### BROADER USE OF

STEEL SLAG AGGREGATES IN CONCRETE

JIGAR P. PATEL

Bachelor of Science in Civil Engineering Maharaja Sayajirao University of Baroda, India May 2006

Submitted in partial fulfillment of requirement for the degree

MASTERS OF SCIENCE IN CIVIL ENGINEERING

At the

CLEVELAND STATE UNIVERSITY December, 2008This thesis has been approved For the Department of Civil and Environmental Engineering and the College of graduate studies by

Thesis Chairperson, Dr. Norbert Delatte

Department /Date

Dr. Paul Bosela

Department /Date

Dr. Lutful I. Khan

Department /DateACKNOWLEDGEMENT

First of all, I would like to thank my parents, my sister and all my friends for their blessings and supporting me throughout my education. I would like to thank the Department of Civil and Environmental Engineering at the Fenn College of Engineering at Cleveland State University. I would like to thank to my advisor, Dr. Norbert Delatte. He not only provided support throughout this entire research but also throughout my entire graduate carrier. I would like to thank to the rest of my committee members Dr. Bosela and Dr. L.I.Khan. I would like to thank to my fellow graduate and undergraduate students who helped me with this project, which include Richard S. Obratil, Matthew A. Pastorelle, Vince Spisak, Daniel Fabriziana, and Tom Hyatt of Fenn College of Engineering at Cleveland State University and also the assistance of John Cleary of the Department of Civil Engineering at Case Western Reserve University. The help from Dave Epperly and Ali Kaddah in the lab was invaluable. I would also like to thank Mehul Maheria, Vikas Patel, Archan Shah, Mayur Patel, Hardika Gandhi, Dhaval Tamboli, Kinjal Mistry, Arpan Desai, Kuvleshay Patel, Jaimin Bhatt and many more friends for their support and co-operation during the

research.iv



### BROADER USE OF STEEL SLAG AGGREGATES IN CONCRETE

JIGAR P. PATEL

ABSTRACT

Steel slag is an industrial byproduct obtained from the stee l manufacturing industry. It is produced in large quantities during the steel-making operations which utilize Electric Arc Furnaces (EAF). Steel slag can al so be produced by smelting iron ore in the Basic Oxygen Furnace (BOF). Steel slag can be used in t he construction industry as aggregates in concrete by replacing natural aggregates. Natural aggregates are becoming increasingly scarce and their production and shipment is becoming more difficult. Steel slag is currently used as aggregate in hot m ix asphalt surface applications,

but there is a need for some additional work to determine the feas ibility of utilizing this industrial by-product more wisely as a replacement for both f ine and coarse aggregates in

a conventional concrete mixture. Most of the volume of concrete is aggregates. Replacing all or s ome portion of natural aggregates with steel slag would lead to considerable e nvironmental benefits. Most of the natural aggregates in the state of Ohio are shipped i n from out of the state, whereas large steel slag deposits are locally available . The primary aim of this research was to evaluate the durability of concrete made with steel s lag aggregates. This research has shown that replacing some percentage of natural aggregates by steel slag aggregates causes negligible degradation in strength. It is shown that as the amount of steel slag is increased beyond 75%; the workability of the concrete mixture bec ame an important issue which eventually requires larger amounts of water reducing adm ixtures to achieve av

minimum slump. The results showed that replacing about 50 to 75% of s teel slag aggregates by volume for natural aggregates will not do any har m to concrete and also it will not have any adverse effects on the strength and durability.vi TABLE OF CONTENTS

ACKNOWLEDGEMENT .............................................................................................. iii

ABSTRACT .................................................................................................................... iv

LIST OF TABLES .......................................................................................................... vi LIST OF EQUATIONS ................................................................................................. vii

CHAPTER I: INTRODUCTION ..................................................................................... 1

1.1 Background............................................................................................................................. 1 1.2 Purpose ................................................................................................................................... 3 1.3 Scope ...................................................................................................................................... 4

CHAPTER II LITERATURE REVIEW .......................................................................... 5

2.1 Overview ................................................................................................................................ 5 2.2 Concrete .................................................................................................................................. 5 2.3 Aggregates .............................................................................................................................. 6 2.4 Properties of Aggregates required for Mix design ............................................................ 7 2.5 Non traditional aggregates ............................................................................................. 8 2.6 Steel Slag and its production .................................................................................................. 9 2.7 Current uses of steel slag ............................................................................................. 11 2.8 Properties of Steel Slag ................................................................................................ 12 2.8.1 Physical Properties ............................................................................................................ 13 2.8.2 Chemical and Mineralogical composition ................................................................... 14 2.8.3 Mechanical Properties

............................................................................................... 15 2.8.4 Effect on environment and health

.............................................................................. 16 2.9 Problem associated with Steel slag aggregates

............................................................... 16 2.10 Aging of steel slag and Stockpiling of Steel slag aggregates

......................................... 17 2.11 Past studies on steel slag aggregates

............................................................................ 20vii

CHAPTER III: EXPERIMENTAL DESIGN ................................................................ 25

3.1 Overview .............................................................................................................................. 25 3.2 Concrete Mix Design ............................................................................................................ 26 3.3 Gradation .............................................................................................................................. 27 3.4 Properties of concrete ........................................................................................................... 28 3.5 Modulus of Rupture .............................................................................................................. 33 3.6 Compressive Strength of concrete ................................................................................. 33 3.7 Splitting Tensile Strength of concrete ........................................................................... 34 3.8 Change of length of Hardened Concrete ........................................................................ 35 3.9 Resistance to Rapid Freezing and Thawing ................................................................... 35 3.10 Research Plan

............................................................................................................ 37

CHAPTER IV: MATERIALS ....................................................................................... 38

4.1Overview ............................................................................................................................... 38 4.2 Portland cement .................................................................................................................... 38 4.3 Steel Slag .............................................................................................................................. 39 4.4 Fine Aggregates .................................................................................................................... 41 4.5 Coarse Aggregates ................................................................................................................ 41 4.6 Chemical Admixtures ........................................................................................................... 42

CHAPTER V: EXPERIMENTAL RESULTS ............................................................... 44

5.1 Overview .............................................................................................................................. 44 5.2 Gradations............................................................................................................................. 44 5.3 Fresh concrete properties ............................................................................................. 46 5.3.1 Workability ........................................................................................................................ 46 5.3.2 Air Content ........................................................................................................................ 46 5.3.3 Unit weight ........................................................................................................................ 48 5.4 Hardened concrete properties ....................................................................................... 50 5.4.1 Modulus of Rupture ........................................................................................................... 50 5.4.2 Compressive strength for concrete specimens and Flexure beams ................................ 51 5.4.3 Splitting Tensile Strength .......................................................................................... 54 5.4.4 Freeze-Thaw Durability ............................................................................................ 57 5.4.5 Change in length of concrete specimens ..................................................................... 69viii

CHAPTER VI: DISCUSSION ....................................................................................... 70

6.1 Overview .............................................................................................................................. 70 6.2 Overall Experimental observations ............................................................................... 70 6.3 Compressive strength of concrete ................................................................................. 71 6.4 Split Tensile strength ............................................................................................................ 72 6.5 Flexural strength of concrete ................................................................................................ 73 6.6 Freeze-thaw durability .......................................................................................................... 73 6.7 Measurement of linear expansion or contraction of concrete specimens ............................. 76

CHAPTER VII: CONCLUSION................................................................................................ 77 7.1 Summary............................................................................................................................... 77

7.2 Some limitations of test methods. ......................................................................................... 78

7.3 Suggestion for Future research ............................................................................................. 79

REFERENCES ........................................................................................................................... 81ix 

### LIST OF TABLES

Table I: Typical Physical properties of steel slag ............................................................ 13 Table II: Typical Steel Slag chemical compositon............................................................ 14 Table III: Typical Mehanical properties of steel slag.......................................... 15 Table IV: Concrete Mixture Proportions .......................................................................... 26 Table V: Testing Program ................................................................................................. 37 Table VI: Cement Compostion and Physical Properties. .................................................. 39 Table VII: Steel Slag chemical compostion and properties .............................................. 40 Table VIII: Measured slump and volume of addmixture .................................................. 46 Table IX: Measured air content and volume of addmixture ............................................. 47 Table X: Designed Unit weight and Measured unit weight .............................................. 49 Table XI: Flexural strength of concrete ............................................................................ 50 Table XII: 7 & 28 days compressive strength of concrete specimens .............................. 52 Table XIII: 7 & 28 days compressive strength for flexure beam spec imens .................... 53 Table XIV: 7 & 28 days split tensile strength on concrete specimens .............................. 54 Table XV: 7 & 28 days Split tensile strength on flexure specimens................................. 56 Table XVI: Weight of specimens at various Freeze thaw cycles ...................................... 58 Table XVII: Percentage Mass loss in %............................................................................ 59 Table XVIII: Relative Dynamic Modulus ......................................................................... 60 Table XVIII: Expansion length of concrete specimens .................................................... 69x 

### LIST OF FIGURES

Figure 1: Schematic illustration of Basic oxygen furnace and Electric arc furnace........11 Figure 2: Stockpilling of steel slag aggregates at Stein Inc .............................................. 19 Figure 3: Fig show steel slag used for reasearch and sieve analysis te st .......................... 27 Figure 4: Air test being conducted on concrete sample .................................................... 29 Figure 5: Slump test being conducted on concrete sample ............................................... 30 Figure 6: Fig A & B shows compression test and split tensile test on c oncrete sample ... 31 Figure 7: Freeze thaw test on concrete sample for durablity. ........................................... 32 Figure 8: Sieve analysis result compared with FA and CA aggregates ............................ 45 Figure 9: Comparison of replacement mixtures to ODOT class C paving mixture .......... 45 Figure 10: Graph showing air content v/s volume of aggregates replaced by s teel slag .. 47 Figure 11: Graph showing Unit weight v/s volume of aggregates replaced by s teel slag 49 Figure 12: Graph showing Modulus of Rupture for concrete beams ................................ 51 Figure 13: 7 & 28 days compressive strength of concrete specimens .............................. 52 Figure 14: 7 & 28 days compressive strength of flexure beams ....................................... 53 Figure 15: 7 & 28 days split tensile strength of concrete specimens ................................ 55 Figure 16: 7 & 28 days split tensile strength for flexure beams ....................................... 56 Figure 17: Relative Dynamic Modulus v/s nos of freeze-thaw cycles for 0% .................. 61 Figure 18: Percentage Mass loss v/s nos of freeze thaw cycles for 0% ............................ 61 Figure 19: Relative Dynamic Modulus v/s nos of freeze-thaw cycles for 25% ................ 62 Figure 20: Percentage Mass loss v/s nos of freeze thaw cycles for 25% .......................... 62 Figure 21: Relative Dynamic Modulus v/s nos of freeze-thaw cycles for 50% ................ 63 Figure 22: Percentage Mass loss v/s nos of freeze thaw cycles for 50% .......................... 63 Figure 23: Relative Dynamic Modulus v/s nos of freeze-thaw cycles for 75% ................ 64 Figure 24: Percentage Mass loss v/s nos of freeze thaw cycles for 75% .......................... 64 Figure 25: Relative Dynamic Modulus v/s nos of freeze-thaw cycles for 100% .............. 6 5 Figure 26: Percentage Mass loss v/s nos of freeze thaw cycles for 100% ........................ 65 Figure 27: Durability factor v/s freeze thaw cycle for 0 % replaceme nt .......................... 66 Figure 28: Durability factor v/s freeze thaw cycle for 25 % replaceme nt ........................ 66 Figure 29: Durability factor v/s freeze thaw cycle for 50% replaceme nt ......................... 67 Figure 30: Durability factor v/s freeze thaw cycle for 75 % replaceme nt ........................ 67 Figure 31: Durability factor v/s freeze thaw cycle for 100 mk1 % replacem ent .............. 68 Figure 32: Durability factor v/s freeze thaw cycle for 100 mk2 % replacem ent .............. 68 Figure 33: Photograph showing behaviour of 100% steel slag concrete specimen .......... 75xi 

### LIST OF EQUATIONS

Equation I: Modulus of Rupture ASTM C 78...................................................................33 Equation II Splitting Tensile strength ASTM C496 ....................................... ....34 Equation III: length change ASTM C 15.......................................................................... 35 Equation IV Relative Dynamic Modulus of elasticity ASTM C 666.........................36 Equation V: Durability Factor ASTM C 666................................................... 361 CHAPTER I

INTRODUCTION

1.1 Background Concrete is the most widely used material on earth after water. Many aspects of our daily life depend directly or indirectly on concrete. Concrete is prepared by mixing various constituents like cement, aggregates, water, etc. which are economically available. Concrete is unique among major construction materials because it is designed specifically for particular civil engineering projects. Concrete is a composite material composed of granular materials like coarse aggregates embedded in a matrix and bound together with cement or binder which fills the space between the particles and glues them together (Mindess et al. 2003).

