BEHAVIOUR OF HIGH STRENGTH CONCRETE REINFORCED WITH

DIFFERENT TYPES OF STEEL FIBRE

Emdad K.Z. Balanji, M. Neaz Sheikh, Muhammad N.S. Hadi

School of Civil, Mining and Environmental Engineering, University of Wollongong, Australia

22-25 November 2016

Table of Content

• Introduction

• Objectives

• Experimental Program

• Results and Discussions

• Conclusions

Introduction

Definition of High Strength Concrete (HSC)

South Wacker Drive Concrete Buildings Constructed in (1990)Chicago’s Water Tower Place (1976)

• The term of HSC is used for concrete which has higher durability, excellent environmental resistance and a higher

compressive strength than Normal Strength Concrete (NSC).

• Australian Standard (AS1379-2007) has defined HSC as “For concrete strength greater than 50 MPa, the concrete shall

consider as special class concrete”.

• ACI 363R-92 has defined HSC as concrete having a specified compressive strength for design of 55 MPa, or greater.

Introduction

Difference Between NSC and HSC

• Stress-strain Relationship

Failure Mode For Concrete Specimens Under Uniaxial Compression.

NSC HSC

Axial Stress Vs. Axial Strain and Lateral Strain For Concrete (Ahmad and

Shah (1982).

• Failure Mode

Introduction

Steel Fibre Reinforced Concrete (SFRC)

5

Using Steel Fibres

To Enhance tensile strength

To Prevent Brittle Failure

Types of Fibres

Introduction

Factors Affecting the Properties of Steel Fibre Reinforced Concrete (SFRC)

1. Volume of Steel Fibres (vf%) 2. Aspect Ratio of Steel Fibre (l/d)

Compressive Stress Vs Axial Strain Curve Influence of Aspect Ratio of Steel Fibre on the Compressive

Stress-Strain Curve

Introduction

7

Tensile Stress-Strain Curves For Steel Fibre Reinforced Mortars (Shah 1978).

4. Orientation of Fibre 3. Shape of Steel Fibre

Factors Affecting the Properties of the SFRC

Single Fibre Bridging a Crack in a Matrix (Foster, 2001).

Introduction

Micro (Short) and Macro (Long) Fibres

Löfgren (2005)

8

Classification of Fibres

Macro Fibre

A Cross-Sectional Diameter Higher Than That of Cement

Grains

Length Larger Than the Maximum Size Aggregate

Micro Fibre

Same Cross-Sectional Diameter As the Cement

Grain.

Length Less Than the Maximum Size Aggregate

Performance of Micro and Macro FibresLawler et al. (2003)

• Found that a blend of micro-fibre (less than 0.022 mm diameter) and macro-fibre (0.5 mm diameter) in a mortar mixture has a

positive effect on reducing the crack growth at different stages of failure process.

9Illustration of Different Size of Fibre on Crack Bridging

Introduction

Introduction

Objectives

• To find the optimum quantity of the micro steel fibre (MI), macro steel fibre (MA) and hybrid

steel fibres (HY) reinforced High Strength Concrete (HSC).

• To determine the effect of type, volume content and aspect ratio of the different types of steel

fibres on the mechanical properties of HSC.

10

Mix

Volume content of

Micro steel fibres (%) Macro steel fibres (%)Hybrid steel

Fibres (%)

R - - -

MI-1 2 - -

MI-2 3 - -

MI-3 4 - -

MA-1 - 1 -

MA-2 - 2 -

MA-3 - 3 -

HY-1 - -1.5

(1% micro + 0.5% macro)

HY-2 - -2.5

(1.5% micro + 1% macro)

HY-3 - -3.5

(2% micro + 1.5% macro)

Experimental Program

• Test Matrix

Experimental Program

Materials

• Ordinary Portland Cement (OPC) (505 kg/m3)

• Silica fume (35 kg/m3)

• Sand (616 kg/m3)

• Coarse aggregate (977 kg/m3)

