14-05-2013, 04:25 PM
EXPERIMENTAL INVESTIGATION ON HIGH PERFORMANCE CONCRETE USING SILICA FUME
EXPERIMENTAL INVESTIGATION.ppt (Size: 611 KB / Downloads: 119)
ABSTRACT
An experimental investigation has been carried out to study the effect of addition of an industrial waste product using Silica fume as a partial replacement to cement in various percentages and incorporating of GGBS on compressive strength and flexural strength of M60 grade concrete. The variables considered were various percentages of replacement of cement with silica fume of 0, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 35%, 45%, 55%, 65% with GGBS. Water cement ratio 0.35 and coarse aggregate of size 12.5mm is used.
From the experiment conducted by replacing the cement by GGBS and silica fume, it is found that the compressive strength values of the design mix are gradually decreased with the increase of the replacement of GGBS up to 45%. After the addition of 45% of (GGBS) Ground granulated blast furnace slag, the compressive strength keeps decreasing. It is also proposed that the replacement of the cement by 45% of GGBS is preferred for reinforced concrete works.
OBJECTIVE
The objectives of the present investigation are to get the thoroughness with the existing mix design procedures for high performance concrete by varying the percentage replacement of cement by SF (0-15%) at a constant dosage of super plasticizer based on BIS and ACI code methods of mix design procedure and available literatures on HPC.
Investigations were carried out on HPC mixes for M60 grade using 12.5mm maximum size of aggregates to ascertain the workability and the mechanical properties of the designed mixes and to find the optimum cement replacement by silica fume.
Hence in the present investigation more emphasis is given to study the HPC using SF and super plasticizer so as to achieve better concrete composites and also to encourage the increased use of SF to maintain ecology.
SILICA FUMES
Silica fume and fly ash ground granulated blast furnace slag are the well known industrial by products which are being extensively used as supplementary cementitious materials. Silica fume is a by product from the electric are furnaces used in the manufacture of silicon metal or silicon alloys
METHODOLOGY
According to Neville “HPC” is a concrete to fulfill specified purpose and no special mystery about it, no unusual ingredients or special equipments to be used. Concrete is a three phase composite material the first two phases being aggregates and bulk hydrated cement paste (HCP) and third being the “transition zone”. The transition zone is the interfacial region between the aggregate particles and bulk (HCP). It is the weakest link and if this is strengthened, then the strength and impermeability of the concrete are improved to greater extent. This is made possible by reducing w/b ratio and use silica fume. Silica fume improves the above properties by pozzolanic action and by reactive filler effect. Silica fume contains a very high percentage of amorphous silicon dioxide which reacts with large quantity of Ca(OH)2 produced during hydration of cement to form calcium silicate hydroxide (C-S-H) gel. This gives strength as well as improves durability. This is known as pozzolanic action. This results in well packed concrete mix. Due to pozzolanic action between silica fume and Ca(OH)2, the larger size crystals of Ca (OH)2 converts to crystal of C-S-H gel this is dense, leading to reduction in pore size. This effect along with the improved particle distribution results in reduction of the thickness of transition zone and leads to densely packed stronger and less permeable concrete.
TESTS ON HARDENED CONCRETE
For hardened concrete, cube compressive strengths tests on 150 mm size cubes at the age of 7 days, and 28 days have to carry as per IS : 516 – 1959. Also, compression strength and flexural tests on 150mm 300mm cylinders have to carry 7 days, and 28 days curing specimens as per IS specifications.
TESTS ON CUBES FOR COMPRESSIVE STRENGTH
In the design of concrete mixes, the compressive strength of concrete is generally the main target since it usually represents an overall picture of the quality of concrete. The compressive strength is the maximum load per unit area sustained by a concrete specimen before failure under compression. Since the strength development of concrete depends on both time and temperature it can be said the strength is a function of summation of product of time and temperature. This summation is called maturity of concrete.
The cube specimens cured as above are tested as per standard procedure after removal from the curing tank and allowed to a dry under shade. The cube specimens tested under micro processor based compression testing machine of 2000 KN capacity are tabulated.