BEHAVIOR OF SELF-COMPACTING CONCRETE USING PPC AND OPC WITH DIFFERENT PROPORTIONS OF FLY ASH

Abstract

Self compacting concrete has been playing vital role in the mass concreting nowadays especially in the structures where reinforcement used is very dense and in narrow tubular sections. This paper talks about its comparison in behavior using PPC and OPC with different proportions of fly ash in the mix which were taken as 15%, 25%, and 35% in place of cement. For one proportion, a set of 6 cubes was casted and the same was to be tested at 7 days and 28 days for strength. The temperature of sample cubes was kept constant at 24°C for the whole period. The mix design was done for M25 grade. The W/C ratio was kept constant at 0.45. The proportion of fine aggregates to coarse aggregates was kept at 70:30 and maximum size of aggregates was 20 mm. Total powder content was kept at 530 Kg/m 3 . The quantity of super plasticizer was kept at 450 ml for the samples which was 1% of the total volume. The properties were checked by conducting slump test, J-Ring Test, L-Box Test, V-funnel Test, and UBox Test with compressive strength test after 7 days and 28 days. The slump value was maximum for 35% replacement of cement with fly ash and lowest for 25% replacement in PPC mix whereas in OPC mix this value increased with increasing proportion of fly ash. V-funnel value was decreasing in both cases with increasing proportions of fly ash. J-ring value was highest for 25% replacement in both cases. U-box value was maximum for 25% replacement in both cases and showed almost the same trend. Lbox value was lowest for 25% replacement in both cases and showed the same trend as in U-box test. The most important compressive strength test showed very surprising results. Only 15% replacement samples showed characteristic strength after 7 and 28 days whereas 25 % replacement samples gained only 55% of desired strength and 35% replacement samples gained only 33% of desired strength after 7 days and gained 92% and 80% of desired strength after 28 days respectively in PPC samples. The similar tests conducted on OPC samples showed the same pattern but overall strength gain was higher than PPC samples and the margin was spectacularly high ranging between 40%-60%.