FIELD OF THE INVENTION
The present invention relates to a process of manufacturing concrete by blending
weld slag waste generated from various welding processes in power equipment
manufacturing plants with fine aggregate.
BACKGROUND OF THE INVENTION
Tubular components of boiler industries are fabricated using welding for
producing coils, super heaters, re-heater, economizers, water walls etc. Weld
slag is a by-product of the welding process. A substantial quantity of weld slag
waste is generated in manufacturing industries all over the world on regular
basis. As of now, the weld slag which is generated is being dumped as landfill
which involves transportation costs and causes environmental pollution. Due to
an unprecedented demand for fine aggregate i.e. natural sand, mining of river
sand in huge quantities is resorted to, causing undercutting and collapse of river
banks, the loss of adjacent land and/or structures, upstream erosion as a result
of an increase in channel slope and changes in flow velocity, downstream erosion
due to increased carrying capacity of the stream, downstream changes in
patterns of deposition and changes in channel bed and habitat type. Unplanned
mining and dredging activities, lead to stockpiling and an uncontrolled dumping
of the overburden including chemical/fuel spills and further causes reduced water
quality for downstream users, increased cost for downstream water treatment
plants and poisoning of aquatic life. Hence there is a need to innovate a novel
method of disposing the waste weld slag in an eco-friendly manner with
capability of having industrial application for example, making concrete mixture
with blending of suitable alternate material along with fine aggregate without
compromising the quality of concrete.

Indian patent 244063 provides a process for manufacture of concrete through
total replacement of sand by pond ash. The invention also provides a method for
effective recycling of the waste residue such as pond ash obtained from
combustion of coal. Further, the invention allows enhancing the strength of the
concrete formed by the total replacement of sand with pond ash through
effective utilization of particle packing and ratio adjustment.
US patent 6743287 describes a concrete in which the aggregate of sand and
stones are partially replaced by crushed glass. The sand fraction may be replaced
by a glass of grain size 0-5 mm, a non-alkali reactive mineral with grain size 0-5
mm or a combination thereof. The stone fraction may be replaced by glass of
grain size 5-20 mm. The concrete may further comprise silica dust, fly ash or
crushed slag.
US patent 5624491 teaches a method of using fly ash for cement in percentages
varying from 15% to 25%.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a process for producing
concrete that utilizes weld slag waste as a partial replacement to fine aggregate
by blending with fine aggregate in concrete.
Another object of the invention is to propose a process for producing concrete
that utilizes weld slag waste as a partial replacement to sand by blending with
fine aggregate in concrete, which possesses high compressive strength, flexural
strength, split tensile strength, modulus of elasticity and Poisson's ratio.

A further object at the invention is to propose a process for producing concrete
that utilizes weld slag waste as a partial replacement to sand by blending with
fine aggregate in concrete, which prevents environmental pollution due to
deposition of weld slag in open land by using it up in concrete.
A still object of the invention is to propose a process for producing concrete that
utilizes weld slag waste as a partial replacement to sand by blending with fine
aggregate in concrete, which reduces the cost of producing concrete.
SUMMARY OF THE INVENTION
Accordingly, there is provided a process for producing concrete that utilizes weld
slag waste as a partial replacement to fine aggregate by blending with fine
aggregate in concrete, comprising the steps of combining water, cement, fine
aggregate and coarse aggregate, the fine aggregate containing natural sand and
crushed weld slag of grain size less than 5mm in percentage varying from 10%
to 75% by weight of fine aggregate based on the availability of weld slag waste.
Further, the invention process allows economical and alternate way of disposing
the weld slag by utilizing it as fine aggregate in concrete. Hence according to one
aspect of the present invention, crushed weld slag waste is blended with sand as
the fine aggregate in the manufacture of concrete thereby reducing the
environment pollution due to deposition of weld slag waste as landfills and also
reduces the demand on natural resource i.e. sand. In another aspect, the
present invention provides a concrete material with necessary compressive
strength, flexural strength, split tensile strength, modulus of elasticity and
Poisson's ratio. Further, a reduction in cost of producing concrete is achieved.

Further objects features and advantages will become apparent from the following
description, claims and drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows a method of crushing weld slag waste for utilization as fine
aggregate
Figure 2a shows the weld slag waste as obtained from a machine, Figure 2b
shows the weld slag waste retained in 4.75mm sieve, Figure 2c shows the weld
slag passing through a 4.75mm sieve.
Table 1 shows the chemical composition of the weld slag as obtained by
sampling as per IS 2430-1986 and the analytical result obtained through known
method of inductively coupled plasma mass spectrometry
Table 2 shows a mix proportioning details (kg/m33) for a known control concrete
(CC) at different replacement levels of weld slag for fine aggregate namely
WS10, WS20, WS30, WS50 and WS75 containing 10%, 20%, 30%, 50% and
75% respectively.
Figure 3 shows a representative graph of variation of percentage passing with
grain size distribution for three representative samples of crushed Weld Slag
(WS1, WS2, WS3) (i.e. < 4.75mm sieve)
Figure 4 shows a variation in density for various mixes viz. WS10, WS20, WS30,
WS50, WS75 and CC.

