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INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING

Volume 3, No 1, 2012

© Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0

Research article ISSN 0976 – 4399

Received on March, 2012 Published on August 2012 117

Experimental investigation of using slag as an alternative to normal

aggregates (coarse and fine) in concrete Mohammed Nadeem

1, Arun D. Pofale

2

1- Research scholar, Civil engineering department, Visvesvaraya National Institute of

Technology, Nagpur, India

2- Professor, Civil engineering department, Visvesvaraya National Institute of Technology,

Nagpur, India

[email protected]

doi:10.6088/ijcser.201203013011

ABSTRACT

These paper present results of experimental investigations carried out to evaluate effects of

replacing aggregate (coarse and fine) with that of slag on various concrete properties. The

basic objective of this study was to identify alternative source of good quality aggregates

which is depleting very fast due to the fast pace of construction activities in India. Use of slag

- a waste industrial byproduct of iron and steel production provides great opportunity to

utilize it as an alternative to normally available aggregates (coarse and fine). In this study,

concrete of M20, M30 and M40 grades were considered for a W/C ratio of 0.55, 0.45 and

0.40 respectively for the replacements of 0, 30, 50, 70 and 100% of aggregates (Coarse and

Fine) by slag. Whole study was done in two phases, i.e. replacement of normal crushed

coarse aggregate with crystallized slag and replacement of natural fine aggregate with

granular slag. The investigation revealed improvement in compressive strength, split tensile

and flexure strength over control mixes by 4 to 8 %. The replacement of 100 % slag

aggregate (coarse) increased concrete density by about 5 to 7 % compared to control mix.

Based on the overall observations, it could be recommended that slag could be effectively

utilized as coarse and fine aggregates in all the concrete applications.

Keywords: Slag aggregate, fine aggregate replacement, alternative materials for concrete.

1. Introduction

Sustainable construction mainly aims at reduction of negative environmental impact resulted

by construction industry which is the largest consumer of natural resources. Over a period of

time, waste management has become one of the most complex and challenging problem in

the world which is affecting the environment. The rapid growth of industrialization gave birth

to numerous kinds of waste byproducts which are environmentally hazard and creates

problems of storage. Always, construction industry has been at forefront in consuming these

waste products in large quantities. The consumption of Slag 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 as shown in figure 1. Slag is a nonmetallic inert

waste byproduct primarily consists of silicates, alumino silicates, 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. Presently, total steel production in India is about 72.20

Experimental investigation of using slag as an alternative to normal aggregates (coarse and fine) in concrete

Mohammed Nadeem, Arun D. Pofale

International Journal of Civil and Structural Engineering

Volume 3 Issue 1 2012

118

Million Metric Tonnes and the waste generated annually is around 18 Million Metric Tonnes but

hardly 25 % is being used mostly in cement production.

Figure 1: General Schematic view of blast furnace operation and Slag production

1.1 Study scope

In this study, concrete of M20, M30 and M40 grades were considered for a W/C ratio of 0.55,

0.45 and 0.40 respectively with the targeted slump of 100±25 mm for the replacement of 0,

30, 50, 70 and 100 % of normal crushed coarse aggregate and fine aggregate with that of slag

aggregates(Crystallized and granular). These concrete mixes were studied for the properties

like density, workability (slump and compaction factor), compressive, split tensile and

flexure strengths.

2. Experimental investigation

2.1 Raw materials

In this investigation, Slag from local steel making plant, normal crushed coarse aggregate

from Panchgaon Basalt query, natural sand from Kanhan river and Portland Pozzolana

cement were used as shown in Figure 2and3. All the chemical and physical properties of the

materials are given in the table 1.

Table 1: Physical and chemical properties of materials

Slag (Crystallized) Natural

Aggregate

Natural Sand

Chemical Analysis Physical Properties Physical

Properties

Physical

Properties

Constituents (%) Specific

Gravity

3.28 2.85 2.65

Loss on

Ignition

4.00 Water

Absorption

0.44% 0.55% 0.65%

Silica 10.80 Dry loose bulk 1452 1322 Kg/cum 1468 Kg/cum





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density Kg/cum

R2O3 33.60 Soundness 0.50% 0.55% 0.90%

Fe2O3 15.97 Fineness

modulus.

