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Sampling and Characterizing Plaster

Sampling and Characterizing Plaster. Roger G. Morse AIA Dyanki, Inc. Sampling and Characterizing Plaster . A New System for Sampling and Characterizing Plaster in Three Dimensions. Homogeneous areas based on surface characteristics

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Sampling and Characterizing Plaster

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  1. Sampling and Characterizing Plaster Roger G. Morse AIA Dyanki, Inc.

  2. Sampling and Characterizing Plaster A New System for Sampling and Characterizing Plaster in Three Dimensions

  3. Homogeneous areas based on surface characteristics One type of plaster can have different surface characteristics Frequently results in large numbers of samples Typical Survey Looks at Plaster in Two Dimensions

  4. Smooth wall plaster Lumpy wall plaster Wainscot plaster Crown molding Molded plaster Sandy wall plaster Spattered plaster Knobby plaster Smooth ceiling Lumpy ceiling Applied decorations Sandy ceilings Highly painted ceilings Dashed ceilings High relief molded ceilings Example of Homogeneous Plasters in Two Dimensions

  5. Same Plasters in Three Dimensions • Smooth white finish plaster • Sandy white finish plaster • Gray-beige base plaster

  6. Plaster Classification

  7. Initial Inspection • Make an initial determination of likely homogeneous plaster types • Collect a sufficient number of each type to meet AHERA requirements for surface treatments • 1,000 SF – 3 samples • 1,000 to 5,000 SF – 5 samples • Over 5,000 SF – 7 samples

  8. Sample Collection • Core drill connected to HEPA vacuum • Clean dust from surface of cores in sealed cabinet with HEPA local exhaust

  9. Plaster Core

  10. Evaluate Plaster Cores • Evaluate with stereo microscope • Assign plaster type to each layer • Verify that number of samples meets AHERA requirements

  11. Gross Characteristics of Each Layer • Layer – (top, middle, bottom) • Function – (finish, base, scratch) • Gross Color – Munsell Color System • Thickness

  12. Components of Each Layer • Cement • Aggregate • Fiber

  13. Cement - Type • Gypsum • Lime • Gypsum/Lime • Portland Cement • Clear Adhesive

  14. Cement Color • White • Off White • Gray • Exact colors from Munsell Color System

  15. Aggregate - Type • Sharp mason’s sand • Perlite • Vermiculite • Mica • Washed sand • None

  16. Aggregate Color • Colorless • Tan • Brown • Black • Red Brown • Exact color definition with Munsell Color System

  17. Fiber - Type • Hair – cattle or horse • Wood fiber • Jute • Fiberglass • Cellulose • Suspected of being asbestos

  18. Engineering Properties • Plaster strength • Bond between layers • Useful for engineering design purposes

  19. Determine Plaster Type • Atlas of plasters • Physical standards

  20. Analyze Samples • PLM • Gravimetric Reduction • Point Count (1000 points – Chatfield Method) • Report concentrations of plaster components • Report lime to gypsum ratio • Determine if analysis verifies plaster type determination

  21. Plaster Types • Job mixed plasters • Modern plasters • Acoustical plasters • Skim coats • Plaster substrates • Coatings

  22. Job Mixed Plasters • Colored sand plaster • White smooth plaster • White sand plaster • Bond plaster • Portland cement plaster (Stucco) • Mortar and concrete

  23. Modern Plasters • Perlite aggregate • Synthetic fiber reinforcing • Gray granular gypsum cement • Vermiculite aggregate

  24. Acoustical Plasters • Manufactured products • Open porous texture • Usually friable • Each must be considered separately • Frequently contain asbestos

  25. Skim Coats • Drywall taping compound • Clear adhesive • Fine aggregate (limestone, talc, marble) • May be between layers of paint • May not be able to find sufficient samples to meet AHERA requirements • Evaluate separately for each facility

  26. Plaster Substrates • Gypsum lath • Gypsum block • Gypsum panels (drywall systems)

  27. Coatings • Textured coatings • Heavy hard cementitous coatings (Thorocoat) • May contain tremolite

  28. Roger G. Morse AIA Dyanki, Inc. 504 Snake Hill Road Poestenkill, NY 12140

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