Figure 5 shows a variation in compressive strength for various mixes viz. WS10,
WS20, WS30, WS50, WS75 and CC for 3rd, 7th and 28th day.
Figure 6 shows a variation in flexural strength for various mixes viz. WS10,
WS20, WS30, WS50, WS75 and CC for 3rd, 7th and 28th day.
Figure 7 shows a variation in split tensile strength for various mixes viz. WS10,
WS20, WS30, WS50, WS75 and CC for 3rd, 7th and 28th day.
Figure 8 shows a variation of modulus of elasticity for various mixes viz. WS10,
WS20, WS30, WS50, WS75 and CC for 28th day.
Figure 9 shows a variation of Poisson's ratio for various mixes viz. WS10, WS20,
WS30, WS50, WS75 and CC for 28th day.
Table 3 shows a cost comparison per cubic metre for a known control concrete
(CC) and weld slag Concrete.
DETAILED DESCRIPTION OF THE INVENTION
The process for manufacture of a concrete generally comprises combining
ingredients such as cement, fine aggregate, coarse aggregate and water in a
known ratio. The fine aggregate is usually sand. In the preferred embodiment of
the present invention, the weld slag waste from manufacturing industries is
blended with" the fine aggregate. The weld slag obtained is brittle and flaky and
is of about 5mm to 25mm m size (Figure 2a). Further, the said blending of the
weld slag waste involves utilizing the weld slag by grinding it into size less than
4.75mm by the process as shown in Figure 1 The samples were collected as per

IS 2430:1986 specifications for sampling from stock piles and tests were
conducted to determine the physical and chemical characteristics.
Chemical characterization of the weld slag waste samples indicate that properties
such as percentage content of silica, alumina, alkalis, oxides of iron, calcium and
magnesium are well within the allowable limits for use of the weld slag in the
production of concrete. Further, the weld slag samples were subjected to
physical characterization to determine the specific gravity and grain size
distribution. Specific gravity of weld slag was found to be 3.0. Figure 3 shows the
grading curves of three representative samples of weld slag. The physiochemical
characterization of the weld slag samples, shows that the characteristics are
comparable to sand and thereby enabling the weld slag waste to be blended with
natural fine aggregate in the cement concrete.
As the type M20 is the most common concrete used for industrial flooring and
building purposes, a mix design for the M20 is prepared as per IS 10262-2009
and the mix proportions are shown in Table 2. In the designed control concrete
(CC), fine aggregate is replaced at different percentage replacement levels with
the weld slag viz. 10% for WS10, 20% for WS20, 30% for WS30, 50% for WS50
and 75% for WS75. Concrete cubes, cylinders, flexure beams were cast and
tested as per the standard testing procedures as per IS 516:1959 and tested for
its performances.
Workability is an important parameter to establish the efficiency of the concrete
and normally measured by slump cone test. It has been found that when the
percentage of weld slag increases, the workability reduces slightly but is within
the design limits. The compressive strength, split tensile strength, flexural

strength, modulus of elasticity and Poisson's ratio were estimated for a time
duration of 3,7 and 28 days. From Figure 4, it is found that the density tends to
remain the same for various percentages of weld slag waste with a variation of
less than 1 %. Figure 5 shows that the compressive strength decreases with
increase in percentage of weld slag by as much as 16 % for WS75 mix which is
higher than the target mean strength required to be achieved on 28th day. Up to
WS30, the variation in compressive strength to that of CC, is negligible. From the
obtained test results, it is very clear that WS75 mix can be used for mass
concreting works. Figure 6 shows that the variation in flexural strength to that of
CC is nearly negligible. Even WS75 mix shows a higher flexural strength with an
increase by almost 5% than that of CC. Figure 7 shows that the split tensile
strength decreases with increase in weld slag content by as much as 30 % in the
case of WS75 mix. Up to WS30 mixes, the variation in split tensile strength to
that of CC is approximately 10%. The modulus of elasticity is much greater than
the prescribed value as per IS 456:2000 specifications and the Poisson's ratio is
also within the permissible limits for all the design mixes as shown n Figure 8
and Figure 9 respectively. Table 3 shows the cost analysis for designed concrete
mixes- it is found that Rs.259.15 per cubic meter of concrete is being saved over
and above the cost of CC for WS75. It also reduces the demand on natural
resources (sand) and space required for dumping the weld slag waste as landfill
thereby reducing impact on environment.
According to the present invention, a process for making cement concrete by
blending weld slag waste along with fine aggregate is disclosed, and the
produced concrete with considerable strength has been experimented
successfully for the given mix proportions. Further, the present invention also
provides effective and complete utilization of the waste product weld slag waste
generated from manufacturing industries which enables reduction in

environmental pollution. The percentage of weld slag replacement can be
decided based on the availability of the weld slag and the nature/importance of
the concrete structure. The use of weld slag also reduces the demand on natural
aggregate and the environmental impact due to excessive sand mining can be
avoided.

WE CLAIM
1. A process for producing concrete that utilizes weld slag waste as a partial
replacement to sand by blending with fine aggregate in concrete,
comprising the steps of combining water, cement, fine aggregate and
coarse aggregate, the fine aggregate containing natural sand and crushed
weld slag of grain size less than 5mm in percentage varying from 10% to
75% by weight of fine aggregate based on the availability of weld slag
waste.
2. The process as claimed in claim 1, wherein the weld slag is blended to a
size less than 4.75mm.
3. A process for producing concrete that utilizes weld slag waste as a partial
replacement to sand by blending with fine aggregate in concrete, as
substantially described and illustrated herein with reference to the
accompanying drawings.

ABSTRACT

The invention relates to a process for producing concrete that utilizes weld slag
waste as a partial replacement to sand by blending with fine aggregate in
concrete, comprising the steps of combining water, cement, fine aggregate and
coarse aggregate, the fine aggregate containing natural sand and crushed weld
slag of grain size less than 5mm in percentage varying from 10% to 75% by
weight of fine aggregate based on the availability of weld slag waste.