16-09-2016, 10:17 AM
Utilization of Industrial Waste Slag as Aggregate in
Concrete Applications by Adopting Taguchi’s Approach for
Optimization
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ABSTRACT
This paper presents result of an experimental investigation carried out to evaluate effects of replacing aggregates
(coarse & fine) with that of Slag (Crystallized & Granular) which is an industrial waste by-product on concrete strength
properties by using Taguchi’s approach of optimization. Whole study was done in three phases, in the first phase natural
coarse aggregate was replaced by crystallized slag coarse aggregate keeping fine aggregate (natural sand) common in
all the mixes, in the second phase fine aggregate (natural sand) was replaced by granular slag keeping natural coarse
aggregate common in all the mixes and in the third phase both the aggregates were replaced by crystallized & granular
aggregates. The study concluded that compressive strength of concrete improved almost all the % replacements of normal
crushed coarse aggregate with crystallized slag by 5% to 7%. In case of replacements of fine aggregate and both
type of aggregates, the strength improvements were notably noticed at 30% to 50% replacement level. It could also be
said that full substitution of slag aggregate with normal crushed coarse aggregate improved the flexure and split tensile
strength by 6% to 8% at all replacements and in case of replacing fine aggregate & both the aggregates( Fine & coarse)
with slag, the strength improvement was at 30% to 50% replacements. It is evident from the investigation that Taguchi
approach for optimization helped in indentifying the factors affecting the final outcomes. Based on the overall observations,
it could be recommended that Slag could be effectively utilized as coarse & fine aggregates in all concrete applications.
Introduction
The proper use of waste materials fundamentally affects
our economy and environment. Over a period of time
waste management has become one of the most complex
and challenging problems in India affecting the environment.
The rapid growth of industrialization gave birth to
numerous kinds of waste byproducts which are environmentally
hazard and create problems of storage. The
construction industry has always been at forefront in
consuming these waste products. The consumption of
Slag which is waste generated by steel industry, in concrete
not only helps in reducing green house gases but
also helps in making environmentally friendly material.
During the production of iron and steel, fluxes (limestone
and/or dolomite) are charged into blast furnace along
with coke for fuel. The coke is combusted to produce
carbon monoxide, which reduces iron ore into molten
iron product. Fluxing agents separate impurities and slag
is produced during separation of molten steel. Slag is a
nonmetallic inert byproduct primarily consists of silicates, aluminosilicates, and calcium-alumina-silicates. The molten
slag which absorbs much of the sulfur from the
charge comprises about 20 percent by mass of iron production.
The schematic production details of Slag are
shown in Figure 1.
2. Research Significance in Indian Context
The availability of good quality aggregates is depleting
day by day due to tremendous growth in Indian construction
industry. Aggregates are the main ingredient of
concrete occupying approximately 75% of its volume
and directly affecting the fresh & hardened properties.
Concrete being the largest man made material used on
earth is continuously requiring good quality of aggregates
in large volumes. A need was felt to identify potential
alternative source of aggregate to fulfill the future
growth aspiration of Indian construction industry. Use of
slag as aggregates provides great opportunity to utilize
this waste material as an alternative to normally available
aggregates. The total steel production in India is about 72.20 Million Tones and the waste generated annually is
around 18 Million Tones (considerably higher than the
world average) but hardly 25% are being used mostly in
cement production (information source, Source, world
steel association 2011 data, J. P. Morgan Ernst & Young
analysis).
3. Literature Review
Reviews of literature survey are presented as below,
Chen Meizhu, Zhou Mingkai, Wu Shaopeng, 2007 [1]
worked on mortar made up of ground granulated blast
furnace, gypsum, clinker and steel slag sand. The experimental
results show the application of steel slag sand
may reduce the dosage of cement clinker and increase the
content of industrial waste product using steel slag sand.
Isa Yuksel, Omer Ozkan, Turhan Bilir, 2006 [2] experimented
use of non ground granulated blast furnace
slag as fine aggregate in concrete. The study concluded
that the ratio of GGBs/sand is governing criteria for the
effects on the strength and durability characteristics.
Juan M. Manso, et al., 2004 [3] carried out work in
laboratory to produce concrete with good properties using
oxidizing EAF slag as fine and coarse aggregate. The
concrete was tested for durability characteristics like
soundness, leaching test, accelerated ageing test etc. The
durability of the EAF slag concrete was found to be acceptable,
especially in the geographical region for which
its use was proposed, where the winter temperature
hardly ever falls below 32˚F (0˚C).
Keun Hyeok Yang, Jin Kyu Song, Jae-Sam Lee, 2010
[4] studied alkali activated mortars and concrete using light weight aggregates. Test results showed that the
compressive strength of alkali activated mortar decreased
linearly with the increase of replacement level of light
weight fine aggregate regardless of the water binder ratio.
Li Yun-feng, Yao Yan, Wang Liang, 2009 [5] investtigated
effects of steel slag powder on the workability
and mechanical properties of concrete. Experimental
results show that mechanical properties can be improved
further due to the synergistic effect and mutual activation
when compound mineral admixtures with steel slag
powder and blast furnace slag powder mixed in concrete.
Lun Yunxia, Zhou Mingkai, Cai Xiao, Xu Fang, 2008
[6] used steel slag as fine aggregate for enhancing the
volume stability of mortar. Experimental results indicated
that powder ratio, content of free lime and rate of
linear expansion can express the improvement in volume
stability of different treated methods. Autoclave treatment
process is found more effective steam treatment
process on enhancement of volume stability of steel slag.
L. Zeghichi, 2006 [7] experimented on substitution of
sand by GBF crystallized slag. Tests carried out on cubes
of concrete showed the effect of the substituting part of
sand by granulated slag (30%, 50%) and the total substitution
on the development of compressive strength.
Compressive strength test results at 3, 7, 28, 60 days and
5 months of hardening concluded that the total substitution
of natural coarse aggregate with crystallized slag
affects positively on tensile, flexural and compressive
strength of concrete. The partial substitution of natural
aggregate with slag aggregates permits a gain of strength
at long term but entire substitution of natural aggregates affects negatively the strength (a loss in strength of
38%).
Saud Al-Otaibi, 2008 [8] studied use of recycling steel
mill as fine aggregate in cement mortars. The replacement
of 40% steel mill scale with that of fine aggregate
increased compressive strength by 40%, drying shrinkage
was lower when using steel mill scale.
Sean Monkman, Yixin Shao, Caijun Shi, 2009 [9] investigated
the possibility of using a carbonated LF slag
as a fine aggregate in concrete. The slag was treated with
CO2 to reduce the free lime content while binding gaseous
CO2 into solid carbonates. The carbonated LF slag
was used as a fine aggregate in zero-slump press-formed
compact mortar samples and compare to similar samples
containing control river sand. The 28-day strengths of the
mortars made with the carbonated slag sand were comparable
to the strengths of the normal river sand mortars.
The carbonation of LF slag was found to be suitable for
use as a fine aggregate. Significant amounts of carbon
sequestration could be realized in a potentially useful
form that further utilizes a waste slag material. Carbonated
mortars that used LF slag sand offer the largest
gains in terms of CO2uptake.
Tarun R Naik, Shiw S Singh, Mathew P Tharaniyil,
Robert B Wendfort, 1996 [10] investigated application of
foundry by-product materials in manufacture of concrete
and masonry products. Compressive strength of
concrete decreased slightly due to the replacement of
regular coarse aggregate with foundry slag however
strengths were appropriate for structural concrete.