Effect of silica fume on the mechanical properties of crushed brick concrete

Abstract

This paper presents an experimental investigation on the effect of silica fume on the
mechanical properties of concrete obtained by replacing 50% of weight of stone aggregate by
crushed clay-brick. The only variable considered in this study was the dosage of silica which
it is a percent of cement weight, the percent values of replacement silica fume are (0%, 2%,
4%, 6%, and 8%) of cement weight. The comparative study is focus on the effect of the silica
fume on this type of concrete not the effect of replacement of crushed brick. The added silica
fume has active effect on the strength of crushed brick concrete. The effect of using silica
fume on compressive strength is different for the different replacement of silica fume and it is
more active for the 2% replacement at 7 days age, while the replacement that yield best
enhancement at 28 days is 4%. The compressive strength for 28 days age is about 27.5
MPa,29.5 MPa, 38.5 MPa,31.4MPa, and 10MPa,for (0%, 2%,4%,6%, and8%) of replacement
silica percent.Furthermorethe bestincreasing in tensile strength is at 2%while there is a
smallgradually increasing in gain in modulus of rupture with using silica fumeuntil 6%, which
beyond the least value it starts to drop.The highlevel which is observed in this study beyond
6% reducesthe gain in strength of compressive at 28 days and it gets a compressive strength
less than the control value at 7 days. Furthermore it gets a reduction in tensile strength and
modulus of rupturein at 28days