Concrete plays a critical role in the design and construction of the nationís infrastructure. Almost three quarters of the volume of concrete is composed of aggregates. To meet the global demand of concrete in the future, it is becoming a more challenging task to find suitable alternatives to natural aggregates for preparing concrete.2 Natural aggregates are obtained from natural rocks. They are inert, filler materials and depending upon their size they can be separated into coarse aggregates and fine aggregates. The coarse aggregate fraction is that retained on 4.75 mm (No 4) sieve, while the fine aggregates fraction is that passing the same sieve. According to some estimates after the year 2010, the global concrete industry w ill require annually 8 to 12 billions metric tons of natural aggregates (U.S.G.S and nationalatlas.gov, accessed Nov 2008). ìDuring the past 25 years, the production of crushed stone has increased at an average annual rate of about 3.3 percent. Production of sand and gravel has increased at an annual rate of less than 1 percent. Based on these numbers, by 2020 U.S. production of crushed stone, which is expected to increase by more than 20 percent, will be about 1.6 billion metric tons, while production of sand and gravel will be just under 1.1 billion metric tons, an increase of 14 percent. In essence the amount of crushed stone to be produced in the next 20 years will equal the quantity of all stone produced during the previous century i.e. about 36.5 billion metric tons.î (U.S. Geological survey) Therefore the use of alternative sources for natural aggregates is becoming increasingly important. Slag is a co-product of the iron and steel making process. Iron cannot be prepared in the blast furnace without the production of its co-product; blast furnace slag. Similarly, steel cannot be prepared in the Basic Oxygen Furnace (BOF) or in an Electric Arc furnace (EAF) without making its co-product; steel slag (www.nationalslag.org). The use of steel slag aggregates in concrete by replacing natural aggregates is a most promising concept. Steel slag aggregates are already being used as aggregates in asphalt paving road mixes due to their mechanical strength, stiffness, porosity, wear resistance and water absorption capacity. Studies and tests are being3 conducted on ways to use this steel slag as an aggregate in concrete (Beshr and Maslehuddin et al. 2003). According to the National Slag Association, steel slag is currently used in bituminous asphalt paving, the manufacture of Portland cement, and in roadway construction as a base course, along with some agricultural applications. The only potential problem with steel slag aggregate is its expansive characteristics and undesirable reactions between slag and components of concrete. This might be a perception, but most of the information is anecdotal in nature rather than documented in published research studies.

1.2 Purpose The purpose of this research was to explore the feasibility of utilizing the steel slag produced by steel mills in the Northeastern Ohio region as a replacement for natural aggregate in the concrete. Steel slag aggregates generally exhibit the potential to expand due to the presence of unhydrated free lime and magnesium oxides which hydrate in humid environments. If such a product is used in the concrete, it influences both the mechanical and physical properties of concrete along with its durability. Researchers in the past have successfully incorporated this industrial byproduct as aggregates for hydraulically bound mixtures for road bases. The use of this material as a construction aggregate is being studied, and further research is on going in the United States.4 1.3 Scope The original scope of this research was to investigate the properties of concrete with steel slag aggregates. The fresh and hardened properties of concrete were tested with steel slag aggregates. The freeze-thaw resistance of concrete with steel slag aggregates was studied and the expansion of the concrete specimens was also examined. In addition to this research several tests were also included such as compressive strength, split tensile strength and the flexural strength of concrete with steel slag aggregates. For this research the percentage of the volume of natural aggregates normally used in concrete was replaced by steel slag. This replacement was done in 25% increments until all natural aggregates were replaced by the steel slag. Thus replacing the natural aggregates in concrete applications with steel slag would lead to considerable environmental benefits

and would be economical.5 

### CHAPTER II

LITERATURE REVIEW

2.1 Overview This chapter discusses concrete in general as well as the effects of incorporating steel slag aggregates into the concrete mixture. Topics addressed include steel slag, how it is manufactured, its properties, comparison of steel slag aggregates with natural aggregates, and its feasibility for use as a replacement for natural aggregates in concrete.

2.2 Concrete Concrete is a composite material which is composed of coarse granular materials called aggregates or filler embedded together in the form of a matrix with the help of the cement or binding material that fills the space between the aggregates particles and glues them together. Aggregates are usually obtained from natural rocks, either crushed stones or natural gravels. Cement binds the aggregates together. Other material like fly ash or ground granulated blast furnace slag may also be used as binding material. Aggregates are divided into two parts: fine aggregates and coarse aggregates. Fine aggregates are considered to be the material passing through 4.75mm (No 4) sieve (0.187 in square6 opening) and are predominately retained on a No. 200 sieve. Natural coarse aggregates are generally crushed stones or gravels which are retained on the No.4 sieve. Finally, water is added to initiate the binding process. This makes the mix stiffer and forms the material called concrete, which can be used in construction and forms a basis of our modern society (Mindness.2002).

2.3 Aggregates Aggregates provide dimensional stability and wear resistance for concrete. Not only do they provide strength and durability to concrete, but they also influence the mechanical and physical properties of concrete. Aggregates act as a filler material and lower the cost of concrete. Aggregates should be hard, strong, free from undesirable impurities and chemically stable. They should not interfere with the cement or any of the materials incorporated into concrete. They should be free from impurities and organic matters which may affect the hydration process of cement. The workability, strength, durability and moisture susceptibility of concrete are greatly influenced by the characteristics of aggregates. The size and grading of aggregates are important parameters in the design of a mix for a particular project because they can influence the workability of fresh concrete and its hardened strength. The porosity of aggregates and their absorption capacity affects the resistance of concrete to freezing and thawing (Mindness.2002).7 2.4 Properties of Aggregates required for Mix Design

Certain properties of aggregates must be known before designing a particular mixture for any construction project. These includes shape and gradation, moisture content, unit weight, specific gravity, void ratio and chemical properties For good workability the ideal aggregate particle should be close to spherical in shape, and well rounded with a relatively smooth surface. The shape of aggregates and particle characteristics greatly influences the cement paste requirements. Sufficient cement paste is required to coat the aggregates and to provide enough lubrication to decrease interaction between aggregate particles during mixing. The rough angular shape of crushed aggregates favorably influences the tensile strength of concrete by increasing the amount of surface area for bonding with cement paste and reducing high internal stress concentrations (Mindness.2003). The particle size distribution and maximum size of aggregates affect the economy of overall concrete mixture, as they determine the amount of cement paste required for a particular concrete. The amount of paste depends on the amount of void space, which can be altered by incorporating different size particles. Sieve analysis is carried out to determine the grading of aggregates. Another property of aggregates is their ability to absorb water due to their porosity. Water can also be retained on the surface as adsorbed water in the form of a thin film. This adsorbed water must be considered in the mixture design, as extra water to be added into the mixture must be adjusted depending upon the water/cement ratio.8 Generally aggregates are stockpiled before use in the construction and are in an air dried state (Mindness.2003). Soundness is also an important property of coarse aggregates. Aggregates are said to be unsound when their volume changes depends upon the change in environment i.e. due to chemical reactions. The resistance of concrete to freeze-thaw conditions depends on the high internal stresses developed when the water inside the aggregates freezes and causes a change in volume during cold weather. This leads to series of micro cracks inthe concrete which will ultimately reduce the strength and weaken the concrete. A freezethaw test is conducted to determine the durability of concrete where the concrete specimens are subjected to a set amount of freeze-thaw cycles and changes in the weight of specimens are determined (Mindness.2003).

2.5 Non-traditional Aggregates A wide range of materials can be used as an alternative to natural aggregates. When any new material is used as a concrete aggregate, three major considerations are relevant: (1) economy, (2) compatibility with other materials and (3) concrete properties. (Mindness et al .2003). The economical use of non traditional materials in concrete depends on various factors, like transportation required to bring the materials from industry to the site of construction, quantity available, and the mix design requirements (Mindness et al .2003). Many sources are located very far from their potential markets for concrete with high transportation costs. The separation of any useful materials from undesired substances would be costly as well. Crushing the aggregates to particular sizes9 is also an important issue. The aggregates should not react adversely with other constituents of the concrete mixture. They should not change the properties of the concrete adversely. The aggregates have vital role in concrete and provide strength and durability to concrete. The use of industrial byproducts in the concrete has received increasing attention in the recent years. Blast furnace slag is used as an aggregate for asphalt concrete and also as a cementitous material in concrete. Steel slag which is also an industrial byproduct has potential to be ut ilized as an aggregate in concrete as well.

2.6 Steel Slag and its production:

Steel slag is a byproduct obtained either from conversion of iron to steel in a Basic Oxygen Furnace (BOF), or by the melting of scrap to make steel in the Electric Arc Furnace (EAF). The molten liquid is a complex solution of silicates and oxides that solidifies on cooling and forms steel slag. Steel slag is defined by the American Society for Testing and Materials (ASTM) as ìa non-metallic product, consisting essentially of calcium silicates and ferrites combined with fused oxides of iron, aluminum, manganese, calcium and magnesium that are developed simultaneously with steel in basic oxygen, electric arc, or open hearth furnacesî (Kalyoncu, 2001). The two states producing the most steel slag in the U.S. are Ohio and Indiana. The chemical composition and cooling of molten steel slag have a great effect on the physical and chemical properties of solidified steel slag.10 Steel furnace slag is produced in a Basic Oxygen Furnace (BOF) or Electric Arc Furnace (EAF) as a byproduct of the production of steel. In the Basic Oxygen Furnace (BOF), the hot liquid metal from the blast furnace, scrap and fluxes, which contain lime (CaO) and dolomitic lime, are charged to a furnace (Shi, 2004). A lance is lowered into the converter and then oxygen in injected with high pressure. The oxygen then combines with and removes the impurities as shown in Fig. 1(a). These impurities consist mainly of carbon in the form of gaseous carbon monoxide, silicon, manganese, phosphorous and some iron as liquid oxides, which combine with lime and dolomitic lime to form steel slag. At the end of the refining stage, the steel in the liquid form is poured into the ladle while the slag is retained at the top in the vessel and is then subsequently removed in separate slag pot. This slag is in molten state and is then processed to remove all free metallic impurities with help of magnetic separation and then sized into construction

aggregates. Unlike the Basic Oxygen Furnace (BOF) process, the Electric Arc Furnace (EAF) does not use hot metal, but uses cold steel scraps. Charged material is heated to a liquid state by means of an electric current. The electricity has no electrochemical effect on the metal, making it perfectly suited for melting scrap. During the melting process, other metals are added to the steel to give the required chemical composition. Meanwhile oxygen is blown into the EAF to purify the steel. This slag which floats on the surface of molten steel is then poured off.11 (A) (B) Fig 1 Schematic illustration of Basic Oxygen Furnace and Electric Arc Furnace (NSA accessed, 2008) The main constituents of iron and steel slags are silica, alumina, calcium, and magnesia, which together make about 95% of the total composition. Minor elements included are manganese, iron, sulfur compounds and traces of several other elements (Kalyoncu, 2001). Physical characteristics such as porosity, density, particle gradation, are affected by the cooling rate of the slag and its chemical composition.

2.7 Current Uses of Steel Slag : Some of the current uses of steel slag according to the National Slag Association (NSA accessed, 2008) are as follows: 1. Steel slag is used as an ideal aggregate in hot mix asphalt (HMA) surface mixture application due to its high frictional resistance and skid resistance characteristics. The cubical nature of steel slag and its rough texture provides more resistance than round, smooth and elongated aggregates.122. It is also used in making Stone Matrix Asphalt (SMA) because the particle-toparticle contact of the aggregate does not break down during the manufacturing, laying down, or compaction process. Illinois Department of Transportation (IDOT) has successfully specified steel slag SMA bituminous mixes on roadways.

