STUDY ON DURABILITY OF FLYASH CONCRETE



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INTRODUCTION

Fly ash is a byproduct of coal burning power plants - the ash that flies up their
smokestacks and gets captured in giant filters. It can be used to produce stronger, more
durable and more environmentally friendly concrete. When used in concrete, fly ash acts like
cement, and actually replaces a percentage of the Portland cement normally used. Concrete
with high percentages of fly ash looks and finishes the same as regular concrete, with a few
minor adjustments. Fly ash already replaces around 15% of cement in much of the concrete
used today, but we can do much better by using it to replace 50% or more.


EXPERIMENTAL PROGRAMME
MATERIALS USED

Ordinary Portland Cement (OPC) available in the market conforming to IS 12269 – 1987
was used for casting the specimens. Locally available river sand in dry condition was
used for the preparation of specimens. The grading of sand conforms to Zone-II as per IS
383 – 1970. The specific gravity sand was 2.61 and fineness modulus value was 2.642.
The loose and compacted bulk density values of sand were 1633 and 1765 kg/m3,
respectively.


MIX PROPORTIONING

It is the process of selecting suitable ingredients of concrete and determining their
relative quantities with the purpose of producing economical concrete. The mix
proportion of 1: 1.49: 3.26 [W/C = 0.50] and 1: 1.36: 2.09 [W/C = 0.42], respectively
for the controlled concrete of M20 and M40 grades were arrived as per the specifications
and used throughout the study. Fly ash concrete mixtures were then proportioned by
replacing 10%,20%,30% and 40% of cement with Ennore fly ash ( Class F ) and the
volume of concrete was adjusted by reducing the sand content

PREPARATION OF THE TEST SPECIMENS

A tilting type mixture machine was used to mix the ingredients of concrete mixtures.
Steel moulds were used to cast the specimens and table vibrator was employed to
compact the concrete in the moulds. Curing was started immediately after top surface of
concrete in the moulds became hard and devoid of free water, by covering the moulds
with wet gunny clothes. At the age of about 24 hours after casting, the specimens were
demoulded and kept submerged in water tank for curing till testing.