Annual North QLD Concrete Engineering and Technology Seminar May 6, 2011 Townsville

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1 Concrete JCU Dr. Rabin Tuladhar, James Cook University Australia Annual North QLD Concrete Engineering and Technology Seminar May 6, 2011 Townsville Outline Sustainability: JCU s teaching initiatives and Research - Natural Pozzolans as cement replacement Structural safety: - Concrete slabs with Class-L Reinforcement and Steel Fibres Other ongoing researches 1

2 JCU: Where we are. Great Barrier Reef James Cook University s strategic intents: (1) Advancing Northern Queensland and northern Australia, while looking for our work to benefit the tropics world-wide (2) produce graduates with the expertise and intellectual curiosity required for sustainable development of our communities JCU: Sustainability Initiatives Refreshing existing engineering courses to make sustainability a core focus in undergraduate programs in School of Engineering and Physical JCU Sustainability concepts are embedded into Concrete Engineering to develop graduate attributes such as: - knowledge of sustainable development - understanding of various sustainable practices in concrete engineering - and their applications 2

3 SUSTAINABILITY Social Sustainable Environment Economic Sustainable development is striking a delicate balance of all of 5 the three aspects; often referred as Triple Bottom Line Concrete structures: Social Aspect On social front, concrete structures provide safe, healthy and comfortable living environment - Resistant to weather, earthquake, fire, termite - Better Acoustic, thermal properties Hurricane Katrina, Pass Christian Shimizu Co. Building, Tokyo Japan Cyclone and Flood Resistance Fire Resistance 3

4 Concrete structures: Economic Aspect On economic front, concrete structures have the lowest construction, operational and maintenance cost - Longevity - Low cost and abundantly available raw materials - Efficient construction techniques Pantheon Built in 126 AD Sustainable housing with tilt-up concrete panels Environmental Aspect: Cement Production Clinkers Raw materials Pyroprocessing in Kiln at C Grinding Green house gas emission : - Fossil fuel burning - Calcination of raw material Cement 4

5 Supplementary Cementitious Materials (SCMs) SCMs can either be: - Industry by-products (Fly Ash, Silica Fume, GGBFS) - Natural Pozzolans (volcanic ash, opaline shale, pumicite) Twofold advantages of using SCMs: - Reduce use of cement - Reuse waste materials Potential use of mining-waste as pozzolanic material has not yet been explored intensively Pitchstone Fine as SCM Nychum district, in North QLD Australia has pitchstone deposits with a potential to produce 100 million tonnes Nychum Pitchstone Pitchstone is used to produce light weight aggregates, in horticulture and chemical industry 5

6 Pitchstone Fine Pitchstone is quarried using drill and blast methods followed by crushing and screening Pitchstone Fine 30% of the crushed material has particle size less than 500µm Currently pitchstone fine is stockpiled onsite as mining-waste Pitchstone Fine (PF) as SCM Compressive strength with different cementitious materials (Smith, M, 2008) Compressive strength (MPa) PC FA20 PF10 PF20 PF30 PF Time (Days) 6

7 Pitchstone Fine (PF) as SCM Strength Activity Index (SAI) = Strength with SCM / PC For Pozzolans, SAI for 7 or 28 days > 75% Strength Activity Index (SAI) in % FA20 PF10 PF Time (Days) Pitchstone Fine (PF) as SCM 7 Flexural strength at 28 days with different cementitious materials Flexural Strength at 28-day (MPa) PC FA20 PF10 PF20 PF30 PF40 7

8 Life cycle assessment of PF (Ongoing..) CO 2, Energy Extraction of raw materials Manufacturing and Processing Cradle to Gate - LCA CO 2, Energy CO 2, Energy Concrete Plant Transportation Steel Fibre Reinforced Concrete Slabs with Class L Reinforcement 8

9 Class L Reinforcement Class L - low ductility welded wire mesh Used in ground slabs, footpaths and residential slabs Why it is used? -Installation requires less labour -Greater spacing accuracy -Shorter splice length Concrete Slabs with Class L Reinforcement Concrete slabs with Class-L mesh are more likely to fail catastrophically 9

10 Steel Fibre Reinforced Slabs with Class L Reinforcement Objective: Enhance ductility of concrete slabs with Class L mesh using Steel Fibres Steel Fibres: - Improves tensile strength - Improves post-cracking behaviour SFRC Section One-way Slab Tests 8 simply supported one-way slabs were tested (Lancini, 2010) - Class N reinforcement - Class L reinforcement - Class L + Steel fibres 10

