n t 6 -r e s san te .

- o b s e r v e d i n d i c a t i o n s o f in s t a b i l i ty ;G F .

7 . 2 . A d d i t i o n a l i n f o r m a t i o n

- t y p e o f c o n c r e te ;

type o f c e m e n t ;

type o f a g g r e g a t e ;- c e m e n t c o n t e n t a n d m i x p r o p o r t i o n s o f c o n c r e te ;

a g e a t t e s t i n g ;

- c o m p r e s s i v e s t re n g t h , i n c l u d i n g m e t h o d o f d e t e r m i n a -t i o n ;

- t e n s i l e s t r e n g th , in c l u d i n g m e t h o d o f d e t e r m i n a t io n ;

- e l a s t i c m o d u l u s , i n c l u d i n g m e t h o d o f d e t e r m i n a t i o n ;

- d e n s i t y ;

- a n y u n u s u a l f e a t u r e s o r i n t e r e s t i n g o b s e r v a t i o n s .

29