3. It is also used for manufacture of Portland cement. 4. It is used in base application, construction of unpaved parking lots, as a shoulder material, and also in the construction of berms and embankment. 5. It is also used in agriculture because it has minerals like iron, manganese, magnesium, zinc and molybdenum which are valuable plant nutrients. 6. It is environment friendly. During the production of cement, the CO 2 emissions are reduced as slag has previously undergone the calcination process. 7. Steel slag aggregates are used for soil stabilization or soil improvement material

and for remediation of industrial waste water run-off.

2.8 Properties of Steel Slag The United States Department of Transportation and the Federal Highway Administration along with the Turner Fairbank Highway Research Center (TFHRC) have listed some of the properties of steel slag:13 2.8.1 Physical properties Steel slag aggregates are fairly angular, roughly cubical pieces having flat or elongated shapes. They have rough vesicular nature with many non-interconnected cells which gives a greater surface area than smoother aggregates of equal volume; this feature provides an excellent bond with Portland cement (NSA accessed Nov 2008 ). Steel slag has a high degree of internal friction and high shear strength. The rough texture and shape ensure little breakdown in handling and construction (NSA accessed Nov 2008). Steel slag has high bulk specific gravity and less than 3% water absorption. Steel slag aggregates have high density, but apart from this feature most of the physical properties of steel slag are better than hard traditional rock aggregates. Below are listed some of the positive features of steel slag. (GeoPave, 1993) 1. They are strong and durable. 2. They have excellent angular shape which helps to develop very strong interlocking properties. 3. They have high resistance to abrasion and impact. Table 1 lists some typical physical properties of steel slag . ( TFHRC-Steel slag material description, accessed Nov 2008)

Property Value Specific Gravity > 3.2 - 3.6 Approx Dry rodded Unit Weight, kg/m 3 (lb/ft 3 ) 1600 - 1920 (100 ñ 120) Water Absorption up to 3%

Table I. Typical physical properties of steel slag. (TFHRC accessed 2008)14 2.8.2 Chemical and Mineralogical composition Blast furnace slag usually contains four major oxides, namely lime, magnesia, silica and alumina. Minor elements include sulfur, iron, manganese, alkalis and trace amount of several others. The chemical composition of slag is generally expressed in terms of simple oxides calculated from elementary analysis determined from x-ray fluorescence. Table II shows the list of various ranges of compounds presents in steel slag from a typical oxygen furnace. ( TFHRC-Steel slag material description, accessed Nov 2008). The mineralogical form of slag is highly dependent on the rate of cooling of slag in the steel making process. Most of the blast-furnace slag produced in the U.S. has compositions within the ranges as shown in table II.

Constituent Composition (%) by TFHRC Composition (%) by NSA CaO 40 - 52 42 SiO 2 10 ñ 19 15 FeO 10 - 40 (70 - 80% FeO, 20 - 30% Fe 2 O 3 ) 24 MnO 5 ñ 8 5 MgO 5 ñ 10 8 Al 2 O 3 1 ñ 3 1-5 P 2 O 5 0.5 ñ 1 0.8

S < 0.1 0.08 Metallic Fe 0.5 ñ 10 - Table II. Typical steel slag chemical composition (TFHRC) The rate of cooling of steel slag is generally kept lower so that the crystalline compounds are formed. The predominant compounds in steel slag are dicalcium silicate, tricalcium silicate, dicalcium ferrite, merwinite, calcium aluminate, calcium-magnesium iron oxides, some free lime and magnesia. Steel slag is mildly alkaline, with a solution pH generally in range of 8 to 10. However, the pH of leachate from steel slag can exceed15 11, a level that can be corrosive to aluminum or galvanized steel pipes placed in direct contact with the slag.

According to Department of Transportation (DOT) and Federal Highway Administration (FHA), the amount of free calcium and magnesium oxides is not completely consumed in steel slag. The hydration of unslaked lime and magnesia in contact with moisture is largely responsible for the expansive nature of most steel slag. The free lime hydrates very rapidly and can cause large changes in volume over a relatively short period of time, i.e. weeks, while magnesia hydrates much more slowly and contributes to long term expansion which may continue for many years.

Free lime (Calcium oxide) (CaO) + water (H 2 O) = Calcium carbonates (CaCO 3 )

Magnesium oxide (MgO) + water (H 2 O) = Magnesium carbonates (MgCO 3 )

2.8.3 Mechanical Properties

According to TFHRC (www.tfhrc.gov ) the processed steel slag has favorable mechanical properties for use as aggregates in construction; these include good abrasion resistance, good soundness characteristics, and high bearing strength.

Table III. Typical mechanical properties of steel slag. (TFHRC accessed 2008) Property Value Los Angeles Abrasion (ASTM C131), % 20 - 25 Sodium Sulfate Soundness Loss (ASTM C88), % <12 Angle of Internal Friction 40° - 50° Hardness (measured by Moh's scale of mineral hardness)* 6 - 7 California Bearing Ratio (CBR), % top size 19 mm (3/4 inch)** up to 300 * Hardness of dolomite measured on same scale is 3 to 4. ** Typical CBR value for crushed limestone is 100%.16 2.8.4 Effect on the Environment and Health A Steel Slag Coalition (SSC) was formed in 1995 to provide a comprehensive study of steel slag. This coalition consisted of iron and steel manufacturers, slag processors, chemical laboratories and risk assessment teams, environmental scientists and toxicologists to conduct an industry-wide ìHuman Health and Ecological Risk Assessment (HERA)î on iron and steel slag. (NSA accessed Nov 2008). The result of this study confirmed that the iron and steel slag have no threats to human health or the environment when used in residential, agricultural, industrial and construction applications. ìSlag has also been effectively used to treat acid mine drainage discharge and is also useful in the removal of excess phosphorous from waste water discharges, thus rendering the waste water more ecologically beneficialî (Wagaman and Stanley, 2005).

2.9 Problems associated with Steel Slag aggregates Steel slag aggregates have two main features which are of concern to their use in construction, namely, volume expansion and high particle density. During the making of steel there is a small percentage of calcium and magnesium oxides which is left undissolved in the slag. These non hydrated calcium and magnesium oxides then later come in contact with moisture which leads to hydration process. The volume expansion is primarily caused by the reaction between the free lime in slag and water during the hydration process to produce calcium hydroxide. As a result there is a great increase in volume due to the difference of specific density of the hydration product. These changes in volume can occur either in a few weeks after production of slag or may occur many17 years later if the slag is initially protected from contact with water (GeoPave, 1993). A general method usually used to overcome the expansion problem is to store the slag for aging in stockpiles for some four to six months before using it. Density of steel slag is also an important issue to be considered. Steel slag is a heavier material than natural rock types such as basalt, granite, or limestone. Thus, any given volume would require about 15 to 25% greater tonnage of steel slag than traditional natural aggregates which may create an economic disadvantage for steel slag in some applications where transportation costs are significant (GeoPave, 1993).

2.10 Aging of Steel Slag and Stockpiling of Steel slag aggregates

After initial crushing, the slag comes out from the factory and the potential expansion of oxidizing slag may then evaluated according to the ASTM D-4792 on samples taken at random from the stock piles. ASTM D-4792 is a test method for determining the compliance of steel slag and other materials containing components subjected to hydration. The test method consist of measuring the volume expansion of compacted specimens and to accelerate hydration reaction, the specimens are stored in water at 70 ± 3°C (158 ± 5°C) for minimum of 7 days. Three representative samples are taken from random location from the stock piles approximately 45kg (100 lbs) and samples are then reduced to testing size of two 18kg (40 lbs) according to ASTM C 702 - Practice for reducing samples of aggregates to testing size. Sieve analysis of the samples is done. Three expansion test specimens should be prepared according to ASTM D 1883. After placing the stem and perforated plate surcharge weights 4.54 kg (10 lbs) is placed18 and then it submerged in hot water for 30 minutes to allow thermal expansion of test apparatus and dial gage measurements are taken. For 7 days heated water is added continuously and the percentage expansion is calculated each day. An accelerated aging test is also sometimes carried out in which the specimens of 150 x 300mm are aged for 28 days in a moist room (Manso et al. 2004 and Emery, 1984). These specimens are then submerged in water at 70°C and are kept for 32 days. After that the specimens are dried and kept for 90 days exposed to weather but direct impact of rain is avoided. These specimens when tested showed a considerable improvement in the compressive strength as compared to normal conventional concrete cured continuously in moist room from 28 to 90 days (Manso et al. 2004). The objective of this test is to evaluate the hydration of the free lime and free magnesium of the slag aggregates in hot water.

The steel slag used for this research was obtained from a company located in Cleveland Ohio. The steel slag was processed in compliance with Ohio Department of Transportation Construction and Material Specifications, 2005. Section 703.14 D gives the specifications regarding the stockpile requirements, which states that ì water is added to the stockpile material to provide a uniform moisture content not less than absorbed moisture and maintained in moist condition during the stockpiling period.î The minimum aging time was six months, but has been decreased to three months. The Expansion test can be performed according to Pennsylvania Department of Transportation PTM No.130 Method of Test for Evaluation of Potential Expansion of Steel slag. PTM 130 is similar to ASTM D 4792 which is the Standard Test method for Potential Expansion of Aggregates from Hydration Reaction which is referenced for expansion testing of steel slag19 aggregates in supplement 1071. The maximum allowable total expansion for the test is less than 0.5 %.( Bosela et al. 2007). The conditioning of the slag for its use as aggregate in concrete requires it to be crushed, homogenized, weathered and aged. The concrete obtained with oxidized slag as aggregates have good properties on hard and fresh state.

Steel slag must be allowed to undergo the weathering process before using as an aggregate in construction because of its expansive nature. This is done in order to reduce the quantity of free lime to acceptable limits. The steel slag is allowed to stand in stockpiles for a period of at least 4 months and exposed to weather. During this weathering process, the steel slag is required to be in contact with water so that the hydration process between lime and water takes place. Hydration of free lime (CaO) or free magnesia (MgO) is responsible for expansive nature of steel slag.

Figure 2: Stockpiling of steel slag aggregates at Stein Inc 200820 2.11 Past studies on Steel Slag aggregates The successful incorporation of steel slag as an aggregate in concrete has been studied in the past. Steel slag is an industrial byproduct and instead of disposing it in the landfill, the use of such product in the construction market would increase efficiency and economy. The physical and chemical characteristics of steel slag have been examined carefully. Due to its potentially expansive properties, it require special care if used in construction or other specific applications. The possibility of utilizing such product as a concrete aggregates with ecological benefits has been globally studied by several researchers like Anastasiou and Papayianni, (2006). They conducted several tests with slag aggregates in concrete and found out that the 28 day strength was increased by 21% with replacement of natural aggregates, while there was no increase in the setting time of concrete mixtures. The cement-aggregate interface seemed to be very dense without cracks or other discontinuities. The concrete that is produced with steel slag aggregates is of high specific gravity compared to conventional concrete. However the specific gravity can be increased or reduced proportionally by the combination of different types of aggregates (Anastasiou and. Papayianni, 2006). A study on durability of the concrete made with Electric Arc Furnace slag as an aggregate was done by Manso and Gonzalez (2004), and the results showed that it was acceptable. The concrete mixes using conditioned EAF slag showed good fresh and hardened properties and acceptable behavior against aggressive environmental conditions. It was observed that the compressive strength was similar to that of traditional concrete. The durability was slightly lower than conventional concrete. The concrete had21 good physical and mechanical properties, but results showed that special attention should be paid to the gradation and crushing process. The results showed that the high porosity of EAF slag aggregates affects concrete resistance to freezing and thawing but improvements in the field could be possibly obtained by adding air entraining

