Fly Ash, Slag, Silica Fume, and Natural Pozzolans

Transcription

1 Silica Fume, and

2 Fly Ash, Slag, Silica Fume, and Also known as Supplementary Cementing Materials (SCMs) a material that, when used in conjunction with portland cement, contributes to the properties of the hardened concrete through hydraulic or pozzolanic activity, or both.

3 Supplementary Cementitious Materials (SCMs) From left to right: Fly ash (Class C) Metakaolin (calcined clay) Silica fume Fly ash (Class F) Slag Calcined shale Fly Ash, Slag,

4 Supplementary Cementing Materials Pozzolans Pozzolan a siliceous or alumino-siliceous material that, in a finely divided form and in the presence of moisture, chemically reacts with calcium hydroxide released by the hydration of portland cement to form compounds possessing cementing properties. Fly Ash, Slag, a natural material which may also be calcined and/or processed ( eg. metakaolin, rice husk, volcanic ash, calcined shale)

5 Specification and Class of Natural Pozzolans ASTM C 618 (AASHTO M 295) Fly Ash, Slag, Metakaolin Class N Raw or calcined natural pozzolans including: Diatomaceous earths Opaline cherts and shales Tuffs and volcanic ashes or pumicites Calcined clays, including metakaolin, and shales

6 SEM Micrograph of Calcined Clay Particles

7 SEM Micrograph of Calcined Shale Particles

8 Specifications and Classes of Fly Ash ASTM C 618 (AASHTO M 295) Fly Ash Class F Fly ash with pozzolanic properties Class C Fly ash with pozzolanic and cementitious properties Fly Ash, Slag,

9 SEM Micrograph of Fly Ash Particles

10 Specifications and Grade of Ground Granulated Iron Blast-Furnace Slags ASTM C 989 (AASHTO M 302) Grade 80 Slags with a low activity index Grade 100 Slags with a moderate activity index Grade 120 Slags with a high activity index

11 SEM Micrograph of Slag Particles

12 Applications for Fly ash, Slag, Calcined Clay or Calcined Shale

13 Specification for Silica Fume ASTM C 1240 Silica Fume finely divided residue resulting from the production of silicon, ferro-silicon, or other silicon-containing alloys that is carried from the burning surface area of an electric-arc furnace by exhaust gases.

14 SEM Micrograph of Silica Fume Particles

15 Applications for Silica Fume and Metakaolin

16 Chemical Analysis of Typical Fly Ash, Slag, Silica Fume, Calcined Clay, Calcined Shale, and Metakaolin Class F fly ash Class C fly ash Ground slag Silica fume Calcined clay Calcined shale Metakaolin SiO 2, % Al 2 O 3, % Fe 2 O 3, % CaO, % SO 3, % Na 2 O, % K 2 O, % Fly Ash, Slag, Total Na eq. alk, %

17 Selected Properties of Typical Fly Ash, Slag, Silica Fume, Calcined Clay, Calcined Shale, and Metakaolin Class F fly ash Class C fly ash Ground slag Silica fume Calcined clay Calcined shale Metakaolin Loss on ignition, % Blaine fineness, m 2 /kg , ,000 Fly Ash, Slag, Relative density

18 Typical Amounts of SCM in Concrete by Mass of Cementing Materials Fly ash Fly Ash, Slag, Class C 15% to 40% Class F 15% to 20% Slag 30% to 45% Silica fume 5% to 10% Calcined clay 15% to 35% Metakaolin 10% Calcined shale 15% to 35%

19 Effect of Fly Ash on Mixing Water Requirements Class of fly ash C F C F Fly ash content, % by mass of cementing material Change in mixing water requirement compared to control, % Fly Ash, Slag,

20 Effect of Fly Ash on Bleeding of Concrete Fly ash mixtures Percent Bleeding ml/cm 2 Average of: Class C Class F Control mixture Fly Ash, Slag,

21 Effect of Fly Ash on Air- Entraining Admixture Dosage and Air Retention Fly ash mixtures C F Control mixture Percent of airentraining admixture relative to control Air content, % Minutes after initial mixing

22 Effect of Slag on Heat of Hydration

23 Effect of Fly Ash on Setting Time of Concrete Fly ash test mixtures Average of: Class C Class F Control mixture Setting time, hr:min Initial Final 4:40 6:15 4:50 6:45 4:15 5:30 Retardation relative to control, hr:min Initial Final 0:30 0:45 0:35 1:15 Fly Ash, Slag,

24 Effects of Supplementary Cementing Materials on Freshly Mixed Concrete Reduced Increased No/Little Effect Varies Fly ash Slag Silica fume Nat. Pozzolans Water Requirements Workability Bleeding and Segregation Air Content Heat of Hydration Setting Time Finishability Fly Ash, Slag, Pumpability Plastic Natural Shrinkage PozzolansCracking

25 Compressive Strength Development

26 Long Term Strength Development

27 Cold Weather Strength Development

28 Abrasion Resistance Vs. Compressive Strength

29 Fly ash Calcined shale Slag Portland cement Fly Ash, Slag,

30 Frost Resistance of Fly Ash Concrete Results at 300 cycles Fly ash mixtures Frost resistance in water, ASTM C 666 Method A (AASHTO T 161) Expansion, % Mass loss, % Durability factor Average of: Class C Class F Control mixture Fly Ash, Slag,

31 Deicer-Scaling Resistance of Fly Ash Concrete Results at 300 cycles Deicer scaling resistance, ASTM C 672 Water cure Curing compound Average of: Class C 3 2 Fly Ash, Slag, Class F Control mixture

32 Scaling Resistance Vs. W/C-Ratio

33 Deicer-Scaling of Fly Ash Concrete (25% Replacement) Fly Ash, Slag,

34 Deicer-Scaling of Fly Ash Concrete (50% Replacement) Fly Ash, Slag,

35 Effect of Fly Ash and Slag on Alkali-Silica Reactivity

36 Reduction of ASR by Calcined Clay and Calcined Shale

37 Effects of Supplementary Cementing Materials on Hardened Concrete Reduced Increased Chemical Resistance Fly Ash, Slag, Carbonation Concrete Color No/Little Effect Varies Strength Gain Abrasion Resistance Freeze-Thaw and Deicer- Scaling Resistance Drying Shrinkage and Creep Permeability Alkali-Silica Reactivity Fly ash Slag Silica fume Nat. Pozzolans