Void at the bottom surface of concrete cylinder indicates the condition of porous concrete. The bottom surface of concrete cylinder was dyed with color stamp pad . The dyed bottom surface was then dried, photographed and compared. The strength of concrete was also determined. This series us ed concretes with designed void ratios of 15%, 20% a n d 25%, flow values of 150, 190 and 230 mm; 1.0% SP; and vibrating energy of 90 kNm/m