admixtures. Comparison of steel slag and crushed limestone aggregate was done by Maslehuddin, et al, (2003). They studied the mechanical properties and durability characteristics of steel slag aggregate concrete in comparison with limestone aggregates. Their results showed that the durability and physical properties of concrete with steel slag aggregates was better than limestone aggregates. They suggested that the use of steel slag aggregates in concrete was beneficial, particularly in areas where good quality aggregates are not available or have to be hauled from far off distances. Abrasion resistance, specific gravity, water absorption, chemical soundness, alkalinity, concentration of chloride and sulfates were tested and compared with lime stone aggregates. Shrinkage and expansion characteristics of steel slag and sand cement mortar specimens were evaluated and length was measured at periodic intervals. Their results showed that the compressive strength of steel slag aggregates increased with the proportion of coarse aggregates from 4550 psi (31.4 MPa) with 45% coarse aggregates to 6190 psi (42.7 MPa) with 65% coarse aggregates. The flexural strength and split tensile strength also increased while the water absorption capacity was reduced. They stated that the shrinkage of steel slag exposed to a dry environment was similar to limestone aggregate with no major expansion i.e. less than 0.05% as specified by ASTM C 33. The time of initiation of reinforcement corrosion22 and time of cracking of concrete specimens was observed to be longer than with lime

stone aggregates. Further study by Manso, Polanco et al (2006) reaffirmed that by proper mix proportions both the mechanical strength and durability of steel slag aggregate concrete can be improved. He conducted two tests for durability: 1) Autoclave test and 2) Accelerated aging test. Autoclave test is used to detect the presence of expansive compounds, free lime or magnesia in Portland cement, while accelerated ageing test is done based on ASTM D-4792. Results showed that the compressive strength was improved after testing. He conducted chemical reactivity test to observe the possible reactions between slag aggregates and other components of concrete. For the freeze-thaw test, three samples were stored in moist room for 28 days and subjected to 25 freezing and thawing cycles. They are then immersed in water at 4oC for 6 hours and maintained in frost storage at -17 oC for 18 hours. Variations in weights and compressive strength were recorded and results showed that Electric arc furnace slag concrete showed greater strength and lower water penetration. He also stated the use of air entraining admixtures increased the freeze-thaw resistance and durability of slag concrete was satisfactory. Industrial by-products like steel slag require a detailed study of its potential toxicity. There are several dangerous heavy metals and salts present in the steel slag. A leaching test is required prior before using the EAF slag as a filling material. Manso et al, (2006) conducted the leaching test for determining the possible attack of concrete in the environment. Analysis of leached water from crushed slag aggregates were used to detect the sulphates, fluorides and total chromium present in it. The results showed that smaller size of crushed slag produces higher concentration of dangerous substances in leached23 water. The cloistering effect was found to be greater in larger sizes of crushed slag. He concluded that the use of EAF slag aggregate in concrete will help to reduce its potential toxicity and the results confirmed an important cloistering effect of cementitous matrix on the contaminants elements. Also some previous research was carried out at the Cleveland State University by (Obratil et al, 2008) who examined the effects of replacing various percentages of natural aggregates with steel slag in a standard concrete pavement mixture which showed satisfactory results. Research on freeze-thaw resistance of steel slag aggregate concrete was done by Takashi et al, (2007). Concrete specimens were prepared with steel slag aggregates, recycled aggregates and crushed stones and compared with each other. The size of steel slag aggregates used for the research ranged from 15-20mm. The samples were cyclically exposed to -18°C to 5°C, every 5 hours in water. Results showed that resistance to freezing and thawing of steel slag aggregates concrete was better than the recycled aggregates and almost same as crushed stone. Results also showed that compressive strength and resistance to freezing and thawing increased with increase in cement

content. In Saudi Arabia, research was conducted to utilize locally available steel slag in concrete by Abdulaziz et al, (1996). The steel slag was used as coarse aggregates in concrete and comparison was made with crushed gravel. The results showed that the compressive and flexural strength for slag concrete was slightly higher than the natural gravel concrete. The splitting tensile strength and modulus of elasticity were higher, while drying shrinkage was lower than the natural gravel concrete. The results were encouraging since they showed no negative effects on short term properties of hardened24 concrete. The slag was analyzed chemically and it did not show any presence of free lime or any other unstable substances, which can cause swelling effects. Four trial mixes were made with different water/cement ratio and compared with reference mix of crushed gravel as coarse aggregates. The Youngís modulus of elasticity E of steel slag aggregates concrete at 28 days was 5 x 10 6 Psi (34.3 GPa) while it was 4 x 10 6 Psi (27.9 GPa) for gravel concrete. The improvement in strength properties of steel slag aggregate concrete may be due to shape of particles and surface texture, which provide better adhesion and bond between particles and the cement matrix.25 

### CHAPTER III

EXPERIMENTAL DESIGN

3.1 Overview The main objective of this research was to utilize the steel slag aggregate in the concrete mixture and identify the properties of the mixture, its durability, expansion and also its fresh and hardened concrete properties. The research started by replacing the percentage of the volume of natural aggregates, normally used in the manufacture of concrete in Northeastern Ohio, with steel slag in increments of 25% until all the natural aggregates were replaced by the steel slag. All concrete mixing was performed in the Concrete Research Laboratory in the Fenn College of Engineering at Cleveland State University. Before mixing commenced, the gradation of steel slag samples was determined and compared with the natural aggregates. The experimental program consisted of first testing the fresh concrete properties, then forming specimens for the following tests: ASTM C 39:26 Compressive Strength of Cylindrical Concrete Specimens. ASTM C 157: Length Change of Hardened Hydraulic-Cement, Mortar, and Concrete. ASTM C 78: Flexural Strength of Concrete. ASTM C 496: Splitting Tensile Strength of Cylindrical Concrete Specimens. ASTM C 666: Resistance of Concrete to Rapid Freezing and Thawing.

3.2 Concrete Mix Design This research primarily focused on the Class C Option 1 Concrete mixture of the Ohio Department of Transportation (ODOT) because of its frequent use in road construction. Table IV show Concrete Mixture Proportions (Quantities per Cubic Yard (m 3 ) and Table V shows the Testing program along with the protocols and methods used during this research.

Table IV: Concrete Mixture Proportions (Quantities per Cubic Yard (m 3 )

Research Mixture Design SSD Aggregate Weight Mixture

Type Fine Aggregate Coarse Aggregate Steel Slag Aggregate Cement Content WaterCement

Ratio lb kg Lb Kg lb kg lb Kg Maximum ODOT Class C 1270 576 1610 730 - - 600 272 0.50 25% 956 434 1171 531 844 383 600 272 0.50 50% 638 289 781 354 1688 766 600 272 0.50 75% 319 145 390 177 2531 1148 600 272 0.50 100% - - - - 3375 1531 600 272 0.5027 3.3 Gradations The steel slag aggregate was provided by Stein Inc. The initial visual examination of the steel slag samples suggested that it consisted of a mixture of both fine and coarse aggregates. Sixteen samples were taken and sieve analysis was done according to ASTM C 136. The average results of the percentage passing each screen for the steel slag were compared to the curves of the natural aggregates it was to replace. This data was also compared to the mixture curves determined for ODOT Class C option 1 pavement

mixture.

(A) FIG 3 (A) and (B) shows sieve analyses conducted to determine gradation.28 (B)

3.4 Properties of Concrete The properties of concrete are classified into two categories: fresh and hardened. The durability of concrete depends upon the mix design and durability of aggregates. The water-cement ratio and addition of admixtures greatly affect the durability of concrete. The properties which affect the strength and durability of a concrete structure change over the life of structure, increasing with time. (A) Fresh Concrete Properties

Fresh concrete properties include slump, unit weight and air content test. The slump of the concrete was tested following ASTM C143: slump of Hydraulic Cement Concrete. The slump test is empirical in nature, and it does not directly measure the workability of concrete mixture. Instead, it is used to ensure the uniformity between the different concrete batches for a given job (Mindess et al. 2003). ODOT specifies the maximum slump of four inches (100mm) for Class C mixture (ODOT 2005). The unit29 weight test is a more reliable test and provides more valuable information than the slump test. The unit weight test will also give information related to air content, water content and changes in the aggregate proportion in the mixture. The unit weight of the mixture was tested according to ASTM C138: Density (unit weight), Yield, and Air Content (Gravimetric) of concrete. The air content test is the most important test for determining the durability of concrete in the freeze thaw conditions. The air content of the fresh concrete was performed following ASTM C231: Air Content of Freshly Mixed Concrete by the Pressure Method. ODOT specifies an air content of 6 ± 2% for Class C Option 1

mixture



### . Air voids in the system protect the concrete from damage but also reduce the strength of the concrete mixture, and therefore great care should be taken not to entrain too much air (Mindess et al. 2003). Fig 4 illustrates how the air tests were conducted using the pressure method in the laboratory. Fig 5 shows the slump test conducted on the concrete sample with 100% steel slag aggregates without super plasticizers. Fig 4: Air test being conducted on the concrete sample .200830 Fig 5: Slump test being conducted on the concrete sample with 100% steel slag .2008

(B) Hardened concrete properties To determine the hardened properties of concrete, the Compression test (ASTM C 39), Splitting tensile test (ASTM C 496), Freeze-thaw durability test (ASTM C 666), and Modulus of rupture (flexural strength test) (ASTM C 78) were conducted. Concrete is much stronger in compression than in tension and so the compressive strength of concrete is an important property of the concrete (Mindess et al. 2003). It is very difficult to directly measure the tensile strength of concrete; therefore the splitting tensile test, an indirect method, was adopted.31 (A) (B) Fig 6: (A) shows the Compression test conducted on a concrete specimen with steel slag aggregates (B) Splitting tensile Test conducted on concrete specimen

.32 Fig (A)

Fig (B) Fig (C)

Fig 7: (A) shows the Fundamental transverse frequency was measured with resonance tester. Fig (B) Freeze-thaw test being conducted and concrete specimens are placed in the freeze-thaw machine and 300 freeze thaw cycle were carried out. Fig (C) Relative dynamic modulus of elasticity of concrete specimen was measured in concrete laboratory at CSU.33 3.5 Modulus of Rupture The modulus of rupture was tested at 7 days for each mixture. At the time of casting two specimens were molded following ASTM C 192. Beam specimens had a cross sectional area of six inches by six inches and were twenty inches long (152mm x 152mm x 508 mm). Specimens were stored in a water tank following ASTM C 511.The beam specimens were tested following ASTM C 78 using third-point loading and the Modulus of rupture calculated using the equation; Equation I: Modulus of Rupture (ASTM C 78)

Where:

R = The Modulus of Rupture. (MPa)

P

= The Maximum applied load indicated by the testing machine. (lbf) (N)

L = The span length. (in) (mm)

b = The average width of the specimen at the fracture. (in) (mm)

d

= The average depth of the specimen at the fracture (in) (mm)

3.6 Compressive Strength of Concrete The concrete specimens were tested for compressive strength at 7 and 28 days. Specimens were made following ASTM C192 and stored in the water curing tank following ASTM C511. The cylindrical specimens prepared for the research were made with a diameter of four inches (102 mm) and a height of eight inches (203 mm). Two specimens were tested at each age, following ASTM C39, on a hydraulic loading34 machine. The compressive strength was determined by dividing the ultimate applied load by the cross-sectional area of the cylinder. The type of fracture of the specimen and the compressive strength was also recorded and compared with ASTM C39.

3.7 Splitting Tensile Strength of Concrete The splitting tensile strength of the concrete specimens was tested at 7 and 28 days. The four inch (102 mm) and eight inch (203 mm) cylindrical specimens were molded at the same time as the compressive strength specimens. The specimens were tested on a hydraulic loading machine following ASTM C 496. The splitting tensile strength can be obtained from the following equations: Equation II: Splitting Tensile Strength (ASTM C 496)

Where: T = splitting tensile strength (psi) (MPa) P = maximum applied load (lbf) (N) l = length (in) (mm) d = diameter (in) (mm) For this research the length (l) was equal to eight inches (203mm) and the diameter (d) of was taken as four inches (102 mm).The splitting tensile strength was equal to the maximum applied load divided by 50 (65,000). Two specimens were tested at 7 and 28 days for each experimental mixture.35 3.8 Change of length of Hardened Concrete The testing program also included the determination of change in length of the specimens due to causes other than externally applied forces. Two prisms measuring 4 x 4 x 10 inches (102 x 102 x 254 mm) were prepared for each mixture. Initial length measurements were taken after the specimen was removed from the mold 24 hours after casting. The prisms were placed into a lime bath until testing at 7, 28, 56, 90 and 120 days. The length change was then calculated using the equation; Equation III: Length change (ASTM C 157)

Where: =The change in length of specimen at any age (%)

CRD = The difference between the comparator reading of the specimen and the reference bar at any age

G

is the gage length (10 inches (250mm)).

