ABSTRACT
T e s t s were a l s o made i n order to determine what e f f e c t the v a r i a t i o n i n q u a l i t y of the crushed b r i c k rubble has on the p r o p e r t i e s of the blocks produced from such rubble. Three concrete manufacturers produced concrete blocks with crushed b r i c k s using 320 kg/nr of C l a s s A b l a s t f u r n a c e s l a g cement. The d e s i r e d concrete s t r e n g t h c l a s s B was 22.5. In the course of three days' production, the 28 days' compressive s t r e n g t h of the concrete produced v a r i e d between 24.9 and 29.8 N/im . The standard d e v i a t i o n between the batches of the i n d i v i d u a l manufacturers was on average 2.4 N/nm . T h i s showed that the e f f e c t of d i f f e r e n t q u a l i t i e s of crushed masonry i s r e l a t i v e l y small and that the s c a t t e r of compressive s t r e n g t h r e s u l t s f o r r e c y c l e d b r i c k concrete i s not n e c e s s a r i l y g r e a t e r than when n a t u r a l aggregate i s used. 11.3 Problems i n p r a c t i c a l a p p l i c a t i o n s Cases of damage on b u i l d i n g s constructed with crushed b r i c k concrete i n B e r l i n a f t e r the Second World War and reported i n the 1980s must not lead to the disparagement of b u i l d i n g m a t e r i a l s made with b u i l d i n g rubble. There have always been v i o l a t i o n s of e s t a b l i s h e d r e g u l a t i o n s i n b u i l d i n g c o n s t r u c t i o n but, as the good s t a t e of the maj o r i t y of the bu i l d i n g s made of r u i n s - d e r i v e d concrete show, the damaged b u i l d i n g s are not t y p i c a l of s t r u c t u r e s made with b u i l d i n g rubble. Griin drew a t t e n t i o n (75) to c e r t a i n sources of de f e c t s i n the production of porous r u i n s - d e r i v e d rubble concrete. These r e f e r r e d p a r t i c u l a r l y to inadequate removal of i m p u r i t i e s , which occurred mainly i n smal l e r , badly equipped r e c y c l i n g i n s t a l l a t i o n s , and which were due to p r o c e s s i n g d e f e c t s which l e d to segregation and i n s u f f i c i e n t water for hydration of the cement paste.
