Flexural Behaviour of Self Curing Concrete with partial replacement of Cement by Silica Fume

Abstract

Scarcity of potable water increases day by day. The use of self curing agent is very important from the point
view that water resources are getting valuable every day. Curing of concrete means maintaining moisture inside the body
of concrete during the early days and beyond in order to develop the desired properties in terms of strength & durability.
A good curing practice involves keeping the concrete damp until the concrete is strong enough to do its job.
This study investigated the strength properties of Silica fume concrete. This work primarily deals with the strength
characteristics such as compressive, Split tensile and flexural strength. Self curing concrete a set of different concrete
mixture were cast and tested with different cement replacement levels (0%, 2.5%, 5%, 7.5% & 10% ) of Silica Fume (SF)
by wt of Cement and/or each trial super plasticizer has been added at constant values to achieve a constant range of
slump for desired work ability with a constant water-binder (w/b) ratio of 0.42 for M40 Grade & 0.39 for M60 Grade.
Specimens were produced and cured in a curing tank for 3, 7, 14 and 28 days for normal concrete and at room
temperature for Self curing concrete. The cubes were subjected to compressive strength tests after density determination
at 3,7,14 and 28 days respectively. The chemical composition and physical composition of Silica Fume and cement were
determined. The density of the concrete decreased with increased in percentage of Silica Fume replacement between
10% to 20% led to a reduction in the compressive strength of hardened concrete. This study has shown that between
7.5% to 10% replacement levels, concrete will develop strength sufficient for construction purposes. Its use will lead to a
reduction in cement quantity required for construction purposes and hence sustainability in the construction industry as
well as aid economic construction.
This project consists of two stages. In the first stage, the effect of PEG400 on compressive strength by varying the
percentage of PEG400 by weight of cement from 0% to 2% were studied for M40, M60 mix. It was found that 0.5% of
PEG400 by weight of cement was optimum for M40, M60 grade concrete respectively, for achieving maximum strength
without compromising on workability.
And in the second stage, a comparative study on flexural strength of beams with normal and self curing concretes for
M40, M60 concrete beams of sizes 0.1X0.15X1.2m, 0.1X0.2X1.2m for over reinforced, under reinforced sections are
found at the age of 30days.
A research study conducted to evaluate the flexural behaviour of self curing structural concrete. Testing of the materials
were done as per relevant IS codes, preparation of materials, weighing of materials and casting of cubes and mixing,
compacting and curing of concrete are done according to IS 516: 1959. The plain samples of cubes were cured for 28
days in water pond and the specimens with PEG400 were cured for 28 days at room temperature by placing them in
shade. Then, the reinforced concrete beams were casted for finding out the flexural behaviour of normally cured
concrete and self curing concrete.
In this project, the results indicated that use of PEG400 during mixing of concrete with 7.5% of silicafume
replacement improved the performance of concrete considerably.