3.9 Resistance to Rapid Freezing and Thawing The resistance of the concrete due to rapid freezing and thawing cycles was tested according to ASTM C 666. The concrete prisms were placed into a Logan Freeze Thaw machine after curing for 14 days. At intervals of approximately 25 cycles the specimens were removed from the machine and their dimensions and weight were determined. The transverse frequency was then recorded utilizing an Olson Engineering Model RT-1 Resonance Tester according to ASTM C 215. From this frequency measurement the relative Modulus of Elasticity was calculated by using the following equation;36 Equation IV: Relative Dynamic Modulus of Elasticity (ASTM C 666)

Where:

P c = Relative dynamic modulus of elasticity after c cycles of freezing and thawing (%).



### N = The Fundamental transverse frequency at 0 cycles of freezing and thawing. N1 = The Fundamental transverse frequency after c cycles of freezing and thawing. ASTM C 666 specifies that the test ends after 300 cycles, or when the relative dynamic modulus of elasticity falls below 60%. The durability factor was then calculated using the equation; Equation V: Durability Factor (ASTM C 666)

Where;

DF = The Durability factor of the test specimen.

P

= The relative dynamic modulus of elasticity at N cycles (%).

N = The Number of cycles at which P reaches the specific minimum value for discontinuing the test or the specified number of cycles at which the exposure is to be terminated, whichever is less,

M is the specified number of cycles at which the exposure is to be determined (usually 300)37 3.10 Research plan Table V show the testing program for the research. ASTM specifications for different test methods to be employed and number of samples to be prepared are also

shown.

Table V: Testing Program

Test Protocols and Methods Number of Tests specimens Aggregate Gradations ASTM C 136 12 samples Fresh Concrete Properties Workability ASTM C 143 2 Air content ASTM C 231 3 Unit weight ASTM C 138 3 Hardened Concrete Properties Compressive strength ASTM C 39, 4î x 8î cylinders 2 ea. at 7 & 28 days, total of 4 Splitting tensile strength ASTM C 496, 4îx 8î cylinders 2 ea. at 7 & 28 days, total of 4 Flexural strength ASTM C 78, 6îx6îx20î beams 2 at 7 days Expansive Properties Length Change ASTM C 157 2 Durability Freeze-thaw ASTM C 666, ASTM C 215 3 at 300 cycles38 CHAPTER IV

MATERIALS

4.1 Overview This chapter provides the overview of materials used for this research. All the materials used during the research program remained the same, except different kind of coarse aggregates were used for flexure strength test and in the rest only the proportions were varied. All the materials aside from the steel slag were those utilized by ODOT District 12 in Northeastern Ohio on their highway projects. A water-cement ratio of 0.5 was maintained constant during the course of the research program.

4.2 Portland Cement The cement used in this project was supplied by St. Maryís Cement Group. This is Type I Portland cement as classified by ASTM C150. The cement properties and its chemical composition were provided by St Maryís is shown in table VI.39 Table VI: Cement Composition and Physical Properties

Chemica l Percent Loss on I g nitio n 1.6 % SiO 2 20.45 % Fe 2 O 3 2.77 % Al 2 O 3 4.55 %

CaO 61.81 % Free CaO 0.93 % M g O 3.15 % SO 3 3.76 % K

2 O 0.53 % N a 2 O 0.30 % TiO 2 0.28 % P 2 O 5 0.17 % M n 2 O 3 0.09 % Insoluble Residue 0.13 % Total Alkali as N a 2 O 0.65 % Color Inde x 28.0 Calculated Com p ounds Percent C 3 S 51 % C 2 S 20 % C 3 A

ñ ASTM 7 % C 3 A

ñ CSA 7.4 % C 4 AF 8 % Ph y sical Pro p erties

Fineness: Blaine 381 m2/k g Retained in #325 sieve 4.0 % Autoclave Ex p ansio n 0.379 %

4.3 Steel Slag The steel slag used in this research was provided by Stein Inc. and originated from Mittal Steel USA located in Cleveland, Ohio, which is involved in the manufacture of many types of steel. Stein Inc. also provided an analysis report compiled by40 Alternative Testing Laboratories Inc. which provided information on the chemical composition of the steel slag along with the percent absorption and SSD Specific Gravity

. The steel slag provided was properly aged in a manner similar to that required by Pennsylvania Department of Transportation (PENNDOT) specification 703.2-4. This specification requires stockpiles to be kept uniformly moist for a period of at least six months. If the total expansion of the material is less than 0.50% than the material is ready to use, but if the expansion is greater than the 0.50% then additional curing of up to two months is necessary.

TABLE VII: Steel Slag Chemical Composition and Properties (Courtesy: Alternative Testing Laboratories Inc)

Constituents Composition (%) by Stein. Inc Composition provided by TFHRC (%) Composition provided by

NSA (%) Aluminum oxide (Al 2 O 3 ) 5.84 1-3 1-5 Calcium oxide (CaO) 30.7 40-52 42 Chromium oxide (Cr 2 O 3 ) 0.28 - - Iron oxide (FeO) 35.6 10-40 24 Magnesium oxide (MgO) 9.95 5-10 8 Manganese oxide (MnO) 3.99 5-8 5 Phosphorus oxide (P 2 O 5 ) 0.61 0.5-1 0.8 Potassium oxide (K 2 O) 0.05 - - Silicon oxide (SiO 2 ) 12.0 10-19 15 Sodium oxide (Na 2 O) 0.09 - - Titanium oxide (TiO 2 ) 0.65 - - Vanadium oxide (V 2 O 5 ) 0.21 - - Water Absorption 3.37 0- 3 - SSD Specific Gravity 3.09 3.2-3.6 -41 Table VII shows steel slag chemical compositions and properties. The values in

the 2 nd column were provided by Stein Inc and determined by Alternative Testing

Laboratories. The values in the 3 rd column are typical steel slag chemical compositions provide by TFHRC lab and 4 th column had typical steel slag chemical compositions provide by NSA (accessed Nov 2008).

4.4 Fine Aggregates The fine aggregate used for the research was Shalersville natural sand from Lafarge Corporation supplied by Cuyahoga Concrete and Stone. This Aggregate has absorption of 1.18%. The Bulk Specific Gravity of the fine aggregate was 2.60 while its SSD Specific Gravity was 2.63.

4.5 Coarse Aggregates Two types of coarse aggregates were used in this research. One was high absorption #57 Marblehead limestone with a nominal maximum size of 1 inch (25 mm), supplied by Cuyahoga concrete. These aggregates were used for making the freeze-thaw specimens, compressive test and tensile test specimens. The absorption of these coarse aggregates was 3.03%. The Bulk Specific Gravity provided by the supplier was 2.49 with an SSD Specific Gravity of 2.57. The second type of coarse aggregates was the medium absorption coarse aggregate #57 Hanson Sandusky crushed limestone provided by Mack Concrete of Akron Ohio, which was used for making the flexural strength beam mixtures. This absorption of these aggregates was reported as 2.14% with an SSD Specific Gravity of 2.58. Two coarse aggregates were used because we had shortage of42 #57 Marblehead limestones and none was left when we later decided to conduct the flexural strength test for the beam.

4.6 Chemical Admixtures

Two chemical admixtures were used in this research: high range water reducer and air entrainment admixture. The air entrainment admixture MB-AE 90 was applied to all mixtures, while a few mixtures required the use of the High range water reducer Glenium 3030 NS. These chemicals were provided by BASF/Master Builders. Glenium meets ASTM C494 requirements for Type A, water-reducing, and Type F, high-range water reducing, admixtures. The high range water reducing admixtures were added in the freeze thaw specimens with 100% steel slag aggregates and also in the flexural beams with 75% steel slag aggregates. The air entrainment admixture was MB-AE 90. MB-AE 90 meets the requirements of ASTM C 260.

Importance of chemical admixtures in the concrete All porous materials are susceptible to damage during freezing and thawing. Concrete can be made frost resistant by adding air entraining admixtures. These admixtures increase the amount of air in concrete during mixing. Depending upon the type of mixer, rate of mixing, time of mixing and amount of concrete to be mixed, the total required volume of air entraining admixtures is calculated and added accordingly. These air entraining admixtures form tiny bubbles, approximately spherical in shape and randomly dispersed throughout the mixture which help water to accumulate in them during the freezing condition and give space to water molecules to expand and reduce43 high internal stresses and prevents micro cracks in concrete. (Mindness.2003). A well distributed system of small bubbles protects the whole paste volume. Bleeding and segregation are also reduced in the wet mixture and the concrete can be easily handled and transported. However there are also some disadvantages of incorporating air into the concrete. If too much air is trapped in the paste, it weakens the concrete resulting in lower strength and possibly lower ductility. Proper care should be taken during mixing of concrete and the time elapsed between the mixing and casting into the mould to minimize the amount of entrapped air. A high amount of entrapped air would seriously affect the durability of

concrete and its freeze-thaw resistance.44 CHAPTER V

EXPERIMENTAL RESULTS

5.1 Overview The chapter discusses the results obtained from various tests. The results presented in this chapter are the average results when more than one sample each of

mixture was tested.

5.2 Gradations The sieve analysis of the steel slag samples revealed that the material was a combination of both fine aggregates and coarse aggregates. Figure 8 shows the results of sieve analysis of Steel slag obtained from Stein when compared with Shalersville fine aggregates and Marblehead #57 coarse aggregates. Figure 9 illustrates the comparison between the replacement mixtures and the Class C pavement mixture. As can be seen in Figure 9 the overall mixture became finer45 as more steel slag was used. The steel slag aggregates fractions lies between the fine aggregates and coarse aggregates.

FIGURE 8: Sieve analysis results compared with fine and coarse aggregates.

FIGURE 9: Comparison of replacement mixtures to ODOT class C paving mixture.46 5.3 Fresh concrete properties 5.3.1 Workability According to the ODOT Construction and Material Specifications Manual (2005), from Table 499.03-1 pg 264 the nominal slump for the Class C concrete paving mixture is 1 to 3 inches (25 to 75 mm). Values of slump and admixture added are shown in table VIII below. As Table VIII illustrates, the slumps for all the mixtures except the second 100% mixture, met this specification.

