Ultra Durable, High Strength Concrete and Its Use in Buildings

Transcription

1 NRF-CRP Underwater Infrastructure and Underwater City of the Future Ultra Durable, High Strength Concrete and Its Use in Buildings Slide No. 1

2 Big Thank You to NRF National Research Foundation provides the funding through Competitive Research Programme (CRP) on Underwater Infrastructure and Underwater City of the Future Investigators: Tan Soon Keat (Hydrodynamics) - PI (Principal Investigator) Chu Jian (Geotechnical Considerations) Co-PI Susanto Teng (Structures and Materials) Co-PI Current Researchers in Structures and Materials: - Dr. Liu Yu - Jimmy Chandra, Darren Lim Tze Yang, Khatthanam Chantabouala, - Vahid Afroughsabet - Odd E. Gjorv (Em. Prof. Norway) - Collaborator GGBS (EnGro Corp); Silica Fume (Elkem); Superplasticizer (BASF); Steel Fibres (Bekaert); Grade 600 steel bars (NatSteel); Concrete mixing (Holcim); Specimen Fabrication & Casting (Fongsoon). Partners: JTC, Surbana, HSL Slide No. 2

3 Ultra Durable Concrete An Ultra Durable Concrete material is especially suitable for marine structures that are designed to last 100 years or more without significant damage. Poor quality concrete Slide No. 3

4 A deteriorating concrete bridge Poor quality concrete Slide No. 4

5 Life-spans of some concrete structures The Pyramid, Roman Colosseum, The Parthenon > 1000 years 1. Offshore Concrete Structures 30 to 60 years 2. Durable Concrete Bridges, Tunnels 60 to 100 years? 3. Guggenheim Museum, Bilboa 100 years (built on land) 4. Tjuvholmen Mixed Development, Oslo to 300 years? 5 Slide No. 5

6 Titanium for Buildings The Guggenheim Museum, Bilbao. The building specification of calls for a 100 year life-span, but many are convinced that the titanium exterior should be able to last several hundred years longer. 6 Slide No. 6

7 Mixed Development (condominium and shops) at Tjuvholmen, Oslo Courtesy of Skanska Designed to last 300 Years?! Slide No. 7

8 NTU Research on Ultra Durable Concrete To find a very durable concrete for building a mega-structure which can be partially or entirely submerged under sea water as an alternative to conventional land reclamation technique. The mega marine structure is expected to survive for 300 years or longer in marine environment. The concrete has to possess extremely good durability properties but is still economical. Required Properties: - Effectively block chloride (from seawater) from entering the concrete. - Effectively prevents corrosion of reinforcement for a very long time. - Use normal concrete constituents, possesses high workability, economical, etc. Additional properties obtained: - Compressive strength 120 MPa 150 MPa (typical tall buildings use MPa). - The concrete can be made ductile by adding steel fibres. - Economical (only 50% to 60% more expensive than normal concrete) Slide No. 8

9 Ultra Durable Concrete Constituent Materials Normal Aggregates Normal Sand Portland Cement Water Superplasticizer Ground Granulated Blast- Furnace Slag (GGBS) Silica Fume Slide No. 9

10 Ultra Durable Concrete mix design Mix A B C D E F G H I w/c Ratio A/C Ratio* UFGGBS (%) GGBS (%) USF (%) TCM (kg/m 3 ) F/C Ratio 1 Aggregate Ratio** 0.69 Table 2. Mixture design proportions *Aggregate/Cement Ratio **Ratio by weight Slide No. 10

11 Ultra Durable Concrete (self-compacting reduces manpower) A typical Ultra Durable Concrete can have a flow diameter of 650 to 700 mm. Thus, in terms of workability, the Ultra Durable Concrete is as good as self-compacting concrete. Flow diameter Slide No. 11

12 Cost Comparison Item Grade 60 (kg) Unit Price per kg Grade 135 (Ultra Durable) Unit Price per kg Cement Ultra Fine GGBS Undensified Silica Fume Coarse and Fine Aggregates Water Superplasticizer Material Cost 110 SGD 188 SGD Slide No. 12

13 All the parameters have uncertainties Service Life Analysis Cover Depth, Chloride Permeability, Critical Chloride Content, Curing Duration and Time of Exposure Sea Water Chloride Content and Temperature Fick s Second Law of Diffusion Resistance to withstand the loads (R) C x, t D t = D 0 1 = C s [ 1 erf 1 + t t 1 t t x 2 D t.t ] 1 t 0 t. ke Environmental Loads (S) k e = exp b e T 273 Monte Carlo Simulation Slide No. 13