11 One-way Slab Tests (Fibre Types) Standard Mill Cut Fibre: Length : 50 mm Effective Diameter : 1.15 mm Wave Height : 1.1 mm Aspect ratio : 42 Hooked End Cut Fibre: Length : 60 mm Diameter : 0.9 mm Aspect ratio : 67 Twincon Fibre: Length : 54 mm Diameter : 1.0 mm Head Diameter : 2.0 mm One-way Slab Tests WWF and Deformed Bar Bottom Reinforcement Steel Fibre Slab Reinforcement Type D b A st d ρ L/d Reinforcement Tensile Fibre (mm) (mm 2 ) (mm) (%) Strength (MPa) Length (mm) SN1 D500N Nil N/A N/A SL2 D500SL Nil N/A N/A SL3 D500SL kg Mill Cut fibre/m 3 concrete SL4 D500SL kg Mill Cut fibre/m 3 concrete SL5 D500SL kg Hooked End fibre/m 3 concrete SL6 D500SL kg Hooked End fibre/m 3 concrete SL7 D500SL kg Twincon fibre/m 3 concrete SL8 D500SL kg Twincon fibre/m 3 concrete

12 Experimental setup Data logger 300kN Hydraulic Jack Load cell Concrete strain gauges Test Specimen Steel strain gauges Experimental Results (SN1 and SL2) (Lancini, 2010) SN1 (Class N) SN1 - Plain with Class-N - Peak Moment = kn m - Midspan Deflection = mm SL2 (Class L) SL2 - Plain with Class-L - Peak Moment= kn m - Midspan Deflection = mm 12

13 Experimental Results (SN1 and SL2) Crack Distributions SN1 Class-N reinforcement well distributed cracks SN1 (Class N) SL2 - Class-L reinforcement No crack distribution SL2 (Class L) Experimental Results (SL3 and SL4) Mill Cut Fibre Slabs SL2 SL3 SL4 SL3 30kg/m 3 Mill Cut - Peak Moment= kn m - Midspan Deflection = mm SL4 40kg/m 3 Mill Cut - Peak Moment= kn m - Midspan Deflection = mm No improvement in ductility 13

14 Experimental Results (SL5 and SL6) H o o k E n d F i b r e S l a b s SL5 30kg/m 3 - Peak Moment= kn m - Midspan Deflection = 18.78mm SL6 SL5 SL6 40kg/m 3 - Peak Moment= kn m - Midspan Deflection = 21.45mm SL2 Experimental Results (SL5 and SL6) Hook End Fibre Slabs SL5 30kg/m 3 Hooked End - Crack distribution increased compared to SL2 SL5 (Hooked end 30kg/m 3 ) SL6 40kg/m 3 Hooked End - Extensive cracking on the soffit of the specimen SL6 (Hooked end 40kg/m 3 ) 14

15 Experimental Results (SL7 and SL8) Twincone Fibre Slabs SL7 30kg/m 3 Twincone - Peak Moment= kn m - Midspan Deflection = 21.67mm SL8 SL7 SL2 SL8 40kg/m 3 Twincone - Peak Moment= kn m - Midspan Deflection 20.28mm Experimental Results (SL7 and SL8) SL7 30kg/m 3 Twincone - Similar crack patterns as SL6 Twincone Fibre Slabs SL8 40kg/m 3 Twincone - Well distributed cracks comparable to SN1 - Increased level of distribution due to the fibres conical ends SL7 (Twincone 30kg/m 3 ) SL8 (Twincone 40kg/m 3 ) 15

16 Experimental Results (Ductility) Ductility µ = 2 / 1 1 = midspan deflection when middle reinforcing bar began to yield 2 = midspan deflection when the slab first began to unload Slab Specimen 1 2 µ = 2 / 1 (mm) (mm) (mm) SN SL SL SL SL SL SL SL Further Research Continuous two-span one-way slab with Class L reinforcement and Steel Fibres 1.8m 1m 1m 1m 1m -SL1 (SL82, No Fibres) -SL2 (SL82, 40 kg/m3 Twincone Fibres) -SL3 (SL82, 60 Kg/m3 Twincone Fibres) 16

17 Other ongoing research - Effects of temperature of reinforcement on the concrete-reinforcement bond properties - Finite element analysis of reinforced concrete beams strengthened with fibre reinforced polymer sheets - Enhancing performance of pervious concrete using latex polymer and macro polypropylene fibres Thank you! 17