BEHAVIOUR OF HIGH STRENGTH CONCRETE REINFORCED WITH DIFFERENT TYPES OF STEEL FIBRE

Transcription

1 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 November 2016

2 Table of Content Introduction Objectives Experimental Program Results and Discussions Conclusions

3 Introduction Definition of High Strength Concrete (HSC) 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 (AS ) 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. Chicago s Water Tower Place (1976) South Wacker Drive Concrete Buildings Constructed in (1990)

4 Introduction Stress-strain Relationship Difference Between NSC and HSC Failure Mode NSC HSC Axial Stress Vs. Axial Strain and Lateral Strain For Concrete (Ahmad and Shah (1982). Failure Mode For Concrete Specimens Under Uniaxial Compression.

5 5 Introduction Steel Fibre Reinforced Concrete (SFRC) Types of Fibres Using Steel Fibres To Enhance tensile strength To Prevent Brittle Failure

6 Introduction Factors Affecting the Properties of Steel Fibre Reinforced Concrete (SFRC) 1. Volume of Steel Fibres (v f %) 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

7 Introduction Factors Affecting the Properties of the SFRC 3. Shape of Steel Fibre 4. Orientation of Fibre Tensile Stress-Strain Curves For Steel Fibre Reinforced Mortars (Shah 1978). Single Fibre Bridging a Crack in a Matrix (Foster, 2001). 7

8 Introduction Micro (Short) and Macro (Long) Fibres Löfgren (2005) Classification of Fibres Macro Fibre Micro Fibre A Cross-Sectional Diameter Higher Than That of Cement Grains Same Cross-Sectional Diameter As the Cement Grain. Length Larger Than the Maximum Size Aggregate Length Less Than the Maximum Size Aggregate 8

9 Introduction Lawler et al. (2003) Performance of Micro and Macro Fibres Found that a blend of micro-fibre (less than 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. Illustration of Different Size of Fibre on Crack Bridging 9

10 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

11 Experimental Program Test Matrix Volume content of Mix Hybrid steel Micro steel fibres (%) Macro steel fibres (%) Fibres (%) R MI MI MI MA MA MA HY (1% micro + 0.5% macro) HY (1.5% micro + 1% macro) HY (2% micro + 1.5% macro)

12 Experimental Program Materials Ordinary Portland Cement (OPC) (505 kg/m 3 ) Silica fume (35 kg/m 3 ) Sand (616 kg/m 3 ) Coarse aggregate (977 kg/m 3 ) Water (190 kg/m 3 ) Super-plasticizer was varied from 1.5% to 2% Two types of steel fibres Type of steel fibres Copper-coated micro steel fibres (GDMF, 2014) Deformed macro steel fibres (Fibercon, 2014) Length Diameter Tensile Density Aspect ratio (l) (d) strength of fibre (l/d) (mm) (mm) (MPa) (kg/m 3 ) 6±1 0.2± >

13 Experimental Program Mixing and Casting

14 Experimental Program Testing Compression test Splitting tensile test

15 Slump (mm) Results and Discussions Slump Specimen Slump (mm) Compressive strength (f c ) (MPa) Experimental Split tensile strength (f sp ) (MPa) MI MA HY R MI MI MI MA MA MA HY HY HY Fibre volume content (%)

16 Compressive strength (MPa) Results and Discussions Compressive Strength Relationship between the volume content of steel fibres and the compressive strength for micro steel fibre reinforced HSC Volume content (%)

17 Compressive strength (MPa) Results and Discussions Compressive Strength Relationship between the volume content of steel fibres and the compressive strength for macro steel fibre reinforced HSC Volume content (%)

18 Compressive strength (MPa) Results and Discussions Compressive Strength Relationship between the volume content of steel fibres and the compressive strength for hybrid steel fibre reinforced HSC Volume content (%)

19 Results and Discussions Compressive Strength The effect of the aspect ratio of steel fibres on the compressive strength of HSC.

20 Split tensile strength (MPa) Results and Discussions Splitting Tensile Strength Relationship between volume content of steel fibres and split tensile strength for micro steel fibre reinforced HSC Volume content (%)

21 Split tensile strength (MPa) Results and Discussions Splitting Tensile Strength Relationship between volume content of steel fibres and split tensile strength for macro steel fibre reinforced HSC Volume content (%)

22 Split tensile strength (MPa) Results and Discussions Splitting Tensile Strength Relationship between volume content of steel fibres and split tensile strength for hybrid steel fibre reinforced HSC Volume content (%)

23 Results and Discussions Splitting Tensile Strength The effect of the aspect ratio of steel fibres on the split tensile strength of HSC.

24 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.

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