TABLE VIII: Measured Slump and Volume of Admixture

Mixture Measured slump

(in) Measured slump (mm) Volume of water reducing admixture (mL) Freeze-Thaw 0% 1.75 44.5 0 Freeze-Thaw 25% 2.25 57.2 0 Freeze-Thaw 50% 1.25 31.8 0 Freeze-Thaw 75% 2.5 63.5 0 Freeze-Thaw 100% 1.75 44.5 0 Freeze-Thaw 100% Mk2 0.25 6.35 192 Flexural 0% 2.25 57.2 0 Flexural 25% 2.0 50.8 0 Flexural 50% 1 1/16 27.0 40 Flexural 75% 1 3/8 34.9 170

5.3.2 Air Content Due to the cold climate experienced in Northeastern Ohio, ODOT specifications for Class C option 1 paving concrete mixture specifies an air content of 6 +/- 2%. The regular control mixture and the 25% replacement mixture each used 18 mL (0.6oz) of air entrainment. The 75% mixture used 12 mL (0.4oz) of air entrainment, whereas the 50% mix only used 6 mL (0.2oz). For observing the effects of putting air entrainment in47 concrete some samples of 100% steel slag aggregates were prepared in which no air entraining admixtures were added. This 100% steel slag aggregates concrete mixture had a high amount of entrapped air and less entrained air. Table IX shows the air content for

all the mixtures

TABLE IX: Measured Air Content and Volume of Admixture

Mixture Air Content (%) Volume of air entraining admixture (mL) Freeze-Thaw 0% 5.3 18 Freeze-Thaw 25% 5.9 18 Freeze-Thaw 50% 5.5 6 Freeze-Thaw 75% 7.4 12 Freeze-Thaw 100% 5.8 0 Freeze-Thaw 100% Mk2 6.5 15 Flexural 0% 5.9 18 Flexural 25% 4.6 20 Flexural 50% 5.1 25 Flexural 75% 4.5 20



### Air content

0 1 2 3 4 5 6 7 8

0 % 25% 50% 7 5% 1 00

%

1 00

mk2%

volume of aggregate replaced by slag in %Air content in %

Freeze-Thaw Flexure beam

FIGURE 10: Graph showing Air content v/s volume of aggregates replaced by steel slag48 5.3.3 Unit Weight

Unit weight or density of the fresh concrete can be determined by weighing a known volume of concrete. The sample is generally weighed immediately before the air content is determined. The presence of entrained air affects the unit weight, since air contributes volume, but not weight. The unit weight also gives an approximate indication of air content for concrete made with different materials. As can be seen in Figure 11, the measured unit weight was slightly higher in every instance than the desired design unit weight. Unit weight normally indicates the consistency in all phases of concreting operations. Both the designed unit weight and measured unit weight are reasonably close. Unit weight is a function of initial ingredients of concrete, mix proportions, initial and final water content, air content, volume changes, and degree of consolidation. Therefore with the change in the mixture proportions, there is a slight variation in the designed unit weight and measured unit weight. The unit weight test is the best tool to quickly find the uniformity of sample and possible significant changes in the mixture.49 FIGURE 11: Graph showing Unit weight of aggregates replaced by steel slag

TABLE X: Table shows designed unit weight and measured unit weight for different mixtures

Designed unit weight Measured Unit weight Replacement by steel slag Lbs/ft3 Kg/m3 Lbs/ft3 Kg/m3 0% 139 2243. 145 2352 25% 143 2324 151 2443 50% 148 2405 154 2489 75% 153 2486 155 2508 100 % b 158 2567 168 2717

100& 158 2567 168 271750 5.4 Hardened Concrete Properties 5.4.1 Modulus of Rupture Beam specimens were prepared having a cross section of 6 inches by 6 inches and of 20 inches (152 x 152 x 508 mm) to determine the modulus of rupture. The modulus of rupture was also found at the end of 7 days by following ASTM C 78 using a third point loading on a hydraulic testing machine. The Ohio Department of Transportation (ODOT) specifies that if high early strength of concrete is required, the 3 day modulus of rupture must be above 600 psi (4.14 MPa) (ODOT Spec 2005, pg 264) . Figure 12 shows the results for the modulus of rupture for Class C concrete mixture. All specimens have modulus of rupture for 7 days above 600 psi (4.14MPa).

TABLE XI: Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)

Specimen Identification Maximum load applied Modulus of Rupture (MOR) (lbf) (psi) (MPa) Control A 7389 684 4.72 Control B 8103 750 5.17 25a 6697 620 4.28 25b 7195 666 4.59 50a 6863 635 4.38 50b 7019 650 4.48 75a 6829 632 4.36 75b 7521 696 4.8051 FIGURE 12: Graph showing the Modulus of rupture for concrete beams

5.4.2 Compressive Strength for concrete specimens and Flexure beams

Cylinders were molded with a diameter of 4 inches (102mm) and a length of 8 inches (203 mm) to determine the compressive strength of the concrete mixtures. The cylinders were tested at 7 and 28 days following the ASTM C 39. Ohio Department of Transportation (ODOT) specifies a minimum 28 day compressive strength of 4,000 psi (28 MPa) for Class C concrete mixtures. Table XII provides the compressive strength of concrete for 7 and 28 days. All the concrete mixtures exceeded the compressive strength requirements. Figure 13 shows that at the end of 28 days all the specimens have a compressive strength more than 4,000 psi (28 MPa) and thus met the ODOT 28 dayís requirement. The flexural beam specimens also demonstrated a compressive strength just above 4,000 Psi at the end of 28 days and those specimens also met the ODOT requirements.52 Table XII: 7 & 28 days compressive strength of concrete specimens

FIGURE 13: Graph showing the 7& 28 days Compressive Strength (Average of two samples A & B) 7 Days Compressive Strength 28 Days Compressive Strength Percentage

replaced Sample A Sample B Sample A B Sample B B (Psi) (MPa) (Psi) (MPa) (Psi) (MPa) (Psi) (MPa) 0 % 5090 35 5147 35 6212 43 5072 35. 25% 4617 32 4623 32 4186 29 5141 35 50% 4154 29 4277 29 5051 35 5140 35 75% 3379 23 3358 23 4241 29 4288 30 100 A% 3577 25 2869 20 4158 29 4474 31 100 B% 4411 30 5416 37 6165 42 6069 4253 TABLE XIII: 7 & 28 Days Compressive Strength for Flexure Beam Specimens

FIGURE 14: Graph showing the 7& 28 days Compressive Strength of concrete for flexure beams (Average of two samples A & B) 7 Days Compressive strength for Flex beams 28 Days Compressive strength for Flex beams Percentage

replaced Sample C Sample D Sample C Sample D (Psi) (MPa) (Psi) (MPa) (Psi) (MPa) (Psi) (MPa) 0 % 5468 38 5483 38 6471 45 6661 46 25% 5088 35 5177 36 4683 32 5317 37 50% 4465 31 4419 30 4432 31 4722 33 75% 3886 27 4416 30 5304 37 5265 3654 5.4.3 Splitting Tensile Strength The splitting tensile strength of the concrete specimens was determined at 7 and 28 days following ASTM C 496. As previously mentioned the specimens were molded at the same time as the compressive strength specimens. Cylinders were molded with a diameter of 4 inches (102 mm) and a length of 8 inches (203 mm). Figure 15 displays the average splitting tensile strength of the samples at 7 and 28 days. ODOT does not currently have any specification for splitting tensile strength. Table XIV shows the 7 and 28 days splitting tensile strength on concrete specimens. The splitting tensile strength of concrete specimens at the end of 28 days was approximately about 500 psi. The splitting tensile test for the beams for flexural test also showed that after 28 days the splitting tensile strength was approximately 500 psi except the specimen which has 75 % of steel slag showed less splitting tensile strength.

TABLE XIV: 7 & 28 days Splitting Tensile Strength on Concrete Specimens

* indicates that the specimens were not tested. 7 Days Split Tensile Strength 28 Days Split Tensile Strength Percentage

replaced Sample A Sample B Sample A B Sample B B (Psi) (MPa) (Psi) (MPa) (Psi) (MPa) (Psi) (MPa) 0 % 473 3.26 464 3.20 577 3.98 663 4.57 25% 541 3.73 531 3.66 485 3.35 565 3.90 50% 518 3.57 497 3.43 631 4.35 496 3.42 75% 373 2.57 * * 587 4.05 425 2.93 100 A% 420 2.89 375 2.59 457 3.15 563 3.88 100 B% 593 4.09 470 3.24 589 4.06 580 4.0055 FIGURE 15: Graph showing the 7& 28 days Splitting Tensile Strength of concrete (Average of two samples A & B)56 TABLE XV: 7 & 28 days Splitting Tensile Strength on flexure Specimens

FIGURE 16: Graph showing the 7& 28 days Splitting Tensile Strength of concrete for Flexure beams (Average of two samples A & B) 7 Days Split Tensile Strength for Flexure beams 28 Days Split Tensile Strength for Flexure beams Percentage

replaced Sample C Sample D Sample C Sample D (Psi) (MPa) (Psi) (MPa) (Psi) (MPa) (Psi) (MPa) 0 % 404 2.78 558 3.85 597 4.12 577 3.98 25% 471 3.24 434 2.99 499 3.44 532 3.67 50% 481 3.32 478 3.30 504 3.48 539 3.72 75% 434 2.99 392 2.70 439 3.02 501 3.4657 5.4.4 Freeze-Thaw Durability

The freeze-thaw durability of various concrete mixtures with replacement of steel slag in different increments was tested following ASTM C 666. Table XVIII shows the results for the relative dynamic modulus Figures 17, 19, 21, 23 and 25 shows plots of relative dynamic modulus with respect to the number of Freeze-thaw cycles of different concrete specimens with steel slag aggregates. Figures: 18, 20, 22, 24 and 26 shows plots of percent mass loss with respect to the number of freeze-thaw cycles for different concrete specimens with steel slag aggregates. The result shows that the percentage mass

loss is small and trends are hard to define. Table XVI shows the initial weight of the specimens at various Freeze-thaw cycles and Table XVII provides data for percent mass

loss. Visual examination showed that if a particular sample maintains a dynamic modulus of elasticity above 60% through 300 freeze thaw cycles, the relative dynamic modulus of elasticity will be the same ( i.e. the variables N and M in the equation V will be equal to 300). During this research, all the samples performed in the same manner so the durability factor of each specimen is the same as the dynamic modulus of elasticity. It can be stated from the results that the relative dynamic modulus drops as the number of freeze thaw cycles increases. The control specimen, 25a and 75 % steel slag specimen did not showed any sign of disintegration. The samples which had no air failed in the initial cycles, as their relative dynamic modulus was less than 60 %, and were removed from the freeze-thaw testing machine.58 There might be a possibility of an experimental error while taking readings of the frequency from the testing machine during the 204 cycles for 25% replacement (as shown in figure 28), because the trend of the dynamic modulus is constant thereafter.

Table XVI: Weight of the specimens at various Freeze-thaw cycles.

Weight of the Specimens at various Freeze-thaw cycles in lbs Cycles 0 25 44 77 97 118 149 174 204 244 262 274 300 Control A 16.6 16.8 16.8 16.8 16.8 16.8 16.9 17 16.8 17 16.8 16.6 16.8 Control B 16.4 16.2 16.5 16.4 16.5 16.5 16.9 16.6 16.6 16.6 16.4 16.5 16.5

NA-A 17.0 17.2 17.3 17.2 FAILED

−− −− −− −− −− −− −− −− NA-B 17.0

−− −− −− 17.0 17.0 17.1 17.1 17.2 17.2 FAILED

25a 17.4 17.5 17.6 17.6 17.4 17.6 17.7 17.6 17.6 17.6 17.6 17.4 17.4 25b 17.4 17.4 17.5 17.5 17.6 17.5 17.6 17.5 17.6 17.6 17.6 17.4 17.2 25c 17.4 17.5 17.5 17.6 17.5 17.6 17.6 17.6 17.6 17.6 17.6 17.4 17.4 50a 18.0 18.0 18.0 17.9 18.0 18.0 18.0 17.9 17.9 17.8 17.6 17.5 17.4 50b 18.1 18.1 18.2 18.3 18.2 18.2 18.1 18.2 18.1 18 18 17.8 17.7 50c 18.2 18.2 18.3 18.2 18.2 18.4 18.3 18.4 18.1 18.2 18 18 17.8 75a 17.6 17.9 18.0 17.7 17.9 17.9 17.9 17.9 17.8 17.8 17.9 17.6 17.5 75b 17.6 17.8 17.8 17.8 17.9 17.9 17.8 17.9 17.8 18 17.9 17.7 17.6 75c 17.6 17.8 17.9 17.7 17.8 17.8 17.8 17.8 17.6 17.9 17.8 17.6 17.5 100a 19.4 19.5 19.6 100b 19.3 19.4 19.5 100c 19.5 19.5 19.7 FAILED Specimen Failed FAILED FAILED 100-B-a 19.5 19.6 19.6 19.4 19.6 19.4 19.2 19.1 18.8 19.2 18.8 18.6 18.5 100-B-c 19.5 19.6 19.6 19.4 19.5 19.3 19.1 19 19 18.8 18.8 18.6 18.6 100-B-d 19.7 19.7 19.8 19.8 19.6 19.4 19.3 19.1 19 18.8 19 18.8 18.659 TABLE XVII: Percent Mass Loss

