RE: CONCRETE: "Crazing"[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: CONCRETE: "Crazing"
- From: "John Whitty" <jwhitty(--nospam--at)itac-net.com>
- Date: Wed, 1 Jun 2005 16:46:44 -0400
- Disposition-notification-to: "John Whitty" <jwhitty(--nospam--at)itac-net.com>
This link should help http://www.prmconcrete.com/crazing.htm …but FYI:
“Crazing is the development of a network of fine random cracks or fissures on the surface of concrete or mortar caused by shrinkage of the surface layer. These cracks are rarely more than 1/8 inch [3 mm] deep and are more noticeable on steel-troweled surfaces. The irregular hexagonal areas enclosed by the cracks are typically no more than 1 1/2 inch [40 mm] across and may be as small as 1/2 or 3/8 inch [12 or 20 mm] in unusual instances. Generally, craze cracks develop at an early age and are apparent the day after placement or at least by the end of the first week. Often they are not readily visible until the surface has been wetted and it is beginning to dry out.
Crazing cracks are sometimes referred to as shallow map or pattern cracking. They do not affect the structural integrity of concrete and rarely do they affect durability or wear resistance. However, crazed surfaces can be unsightly. They are particularly conspicuous and unsightly when concrete contains calcium chloride, a commonly used accelerating admixture.”
John T. Whitty, P.E.
From: Polhemus, Bill
Always interesting to review "in house specs" that have been around since forever, that "Project Engineers" (who, in most facilities management outfits are typically NOT structural or civil engineers) just toss into the bid package without thinking anything about it.
I've run across a term that I've never heard before. It appears to be a description of a physical concrete defect. The contextual sentence reads as follows:
"Surface defects include _crazing_ and cracks in excess of 0.01 inch wide or that penetrate to reinforcement or completely through nonreinforced sections regardless for width, spalling, pop outs, honeycomb, rock pockets, and other objectionable conditions."
Excuse me, but "crazing"? I have never seen that before, nor do I have any idea what it can mean.
Of course, until I got into the world of specifications some years back, I'd never heard the term "laitance" either, so there you go.
Anyone out there know what the heck "crazing" is?
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