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Re: Siporex[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Re: Siporex
- From: David Handy <dhandy(--nospam--at)trg.ca>
- Date: Thu, 09 Sep 1999 22:00:17 -0400
>What exactly has been the problem with Siporex slabs that you mention? >We have several structures in Mumbai using Siporex slabs, and the >performance has been *very* interesting. Please also note that >Siporex is a brand-name and other companies may also be making similar >products under a different name. > >Ravi Sinha Ravi I should have used AAC (aerated autoclaved concrete) instead of Siporex. I am pretty sure that the slabs are actually Siporex, but not 100%. The slabs we are concerned about are roughly 25 years old. We had one with a deflection of a couple of inches over 15' +/- span. This occurred during high snow loading condition but not higher than specified design values. The most common problem is unrecoverable deflection. People have been putting owsj at midspan in order to reduce spans in half. A group of engineers and maintenance staff has been assembled in order to address ways of determining whether the slabs are safe. With the assistance of a local University we have tested 5 slabs. Results vary significantly in terms of total load supported. The common result however was that the 6" thk x 18" wide slabs 12' long failed suddenly in shear and not in bending. Deflection was a couple of inches when it snapped. Some slabs have failed at design loads or just under (ie. LL * 1.5 + DL * 1.25). Cracking on the underside was minimal even close to failure so this cannot be used to determine level of distress. Results of compressive forces don't correlate well with load capacity so taking cores doesn't give accurate values of shear strength. It seems that the bubbles are quite coarse in the region of the reinforcing bars. We are wondering if this is typical or was a quality control problem and results in the wide variation. I thought that maybe as the mixture is expanding under the chemical reaction, the bars interupt the flow of the mixture and cause the resulting coarse bubbles. This may be typical in all AAC slabs. Does anyone know? Another problem is that compressive strengths of the cores are less than half of minimum strength values as suggested by the Siporex literature. Are the strengths decaying over time. If the roof leaks then one would think that carbonation of the "concrete" would happen very quickly as the moisture passes quickly through the bubbles in the slab. btw AAC resembles the center of an AERO chocolate bar (if you know what they are) David Handy, P.Eng. dhandy(--nospam--at)trg.ca The Thompson Rosemount Group, Cornwall, Ont. Canada Opinions expressed are personal only.
- Re: Siporex
- From: Dr. Ravi Sinha
- Re: Siporex
- From: David Handy
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