Percent Mass Loss (%) Cycles 25 44 77 97 118 149 174 204 244 262 274 300 Control A -0.01 0.00 -0.01 -0.01 -0.01 -0.02 -0.02 -0.01 -0.02 -0.01 0.00 -0.01 Control B 0.01 -0.01 0.00 -0.01 -0.01 -0.03 -0.01 -0.01 -0.01 0.00 -0.01 -0.01 avg 0.00 0.00 -0.01 -0.01 -0.01 -0.02 -0.02 -0.01 -0.02 -0.01 0.00 -0.01 NA-A -0.01 -0.02 -0.01 - - - - - - - - - NA-B 0.00 0.00 - - 0.00 -0.01 -0.01 -0.01 -0.01 -

25a -0.01 -0.01 -0.01 0.00 -0.01 -0.02 -0.01 -0.01 -0.01 -0.01 0.00 0.00 25b 0.00 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 0.00 0.01 25c -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 0.00 0.00 avg 0.00 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 -0.01 0.00 0.00 50a 0.00 0.00 0.01 0.00 0.00 0.00 0.01 0.01 0.01 0.02 0.03 0.03 50b 0.00 -0.01 -0.01 -0.01 -0.01 0.00 -0.01 0.00 0.01 0.01 0.02 0.02 50c 0.00 -0.01 0.00 0.00 -0.01 -0.01 -0.01 0.01 0.00 0.01 0.01 0.02 avg 0.00 0.00 0.00 0.00 -0.01 0.00 0.00 0.00 0.01 0.01 0.02 0.03 75a -0.02 -0.02 -0.01 -0.02 -0.02 -0.02 -0.02 -0.01 -0.01 -0.02 0.00 0.01 75b -0.01 -0.01 -0.01 -0.02 -0.02 -0.01 -0.02 -0.01 -0.02 -0.02 -0.01 0.00 75c -0.01 -0.02 -0.01 -0.01 -0.01 -0.01 -0.01 0.00 -0.02 -0.01 0.00 0.01 avg -0.01 -0.02 -0.01 -0.02 -0.01 -0.01 -0.01 -0.01 -0.02 -0.01 0.00 0.00 100a -0.01 -0.01 100b -0.01 -0.01 100c 0.00 -0.01 Specimen Failed

100-B-a -0.01 -0.01 0.01 -0.01 0.01 0.02 0.02 0.04 0.02 0.04 0.05 0.05 100-B-c -0.01 -0.01 0.01 0.00 0.01 0.02 0.03 0.03 0.04 0.04 0.05 0.05 100-B-d 0.00 -0.01 -0.01 0.01 0.02 0.02 0.03 0.04 0.05 0.04 0.05 0.06 avg 0.00 -0.01 0.00 0.00 0.01 0.02 0.03 0.03 0.03 0.04 0.05 0.0560 TABLE XVIII: Relative Dynamic Modulus

Table XVIII shows the relative dynamic modulus of elasticity of the various concrete specimens incorporated with steel slag aggregates. The lowest relative dynamics modulus of elasticity was 64. ASTM C 666 specifies that the test ends at 300 cycles or when the relative dynamic modulus of elasticity falls below 60 %. It shows that the concrete specimens performed well during the Freeze-thaw environments and no major change was observed in concrete specimens with 75% steel slag aggregates. Figures 27 to 32 show the plot of Durability Relative Dynamic Modulus (Pc) Cycles 25 44 77 97 118 149 174 204 244 262 274 300 Control A 100 100 100 100. 100 100 100 100 100 100 100 100 Control B 94.0 100 100 100 100 100 100 100 100 100 100 100 Average 97.0 100 100 100 100 100 100 100 100 100 100 100

NA-A 88.6 72.8 34.6 - NA-B - 94.2 88.6 88.6 72.8 54.1 -

25a 100 100 100 100. 100 100 100 100 100 100 100 100 25b 94.0 94.0 94.0 94.0 94.0 94.0 94.0 72.0 94.0 94.0 94.0 94.0 25c 94.0 94.0 94.0 94.0 94.0 94.0 94.0 94.0 94.0 94.0 94.0 94.0 Average 96.0 96.0 96.0 96.0 96.0 96.0 96.0 88.7 96.0 96.0 96.0 96.0 50a 100 100 100 93.4 93.4 93.4 93.4 87.1 81.0 75.1 75.1 64.0 50b 100 100 100 100. 100 100 100 100 93.4 93.4 93.4 87.1 50c 93.7 93.7 93.7 93.7 93.7 93.7 93.7 93.7 87.5 87.5 81.6 75.9 Average 97.9 97.9 97.9 95.7 95.7 95.7 95.7 93.6 87.3 85.3 83.4 75.7 75a 100 100 100 100. 100 100 100 100 100 100 100 100.0 75b 100 100 100 100. 100 100 100 100 100 100 100 100.0 75c 100 100 100 100. 100 100 100 100 100 100 100 100.0 Average 100 100 100 100 100 100 100 100 100 100 100 100

100a 63.5 - 100b 79.7 - 100c 80.4 34.4 Specimen Failed

100-B-a 93.4 93.4 93.4 93.4 93.4 87.1 87.1 87.1 86.4 86.0 85.0 84.7 100-B-c 100.0 100.0 93.2 93.2 86.7 86.7 86.2 86.0 85.5 85.5 84.0 84.0 100-B-d 100.0 100.0 93.4 93.4 93.4 93.4 93.4 93.2 93.2 93.0 93.0 88.6 Average 97.8 97.8 93.3 93.3 91.1 89.0 88.9 88.8 88.4 88.2 87.3 85.861 factor v/s freeze thaw cycles for various percentage increments of different concrete mixtures with steel slag aggregates. Figure 17: Relative Dynamic Modulus v/s Number of Freeze-thaw cycles for average 0% steel slag aggregates concrete mixture

Relative D y namic Modulus v/s Number of Freeze-thaw cycles

80 85 90 95 100 105 110

0 50 100 150 200 250 300 Number of cyclesRelative DynamicModulus

Figure 18: Percentage Mass Loss v/s Number of Freeze-thaw cycles Average 0% steel slag aggregates concrete mixture

Percentage Mass loss v/s Number of Freeze-thaw cycles

-0.02 -0.015

-0.01 -0.005 0 0.005

0.01 0.015

0.02 0.025

0 50 100 150 200 250 300 Number of cyclesPercentMass Loss %62 Figure 19: Relative Dynamic Modulus v/s Number of Freeze-thaw cycles for average 25% steel slag aggregates concrete mixture

Relative D y namic Modulus v/s Number of Freeze-thaw cycles

80 85 90 95 100 105 110

0 50 100 150 200 250 300 Number of cyclesRelative DynamicModulus

Figure 20: Percentage Mass Loss v/s Number of Freeze-thaw cycles Average 25% steel slag aggregates concrete mixture

Percentage Mass loss v/s Number of Freeze-thaw cycles

-0.02 -0.015

-0.01 -0.005 0 0.005

0.01 0.015

0.02 0.025

0 50 100 150 200 250 300 Number of cyclesPercentMass Loss %63 Figure 21: Relative Dynamic Modulus v/s Number of Freeze-thaw cycles for average 50% steel slag aggregates concrete mixture

Relative D y namic Modulus v/s Number of Freeze-thaw cycles

74 79 84 89 94 99 104 109

0 50 100 150 200 250 300 Number of cyclesRelative DynamicModulus

Figure 22: Percentage Mass Loss v/s Number of Freeze-thaw cycles Average 50% steel slag aggregates concrete mixture

Percentage Mass loss v/s Number of Freeze-thaw cycles

-0.01 -0.005 0 0.005

0.01 0.015

0.02 0.025

0.03 0.035

0.04

0 50 100 150 200 250 300 Number of cyclesPercentMass Loss %64 Figure 23: Relative Dynamic Modulus v/s Number of Freeze-thaw cycles for average 75% steel slag aggregates concrete mixture

Relative D y namic Modulus v/s Number of Freeze-thaw cycles

75 80 85 90 95 100 105 110

0 50 100 150 200 250 300 Number of cyclesRelative DynamicModulus

Figure 24: Percentage Mass Loss v/s Number of Freeze-thaw cycles Average 75% steel slag aggregates concrete mixture

Percentage Mass loss v/s Number of Freeze-thaw cycles

-0.02 -0.015

-0.01 -0.005 0 0.005

0.01 0.015

0.02 0.025

0.03

0 50 100 150 200 250 300 Number of cyclesPercentMass Loss %65 Figure 25: Relative Dynamic Modulus v/s Number of Freeze-thaw cycles for average 100% steel slag aggregates concrete mixture

Relative D y namic Modulus v/s Number of Freeze-thaw cycles

80 85 90 95 100 105 110

0 50 100 150 200 250 300 Number of cyclesRelative DynamicModulus

Figure 26: Percentage Mass Loss v/s Number of Freeze-thaw cycles Average 100% steel slag aggregates concrete mixture

Percentage Mass loss v/s Number of Freeze-thaw cycles

-0.01 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07

0 50 100 150 200 250 300 Number of cyclesPercentMass Loss %66 Figure: 27 Durability Factor v/s Freeze Thaw cycle for 0% replacement

Durability Factor vs. Freeze-Thaw Cycle for 0% Replacement

0 10 20 30 40 50 60 70 80 90 100

25 44 77 97 118 149 174 204 244 262 274 300

Freeze-Thaw Cycle #Durability Factor

Specimen A Specimen B Average

Figure: 28 Durability Factor v/s Free ze Thaw cycle for 25% replacement

Durability Factor vs. Freeze-Thaw Cycle for 25% Replacement

0 10 20 30 40 50 60 70 80 90 100 110

25 44 77 97 118 149 174 204 244 262 274 300

Freeze-Thaw Cycle #Durability Factor

Specimen A Specimen B Specimen C Average67 Figure: 29 Durability Factor v/s Free ze Thaw cycle for 50% replacement

Durability Factor vs. Freeze-Thaw Cycle for 50% Replacement

0 10 20 30 40 50 60 70 80 90 100 110

25 44 77 97 118 149 174 204 244 262 274 300

Freeze-Thaw Cycle #Durability Factor

Specimen A Specimen B Specimen C Average

Figure: 30 Durability Factor v/s Free ze Thaw cycle for 75% replacement

Durability Factor vs. Freeze-Thaw Cycle for 75% Replacement

0 10 20 30 40 50 60 70 80 90 100 110

25 44 77 97 118 149 174 204 244 262 274 300

Freeze-Thaw Cycle #Durability Factor

Specimen A Specimen B Specimen C Average68 Figure: 31Durability Factor v/s Freeze Thaw cycle for 100% mk1 replacement

Durability Factor vs. Freeze-Thaw Cycle for 100% mk1 Replacement

0 10 20 30 40 50 60 70 80 90 100 110

25 44 77 97 118

Freeze-Thaw Cycle #Durability Factor

Specimen A Specimen B Specimen C Average

Figure: 32 Durability Factor v/s Freeze Thaw cycle for 100% mk2 replacement

Durability Factor vs. Freeze-Thaw Cycle for 100% mk2 Replacement

0 10 20 30 40 50 60 70 80 90 100

25 55 95 113 125 151 175 200 225 250 275 300 Freeze-Thaw Cycle #Durability Factor

Specimen A Specimen B Specimen C Average69 5.4.5 Change in length of concrete specimens Table XVIII shows the change of length of the concrete specimens and is compared to the initial length at the start of the test procedure. All the specimens were kept at the normal room temperature in the water basin. The result shows that the change in length of concrete specimens was negligible at the end of 120 days. The control specimens showed a sign of expansion but there was slight contraction in length in the specimens with 100% steel slag.

