03-09-2014, 04:35 PM
HIGH PERFORMANCE CONCRETE WITH GGBS AND ROBO SAND
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Abstract
Concrete is a mixture of cement, fine aggregate, coarse aggregate and water. Concrete plays a vital role in the
development of infrastructure Viz., buildings, industrial structures, bridges and highways etc. leading to utilization
of large quantity of concrete. High Performance Concrete (HPC) is a concrete meeting special combinations of
performance and uniformity requirements that cannot be always achieved routinely by using conventional
constituents and normal mixing. This leads to examine the admixtures to improve the performance of the concrete.
On the other side, cost of concrete is attributed to the cost of its ingredients which is scarce and expensive, this
leading to usage of economically alternative materials in its production. This requirement is drawn the attention of
investigators to explore new replacements of ingredients of concrete.
The present paper focuses on investigating characteristics of M30 concrete with partial replacement of cement with
Ground Granulated Blastfurnace Slag (GGBS) and sand with the ROBO sand (crusher dust). The cubes and
cylinders are tested for both compressive and tensile strengths. It is found that by the partial replacement of cement
with GGBS and sand with ROBO sand helped in improving the strength of the concrete substantially compared to
normal mix concrete.
Introduction
Concrete is basically a mixture of cement, fine and coarse aggregates. High-performance concrete (HPC) conforms
to a set of standards above those of the most common applications, but not limited to strength. Some of the standards
are ease of placement, compaction without segregation, early age strength, permeability etc. The researchers have
done considerable work on replacing the cement with fly ash and blast furnace slag without affecting the strength.
River sand (Fine aggregate), which is one of the constituents used in the production of concrete, has become
expensive and scarce. So there is large demand for alternative materials.
The crusher dust produced from granite crushers is one of the alternative materials for river sand. The utilization of
crusher dust which can be called as ROBO sand has been accepted as a building material in the western countries.
Lot of research has been done regarding the crusher dust as alternative materials for river sand. Misra (1984) studied
the effect of complete replacement of sand by stone dust in the cement – sand mortar cubes. Ahmad et. al. (1989)
investigated by replacing sand with crusher sand (fine sand i.e. passing through 75µ). They found that the
compressive strength of concrete having constant slump decreased linearly with increase in percentage of very fine
sand. Similarly the slump of concrete is decreased when increasing the percentage of very fine sand. Sahu et al
(2003) reported significant increase in compressive strength, modulus of rupture and split tensile strength when 40%
of sand is replaced by quarry rock dust in concrete. Rajamane et al (2003) studied the properties of high
performance concrete with partial replacement of cement by GGBS. They found that the compressive strength of
concrete increased by 10.2 MPa at 28 days age compared to conventional concrete. Ilangovan et. al. (2008) studied
on the feasibility of the usage of quarry rock dust as hundred percent substitutes for natural sand in concrete. They
found that the compressive strength, flexural strength of concrete made of quarry rock dust is nearly 10% more than
the conventional concrete.
Ground Granulated Blast Furnace Slag (GGBS)
GGBS is obtained by quenching molten iron slag (a by-product
of iron and steel making) from a blast furnace in water or steam, to produce a glassy, granular product that is then
dried and ground into a fine powder. GGBS is used to make durable concrete structures in combination with
ordinary port land cement and/or other pozzolanic materials. GGBS has been widely used in Europe, and
increasingly in the United States and in Asia (particularly in Japan and Singapore) for its superiority in concrete
durability, extending the lifespan of buildings from fifty years to a hundred years. Use of GGBS significantly
reduces the risk of damages caused by alkali-silica reaction, higher resistance to chloride, and provides higher
resistance to attacks by sulfate and other chemicals. GGBS is procured from vizag steel plant (VSP). The fineness
modulus of GGBS using blaine’s fineness is 320 m2
/kg and other properties of GGBS given in Table
Test Specimens and test procedure
The concrete cubes of 150mm size, cylinders of size 150mm diameter and
300mm length were used as test specimens to determine the compressive strength of concrete and split tensile
strength of concrete for the both cases i.e. normal concrete and modified concrete. The ingredients of concrete were
thoroughly mixed till uniform consistency was achieved. The cubes and cylinders were compacted on a vibrating
table. The properties of fresh concrete were measured according to IS 1199 – 1959.
Conclusions
Based on the present and experimental investigation studies the following conclusions can be drawn
1. Compressive strength of concrete can be improved by using admixtures.
2. From the above experimental results it is proved that, ROBO sand can be used as alternative material for
the fine aggregate i.e. sand. Based on the results the compressive and split tensile strengths are increased as
the percentage of ROBO sand increased.
3. The percentage of increase in the compressive strength are 19.64 and 8.03% at the age of 7 and 28 days and
the percentage of increase in the split tensile strength is 1.83% at the age of 28 days, by replacing 30% of
sand with ROBO sand with 1.5% admixture.
4. GGBS can be used as one of the alternative material for the cement.
5. From the experimental results 50% of cement can be replaced with GGBS.
6. The percentage increase of compressive strength of concrete is 11.06 and 17.6% at the age of 7 and 28 days
by replacing 50% of cement with GGBS and 25% of sand with ROBO sand.