Dipayan Jana. Construction Materials Consultants, Inc. Greensburg, PA USA www-cmc-concrete.com

Transcription

1 Dipayan Jana Construction Materials Consultants, Inc. Greensburg, PA USA www-cmc-concrete.com

2 Consumable product guru in materials science industry -George Blann, Buehler, Ltd. For his 37 years of contribution to sample preparation techniques

3 Wase U. Ahmed, Buehler Ltd. Dr. Don Campbell Campbell Petrographic Services Dr. David Walker, Columbia University George Vander Voort, Buehler Ltd.

4 Books Hutchinson St. John et al. Walker Campbell Buehler Sum-Met Petrography Texts Mineralogy, SEM, & XRD Tests Key Articles Ahmed ASTM Standards [C 295, C 457, C 856, C 1324] French Mielenz Detwiler et al. Miscellaneous Articles ICMA Proceedings CCR Miscellaneous Journals Manufactures Literature 10 Texts Author s Own Practices 50 Articles

5 Sampling Strategy for Different Materials Construction Materials 20 Different Sample Preparation Techniques - Step-by-Step Procedures - Preparation Tips - Information Obtained from a Specific Preparation -Consumables - Instruments - Manufacturers of Consumables & Instruments - Precautions - Advantages & Limitations Misinterpretation of Microstructure due to - Improper Sample Preparation - Inadequate Sample Preparation - Over-Preparation

6 1. Cleaning 2. Fresh Fracturing 3. Oil-immersion Mount Preparation 4. Encapsulation & Vacuum Impregnation 5. Sectioning 6. Lapping & Grinding 7. Polishing 8. Etching & Staining 9. Thin Sectioning (Fluorescent Thin Section Preparation) 10. Grain Thin Sections 11. Polished Grain Mounts (Half section preparation) 12. Thin Section for Aggregate Petrography

7 13. Phenolphthalein and Rainbow Indicators for Determining the Depth of Carbonation 14. Staining Techniques for Rapid Diagnosis of ASR Gel in Concrete 15. Sample Preparation for Air-Void Analysis of Hardened concrete by ASTM C Sample Preparation for Air-Void Analysis by Image Analysis Techniques 17. Conductive Coating for Examination in SEM 18. Ultra-thin-sectioning 19. Sample Preparation for X-ray Diffraction 20. Sample Preparation for Cryo-SEM, ESEM, and X-ray microscopy

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9 Instruments & Consumables A Good Sample Preparation Laboratory Requires: Petrographer and Laboratory Technician Instruments [Sectioning, Grinding, Polishing, Thin-sectioning Cleaning, Drying, & Various Accessories] A Good Machine Shop for Custom-made Tools & Fixtures Consumables [Coolant, Lubricant, Resin/Hardener, Dye, Abrasive Powder/Paste/Suspension/Paper/Disc, Saw Blades, Glass Slides, and Other Miscellaneous Consumables] Instruments and consumables shown here do not necessarily endorse the manufacturers or their products and nor do they indicate the best product available in the market

10 Castable or Cold Mounting Medium Resin/Hardener/Dye -Acrylic - Epoxy Acrylic vs. Epoxy: - Bond - Edge retention - Shrinkage - Exotherm - Reaction to sample or solvents - Viscosity/Impregnation - Curing time Encapsulation & Impregnation Encapsulation - Flexible Molds - Plastic Molds -Metal Molds - Release Agents Why? Edge retention Improved Integrity Ease of Handling Highlighting Cracks & Voids Preservation of microstructure Impregnation - Sample Chamber - Vacuum Pump - Moisture Trap

11 Encapsulation Plastic, Metal, and Flexible Sample Molds

12 Flexible Sample Molds - Silicone -EPDM -Urethane - Natural Rubber Encapsulation Aluminum Molds for Preparing Silicone Molds Not reactive to epoxy Withstand high temperature Reusable Shore Hardness Good tensile strength

13 Impregnation Vacuum Pump Epoxy Dispensing System

14 Large Saws Bench-top or Stand-alone - Resin or metal bonded diamond blades - Water, Oil, or Coolant - Diamond grain-size - Continuous/Segmented Rim - Blade thickness - Blade speed (RPM) & feed rate - Pressure applied; Heat - Coolant supply rate Coolant - Water, Oil, Cutting Fluid, Glycol, Alcohol - Hydraulic food-line mineral oil (Baby oil or Mobil DTE FM32) - Non-flammable, non-hazardous, non-reactive Sectioning Why? Manageable sample Expose internal surface Reduce sample thickness Precision Saws Bench-top - Diamond wafering (ultrathin to in.) blades - Water, Oil, or Coolant - Fine-grained, Low to high diamond concentration - Continuous/Segmented rim - Metal or resin-bonded diamond - Low pressure, Low heat - Coolant supply rate

