ABSTRACT
Figure 20 shows that the r e s u l t i n g curves f o r concrete with and without n a t u r a l sand are f a i r l y s i m i l a r i n shape and are d i s p l a c e d only s l i g h t l y i n r e l a t i o n to each other. Consequently, the e f f e c t of n a t u r a l sand on concrete compressive s t r e n g t h does not seem s i g n i f i c a n t . As w i l l be seen from F i g . 21, t h i s a p p l i e s i n the f i r s t p l a c e to n a t u r a l sand contents of l e s s than 700 kg/m3 . I n c r e a s i n g amounts of n a t u r a l sand produce an i n c r e a s e i n concrete strength, but t h i s i s not c l e a r l y seen i n the r e g r e s s i o n fu n c t i o n chosen.
