Chapter 15 - Coating Concrete Flashcards
What is the process called when concrete cures?
Hydration
Poured concrete an be affected by?
Ambient conditions and vibration.
How can the ambient conditions affect poured concrete?
Hot weather - causes concrete to cure more rapidly than otherwise, resulting in a greater possibility for voids, and a dusty, low-strength surface.applying a curing compound can help mitigate the effects of these conditions. Many entities require a wet burlap curing blanket to be used over freshly placed concrete to prevent this type of drying out.
How can vibration affect poured concrete?
Vibration Is done to remove air pockets and can cause the heavy aggregate to sink to the bottom of the form. Resulting in a weak, sandy surface, creating a fragile layer of sand and cement known as laitance. This condition can occur both at the upper surface and at the concrete/form surface or interface.
What are some of the properties of concrete?
Extremely durable Inorganic Hard Has good compressive strength Improves with age
What is guniting?
Is the process of spraying or slinging shotcrete onto a surface as a coating to restore concrete to its original grade.
What are the several reasons concrete may be coated?
Decoration Waterproofing Enhancing chemical resistance Protection from freeze-thaw steel Decontamination Surface sealer Protection against abrasion and erosion Color coding Protecting purity of water or other products contained Improving and simplifying cleaning Skid resistance
What is laitance?
a weak surface layer of water-rich cement mixture on the surface of fresh concrete caused by the upward movement of water.
What is efflorescence?
Is caused by moisture passing through the concrete and carrying soluble concrete salts with it to the surface. The salts react with carbon dioxide in the atmosphere creating a fluffy white crystalline deposit on the surface.
What surface preparation is generally performed on concrete?
Abrasive blast cleaning Hand and power tool cleaning High-pressure water jetting or cleaning Acid etching Stoning Centrifugal blasting Scarifying
For surface preparation of concrete what is the joint surface preparation standard?
NACE No. 6/ SSPC SP 13
The advantages of waterjetting and wet abrasive blasting on concrete include?
Fast cutting of the surface
Washing dust away
Reducing abrasive and concrete particles in air
What is sacking?
It consists of scrubbing a mixture of cement mortar over the concrete surface using a cement sack, gunny sack, or sponge rubber float.
What is stoning?
Is similar to sacking, except that a carborundum brick, or other appropriate abrasive block, is used to smooth the surface of the concrete
Several generic types of coatings may be used over concrete include?
Bituminous cutbacks Chlorinated rubber Vinyl Epoxy Novalac epoxy Elastomeric polyurethane Sheet materials e.g. rubber Glass-fiber-reinforced plastics Furan resins
