EFFECT OF FLY ASH AND SILICA FUME AS PARTIAL REPLACEMENTS OF CEMENT ON THE MECHANICAL PROPERTIES OF SELF‑COMPACTING CONCRETE

Abstract

Self-compacting concrete (SCC) is a type of concrete that can flow and fill molds without the need for mechanical compaction, thereby improving the overall efficiency of concrete construction projects. The use of fly ash and silica fume in SCC can improve its mechanical properties. Therefore, this study investigates the effect of partial cement replacement using 15% fly ash and 10% silica fume on the fresh and hardened properties of SCC. A total of 48 cylindrical specimens were prepared, consisting of 24 specimens for compressive strength testing and 24 specimens for tensile strength testing. Fresh concrete properties were evaluated using slump flow and V-funnel tests in accordance with ACI 237R-07, while compressive and tensile strengths were tested at curing ages of 7 and 28 days. The results showed that the addition of 15% fly ash increased the slump flow, while 10% silica fume reduced the slump flow due to higher water demand. In terms of mechanical properties, SCC mixtures containing fly ash and silica fume exhibited slightly lower compressive strength at 7 days. However, at 28 days, significant strength improvements were observed. The compressive strength increased by up to 17.75% in the mixture containing 10% silica fume, while the tensile strength showed a maximum increase of 7.50%. These findings indicate that silica fume, in particular, is highly effective in enhancing the long-term mechanical performance of SCC.