Table XVIII: Expansion length of concrete specimens

Specimen Initial CRD CRD 7 Days Length Change CRD 28 Days Length Change CRD 90 Days Length Change CRD 120 Days Length Change mixture

(%) ID# (in.) (in.) (%) (in.) (%) (in.) (%) (in.) (%) Control A ctrl-A 0.0459 0.0462 0.003 0.0459 0.000 0.0430 -0.029 0.0493 0.034 Control B ctrl-B 0.0558 0.0561 0.003 0.0556 -0.002 0.0525 -0.033 0.0574 0.016 25% 25-A 0.0000 0.0000 0.0000 0.0000 0.000 0.0900 0.900 0.000 0.000 25% 25-B 0.0208 0.0207 -0.001 0.0186 -0.022 0.0196 -0.013 0.0232 0.024 50% 50-A 0.0045 0.0055 0.01 0.0044 -0.001 0.0041 -0.004 0.0079 0.034 50% 50-B 0.0004 0.0001 -0.003 0.0000 -0.004 0.0009 0.005 0.0027 0.023 75% 75-A 0.0295 0.0285 -0.01 0.0262 -0.033 0.0266 -0.029 0.0315 0.02 75% 75-B 0.0000 0.0000 0.0000 0.0000 0.000 0.0990 0.99 0.000 0.000 100% 100-A 0.0496 0.0320 -0.176 0.0279 -0.217 0.0000 -0.496 0.0355 -0.141 100% 100-B 0.0298 0.0112 -0.186 0.0095 -0.203 0.0000 -0.298 0.0107 -0.19170 CHAPTER VI

DISCUSSION

6.1 Overview This chapter discusses the results of the experiments conducted. The strength of concrete with steel slag aggregates is analyzed, the resistance of concrete under freezing and thawing environments is evaluated and change in length of concrete specimens

discussed.

6.2 Overall experimental Observations No major difficulty in handling the concrete which incorporated steel slag aggregates was encountered except at 75% or higher replacement percentages. There were no major changes in the fresh or hardened properties of concrete with steel slag aggregates. The size and grading of steel slag aggregates were similar to natural limestone aggregates. Using different ranges of sizes of aggregates enable the smaller particles to pack between larger particles, and thereby reducing the void spaces and lowering the cement paste requirements. The shapes of the steel slag aggregates were71 more or less angular in nature, which made the concrete mixture workable. The water absorption capacity of steel slag aggregates was more than that of limestone, which sometimes made the concrete mixture less workable and so water reducing admixtures were added accordingly. One of the important aspects in the concrete mixture is the amount of air voids in the matrix. Air voids helps the water to seep into the pores, which in turn reduce high internal stresses and thereby reduce micro cracking in the structure. Proper amount of air entraining admixtures are added to introduce air bubbles in the concrete mixture. The reason for failing of concrete samples with 100% steel slag aggregates might be due to presence of excessive entrapped air and less entrained air in the mixture during the mixing of concrete. Proper amount of air entraining admixtures were added accordingly depending upon required air content. During the research, it was found that, as the percentage of steel slag aggregates in concrete increased, the mixture became stiffer and more water or admixtures was required to make the concrete more

workable.

6.3 Compressive strength of concrete Most properties of concrete are directly related to its compressive strength. The compression test on the concrete specimens was carried out according to ASTM C39. The samples were properly molded and cured. The specimens were loaded at a control rate in the compression machine. The results can be seen from the Table XII. The control mixture had both 7 and 28 day strength of more than 5,000 psi (35 MPa). The specimen with 50% steel slag aggregates in concrete had 28 days compressive strength of 5,000 psi while specimen with 100% steel slag aggregate had about 6000 psi (40 MPa). The 100%72 steel slag aggregate sample gave good strength than the rest; the reason might be the water-cement ratio. The mixture was very harsh and water reducing admixtures were added to get minimum slump. The higher strength might be due to the cement paste and the bond strength at the paste-aggregates boundary. Variability of test method might be the reason. The rate of loading and progress of crack around the aggregate particles might be the reason of greater strength. The rest of the specimens had 28 day strength more than 4,000 psi (28 MPa) which exceeded the minimum strength requirements from ODOT specifications. Some additional cylinder samples were prepared from the mixture for flexural beams and compression tests were carried out. The results for 7 and 28 days compressive strength for flexure beams are shown in fig 14. The specimen with 75% steel slag aggregates showed strength of more than 5,000 psi. This shows that concrete with steel slag aggregates achieves similar strength compared to conventional concrete.

6.4 Splitting Tensile strength The splitting tensile test is an indirect way of estimating the tensile strength of cylindrical concrete specimens. Since the concrete is much weaker in tension than in compression, the failure would be at a much lower load than in compression. The cylinders were tested according to ASTM C 496. The results of 7 & 28 days splitting tensile strength are shown in Fig 15. The control mixture showed splitting tensile strength after 28 days around 600 psi while all other specimens had around 500 psi (3.5 MPa). For the ordinary structural concrete the tensile strength is around 400 psi (3 MPa) (Mindness 2002).73 6.5 Flexural Strength of concrete The flexural strength of concrete with steel slag aggregates was tested according to ASTM C 78. The flexural beams were prepared, cured in the standard manner and tested using the three point loading method. The theoretical maximum modulus of rupture R is then calculated from simple beam bending formula for third-point loading shown in Equation I. The testing was done after 7 days and results are plotted in Fig 12. The trend was similar to the control mixture. All the mixtures gave a modulus of rupture more than 600 psi (4.14 MPa) in 7 days. This test is very useful since concrete pavements tend to be loaded in bending rather than in axial tension. The flexure test gives better representation of concrete property. It can be noted that the flexure test gave higher values than the tension test, the reason may be that in tension test total volume of specimen is stressed while in flexure test only a relatively small volume of material near the bottom of the beam is subjected to high stress. The flexural strength for a structural concrete is around 800 psi (6MPa). This shows that the concrete with steel slag aggregates performs well (Mindness 2002).

6.6 Freeze-Thaw Durability The freeze-thaw durability test is used to predict the durability of concrete in freeze-thaw environments. Deterioration of the concrete and D cracking are primarily caused by the expansion of water in the paste of concrete mixture or in aggregates during its conversion from liquid phase to solid phase in cold environments. Concrete beam specimens were prepared and tested for freeze thaw according to ASTM C 666 in an74 automated freezing and thawing machine. The change in the resonant frequency according to ASTM C 215 and change of mass of each specimen was monitored at regular intervals. A small hammer is used to create vibrations inside the specimens and the response is recorded by accelerometer attached to the specimen. A resonance tester was used to measure the frequency. Testing was done at regular intervals, usually 15 to 30 cycles. The dynamic modulus of elasticity was determined by measuring the fundamental transverse frequency of the sample at each test interval. The equation to determine relative dynamic modulus of elasticity is show in Equation IV. According to ASTM C 666, the freeze-thaw resistance test is considered complete when either the specimen is subjected to 300 freeze-thaw cycles or when the dynamic modulus of elasticity drops below 60 %. The results showed that the control mixtures did not undergo any change in the durability factor and the relative dynamic modulus for the control mixture was 100 percent throughout 300 cycles. Similarly the concrete mixture which had 75% of volume replaced by steel slag aggregates also did not undergo any change in durability factor. The worst relative dynamic modulus (Pc) was found to be approximately 64 percent. The concrete specimen which had 100% (A) steel slag aggregates in it failed during the initial Freeze-thaw cycles as the relative dynamic modulus was less than 60%. The reason for the failure of that specimen was that no air entraining admixture was added into the concrete during its preparation and a high amount of entrapped air was found during mixing. The 100% (B) specimen with proper air entrainment showed a relative dynamic modulus after 300 cycles of 85 percent and was still in a good shape with no major deterioration.75 All concrete specimens suffered some mass change (loss). During the freeze-thaw environment there is an increase in series of micro cracks in the sample which will reduce the fundamental transverse frequency and which will ultimately change the mass of the specimens. Scaling deterioration of the sample is expected and will reduce the mass. The results showed that this mass loss was very small. Loss in mass leads to lower frequency and lower durability factor. Figure: 33 Photograph (A) showing the behavior of 100% A steel slag specimen with no air entraining admixtures under the freeze-thaw machine and (B) shows series of micro cracks and deterioration of the concrete after 44 cycles.

Figure: 33(A) 100 % steel slag aggregate specimen A (Top)

Figure: 33(B) 100 % steel slag aggregate specimen A (Bottom)76 6.7 Measurement of linear expansion or contraction of concrete specimens.

This test was conducted in order to observe the change in length of concrete specimens with steel slag aggregates. There was a perception that steel slag aggregates have expansive properties under moist conditions. The specimens were prepared and initial length measurement readings were taken before placing in the water bath. All the specimens were maintained at same temperature range and then compared. The change in length of the concrete specimens can be calculated from Equation III. The change in length of various concrete specimens with steel slag aggregates were taken at 7, 28, 90 and 120 days as shown in Table XVIII. The control specimens showed an increase of 0.034% at end of 120 days. The concrete specimen with 25%A and 75%B showed no change in length at 120 days. All specimens observed slight expansion under saturated conditions except the specimen with 100% steel slag aggregates showed an average shrinkage of 0.166%.77 CHAPTER VII

CONCLUSIONS AND RECOMMENDATIONS

7.1 Summary The main aim of this research was to study the behavior of concrete and changes in the properties of concrete with steel slag aggregates by replacing the use of natural aggregates. Steel slag is a byproduct and using it as aggregates in concrete will might prove an economical and environmentally friendly solution. The demand for aggregates is increasing rapidly and so as the demand of concrete. Thus, it is becoming more important to find suitable alternatives for aggregates in the future. A through literature review was conducted to study and investigate the properties of steel slag aggregates. The results showed that it has properties similar to natural aggregates and it would not cause any harm if incorporated into concrete. A comparison was made between concrete having natural coarse aggregates and concrete with various percentages of steel slag aggregates replaced by volume. The results of this research were encouraging, since they show that using steel slag as coarse aggregates in concrete has no negative effects on the short term properties of hardened concrete.78 The results of the research program can be summarized as follows: 1. Compressive strength, flexural strength and splitting tensile strength for steel slag aggregates concrete were similar to conventional concrete. The strength may be affected with time and so long term effects on hardened properties of concrete require further investigation. 2. Durability of steel slag aggregates concrete under freeze-thaw environment was the main goal in this research, as there was a belief that the steel slag aggregates have expansive characteristics and would cause cracking in concrete. The results proved that if up to 50 to 75 % of steel slag aggregates are incorporated in the traditional concrete, there would not be much change in the durability of concrete. 3. The slight improvement in strength may be due to shape, size and surface texture of steel slag aggregates, which provide better adhesion between the particles and

cement matrix. 4. Proper care should be taken during the aging of steel slag and during the stockpiling of steel slag.

7.2 Some Limitations of testing methods It should be kept in mind that most of the research was conducted in the laboratory environment. There are chances of experimental error which influences the results of the tests. The freeze-thaw test is designed in such a way that concrete specimens are subjected to repeated cycles of freezing and thawing in a very short period of time. There is a rapid rate of cooling in the freeze thaw machine. The prescribed cooling rate during the test method is about 6 to 15°C per hour; this is much higher than79 what concrete would be subjected in the field. Chilling the specimens within a specified period of time, so as to allow many samples to be tested to 300 cycles, generally is not what happen actually in the field. Therefore concrete that passes this severe laboratory

test should be durable in the field. The tests for hardened concrete are susceptible to variation according to the specimen sizes, difference in geometry, rate of loading, temperature at time of testing and other factors. It should be kept in mind that small concrete specimens do no particularly represent the strength of concrete in the structure; they only give comparative data.

7.3 Suggestions for future research

1. A much more extensive field study on a concrete structure made with steel slag aggregates used in the mixture should be conducted and changes in durability and mechanical properties should be investigated and correlated to laboratory results. 2. Further investigation on resistance of concrete with steel slag aggregates to attack by sulfates; alkali silica reactions, carbonation, sea water attack, harmful chemicals and resistance to high temperatures are needed. The behavior of steel slag aggregate concrete under corrosive environments and its fire resistance capacity should also be investigated. The results of such studies would directly benefit the construction industry and broader use of steel slag in concrete would improve overall properties and cost effective solution. 3. The long term behavior of concrete with steel slag aggregates should be studied and its compatibility with reinforcing steel should be analyzed in the future.80 4. It is also suggested to do Petrographic examinations of concrete samples with steel slag aggregates to get insight of the actual behavior of concrete. The relationship between entrained air and entrapped air in concrete should be studied. 5. A comprehensive chemical analysis of steel slag aggregates should to be carried out before using in construction.

6. Due to presence of several dangerous heavy metals and salts in the steel slag aggregates, leaching tests should be carried out to verify its environmental compatibility.81 REFERENCES

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