15 Sectioning Sectioning concrete, mortar, brick, etc. in a large saw & tile saw

16 Sectioning Sample holding fixtures for sectioning small encapsulated and impregnated samples and thin sections in a tile saw

17 Cleaning A sectioned sample must be thoroughly cleaned with water, acetone, or alcohol to remove debris formed by sectioning, and any cutting fluid, and then air or oven dried prior to subsequent grinding and other steps

18 Grinding & Polishing Large (18-24 in. diameter) stand alone or bench top horizontal rotary unit (Plain/Grooved wheel) Abrasive - Loose SiC or Alumina - Metal and resin-bonded diamond grinding discs of variable grit sizes - Polishing cloth charged with diamond, tin oxide, DA, CS abrasive Lubricant -Water - Lapping Oil (Mobil DTM FM32) (Not for polishing) - Ethanol, Glycol, or Alcohol

19 Grinding & Polishing Small (8-12 in. diameter) bench top single or dual-wheel horizontal rotary unit (Plain/Grooved wheel) Abrasive - Loose SiC or Alumina - Metal and resin-bonded diamond grinding discs of variable grit sizes - Polishing Cloths charged with DA, CS, or diamond abrasives Lubricant -Water - Oil (e.g., Mobil DTM FM32) (Not for polishing) - Ethanol, Glycol, or Alcohol

20 Grinding & Polishing Small (2 7 / 8 in. diameter) Glass Platen in a Grinding bowl in Minimet Grinder/Polisher Stationary Roll (or Belt) Grinder Micrometercontrolled vertical diamond cup wheel Abrasive - SiC Paper attached to a glass platen - Loose SiC paste applied directly to a glass platen - Polishing cloth attached to the glass platen and charged with DA, CS, or diamond paste (or suspension) Abrasive SiC Paper Roll Abrasive Diamond impregnated on the wheel Lubricant = Water; Oil (Not for Polishing); Organic Solvent (Ethanol, Glycol, or Alcohol)

21 Grinding & Polishing Manual Grinding/Polishing of Large (Concrete) Sample Metal and Resin-bonded Magnetic Diamond Discs (120, 240, 600, 1200 grits) On Plane or Grooved Iron lapping plate Loose SiC or Alumina Abrasives On Grooved Lapping Plate Lubricant Circulating Water mixed with Corrosion-resistant Chemical

22 Manual Grinding/Polishing of Small (Trimmed) Sample Grinding & Polishing - 3 to 5 min per step - 25 to 40 min per sample Grinding Metal-bonded diamond disc (Water or Oil) Resin-bonded diamond disc or, PSA-backed SiC paper (Water or Oil) Polishing 5-µm Alumina (6-µm diamond) 0.3-µm Alumina (0.25-µm diamond) 1-µm Alumina 0.05-µm Alumina Deagglomerated alumina is used for polishing Buehler TexMet (Distilled Water or Glycol) Buehler TexMet & Microcloth (Distilled Water or Glycol)

23 Grinding & Polishing Abrasive Suspensions for Manual Operations Grinding & Polishing

24 Grinding & Polishing Automated grinding & polishing of multiple samples by a stand alone lapping machine Adding a custom-made fixture on a large stand-alone lapping machine for grinding and polishing of multiple samples

25 Sample holders & weights for grinding Grinding & Polishing

26 Ring Lapper Configuration Grinding & Polishing Automated Grinding & Polishing of Multiple Samples by Horizontal Rotary Grinder/Polisher Lapmaster, Logitech, and Buehler Grinder/Polishers

27 Ring Lapper Configuration Grinding & Polishing Precision grinding fixtures for Lapmaster & Logitech Machines Sample carriers, Conditioning rings, Pads, and weights

28 Thin-sectioning Basic Steps 1. Trimming 2. Cleaning & Drying 3. Encapsulation & Impregnation 4. Fine Grinding 5. Cleaning & Drying 6. Bonding to Glass Slide 7. Precision Sectioning 8. Precision Grinding 9. Final Hand Grinding 10. Cleaning & Drying 11. Polishing (Optional) 12. Cover Slip Protection (Optional) Instruments 1. Tile Saw 2. Sonic Cleaner & Oven 3. Mold & Vacuum Pump 4. Horizontal Rotary Grinder 5. Sonic Cleaner & Oven 6. Bonding Fixture 7. Precision TS Machine 8. Precision TS Machine 9. Horizontal Rotary Grinder 10. Sonic Cleaner & Oven 11. Horizontal Rotary Grinder 12. Hand