- - 2.64

Al2O3 17.63 Zone - - II

Cao 30.20 Silt (Volume) - - 2%

MgO 7.02 Abrasion Value

(%)

20.8 22 -

SO2 0.54 Impact Value

(%)

13.79 16 -

Insoluble

matters

11.00 Crushing Value

(%)

25.47 23 -

Slag (Granular)

Chemical Analysis Physical Properties

Constituents (%) Specific Gravity 2.38

LOI 1.80 Specific Gravity 0.39%

Silica 30.20 Water Absorption 1058 Kg/cum

R2O3 20.20 Dry loose bulk

density

0.90%

Fe2O3 0.60 Soundness 3.14

Al2O3 19.60 Fineness modulus. I

Cao 32.40 Zone 1.38 %

MgO 9.26

SO2 0.27

Insoluble matters 0.80

Cement-Portland Pozzolana Cement –IS 1489 –(Part 1) 1991

Physical Properties Chemical Properties

Specific Surface 380 m2/kg Total Loss on

Ignition

1.40%

Setting time – Initial 195 minutes Magnesia 1.40%

Setting time – Final 280 minutes Sulphuric

Anhydride

2.06%

Soundness-Le-chatelier 0.50 mm Insoluble residue 26.0%

Auto Clave 0.06%

Compressive strength –

3days

34.9 Mpa

7 days 44.2 Mpa

28 days 61.4 Mpa

Chloride 0.04%

Fly ash 28%

Figure 2: Aggregate gradation of normal crushed, slag aggregate, natural sand





120

Figure 3: View of slag, normal crushed coarse aggregate and natural sand

2.2 Mix proportions

The mix proportions were made for a control mix of slump 100 ± 25 mm for M20, M30 and

M40 grade of concrete for w/c ratio of 0.55, 0.45 and 0.40 respectively by using IS-10262-

2009 method of mix design. For each grade of concrete, total five mixes were made by

replacing normal crushed coarse aggregate and fine aggregate with Slag keeping w/c ratio as

constant (control mix) by 0, 30, 50, 70 and 100 % replacements given in table 2.

Table 2: Replacement proportions of aggregates

Mix No. Normal Crushed

Coarse Aggregate -

%

Slag aggregate-% Natural sand-

%

Slag sand-%

Replacement of Coarse aggregate

1 100 0 100 0

2 70 30 100 0

3 50 50 100 0

4 30 70 100 0

5 0 100 100 0

Replacement of Natural Sand

2 100 0 70 30

3 100 0 50 50

4 100 0 30 70

5 100 0 0 100

Table 3 provides mix proportions details for control mixes of M20, M30 and M40 grade.

Table 3: Mix proportions of control mixes

Mix Proportions of Control Mixes

Ingredients (Kg/cum) M20 M30 M40

Cement 348 362 407

Water (W/C ratio, 0.55,0.45 and0.40) 192 163 163

Mass of normal coarse aggregate 1187 1225 1198

Mass of fine aggregate 725 748 731

Super Plasticizer (PC based) 0.00 2.17 3.26

Total Weight 2452 2500 2502





121

2.3 Test set-up

The 100 mm cubes (set of 3) each were cast for compressive (7, 28, 56, 91 and 119 days),

split strength (7 and 28 days) and 100 mm beam mould for flexure strength (7 and 28 days).

After the cast, all the test specimens were finished with a steel trowel and immediately

covered with plastic sheet to minimize the moisture loss. All the cubes were de-mould after

24 hours time and put into the water tank for curing maintaining temperature of 27±2 oC as

per IS requirements as shown in figure 4.

Figure 4: Concreting test set-up

2.4 Fresh Concrete Properties

The concrete was tested for slump cone test, compaction factor test and wet density as per the

IS-1199 –Methods of sampling and analysis of concrete, for each mix of concrete shown in

figure 5.