• Water (190 kg/m3)

• Super-plasticizer was varied from 1.5% to 2%

• Two types of steel fibres

Type of steel fibres

Length

(l)

(mm)

Diameter

(d)

(mm)

Aspect ratio

(l/d)

Tensile

strength

(MPa)

Density

of fibre

(kg/m3)

Copper-coated micro steel

fibres

(GDMF, 2014)

6±1 0.2±0.05 30 >2600 7900

Deformed macro steel

fibres (Fibercon, 2014)18 0.55 33 800 7865

Experimental Program

Mixing and Casting

Experimental Program

Compression test Splitting tensile test

Testing

Results and Discussions

• Slump

SpecimenSlump

(mm)

Experimental

Compressive strength

(𝑓𝑐) (MPa)

Split tensile

strength

(𝑓𝑠𝑝) (MPa)

R 80 65 3.91

MI-1 50 66.7 6.06

MI-2 25 68.9 6.8

MI-3 5 65.8 6.88

MA-1 35 64.5 6.14

MA-2 20 65.8 6.95

MA-3 5 65.1 6.99

HY-1 25 65.2 6.25

HY-2 16 68.4 7.22

HY-3 3 68.0 7.82

0

10

20

30

40

50

60

70

80

90

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Slu

mp

(m

m)

Fibre volume content (%)

MI

MA

HY

Results and Discussions

• Compressive Strength

50

55

60

65

70

75

80

0 2 3 4

Co

mp

ress

ive

stre

ng

th (

MP

a)

Volume content (%)

Relationship between the volume

content of steel fibres and the

compressive strength for micro steel

fibre reinforced HSC

Results and Discussions

• Compressive Strength

50

55

60

65

70

0 1 2 3

Co

mp

ress

ive

stre

ng

th (

MP

a)

Volume content (%)

Relationship between the volume

content of steel fibres and the

compressive strength for macro steel

fibre reinforced HSC

Results and Discussions

• Compressive Strength

50

55

60

65

70

0 1.5 2.5 3.5

Co

mp

ress

ive

stre

ng

th (

MP

a)

Volume content (%)

Relationship between the volume

content of steel fibres and the

compressive strength for hybrid

steel fibre reinforced HSC.

Results and Discussions

• Compressive Strength

The effect of the aspect ratio of

steel fibres on the compressive

strength of HSC.

Results and Discussions

• Splitting Tensile Strength

0

2

4

6

8

0 2 3 4

Sp

lit

tensi

le s

tren

gth

(M

Pa)

Volume content (%)

Relationship between volume content of

steel fibres and split tensile strength for

micro steel fibre reinforced HSC.

Results and Discussions

• Splitting Tensile Strength

0

2

4

6

8

0 1 2 3

Sp

lit

tensi

le s

tren

gth

(M

Pa)

Volume content (%)

Relationship between volume content

of steel fibres and split tensile strength

for macro steel fibre reinforced HSC.

Results and Discussions

• Splitting Tensile Strength

0

2

4

6

8

0 1.5 2.5 3.5

Sp

lit

ten

sile

str

eng

th (

MP

a)

Volume content (%)

Relationship between volume content of

steel fibres and split tensile strength for

hybrid steel fibre reinforced HSC.

Results and Discussions

• Splitting Tensile Strength

The effect of the aspect ratio of steel

fibres on the split tensile strength of

HSC.

Conclusions

• The maximum improvement in the compressive strength of HSC was observed with the inclusion of 3% of

micro steel fibres, 2% of macro steel fibres and 2.5% of hybrid steel fibres.

• The compressive strength of HSC increased when using low aspect ratio (micro steel fibre) with high volume

content of steel fibres.

• The higher improvement in split tensile strength was observed with the inclusion of 4%, 3% and 3.5% of

micro, macro and hybrid steel fibres, respectively.

• The split tensile strength of HSC increased with using high aspect ratio (macro steel fibre) with low volume

content of steel fibres.