29 Thin-sectioning An example of steps of thin section preparation from a concrete core

30 Thin-sectioning

31 Thin-sectioning

32 Thin-sectioning 3 ways to do Precision Sectioning & Precision Grinding A. By hand B. By separate bench-top precision saw and grinder C. By a single bench-top unit housing wafering blade and grinding wheel

33 A. Thin-sectioning by hand (Manual Method) Thin-sectioning Precision Sectioning in a Tile Saw with a Sample Holder in. diamond wafering blade Precision Grinding in a Rotary Grinder with a TS Holder

34 Aggregate Thin Section Two mm thin sections One mm thin section Partitions created by trimmed business cards placed inside the silicone encapsulating mold - Epoxy-mixed particles are placed in each chamber

35 B. Automated Thin Sectioning in Separate Precision Sectioning & Grinding Units Thin-sectioning Precision Sectioning + Precision Grinding Buehler s Isomet 1000 Precision Saw With Diamond Wafering Blade Logitech or Lapmaster s Grinder & Precision Grinding Fixtures

36 Thin-sectioning Buehler s Petrothin Hillquest s Machine Ingram-Ward s Machine Microtec s Microtrim

37 Clinker Preparation An Economical Method of Clinker Sample Preparation Buehler s Isomet Minimet Ecomet Combination + + Precision Sectioning Precision Grinding and Polishing

38 Modes of Clinker & Cement Preparation (From Campbell 1999) Clinker Preparation Polished sections of clinkers and cements Single, Impregnated, Sectioned, and Polished Clinker Crushed, Polished Clinker Fragments mm Cements in drilled epoxy plug, cut & polished Whole Clinkers Sectioned, Polished Crushed Clinkers Ground, Polished Polished Grain Mounts Thin Sections Size-graded, cement, impreg, sectioned, polished Thin sections of whole and crushed clinkers

39 Clinker Preparation An Economical Method of Clinker Sample Preparation Isomet Saw Coolant = Oil (Mobil DTE FM32) Minimet Grinding Abrasive = Mobil FM32 on 320, 600 SiC Paper, then µm Alumina in Propylene Glycol on TexMet Ameritool Grinder Abrasive & Lubricant = 8-in. disc and all above

40 For Fine Powdery Material (Fine Sand, Cement, mm-size Clinker, Pozzolan, Soil, etc.) - Encapsulate dry powder - Vacuum Impregnate - Prepare Regular Thin Section Grain Thin Section - Sprinkle dry powder on an epoxy-coated frosted slide, or - Apply an epoxy paste of powder on a frosted slide -Cure - Grind the sample by holding the slide in a slide holder and using a horizontal rotary grinder - Placing a drop of epoxy on a non-stick paper and add grains to it, or - Place a paste nodule of epoxy mixed grains to a non-stick paper - Place a frosted glass slide on top of it with pressure - Cure; Remove excess epoxy along the edge - Fine grind/polish with a slide holder on a horizontal rotary grinder

41 Grain Thin Section For Coarse Grains (Sand, Crushed Clinker, Pea-sized Whole Clinker, Raw Feed, etc.) Soak grains in epoxy or super-glue Place the epoxy-soaked grains on a working slide Grind/Cut to expose the grains Prepare TS by bonding the ground surface of exposed grains to a frosted glass slide

42 B & W Contrast Black marker pen micron Wollastonite Powder Thanks to Larry, Jeremy, and Michigan Tech

43 Tables in the Article 1. Resins, Dyes, Manufacturers 2. Grinding and Polishing Techniques 3. Etching and staining methods for clinker and cement 4. Staining methods in concrete, aggregate, and clinker raw feeds 5. Equipments, Consumables, and Manufacturers 6. Sample preparation steps for various materials 7. Modes of examinations 8. Examples of misinterpretation of microstructure due to improper sample preparation No. 325 Sieve

44 Misinterpretations 1. Microcracks in paste in thin section from oven drying (Drying shrinkage) 2. Grain cracking from grinding (ASR) 3. Concrete-Floor cover separation during drying (Condensation) No. 325 Sieve 4. Inadequate epoxy filling of air voids (Excessive fly ash) 5. Bright fluorescence from excess dye dosage or thickness (Erroneously high w/c) 6. Patchy paste in thin section from incomplete epoxy penetration 7. Cracks, holes, pits, scratches on polished clinker from abrasives and solutions 8. Excess air voids in image analysis from incomplete B/W contrasting 9. Erroneous elemental analysis in SEM-EDS from inadequately cleaned sample