Figure 5: Concrete workability measurement

3.5 Hardened concrete properties

Figure 6: Test set-up of concrete testing





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The set of 100 mm cubes (3 nos.) were tested for compressive strength at 7, 28, 56, 91 and

119 days. Similarly, 100 mm cubes and 100x100x500 mm beams were tested for split tensile

and flexure strength respectively after 7 and 28 days time as per the IS-516-1991 – Methods

of test of strength of concrete shown in figure 6.

3. Results and discussion

3.1 Compressive strength with coarse aggregate replacements

Compressive strength of concrete mixes of M20, M30 and M40 grade made by 0, 30, 50, 70

and 100% replacement of corase aggregate with slag aggregate was tested after 7, 28, 56, 91

and 119 days of curing for the w/c ratio of 0.55, 0.45 and 0.40 respectively. The results

indicated that compressive strength was higher by 2 to 4% in all the mixes at all ages. The

strength improvement was notably observed at 100% replacement level in the range of 5 to

7% compared to the control mix. The improvement was due to good adhesion between

crystallized slag aggregate and cement paste due to rough surface of slag aggregate as shown

in figure 7.

Figure 7: Concrete compressive strength

3.2 Compressive strength with fine aggregate replacements

The results indicated that compressive strength was higher by 4 to 6% in all the mixes at all

ages for the replacement level inbetween 30 to 50%. Strength reduction was observed at

100% replacements of fine aggregate with granular slag by 7 to 10% which was attributed

due to coarser particles affected on cohesive properties of concrete as shown in figure 8.

Figure 8: Concrete compressive strength





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3.3 Split tensile and flexure strengths with coarse aggregate replacements

The split tensile and flexure strength at 7 and 28 days time for all the concrete mixes gave

higher results in the range of 6 to 8% over control mixes at all ages. The increase in strength

was due to the excellent rugosity of slag aggregate which ensured strong bonding and

adhesion between aggregate particles and cement paste as shown in figure 9.

Figure 9: Concrete split tensile and flexure strength

3.4 Split tensile and flexure strengths with fine aggregate replacements

The split tensile and flexure strengths found improved by 5 to 6% at 30 to 50% replacement

levels but it reduced by 6 to 8% at 100% replacements as shown in figure 10.

Figure 10: Concrete split tensile and flexure strength





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3.5 Co-relation between flexure and split tensile strengths

The co-relation between flexure and split tensile strengths at the age of 28 days were drawn

for M20, M30 and M40 grade concrete at 0, 30, 50, 70 and 100% replacement of normal

crushed aggregate, fine aggregate with slag shown in figure 11.

Figure 11: Co-relation between flexure and split tensile strength

The co-relation equation indicates a linear relation between both the parameters as indicted in

table 4.

Table 4: Co-relation between flexure and split tensile strength

Sr. No. Grade Flexure ∞ split strength co-relation

equations

Replacmenet with coarse aggregate

1. M20 Grade Y= 1.484 x – 0.575, R2 = 0.964

2. M30 Grade Y= 1.293 x- 0.658, R2 = 0.955

3. M40 Grade Y= 1.341 x –0.971, R2 = 0.973

Replacmenet with fine aggregate

1. M20 Grade Y= 1.141 x + 0.316, R2 = 0.890

2. M30 Grade Y= 1.130 x - 0.050, R2 = 0.758

3. M40 Grade Y= 1.234 x –0.459, R2 = 0.979

4.6 Workability

The workability of concrete decreased from 0% to 100% replacement level in M20 grade

concrete by about 33% but in M30 and M40 grade of concrete it improved upto 30 to 50%

replacement level and later dropped at 100% replacements by about 8% in case of replacing

coarse aggregate with slag. The phenomenon could be due to the rough surface of slag

aggregated requiring more finer material to overcome the frictional forces. The workability

improved in higher grades of concrete (M30 and M40) due to potential availability of finer





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materials. In case of replacing fine aggregate with slag the workability improved upto 50%

replacement level by 20% and later dropped at 100% replacement level as shown in figure 12.