14 Probability of Failure Beyond 150 or 200 years, the analyses are purely theoretical Slide No. 14

15 Use of High Strength Concrete in Buildings Slide No. 15

16 CapitaGreen (Takenaka Corp Main Contractor) Some columns (lower floors) are made of Grade 80 and 100 MPa concrete. Slide No. 16

17 Mechanical Property Compressive Strength & Modulus of Elasticity Flexural Tensile Strength Slide No. 17

18 Long-Term Tests Shrinkage measurement using Length Comparator and Strain Gauges Typical Creep test Slide No. 18

19 Creep Properties The creep coefficient for the Ultra Durable Concrete is about 0.5 for 30 yr period compared to that of normal concrete (about 2.0 in Singapore) Slide No. 19

20 Shrinkage Properties The shrinkage strain is about 240 micro-strain (30 yr value). These are very low values compared to that of normal concrete (500 micro-strain) Slide No. 20

21 Advantages of Ultra Durable, High Strength Concrete Very high durability (delay corrosion of rebars) Very high workability (self-compacting) Resistance to aggressive environments. Longer span lengths and smaller/thinner member sizes. Reduction in concrete volume and structural weight. Reduction in maintenance cost and extension of service life. High compressive & tensile strengths (f r = 10 MPa versus 4 MPa) High modulus of elasticity (40 GPa versus 25 GPa) Very low creep coef & shrinkage strain (0.5 & 240 versus 2 & 500) Green (use of slag 30%, silica fume 10%) The concrete is recyclable as coarse aggregates 21 Slide No. 21

22 Horizontally Spanning Buildings - The Interlace Contractor - Woh Hup ; Consultant - T.Y. Lin Slide No. 22

23 Horizontally Spanning Buildings - The Interlace Creep & Shrinkage Analysis of Prestressed Transfer Floor Transfer Floor f cu = 60 MPa Columns f cu = 80 MPa c c Slide No. 23

24 Horizontally Spanning Buildings - The Interlace Transfer Floor f cu = 60 MPa Columns f cu = 80 MPa Slide No. 24

25 Horizontally Spanning Buildings - The Interlace Initial upward camber due to prestressing = + 9 mm 50 Year deflection with all loads = - 25 mm c A/Prof c Susanto Teng Slide No. 25

26 Vertically Curved & Irregular Building on Grange Road LSW Consulting Engineers Construction Stage Modeling (Stages 4, 18, and 26) Slide No. 26

27 Vertically Curved & Irregular Building on Grange Road Principal tensile stresses (Level 20 th ) Slide No. 27

28 Storey Level Storey Level Vertically Curved & Irregular Building on Grange Road U2, Excl Reinf, w/ PD U2, Incl Reinf, w/ PD days 224 days days 224 days 15 1 yr 15 1 yr Column C13: Lateral Deflection (mm yrs + sustained load 5 yrs + sustained load 50 yrs + sustained load Column C13: Lateral Deflection (mm) 2 yrs + sustained load 5 yrs + sustained load 50 yrs + sustained load 1 yr 224 th day Creep and Shrinkage Analysis & Construction Stage Modeling (Stages 4, 18, and 26) 56 th day Deflection (50 yrs) Slide No. 28

29 Designing Concrete Members (Future Seminars) Eurocodes cover: Concrete strengths of up to C90/105 MPa (f ck_cyl /f ck_cube or old notation f c /f cu ) Steel yield strengths f yk of up to 600 MPa. But, there is no design guide for f yk > 500 MPa (equiv. to f y 460 MPa BS8110) For shear design (Singapore N.A.), concrete strength is limited to C50/60 (f cu = 60 MPa) unless proven by experiment. So, structural design guides are needed for Ultra Durable, High Strength Concrete (f cu > 105 MPa) and for High Strength steel bars (Grade > 500 MPa). Slide No. 29

30 Experiments Fibre Reinforced Concrete tensile strength of > 20 MPa. Beams, Slabs, and Walls (f cu = 120 MPa or higher) with or without fibres Beam depth (d): 450, 900, 1350, 1800 (mm) Walls with H/B up to 2 and overall height up to 4 m overall height. Slabs with low reinforcement ratios Slide No. 30

31 Thank you Slide No. 31