Abstract:
In high rise structures, high strength concrete has been successfully used in various
countries across the world. High-strength concrete is used for resisting high
compressive load and improved strength. But, the Cement content of the mix
proportion for high-strength concrete is particularly high compared with
conventional concrete strength. On the other hand, the production of cement involves
the emission of large amounts of carbon-dioxide gas into the atmosphere; which
aggravates global warming. So, because of this adverse impact on the environment, it
needs to see another cementitious material. Fly ash is by product of coal burning,
such material are used as partial replacement of cement in high strength concrete
which reduce carbon-dioxide gas emission in to atmosphere and also minimizing the
negative impact on the environment which released from industrial waste disposal as
land fill. The objective of this study was to investigate the effect of fly ash on high
strength concrete properties.
Experimental laboratory tests were conducted. Slump height is measured to determine
the workability of fresh concrete. The Cube size is (150mmx150mmx150mm) which is
used for testing compressive strength for the age of 7, 14 and 28 days of curing. The
percentage replacement of cement with fly ash varies from 0% to 30% by the
increment of 5%. The total numbers of samples conducted are one hundred twenty six
(126).
The result of the study shows that the replacement of cement by fly ash up to10%
increases the slump values. However, the replacement of cement beyond 10% by fly
ash decreases the workability of fresh concrete. Regarding density and compressive
strength, the replacement of cement by fly ash decreased the density of concrete.
Besides, the compressive strength of concrete becomes improved and increased when
the cement is replaced by fly ash up to 10%. At the curing age of 28th days, the
concrete containing 5% and 10% fly ash as cement, gained 1.66% and 2.97% of
strength respectively. So, this study suggests that partial replacement of cement by fly
ash up to 10% increases the capacity of high strength concrete and workability of
fresh concrete, So that the optimum percentage of fly ash to replace cement is 10% for
high strength concrete.