Figure 12: Workability – Coarse and Fine aggregates (Slump – mm)

3.7 Concrete density

The bulk density of slag aggregate was found to be 9.83% higher than normal crushed

aggregate which enhanced density of concrete. The concrete density was higher by 5 to 7%

than control mix concrete using slag aggregate. The highest density was found in M30 grade

of concrete at 100% replacement of slag aggregate. The bulk density of granular slag is 27%

lighter than naturally fine aggregate which was reflected in the concrete density also by 3%

as shown in figure 12.

Figure 12: Concrete density by replacing coarse and fine aggregates with Slag





126

5. Summary and conclusions

The conclusions are drawn as below,

1. The study concluded that compressive strength of concrete improved by 4 to7 % at all

the % replacements of normal crushed coarse aggregate with crystallized slag. In case

of replacements of fine aggregate, the strength improvements was notably observed at

30 to 50 % replacement level by 4 to 6%.

2. It could be said that full substitution of slag aggregate with normal crushed coarse

aggregate improved the flexure and split tensile strength at all replacements by 6 to

8% and in case of replacing fine aggregate with slag, the strength improvement was at

30 to 50 % replacement levels by 5 to 6%.

3. The workability of concrete decreased with 100% replacements of normal crushed

coarse aggregate with slag aggregate by about 30% in M20 grade and about 8 % in

M30 and M40 grade of concrete compared to control mix of concrete. The drop in

workability could be attributed to porous and rough surface of slag aggregate which

improved in higher grade of concrete due to availability of finer contents.The

workability improved by 20% by replacing fine aggregate with granular slag upto

50% replacement level.

4. It could be said that 100% replacements of crushed coarse aggregate with crstalised

slag enhanced concrete density by 5 to 7% in all the concrete mixes and reduces

concrete density by 3 % in case of replacing fine aggregate with granular slag. The

improvement in density was due to the higher unit weight of Crystallized slag

aggregate which is 9% heavier than natural aggregate.

Hence, it could be recommended that slag aggregate could be effectively utilized as coarse

and fine aggregate in all concrete applications either as partial or full replacements of normal

crushed coarse and natural fine aggregates.

6. References

1. Isa Yuksel, Omer Ozkan, turhan Bilir. (2006), Use of granulated blast furnace slag in

concrete as fine aggregate, ACI materials journal, May-June, pp 203-208.

2. Isa yuksel, Ayten Genc, (2007), Properties of concrete containing nonground ash and

slag as fine aggregate, ACI materials journal, July-August, pp 397-403.

3. Juan M. Manso, Javier J. Gonzalez, Juan A. Polanco, (2004), Electric arc furnace slag

in concrete, Journal Of Materials In Civil Engineering, November/December, pp 639-

645.

4. Keun Hyeok Yang, Jin Kyu Song, Jae-Sam Lee, (2010), Properties of alkali activated

mortar and concrete using lightweight aggregates, Materials and structures, 43, pp

403-416.

5. Li Yun-feng, Yao Yan, Wang Liang, (2009), Recycling of industrial waste and

performance of steel slag green concrete, Journal of Central South university of

technology, 16, pp 768-773.





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6. Lun Yunxia, Zhou Mingkai, Cai Xiao, Xu Fang, (2008), Methods for improving

volume stability of steel slag as fine aggregate, Journal of Wuhan University of

Technology-Material science edition, October, pp 737-742.

7. L. Zeghichi, (2006), The effect of replacement of naturals aggregates by Slag products

on the strength of concrete, Asian Journal of Civil Engineering (Building and

Housing), 7, pp 27-35.

8. Tarun R Naik, Shiw S Singh, Mathew P Tharaniyil, Robert B Wendfort, (1996),

Application of foundry by product materials in manufacture of concrete and masonry

products, ACI Materials Journal, 93, pp 41-50.

9. Xu Delong, Li hui, (2009), Future resources for eco building materials – Metallurgical

slag, Journal of Wuhan university of technology-Material Science edition, June, pp

451-456.

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