Why are we still having problems with moisture and concrete floor slabs?

(after Howard Kanare)

Water is an essential ingredient in concrete, but uncontrolled excessive moisture can create a whole host of problems with concrete floor slabs. Some of the modes of distress include:

· Adhesive breakdown of adhered finish floor coverings

· Debonding of coatings

· Osmotic blisters of epoxy systems including coatings and epoxy terrazzo

· High pH (alkalai) attack of floor finishes

· Microbial growths

· Flooring expansion, such as cupping of wood strips or planks

· Reactions between incompatible floor patching/ leveling materials.

Despite the development of many excellent, longstanding practices, there are still a large number of moisture-related problems. Some contributing factors include: design professionals specify a blotter/ cushion/ subbase layer over a vapour retarder; vapor retarders are not carefully protected during construction; concrete floor slab mixes often are made with smaller than desirable aggregate and mixes are not optimized for minimum shrinkage; inappropriate moisture tests still are specified; moisture resting is not always done correctly; some unreasonably moisture-sensitive adhesives are still on the market; there is no performance specification or test method for moisture resistance of adhesives or floor coatings; and failures of some moisture-suppression products occur because there are no performance specifications for moisture suppression products.

(CONCRETE CONSTRUCION, November 15, 2007)

b) Find additional information on distresses listed and speculate on the remediation. Use the linking words/phrases from Appendix 1:

21 Read the information below and discuss it with your partner: